My problems with time
Beacon
says:
Because light travels at a large but finite speed, it takes time for light
to cover large distances. Thus, when we see the light of very distant
objects in the universe, we are actually seeing light emitted from them a
long time ago: we see them literally as they were in the distant past.
For example, Supernova 1987a occurred in a "nearby" galaxy called the Large
Magellanic Cloud (adjacent figure). Its light was observed on Earth in 1987,
but the distance to the Large Magellanic Cloud is about 190,000 light years.
Thus, we normally say that Supernova 1987a occurred in 1987, but it really
happened about 190,000 years earlier; only in 1987 did the light of the
explosion reach the Earth! If we want to know what the Large Magellanic
Cloud looks like "now", we will have to wait 190,000 years.
In comparison, the Sun is only about 8 light-minutes away. So the light we
see from the Sun represents what the Sun looked like 8 minutes ago, and we
must wait another 8 minutes to see what it looks like "now".
[end quote]
The problem I have with this is that "now" is when we see it. What is the
significance of saying that we are looking at the a sunset but the sun is
"really" under the horizon. Surely the Sun is where we see it now?
I am also aware that the cosmic background radiation gives us ideas about
how the universe evolved "in the past" . But what does this "in the past"
mean?
When I hear astronomers say "the light from that star is 1,500 years old"
that irks me since to me the light is current and to attribute some
significance to the fact that it is 1,500 light years away is only valid if
we could be here and there at the same time.
Maybe I am not being clear about this. Is it a locality/ privileged
observer/ action at a distance problem? Can anyone understand the problem I
have? I feel something is funny here. Something worth explaining to the
public. Why do I feel that? Is it a problem with the word "now"? With what
an event is?
I just get upset at the idea of an explosion 190,000 years ago since to me
the explosion was 16 years ago, just like the sun is on the horizon at
sunset. Am I wrong?
Is there an FAQ or source of information to explain my apparent problem?
John Enockson
Fireworks demonsrate this well when distant. You see the flash but hear
the boom when the flash is already faded. The sound is moments old and
the event over to your eyes but still current to your ears. Light waves
can be broadcast years ago and those packets are still streaming towards
you. Its just waves traveling through the media of air or space.
Beacon
"John Enockson" <jeno...@wi.rr.com> wrote in message
news:3DEF3801...@wi.rr.com...
My problem is what do you mean by "broadcast years ago"? You do not know
until you see it. Your "now" is here and now and not some ability to be
light years away where some event is happening at the same time as you are
here. It is not an event to you until you "receive the brodcast".
The Chroniclae of Thomas Covenant a- a Lord of the Rings type tome - had
charachters called Bloodguard who sometimes used sentient horses for travel.
the horses came from a weeks travel away. Yet whenever they went outside to
call them somehow the horses had got the call a week or two ago and arrived
just after they were called.
Something is amiss here? What is it that is bothering me about stars which
are "like looking into the past"?
Andy
news:RsHH9.33294$zX3....@news.indigo.ie...
> My problem is what do you mean by "broadcast years ago"? You do not know
> until you see it. Your "now" is here and now and not some ability to be
> light years away where some event is happening at the same time as you are
> here. It is not an event to you until you "receive the brodcast".
Because light has a finite speed for a certain medium, this is measureable
and consistent. From the speed, the time delay for a fixed distance is
easily measured. Once the effect (flash) has been noticed, the cause (nova)
can be deduced.
'It is not an event to you until you "receive the brodcast".' You are
entering the realm of metaphysics here - if a tree falls and nobody is there
to witness it............
Andy
Fritz Weaver
>I just get upset at the idea of an explosion 190,000 years ago since to me
>the explosion was 16 years ago, just like the sun is on the horizon at
>sunset. Am I wrong?
I'm afraid the distances in space are just overwhelming. Light travels at
186,286 miles per second. Sixty seconds of light traveling at 186,286 miles
per second is called a light minute. The distance light travels in a year
is called a light year. Using the light year standard of measuring distance
is just a lot simpler than some number with lots of zeros which means
nothing to most people.
It takes about i minutes for light from the sun to reach Earth traveling at
286,282 miles per second. If it take 8 minutes for light from the sun to
reach Earth at 286,282 miles per second then how far away would the sun be
from Earth?
The Magellic Clouds you refer to are small galaxies that trail along behind
the Milky Way, where we are. They may be considered part of the Milky Way
because usually Andromeda is referred to as the nearest galaxy and it is
heading right for us at about 200,000 miles per hour!
Regards,
Fritz Weaver ICQ:1674329
============================
http://www.internet-skeptics.org
============================
One thing I have learned in a long life: that all our science, measured against reality, is primitive and childlike -- and yet it is the most precious thing we have.-- Albert Einstein
Miss Terri
news:ojGH9.33277$zX3....@news.indigo.ie...
> http://csep10.phys.utk.edu/astr162/lect/cosmology/lightspeed.html
> Is there an FAQ or source of information to explain my apparent problem?
Relativity Tutorial http://www.astro.ucla.edu/~wright/relatvty.htm
Dave Ulmer
"Beacon" <openm...@mydeja.com> wrote in message
news:ojGH9.33277$zX3....@news.indigo.ie...
> http://csep10.phys.utk.edu/astr162/lect/cosmology/lightspeed.html
snip...
Your problem with "now" is that you don't seem to understand that there are
different kinds of "time". In our universe there is only One-Time that that
is "now" and it is the same time everwhere in the universe. We measure
Time-Intervals using the speed of light, clocks, etc. but these
time-intervals are not time, they are recorded history. The light you see
now is energy data that has been recorded in time and stored in space ever
since that previous "now" time.
The state of the universe at any one-and-only-time can be recorded in mass,
energy, or space and this recording can be played back at a later time.
Dave...
Spaceman
>I just get upset at the idea of an explosion 190,000 years ago since to me
>the explosion was 16 years ago, just like the sun is on the horizon at
>sunset. Am I wrong?
Roll a ball down a slight hill,
ru past the ball to the bottom and look at the ball coming
do you think it was "rolled" just now"
or "when you rolled it?
Or
"when you first "saw it from the bottom"?
The distance it travels is a "space" that must be moved in,
and moving in space creates the abstract loop to count such known
as time.
Time = abstract counting of motion of a mass compared to another motion of a
mass.
That is the never ending, looping "ratio" known as time.
It is not "the real", it is "abstractly" created by the reals.
James M Driscoll Jr
Spaceman
http://www.realspaceman.com
Uncle Al
>
> http://csep10.phys.utk.edu/astr162/lect/cosmology/lightspeed.html
> says:
> Because light travels at a large but finite speed, it takes time for light
> to cover large distances.
It takes time to cover small distances, too - a foot/nanosecond near
enough.
[snip]
> In comparison, the Sun is only about 8 light-minutes away. So the light we
> see from the Sun represents what the Sun looked like 8 minutes ago, and we
> must wait another 8 minutes to see what it looks like "now".
>
> [end quote]
>
> The problem I have with this is that "now" is when we see it. What is the
> significance of saying that we are looking at the a sunset but the sun is
> "really" under the horizon. Surely the Sun is where we see it now?
Sure, except delayed by about 8 minutes deepending on where in its
orbit the Earth is. Look at your feet in a swimming pool. Are they
where they appear to be or where they are?
> I am also aware that the cosmic background radiation gives us ideas about
> how the universe evolved "in the past" . But what does this "in the past"
> mean?
Take a dollar bill out of your wallet. See the date? That's a dollar
bill created in the "past."
> When I hear astronomers say "the light from that star is 1,500 years old"
> that irks me since to me the light is current and to attribute some
> significance to the fact that it is 1,500 light years away is only valid if
> we could be here and there at the same time.
Open a bottle of vintage 1995 red wine. How old is the wine when you
open the bottle?
> Maybe I am not being clear about this. Is it a locality/ privileged
> observer/ action at a distance problem? Can anyone understand the problem I
> have? I feel something is funny here. Something worth explaining to the
> public. Why do I feel that? Is it a problem with the word "now"? With what
> an event is?
All points in the universe are at its center. Every direction points
toward the beginning. You do the math and believe the results until
contradicted by observation. Geometry and algebra are united by
Euler's equation. That's a pat hand. Quantum mechanics uses "math as
metaphor." Its only justification is that it works (given enough
fudge factors - the Standard Model doesn't include mass, and requires
some 19 artificial parameters to accomodate it. That's pitiful.)
> I just get upset at the idea of an explosion 190,000 years ago since to me
> the explosion was 16 years ago, just like the sun is on the horizon at
> sunset. Am I wrong?
Yes, you are wrong. Go to an outdoor concert and sit in a back row.
A guy whumps a drum - you see it! Where is the sound? It gets to you
eventually, one millisecond/foot, long after the guy's drumstick is
someplace else. The light is also delayed, one nanosecond/foot. What
you here is not what is happening locally. What you see is not what
is happening locally, either.
--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
"Quis custodiet ipsos custodes?" The Net!
John Jones
1000000000 light years away sends us light. When we get
that light it is 1000000000 years old. Therefore, we
say that by viewing this 1000000000 year old light we
say the universe is 1000000000 years old.
Bad idea.
Because if the galaxy took 10000000000000 years to get
there, it would be 1000000000000000 years old.
Beacon <openm...@mydeja.com> wrote in message
news:ojGH9.33277$zX3....@news.indigo.ie...
>
http://csep10.phys.utk.edu/astr162/lect/cosmology/light
speed.html
Seppo Pietikainen
To add to the confusion.... A photon doesn't recognize 'time'. To a
photon *everything* happens simultaneously.
Seppo P.
Dirk Van de moortel
For starters, the atmosphere refracts the light in such a way that during
sunset, when the sun is fully visible but seems to touch the horizon, it
already is below it. If there was no atmosphere, and you would look at
the sun at the same time, it would just seem to be below the horizon.
On top of that, the light you see is 8 minutes old. It left the sun 8 minutes
ago. Saying that what you "see now" on the sun is "happening now",
would be like saying that you "are" in front of yourself when you look
at yourself in a mirror.
The convention is that something happening and your seeing it are two
different events taking place at different places and at different times.
Dirk Vdm
Siamak
> [...]
I'm not a physicist, but I guess the problems is:
you take "NOW" as a point in space-time,
but what usually is denoted by "NOW" is a hyperspace that is determined by t=0.
Mike Varney
> says:
> Because light travels at a large but finite speed, it takes time for light
> to cover large distances.
It takes light time to cover any distance.
> Thus, when we see the light of very distant
> objects in the universe, we are actually seeing light emitted from them a
> long time ago: we see them literally as they were in the distant past.
> For example, Supernova 1987a occurred in a "nearby" galaxy called the
Large
> Magellanic Cloud (adjacent figure). Its light was observed on Earth in
1987,
> but the distance to the Large Magellanic Cloud is about 190,000 light
years.
> Thus, we normally say that Supernova 1987a occurred in 1987, but it really
> happened about 190,000 years earlier; only in 1987 did the light of the
> explosion reach the Earth! If we want to know what the Large Magellanic
> Cloud looks like "now", we will have to wait 190,000 years.
>
> In comparison, the Sun is only about 8 light-minutes away. So the light we
> see from the Sun represents what the Sun looked like 8 minutes ago, and we
> must wait another 8 minutes to see what it looks like "now".
>
> [end quote]
>
> The problem I have with this is that "now" is when we see it. What is the
> significance of saying that we are looking at the a sunset but the sun is
> "really" under the horizon. Surely the Sun is where we see it now?
No.
> I am also aware that the cosmic background radiation gives us ideas about
> how the universe evolved "in the past" . But what does this "in the past"
> mean?
Before now.
> When I hear astronomers say "the light from that star is 1,500 years old"
> that irks me since to me the light is current
Current in time? Or as a current? How old are you?
> and to attribute some
> significance to the fact that it is 1,500 light years away is only valid
if
> we could be here and there at the same time.
Nope.
> Maybe I am not being clear about this. Is it a locality/ privileged
> observer/ action at a distance problem? Can anyone understand the problem
I
> have? I feel something is funny here. Something worth explaining to the
> public. Why do I feel that? Is it a problem with the word "now"? With what
> an event is?
What you need to do is read quite a few books, then you will have the
language to express your remaining concerns and understand the answers.
> I just get upset at the idea of an explosion 190,000 years ago since to me
> the explosion was 16 years ago, just like the sun is on the horizon at
> sunset. Am I wrong?
The universe does not care if you get upset with it. Feel lucky that it
does not care.
> Is there an FAQ or source of information to explain my apparent problem?
www.google.com "how to use google"
http://math.ucr.edu/home/baez/physics/
Dirk Van de moortel
"Mike Varney" <var...@collorado.edu> wrote in message news:asoh7r$s0k$1...@peabody.colorado.edu...
>
> "Beacon" <openm...@mydeja.com> wrote in message
> news:ojGH9.33277$zX3....@news.indigo.ie...
> > http://csep10.phys.utk.edu/astr162/lect/cosmology/lightspeed.html
> > says:
[snip]
>
> > I just get upset at the idea of an explosion 190,000 years ago since to me
> > the explosion was 16 years ago, just like the sun is on the horizon at
> > sunset. Am I wrong?
>
> The universe does not care if you get upset with it. Feel lucky that it
> does not care.
:-))
Welcome!
http://users.pandora.be/vdmoortel/dirk/Physics/ImmortalGems.html#Care
Dirk Vdm
Mike Varney
"Dirk Van de moortel" <dirkvand...@ThankS-NO-SperM.hotmail.com> wrote
in message news:vZPH9.37079$Ti2....@afrodite.telenet-ops.be...
:-D
Lester Zick
wrote:
>Beacon wrote:
>>
>> http://csep10.phys.utk.edu/astr162/lect/cosmology/lightspeed.html
>> says:
>> Because light travels at a large but finite speed, it takes time for light
>> to cover large distances.
>
>It takes time to cover small distances, too - a foot/nanosecond near
>enough.
Yes, as I recall, one foot = a light nanasecond approximately. So,
perhaps, we should be measuring our memories in terms of feet?
>
[ . . . snipperoly]
Regards - Lester
remove DEL in address for email
Beacon
"Seppo Pietikainen" <s.piet...@kolumbus.fi> wrote in message
news:3DEF97A2...@kolumbus.fi...
>
>
> Dave Ulmer wrote:
> > "Beacon" <openm...@mydeja.com> wrote in message
> > news:ojGH9.33277$zX3....@news.indigo.ie...
> >
> >>http://csep10.phys.utk.edu/astr162/lect/cosmology/lightspeed.html
> >
> >
> > snip...
> >
> > Your problem with "now" is that you don't seem to understand that there
are
> > different kinds of "time". In our universe there is only One-Time that
that
> > is "now" and it is the same time everwhere in the universe. We measure
> > Time-Intervals using the speed of light, clocks, etc. but these
> > time-intervals are not time, they are recorded history. The light you
see
> > now is energy data that has been recorded in time and stored in space
ever
> > since that previous "now" time.
> >
> > The state of the universe at any one-and-only-time can be recorded in
mass,
> > energy, or space and this recording can be played back at a later time.
> >
> > Dave...
What does this above mean? I believe that there is "one time" for a
particular observer but that the idea of a "same tine" (I really would
prefer "siimiltanuous event" ) elsewhere does not gel with me. It only
becomes an event (as I see it - I mean in my opinion) as I see it.
> >
>
> To add to the confusion.... A photon doesn't recognize 'time'. To a
> photon *everything* happens simultaneously.
Really? And when did you last interview a photon? Come to think of it what
is a photon? I don't suppose I could answer that but it is worth thinking
about.
Beacon
"Uncle Al" <Uncl...@hate.spam.net> wrote in message
news:3DEF83D8...@hate.spam.net...
> Beacon wrote:
> >
> > http://csep10.phys.utk.edu/astr162/lect/cosmology/lightspeed.html
> > says:
> > Because light travels at a large but finite speed, it takes time for
light
> > to cover large distances.
>
> It takes time to cover small distances, too - a foot/nanosecond near
> enough.
>
> [snip]
>
> > In comparison, the Sun is only about 8 light-minutes away. So the light
we
> > see from the Sun represents what the Sun looked like 8 minutes ago, and
we
> > must wait another 8 minutes to see what it looks like "now".
> >
> > [end quote]
> >
> > The problem I have with this is that "now" is when we see it. What is
the
> > significance of saying that we are looking at the a sunset but the sun
is
> > "really" under the horizon. Surely the Sun is where we see it now?
>
> Sure, except delayed by about 8 minutes deepending on where in its
> orbit the Earth is. Look at your feet in a swimming pool. Are they
> where they appear to be or where they are?
Interesting.
But I can feel my feet. I only "feel" the sun on my face when the rays from
it hit my face.>
And my feet are where they are and also where they appear to be. The Sun
being really below the horizon is to me not a "Trick" of light but a
consequence of the speed of light and what you might call "now"
> > I am also aware that the cosmic background radiation gives us ideas
about
> > how the universe evolved "in the past" . But what does this "in the
past"
> > mean?
>
> Take a dollar bill out of your wallet. See the date? That's a dollar
> bill created in the "past."
No it isnt. Though the date on it is a representation of a past event.
>
> > When I hear astronomers say "the light from that star is 1,500 years
old"
> > that irks me since to me the light is current and to attribute some
> > significance to the fact that it is 1,500 light years away is only valid
if
> > we could be here and there at the same time.
>
> Open a bottle of vintage 1995 red wine. How old is the wine when you
> open the bottle?
Not a good year for starters but the wine is new. Though it has been resting
in the bottle for seven years. there is a sense to me of the bottling event
seven years ago but that is a different event to the opening/tasting event.
The wine "IS". It is not something which just mysteriously apperaed form the
past after seven years.
>
> > Maybe I am not being clear about this. Is it a locality/ privileged
> > observer/ action at a distance problem? Can anyone understand the
problem I
> > have? I feel something is funny here. Something worth explaining to the
> > public. Why do I feel that? Is it a problem with the word "now"? With
what
> > an event is?
>
> All points in the universe are at its center.
Well I would say we can assume and possibly measure points to be the same as
other points - i.e. no priviliged observer.
> Every direction points
> toward the beginning.
Now this is exactly related to my problem. Because the experience of the
"beginning" or say 300,000 years after that beginning is impinging on us now
but we assume that the region we exprience this background radiation coming
from from is just like ourt region now.
>You do the math and believe the results until
> contradicted by observation. Geometry and algebra are united by
> Euler's equation. That's a pat hand. Quantum mechanics uses "math as
> metaphor."
But up to now you mentioned only Cosmology not a quantum theory of
cosmology. why should I do the math? Explain the problem if there is one.
> Its only justification is that it works (given enough
> fudge factors - the Standard Model doesn't include mass, and requires
> some 19 artificial parameters to accomodate it. That's pitiful.)
But what has the change in rate of expansion of the universe got to do with
the fact that I believe that a sun setting "now" is not a Sun eight minutes
below the horizon?
>
> > I just get upset at the idea of an explosion 190,000 years ago since to
me
> > the explosion was 16 years ago, just like the sun is on the horizon at
> > sunset. Am I wrong?
>
> Yes, you are wrong. Go to an outdoor concert and sit in a back row.
> A guy whumps a drum - you see it!
> Where is the sound? It gets to you
> eventually, one millisecond/foot, long after the guy's drumstick is
> someplace else. The light is also delayed, one nanosecond/foot. What
> you here is not what is happening locally. What you see is not what
> is happening locally, either.
But what I see Is what is happening to me. I can only be aware of the drum
being banged when I witness it. I can not witness it faster than em
radiartion could get to me so therefore it is "real" to me when I see it.
The fact that sound comes later does not remove that reality.
Beacon
"John Jones" <scooby...@btopenworld.com> wrote in message
news:aso1bt$sll$5...@knossos.btinternet.com...
> The furthest galaxy, just for example, that is
> 1000000000 light years away sends us light. When we get
> that light it is 1000000000 years old. Therefore, we
> say that by viewing this 1000000000 year old light we
> say the universe is 1000000000 years old.
Actually we (cosmologists) don't. The horizon of out experience and the
apparent size of the universe and the actual size are horses of different
colours. In any case a size of the Universe "now" brings us back to my
point.
[snip]
Beacon
>
[snip]
>
> For starters, the atmosphere refracts the light in such a way that during
> sunset, when the sun is fully visible but seems to touch the horizon, it
> already is below it.
I wasnt referring to diffraction (or gravatational lensing effects) for that
matter. But to take you up when you state the Sun really isn't there, where
is this "there" of which you speak. Is it somewhere eight and a half light
minutes away which you can imagine being in at the same time as here?
>If there was no atmosphere, and you would look at
> the sun at the same time, it would just seem to be below the horizon.
>
Dont get silly. If it was below the horizon you would not see it.
> On top of that, the light you see is 8 minutes old.
Here we go again.
>It left the sun 8 minutes
> ago. Saying that what you "see now" on the sun is "happening now",
> would be like saying that you "are" in front of yourself when you look
> at yourself in a mirror.
So if I face two mirrors to each other to reflect off each other with a
powerful telescope I will see myself as a baby eh? :)
Just because the light from the mirror (or a distant star) does not arrive
instantaneously does not mean my reality my "now" changes. If I move the
mirror far enough away I will indeed see myself as I was tin the past. ndeed
even near me it is a tiny amount in the past. But in MY past. Starlight from
1,500 years ago are not in my past. Not until it arrives do I have any idea
of it occupying a past that I did. My reflection is a different animal. It
shares events in tha past with me.
>
> The convention is that something happening and your seeing it are two
> different events taking place at different places and at different times.
This is oddly what I hace come to believe. It seems odd and not conventional
but I am led to that belief. But I would add that my experience of something
happening does not take the something else happening elsewhere when
something happened here. Not until I have information about the elsewhere
event.
>
> Dirk Vdm
>
>
Mike Varney
<SNIP>
" Philosophers say a great deal about what is absolutely necessary for
science, and it is always, so far as one can see, rather naive, and probably
wrong."
"People may come along and argue philosophically that they like one better
than another; but we have learned from much experience that all
philosophical intuitions about what nature is going to do fail."
"If science is to progress, what we need is the ability to experiment,
honestly in reporting the results-- the results must be reported without
somebody saying what they would like the results to have been-- and
finally-- an important thing-- the intelligence to interpret the results. An
important point about this intelligence is that it should not be sure ahead
of time what must be. It cannot be prejudiced, and say 'That is very
unlikely; I don't like that'."
R. P. Feynman
http://www.lorentz.leidenuniv.nl/vanbaal/relative.html
"One can always tell the philosophers at a cocktail party... they are the
ones standing around making stupid comments."
Go away cocktail philosopher.
Beacon
> >
> > The problem I have with this is that "now" is when we see it. What is
the
> > significance of saying that we are looking at the a sunset but the sun
is
> > "really" under the horizon. Surely the Sun is where we see it now?
>
> No.
So it is somewhere else? Not where we see it. But to say it is "really "
below the horoizon when we witness a sunset presupposes that we can suddenly
jump one AU to witness where the sun is "really " is.
>
> > I am also aware that the cosmic background radiation gives us ideas
about
> > how the universe evolved "in the past" . But what does this "in the
past"
> > mean?
>
> Before now.
>
> > When I hear astronomers say "the light from that star is 1,500 years
old"
> > that irks me since to me the light is current
>
> Current in time?
Yes time. Otherwise the thread title might be my problems with electricity.
[snip]
How old are you?
Ask my twin brother that. He left me moving at ninety five percent of the
speed of light ten years ago. He is due back tomorrow.
>
> > and to attribute some
> > significance to the fact that it is 1,500 light years away is only valid
> if
> > we could be here and there at the same time.
>
> Nope.
Direct contradiction is not really helping me here.
>
> > Maybe I am not being clear about this. Is it a locality/ privileged
> > observer/ action at a distance problem? Can anyone understand the
problem
> I
> > have? I feel something is funny here. Something worth explaining to the
> > public. Why do I feel that? Is it a problem with the word "now"? With
what
> > an event is?
>
> What you need to do is read quite a few books, then you will have the
> language to express your remaining concerns and understand the answers.
Argument from authority is not helping us either.
>
> > I just get upset at the idea of an explosion 190,000 years ago since to
me
> > the explosion was 16 years ago, just like the sun is on the horizon at
> > sunset. Am I wrong?
>
> The universe does not care if you get upset with it. Feel lucky that it
> does not care.
I didn't mention the Universe being callous or otherwise. I find many ideas
I get come from what seems to be very simple but incomplete explanations.
>
> > Is there an FAQ or source of information to explain my apparent problem?
>
> www.google.com "how to use google"
> http://math.ucr.edu/home/baez/physics/
Thanks. I saw this before but not such an "up to date" (excuse pun) version.
I thought maybe Alsin Aspect's experiment and Bell's inequality would
explain it all but it does not seem to have yet.
Jacqueline Woodward
Bob
wrote:
>
>"John Enockson" <jeno...@wi.rr.com> wrote in message
>news:3DEF3801...@wi.rr.com...
>>
>>
>> Fireworks demonsrate this well when distant. You see the flash but hear
>> the boom when the flash is already faded. The sound is moments old and
>> the event over to your eyes but still current to your ears. Light waves
>> can be broadcast years ago and those packets are still streaming towards
>> you. Its just waves traveling through the media of air or space.
>
>My problem is what do you mean by "broadcast years ago"? You do not know
>until you see it. Your "now" is here and now and not some ability to be
>light years away where some event is happening at the same time as you are
>here. It is not an event to you until you "receive the brodcast".
>
Not sure whether your issue is primarily semantic (how to use the word
"now") or is about the science.
Taking your last sentence... yes, but if you understand what happened,
then you may realize that the event happened "before". Take the
sunlight for example. You get it "now". But knowing it is sunlight,
and knowing how long it takes for sunlight to travel from sun to
earth, you interpret that new sunlight as having been sent 8 min ago.
If you have an idealized very good sound system, you cannot tell from
the sound alone whether the music is live in your room or from a CD.
But you often know that you put on a CD (maybe the musicians are even
dead), and so you know the original event was at some earlier time.
Some CD even give the recording date.
So I think the point is that interpreting the event time requires
knowledge about the event.
bob
The Ghost In The Machine
<openm...@mydeja.com>
wrote
on Thu, 5 Dec 2002 10:58:22 -0000
<ojGH9.33277$zX3....@news.indigo.ie>:
> http://csep10.phys.utk.edu/astr162/lect/cosmology/lightspeed.html
> says:
> Because light travels at a large but finite speed, it takes time for light
> to cover large distances.
Depends on how one looks at it. If you work it out, from
the viewpoint of the light quanta it takes no time at
all to traverse the Universe from end to end. Of course
from our viewpoint it will take 15 or so billion years
from the Big Bang to our eyeballs -- or, more accurately,
a piece of microwave equipment.
> Thus, when we see the light of very distant
> objects in the universe, we are actually seeing light emitted from them a
> long time ago: we see them literally as they were in the distant past.
> For example, Supernova 1987a occurred in a "nearby" galaxy called the Large
> Magellanic Cloud (adjacent figure). Its light was observed on Earth in 1987,
> but the distance to the Large Magellanic Cloud is about 190,000 light years.
> Thus, we normally say that Supernova 1987a occurred in 1987, but it really
> happened about 190,000 years earlier; only in 1987 did the light of the
> explosion reach the Earth! If we want to know what the Large Magellanic
> Cloud looks like "now", we will have to wait 190,000 years.
>
> In comparison, the Sun is only about 8 light-minutes away. So the light we
> see from the Sun represents what the Sun looked like 8 minutes ago, and we
> must wait another 8 minutes to see what it looks like "now".
>
> [end quote]
>
> The problem I have with this is that "now" is when we see it. What is the
> significance of saying that we are looking at the a sunset but the sun is
> "really" under the horizon. Surely the Sun is where we see it now?
Yes and no. Bear in mind that the Sun isn't really moving
(at least, not in a fairly conventional reference), but
the Earth is rotating, which means the person is going
from the light side to the shadow side of the Earth.
It gets even weirder since the atmosphere bends the light
as well; in a sense, the Sun has already set when one sees
it go behind the mountains. (This also explains why the
setting Sun might look slightly squished.)
>
> I am also aware that the cosmic background radiation gives us ideas about
> how the universe evolved "in the past" . But what does this "in the past"
> mean?
>
> When I hear astronomers say "the light from that star is 1,500 years old"
> that irks me since to me the light is current and to attribute some
> significance to the fact that it is 1,500 light years away is only valid if
> we could be here and there at the same time.
In fact, the light is fresh and new. Work it out,
using the Lorentz-Fitzgerald contraction; the length at
lightspeed becomes 0, and the quantum travels the length
of the Universe in the blink of an eye -- or even less,
subjective. As I understand it, light quanta don't degrade
as they travel, either; an electron, by contrast, will
spread out, assuming a more or less flat Universe.
So light can't be 1,500 years old anyway. At best,
we can state with some qualifications that an event is
1,500 light-years away, 1,500 years away (remember that
the invariant is x^2 + y^2 + z^2 - c^2*t^2, and that c,
the speed of light, is equal to 1 light-year per year),
or a combination of both.
>
> Maybe I am not being clear about this. Is it a locality/ privileged
> observer/ action at a distance problem? Can anyone understand the problem I
> have? I feel something is funny here. Something worth explaining to the
> public. Why do I feel that? Is it a problem with the word "now"? With what
> an event is?
Yes, there's a massive problem with "now", mostly because
it's subjective no matter what one does with it. We are
here, at point (0,0,0) (the coordinate system is slightly
arbitrary but we're defining it so why not? :-) ).
They are over there, at point (+1500ly,0,0,0). We see
something in the direction of that point. What can we
conclude, absent such things as gravitational lensing,
the Moon getting in the way, etc? Not a lot beyond the
fact that something interesting happened over there some
time back and we get to see it "now". (This is assuming
we even have the length accurate, of course.)
Someone over at (0,+1500ly,0) will probably see things
similarly but would be unable to throw that info our way
that we'd see for an additional 2,100 years or so.
(Assuming they even could; terristrial lasers can be
reflected from the Moon but we might get a few paltry
photons back. Perhaps we need better mirrors on the ends
of the excitation rods -- or longer rods.)
Someone on a rocket ship moving near the speed of light
towards "there" would see things even more weirdly.
However, I'd have to look up the specifics.
>
> I just get upset at the idea of an explosion 190,000 years ago since to me
> the explosion was 16 years ago, just like the sun is on the horizon at
> sunset. Am I wrong?
>
> Is there an FAQ or source of information to explain my apparent problem?
>
Dunno, but you might be able to find something relating
to special relativity and the problem of simultaneity.
You might also be able to find things on the "Twin
Paradox", which might shed some more fresh, new light on
the problem. :-)
--
#191, ewi...@earthlink.net
It's still legal to go .sigless.
Laurel Amberdine
> "Seppo Pietikainen" <s.piet...@kolumbus.fi> wrote in message
> news:3DEF97A2...@kolumbus.fi...
>>
>> To add to the confusion.... A photon doesn't recognize 'time'. To a
>> photon *everything* happens simultaneously.
>
> Really? And when did you last interview a photon? Come to think of it what
> is a photon? I don't suppose I could answer that but it is worth thinking
> about.
:) I was wondering if someone was going to bring this up. It's one of
my most favorite aspects of reality.
(Apologies for my imprecise newbie answer, but this is what I
understand.)
Basically, everything moves at the same total "speed" in spacetime,
which has four dimensions (three spatial + time). We move so slowly
that we do most all of our motion in time.
However, a photon moves at maximum spatial speed, so it doesn't move in
time at all. (This is that special relativity thing where more motion
in space means less motion in time: time contraction.)
For a really good explanation, you might want to read chapter two of
_The Elegant Universe_ by Brian Greene.
-Laurel
Laurel Amberdine
Okay, I think I am starting to understand what your issue is. Perhaps
you are attributing some quality to "seeing" and to "light" that is not
there.
A star emits some light. The light is energy that comes from the
star, it's not the star *itself*.
The light travels toward you, taking time in the process. The light
eventually reaches your eye, where your brain puts it together into an
image: "Hey, I see a star." You're constructing a concept from the
light, which is (of course) what you do when you see anything. You
aren't actually in some sort of perceptual contact with the star itself.
So, you see a star. I suppose you make a semi-valid claim that the
star is a current event, present in your immediate reality. You could
say that things are only real at the moment you percieve them.
<Something or other about trees falling in forests...>
Alas, in the more fundamental *now* (which you can't explicitly
percieve, because signals do take time to travel) that light did take a
while to reach you, so the information of starness you recieve is not
current. Saying that what you percieve in the present is what is real
isn't very useful for science; it doesn't take all that much distance
for EM to have a noticable lag. You see past events because the light
takes a while to get to you. Just like if the post service was
incredibly bad, you might be getting letters from 250 years ago, and
finding out the latest happenings of colonial times. If you were really
isolated, you might even think the letters described was what was going
on outside. :)
Well, hrm, I don't know if I helped any or not!
-Laurel
Dirk Van de moortel
"Beacon" <openm...@mydeja.com> wrote in message news:xmRH9.33432$zX3....@news.indigo.ie...
>
> "Dirk Van de moortel" <dirkvand...@ThankS-NO-SperM.hotmail.com> wrote
> in message news:QJMH9.36598$Ti2....@afrodite.telenet-ops.be...
> >
> [snip]
> >
> > For starters, the atmosphere refracts the light in such a way that during
> > sunset, when the sun is fully visible but seems to touch the horizon, it
> > already is below it.
>
> I wasnt referring to diffraction (or gravatational lensing effects) for that
> matter. But to take you up when you state the Sun really isn't there, where
> is this "there" of which you speak.
There is where you look and think you see it. Like in the
mirror.
Besides, there is nothing "to take me up": either you learn
something here, or you don't. I don't think you will, despite
your pseudonym.
> Is it somewhere eight and a half light
> minutes away which you can imagine being in at the same time as here?
I don't understand that question.
Do not insist.
>
> >If there was no atmosphere, and you would look at
> > the sun at the same time, it would just seem to be below the horizon.
> >
>
> Dont get silly. If it was below the horizon you would not see it.
If you would look where you look now, it wouldn't be there
anymore. It would be below the horizon.
>
> > On top of that, the light you see is 8 minutes old.
>
> Here we go again.
Yes, here we all go where very young children and most
animals can't go. It takes a critical amount of intelligence.
>
> >It left the sun 8 minutes
> > ago. Saying that what you "see now" on the sun is "happening now",
> > would be like saying that you "are" in front of yourself when you look
> > at yourself in a mirror.
>
> So if I face two mirrors to each other to reflect off each other with a
> powerful telescope I will see myself as a baby eh? :)
> Just because the light from the mirror (or a distant star) does not arrive
> instantaneously does not mean my reality my "now" changes. If I move the
> mirror far enough away I will indeed see myself as I was tin the past. ndeed
> even near me it is a tiny amount in the past. But in MY past. Starlight from
> 1,500 years ago are not in my past. Not until it arrives do I have any idea
> of it occupying a past that I did. My reflection is a different animal. It
> shares events in tha past with me.
>
> >
> > The convention is that something happening and your seeing it are two
> > different events taking place at different places and at different times.
>
> This is oddly what I hace come to believe. It seems odd and not conventional
> but I am led to that belief. But I would add that my experience of something
> happening does not take the something else happening elsewhere when
> something happened here. Not until I have information about the elsewhere
> event.
Solipsism in action.
Dirk Vdm
Denis Loubet
news:3DEF3801...@wi.rr.com...
>
>
> Fireworks demonsrate this well when distant. You see the flash but hear
> the boom when the flash is already faded. The sound is moments old and
> the event over to your eyes but still current to your ears. Light waves
> can be broadcast years ago and those packets are still streaming towards
> you. Its just waves traveling through the media of air or space.
The fireworks analogy is excellent.
Beacon, you know that the flash and bang of the firework occurs at the same
time, so when is the "now" of the explosion: the flash or the bang?
If you say the flash, then obviously your "now" is displaced in time with
respect to the bang, and visa versa.
Same for stars.
Denis Loubet
dlo...@io.com
http://www.io.com/~dloubet
Martin Hogbin
"Beacon" <openm...@mydeja.com> wrote in message news:ojGH9.33277$zX3....@news.indigo.ie...
> http://csep10.phys.utk.edu/astr162/lect/cosmology/lightspeed.html
> says:
> Because light travels at a large but finite speed, it takes time for light
> objects in the universe, we are actually seeing light emitted from them a
> In comparison, the Sun is only about 8 light-minutes away. So the light we
> see from the Sun represents what the Sun looked like 8 minutes ago, and we
> must wait another 8 minutes to see what it looks like "now".
>
> [end quote]
>
> The problem I have with this is that "now" is when we see it. What is the
> significance of saying that we are looking at the a sunset but the sun is
> "really" under the horizon. Surely the Sun is where we see it now?
This is indeed a good question. Physics does not attempt to say what
is 'really' happening it tries to produce a consistent and useful mathematical
model.
>
> I am also aware that the cosmic background radiation gives us ideas about
> how the universe evolved "in the past" . But what does this "in the past"
> mean?
>
> When I hear astronomers say "the light from that star is 1,500 years old"
> that irks me since to me the light is current and to attribute some
> significance to the fact that it is 1,500 light years away is only valid if
> we could be here and there at the same time.
>
That is a good point. The theory of relativity tells us that no physical
object or information can travel faster than the speed of light (in a vacuum).
Thus, if we take two events, say a flare on a distant star and the
observation of that flare on earth, it is not possible for any effects
of that flare to be detected on Earth before the flare is observed. In
terms of relativity, the spacetime interval between the two events is zero.
> Maybe I am not being clear about this. Is it a locality/ privileged
> observer/ action at a distance problem? Can anyone understand the problem I
> have? I feel something is funny here. Something worth explaining to the
> public. Why do I feel that? Is it a problem with the word "now"? With what
> an event is?
It was thoughts of this kind that got Einstein thinking about relativity, but
it is not necessary to dismiss the idea of a time difference between two
events completely.
For example what do we mean when we say 'the speed of light'. How could
we measure it. Let me suggest two ways that should seem reasonable to you.
1) Take one clock and measure the time it takes for a pulse of light
to travel to a mirror and back. At what time would you say that the light
reached the mirror.
2) Take two similar clocks and whilst they are together, synchronise them.
Slowly (important) and carefully separate the clocks and then use them to
measure how long it takes a light pulse to travel from one to the other.
As a check, you could slowly and carefully move the clocks back together
and check that they were still synchronised.
Using this procedure you would measure a time between the event of the light
leaving the first clock and the event of its reception at the second. In the frame
of reference of your two clocks there is a time difference between these two
events although the spacetime interval is zero.
When measurements are made on light from moving objects, the results are
not what you might expect. It was from this type of experimental observation
that Einstein developed his theory of relativity.
> I just get upset at the idea of an explosion 190,000 years ago since to me
> the explosion was 16 years ago, just like the sun is on the horizon at
> sunset. Am I wrong?
A good book on the subject that most physicists on this group would recommend
is:
Spacetime Physics : Introduction to Special Relativity
by Edwin F. Taylor, John Archibald Wheeler, Archibald Wheeler (Contributor)
Paperback - 312 pages 2nd edition (December 1992)
W H Freeman & Co.; ISBN: 0716723271
I am not sure whether this will answer all your questions but it is well worth
a read.
Martin Hogbin
Vis Mike
What the hell am I looking at? When does
this happen in the movie?
Now. You're looking at now, sir. Everything
that happens now, is happening now.
What happened to then?
We passed then?
When?
Just now. We're at now, now.
Go back to then.
When?
Now.
Now?
Now.
I can't.
Why?
We missed it.
When?
Just now.
When will then be now?
...
Soon.
"Beacon" <openm...@mydeja.com> wrote in message
news:ojGH9.33277$zX3....@news.indigo.ie...
> http://csep10.phys.utk.edu/astr162/lect/cosmology/lightspeed.html
> says:
> Because light travels at a large but finite speed, it takes time for light
> to cover large distances. Thus, when we see the light of very distant
> objects in the universe, we are actually seeing light emitted from them a
> long time ago: we see them literally as they were in the distant past.
> For example, Supernova 1987a occurred in a "nearby" galaxy called the
Large
> Magellanic Cloud (adjacent figure). Its light was observed on Earth in
1987,
> but the distance to the Large Magellanic Cloud is about 190,000 light
years.
> Thus, we normally say that Supernova 1987a occurred in 1987, but it really
> happened about 190,000 years earlier; only in 1987 did the light of the
> explosion reach the Earth! If we want to know what the Large Magellanic
> Cloud looks like "now", we will have to wait 190,000 years.
>
> In comparison, the Sun is only about 8 light-minutes away. So the light we
> see from the Sun represents what the Sun looked like 8 minutes ago, and we
> must wait another 8 minutes to see what it looks like "now".
>
> [end quote]
>
> The problem I have with this is that "now" is when we see it. What is the
> significance of saying that we are looking at the a sunset but the sun is
> "really" under the horizon. Surely the Sun is where we see it now?
>
> I am also aware that the cosmic background radiation gives us ideas about
> how the universe evolved "in the past" . But what does this "in the past"
> mean?
>
> When I hear astronomers say "the light from that star is 1,500 years old"
> that irks me since to me the light is current and to attribute some
> significance to the fact that it is 1,500 light years away is only valid
if
> we could be here and there at the same time.
>
> Maybe I am not being clear about this. Is it a locality/ privileged
> observer/ action at a distance problem? Can anyone understand the problem
I
> have? I feel something is funny here. Something worth explaining to the
> public. Why do I feel that? Is it a problem with the word "now"? With what
> an event is?
>
> I just get upset at the idea of an explosion 190,000 years ago since to me
> the explosion was 16 years ago, just like the sun is on the horizon at
> sunset. Am I wrong?
>
Galen
Of course, c is a constant so every vector for everything has the same
magnitude. The difference is in the direction of the vector as oriented in
spacetime. Did Brian Greene illustrate his point with vectors?
"Laurel Amberdine" <lau...@sff.net> wrote in message
news:aspgrd$t9u7f$1...@ID-45790.news.dfncis.de...
Spaceman
>Here is a website I think you find helpful.
I think "just because you find it helpfull" is not a reason
anyone else would.
You do not know how clocks work huh Jacqueline?
You think "time" actually exists as a "physical force"?
I hope that is not what your link teaches.
because simply.
time has no force.
and no physical reality to have a such a force at all.
James M Driscoll Jr
Spaceman
http://www.realspaceman.com
Beacon
>
> "Beacon" <openm...@mydeja.com> wrote in message
> news:I4RH9.33428$zX3....@news.indigo.ie...
<SNIP>
>
So your philosophy of Science is "when the going gets tough and you can't
refute a scientific position then order the person to go away" ? I happen to
have a different point of view. You do not recognise it a scientific. You
quote from philosophers of science but you do not show how my point of view
is not scientific.
Beacon
But "where you look and think you see it" is somewhere I imagine. Where is
the Sun "really" at sunset? you maintain below the horizon. I maintain that
that concept is non local and therefore only valid if you could actually be
there and here at the same time.
>
> >
> > >If there was no atmosphere, and you would look at
> > > the sun at the same time, it would just seem to be below the horizon.
> > >
> >
> > Dont get silly. If it was below the horizon you would not see it.
>
> If you would look where you look now, it wouldn't be there
> anymore. It would be below the horizon.
I am sorry I do not understand you. I am not really concerned with the
"nothing is really as we see it" argument. While I accept it has some
attraction I do believe that the Sun "really " exists. It is where it is as
you see it. We can measure things about it but those things are only valid
to the instant in time we see it. the idea of everything being "somewhere
else" when we measure it is central to my problem. Maybe I should not bother
with usenet on this. thanks for your opinion anyway.
>
>
>
> >
> > > On top of that, the light you see is 8 minutes old.
> >
> > Here we go again.
>
> Yes, here we all go where very young children and most
> animals can't go. It takes a critical amount of intelligence.
Ad hominem does not assist your position.
When Einstein asked "when I look in a mirror -even travelling at light
speed- do I see my own reflection?" it brought him to one of the two
postulates of relativity. Do you not think he considered what he would see
when he looked behind him? I do not think the questions I ask merit
dismissal just because anyone claims that are philosophical and not
scientific.
Beacon
"Jacqueline Woodward" <jacqueline...@att.net> wrote in message
news:f2UH9.45385$hK4.3...@bgtnsc05-news.ops.worldnet.att.net...I hope so. thanks.
Dirk Van de moortel
Fritz Weaver
And things seem sad or tough
And people are useless, or obnoxious, or daft,
And you feel that you've had quite enough...
Verse 1:
Just remember that you're standing on a planet that's evolving
revolving at nine-hundred miles an hour
and orbiting at nineteen miles a second, so it's reckoned,
a sun that is the source of all our power.
Now the sun and you and me, and all the stars that we can see
Are moving a million miles a day
In an outer spiral arm at forty thousand miles an hour
of the galaxy we call the Milky Way.
Verse 2:
Our galaxy itself contains a hundred million stars,
it's a hundred thousand light-years side to side,
it bulges in the middle, sixty thousand light-years thick,
but out by us it's just three thousand light-years wide.
We're thiry thousand light-years from galactic central point
We go 'round every two hundred million years,
and our galaxy itself is one of millions of billions in this
Amazing and Expanding Universe!
Verse 3:
The universe itself keeps on expanding and expanding
in all of the directions it can whiz,
as fast as it can go, the speed of light, y'know,
twelve million miles a minute, and that's the fastest speed there is,
So remember when you're feeling very small and insecure
How amazingly unlikely is your birth,
And pray that there's intelligent life somewhere up in space,
'Cause there's bugger-all down here on Earth.
From "Monty Python's The Meaning Of Life"
Beacon
"The Ghost In The Machine" <ew...@sirius.athghost7038suus.net> wrote in
message news:9ql5c-...@lexi2.athghost7038suus.net...
> In sci.skeptic, Beacon
> <openm...@mydeja.com>
> wrote
> on Thu, 5 Dec 2002 10:58:22 -0000
> <ojGH9.33277$zX3....@news.indigo.ie>:
> > http://csep10.phys.utk.edu/astr162/lect/cosmology/lightspeed.html
> > says:
> > Because light travels at a large but finite speed, it takes time for
light
> > to cover large distances.
>
> Depends on how one looks at it.
Oops! Relativity rears its head.
>If you work it out, from
> the viewpoint of the light quanta it takes no time at
> all to traverse the Universe from end to end.
This was mentioned above and I asked when the commentator last interviewed a
photon or if what a photon "really " was could be answered ?
Flippancy aside we can measure such effects. Maybe I am assuming an "at
rest" reference frame which I can not show to be as such?
> Of course
> from our viewpoint it will take 15 or so billion years
> from the Big Bang to our eyeballs -- or, more accurately,
> a piece of microwave equipment.
>
[snip]
> >
> > The problem I have with this is that "now" is when we see it. What is
the
> > significance of saying that we are looking at the a sunset but the sun
is
> > "really" under the horizon. Surely the Sun is where we see it now?
>
> Yes and no.
> Bear in mind that the Sun isn't really moving
> (at least, not in a fairly conventional reference), but
> the Earth is rotating, which means the person is going
> from the light side to the shadow side of the Earth.
> It gets even weirder since the atmosphere bends the light
> as well; in a sense, the Sun has already set when one sees
> it go behind the mountains. (This also explains why the
> setting Sun might look slightly squished.)
Okay on a "flat" rotating Earth (or mush less massive Earth sized object)
without atmosphere then?
> >
> > I am also aware that the cosmic background radiation gives us ideas
about
> > how the universe evolved "in the past" . But what does this "in the
past"
> > mean?
> >
> > When I hear astronomers say "the light from that star is 1,500 years
old"
> > that irks me since to me the light is current and to attribute some
> > significance to the fact that it is 1,500 light years away is only valid
if
> > we could be here and there at the same time.
>
> In fact, the light is fresh and new.
As far as the light is concerned. I haven't asked it recently but this does
help.
>Work it out,
[snip ]
I have thought about that before but not tied it to the idea fo the observer
waiting 15Ga for it to arrive.
>
> So light can't be 1,500 years old anyway. At best,
> we can state with some qualifications that an event is
> 1,500 light-years away, 1,500 years away (remember that
> the invariant is x^2 + y^2 + z^2 - c^2*t^2, and that c,
> the speed of light, is equal to 1 light-year per year),
> or a combination of both.
Yes while a spacetime geodeisic describes its path the light as it arrives
is "unchanged" or "new" or "now". Indeed It might not even be aware of all
that distance in between.
>
> >
> > Maybe I am not being clear about this. Is it a locality/ privileged
> > observer/ action at a distance problem? Can anyone understand the
problem I
> > have? I feel something is funny here. Something worth explaining to the
> > public. Why do I feel that? Is it a problem with the word "now"? With
what
> > an event is?
>
> Yes, there's a massive problem with "now", mostly because
> it's subjective no matter what one does with it. We are
> here, at point (0,0,0) (the coordinate system is slightly
> arbitrary but we're defining it so why not? :-) ).
> They are over there, at point (+1500ly,0,0,0). We see
> something in the direction of that point. What can we
> conclude, absent such things as gravitational lensing,
> the Moon getting in the way, etc? Not a lot beyond the
> fact that something interesting happened over there some
> time back and we get to see it "now". (This is assuming
> we even have the length accurate, of course.)
Well this is exactly my point. I couldn't have put it better. Thanks. I now
(no pun intended ) feel a lot more comfortable.
>
> Someone over at (0,+1500ly,0) will probably see things
> similarly but would be unable to throw that info our way
> that we'd see for an additional 2,100 years or so.
Yes that is a I view it (no pun) also. So I wasn't unscientific.
> (Assuming they even could; terristrial lasers can be
> reflected from the Moon but we might get a few paltry
> photons back. Perhaps we need better mirrors on the ends
> of the excitation rods -- or longer rods.)
>
> Someone on a rocket ship moving near the speed of light
> towards "there" would see things even more weirdly.
> However, I'd have to look up the specifics.
Well I was considering light "funnelling" of "tunelling"(not in a quantum
sense ) in that 90 degrees to straight ahead would be dark i.e. no info from
there.
> >
> > I just get upset at the idea of an explosion 190,000 years ago since to
me
> > the explosion was 16 years ago, just like the sun is on the horizon at
> > sunset. Am I wrong?
> >
> > Is there an FAQ or source of information to explain my apparent problem?
> >
>
> Dunno, but you might be able to find something relating
> to special relativity and the problem of simultaneity.
> You might also be able to find things on the "Twin
> Paradox", which might shed some more fresh, new light on
> the problem. :-)
I am aware of that also and can do all the calculations associated with it
( actually the original equations are in a case on the wall of the physics
department ) but I haven't accomodated some of the "wierd" implications of
"Similtaneous" meaninf "not similtanuous". It is a bit like the child who
when told two apples and three apples were five apples and two oranges and
five oranges were five oranges could not tell the teacher what two bananas
and two bananas were because he could only count in apples and oranges. The
formal framework is there (though I frequently have illogical reasoning) but
the implications do not become concrete.
Thanks again
Dirk Van de moortel
"Beacon" <openm...@mydeja.com> wrote in message news:u32I9.33499$zX3....@news.indigo.ie...
>
> "Dirk Van de moortel" <dirkvand...@ThankS-NO-SperM.hotmail.com> wrote
> in message news:uEYH9.37375$Ti2....@afrodite.telenet-ops.be...
> >
> > "Beacon" <openm...@mydeja.com> wrote in message
> news:xmRH9.33432$zX3....@news.indigo.ie...
> > >
> > > "Dirk Van de moortel" <dirkvand...@ThankS-NO-SperM.hotmail.com>
> wrote
[snip]
> > > > On top of that, the light you see is 8 minutes old.
> > >
> > > Here we go again.
> >
> > Yes, here we all go where very young children and most
> > animals can't go. It takes a critical amount of intelligence.
>
> Ad hominem does not assist your position.
But it was not ad hominem. It was ad some life form that asks
questions and then awaits the replies with its fingers in its ears.
Dirk Vdm
Beacon
"Martin Hogbin" <sp...@hogbin.org> wrote in message
news:aspq4u$eov$1...@venus.btinternet.com...
Yes. But the map is not the territory. Childrwen and others not bothered
with the maths (which is really quite simple but turned by myth into
siomething difficult) Understanding Joyce's Finnegans Wake now thats not
easy. Anyway they [the public] want concrete images.
> >
> > I am also aware that the cosmic background radiation gives us ideas
about
> > how the universe evolved "in the past" . But what does this "in the
past"
> > mean?
> >
> > When I hear astronomers say "the light from that star is 1,500 years
old"
> > that irks me since to me the light is current and to attribute some
> > significance to the fact that it is 1,500 light years away is only valid
if
> > we could be here and there at the same time.
> >
> That is a good point. The theory of relativity tells us that no physical
> object or information can travel faster than the speed of light (in a
vacuum).
> Thus, if we take two events, say a flare on a distant star and the
> observation of that flare on earth, it is not possible for any effects
> of that flare to be detected on Earth before the flare is observed. In
> terms of relativity, the spacetime interval between the two events is
zero.
Great! I thought I was on my own and being labelled as an unscientific
crackpot. It is sensible then.
>
> > Maybe I am not being clear about this. Is it a locality/ privileged
> > observer/ action at a distance problem? Can anyone understand the
problem I
> > have? I feel something is funny here. Something worth explaining to the
> > public. Why do I feel that? Is it a problem with the word "now"? With
what
> > an event is?
>
> It was thoughts of this kind that got Einstein thinking about relativity,
but
> it is not necessary to dismiss the idea of a time difference between two
> events completely.
I wouldn't put myself in his league. After all he failed maths and was quite
lazy. I am much more extreme than that :)
Yeah I have read Wheeler and he is a writer which can be relevant outside of
academe. Bohm is too heavy. Popper a tad rational. The ither extreme of
"make it up as you go along" constructivists and Newtons Principa was a
"rape manual" feminists I dont like
Thanks for that reference Martin..
Beacon
"Vis Mike" <visionary25@_nospam_hotmail.com> wrote in message
news:aspq84$mmb$1...@bob.news.rcn.net...
> This thread asked for it on a silver plate... :)
>
> What the hell am I looking at? When does
> this happen in the movie?
> Now. You're looking at now, sir. Everything
> that happens now, is happening now.
> What happened to then?
> We passed then?
> When?
> Just now. We're at now, now.
> Go back to then.
> When?
> Now.
> Now?
> Now.
> I can't.
> Why?
> We missed it.
> When?
> Just now.
> When will then be now?
> ...
> Soon.
Excellent. Samuel Beckett couldnd do better.
Didnt like the movie though it had gems like this
http://www.geocities.com/dragondan84/movies2.html
Beacon
Dirk Van de moortel
"Beacon" <openm...@mydeja.com> wrote in message news:SP2I9.33510$zX3....@news.indigo.ie...
As I stated, due to absentia hominis it cannot have been
ad hominem.
Dirk Vdm
Seppo Pietikainen
Beacon wrote:
> "The Ghost In The Machine" <ew...@sirius.athghost7038suus.net> wrote in
> message news:9ql5c-...@lexi2.athghost7038suus.net...
>
>>In sci.skeptic, Beacon
>><openm...@mydeja.com>
>> wrote
>>on Thu, 5 Dec 2002 10:58:22 -0000
>><ojGH9.33277$zX3....@news.indigo.ie>:
>>
>>>http://csep10.phys.utk.edu/astr162/lect/cosmology/lightspeed.html
>>>says:
>>>Because light travels at a large but finite speed, it takes time for
>>
> light
>
>>>to cover large distances.
>>
>>Depends on how one looks at it.
>
>
> Oops! Relativity rears its head.
>
>
Good thing you didn't say "Relativity rears its ugly head".
(You know, it's just "Relatively" ugly, to some :^)
>>If you work it out, from
>>the viewpoint of the light quanta it takes no time at
>>all to traverse the Universe from end to end.
>
>
> This was mentioned above and I asked when the commentator last interviewed a
> photon or if what a photon "really " was could be answered ?
> Flippancy aside we can measure such effects. Maybe I am assuming an "at
> rest" reference frame which I can not show to be as such?
>
I don't think a fixed frame of reference exists as far as photons are
concerned (I could be wrong and probably am).
<snip for readability>
>
>> Of course
>>from our viewpoint it will take 15 or so billion years
>>from the Big Bang to our eyeballs -- or, more accurately,
>>a piece of microwave equipment.
>>
>
> [snip]
>
>
>>>The problem I have with this is that "now" is when we see it. What is
>>
> the
>
>>>significance of saying that we are looking at the a sunset but the sun
>>
> is
>
>>>"really" under the horizon. Surely the Sun is where we see it now?
>>
>>Yes and no.
>
>
>
>
>>Bear in mind that the Sun isn't really moving
>>(at least, not in a fairly conventional reference), but
>>the Earth is rotating, which means the person is going
>>from the light side to the shadow side of the Earth.
>>It gets even weirder since the atmosphere bends the light
>>as well; in a sense, the Sun has already set when one sees
>>it go behind the mountains. (This also explains why the
>>setting Sun might look slightly squished.)
>
>
> Okay on a "flat" rotating Earth (or mush less massive Earth sized object)
> without atmosphere then?
>
I don't quite understand what you mean by "flat rotating earth". Could
you elaborate, please.
<another snippage for readability>
>>>an event is?
>>
>>Yes, there's a massive problem with "now", mostly because
>>it's subjective no matter what one does with it. We are
>>here, at point (0,0,0) (the coordinate system is slightly
>>arbitrary but we're defining it so why not? :-) ).
>>They are over there, at point (+1500ly,0,0,0). We see
>>something in the direction of that point. What can we
>>conclude, absent such things as gravitational lensing,
>>the Moon getting in the way, etc? Not a lot beyond the
>>fact that something interesting happened over there some
>>time back and we get to see it "now". (This is assuming
>>we even have the length accurate, of course.)
>
>
> Well this is exactly my point. I couldn't have put it better. Thanks. I now
> (no pun intended ) feel a lot more comfortable.
>
Maybe you shouldn't (pun intended). Someone *looong* ago told me that
those who are comfortable with these things are either lying or utterly
mad...
You don't sound like you're lying and I don't think you're more mad than
I am...[then again, some people think I'm totally gone...] :^)
Seppo P.
Beacon
> From "Monty Python's The Meaning Of Life"
Using Multiple Intelligence in science teaching and learning
and added the following verses:Reflecting on comments above [in the paper] about the lack of Solar System and planetary science in the proposed Physical Science Curriculum, the author has added the following two verses. [add in verses]
Our Sun is at one focus of the planet’s planes of orbit
There are nine all in concentric oval lanes
The inner four are rocks as is the ninth the smallest Pluto
Which departs a lot others planets’ planes
The fifth to eight are gas balls mostly Hydrogen and Helium
Mixed three to one just like the Big Bang made this mess
The Sun has the same mixture and 98 percent of mass
And Jupiter over two thirds of the rest
Each planet sweeps through space cutting the same amount of pie
In the same amount of time it takes to cut
They would travel on forever in a never ending line
But the Sun attracts them to it – that’s an awfully big but
As the strength of their attraction is their masses times each other
But gets weaker by their distance times itself
So the planets don’t go straight and its the Sun that makes them curve
Forcing a change of their momentum each second
In addition to introducing the Kant-Laplace nebular hypothesis of the formation of the solar system from an accretion disk, these verses are an attempt to integrate both Kepler's and Newton's First and Second Laws, as well as Newton's Law of Universal Gravitation and the cosmological Hydrogen Helium ratio into the song.
Spaceman
>'Cause there's bugger-all down here on Earth.
It's very close to all true.
:)
thanks for the lyrics,
I have the song and always wanted to sing along a little
better.
:)
Gregory L. Hansen
Beacon <openm...@mydeja.com> wrote:
>http://csep10.phys.utk.edu/astr162/lect/cosmology/lightspeed.html
>says:
>Because light travels at a large but finite speed, it takes time for light
>objects in the universe, we are actually seeing light emitted from them a
>For example, Supernova 1987a occurred in a "nearby" galaxy called the Large
>Magellanic Cloud (adjacent figure). Its light was observed on Earth in 1987,
>but the distance to the Large Magellanic Cloud is about 190,000 light years.
>Thus, we normally say that Supernova 1987a occurred in 1987, but it really
>happened about 190,000 years earlier; only in 1987 did the light of the
>explosion reach the Earth! If we want to know what the Large Magellanic
>Cloud looks like "now", we will have to wait 190,000 years.
>
>see from the Sun represents what the Sun looked like 8 minutes ago, and we
>must wait another 8 minutes to see what it looks like "now".
>
>[end quote]
>
>significance of saying that we are looking at the a sunset but the sun is
>"really" under the horizon. Surely the Sun is where we see it now?
It's customary to attribute an objectivity to the world; things happen
largely independently of our being there or watching them.
Return to the fireworks example. A cracker goes off and you first see the
flash, then hear the report. You might suspect they're both caused by
the same event, the explosion, and vary your distance until you're right
next to the cracker and they both happen almost simultaneously. When you
see the flash you'll know the cracker has already exploded, and that
you'll soon hear the report. When you hear the report you'll know the
cracker exploded some time in the past, at least as far back as when you
saw the flash. Obviously sound goes slower than light.
You can measure the speed of light, too, and it's finite. Reflect a laser
from a distant mirror, some time will pass before you shoot it and the
reflection returns to you. When you see the reflection you'll know it was
caused by the laser beam you shot out some time in the past. With a
second laser and a friend (or electronic device) that shoots a
different-colored beam back at you when it sees yours, and if you shoot a
second beam the moment you see the return, you can verify the delay is the
same in both directions.
Saying that "now" is when you see it really breaks down when there are
two observers.
--
"A nice adaptation of conditions will make almost any hypothesis agree
with the phenomena. This will please the imagination but does not advance
our knowledge." -- J. Black, 1803.
The Ghost In The Machine
<visionary25@_nospam_hotmail.com>
wrote
on Fri, 6 Dec 2002 01:22:12 -0800
<aspq84$mmb$1...@bob.news.rcn.net>:
> This thread asked for it on a silver plate... :)
>
> What the hell am I looking at? When does
> this happen in the movie?
> Now. You're looking at now, sir. Everything
> that happens now, is happening now.
> What happened to then?
> We passed then?
> When?
> Just now. We're at now, now.
> Go back to then.
> When?
> Now.
> Now?
> Now.
> I can't.
> Why?
> We missed it.
> When?
> Just now.
> When will then be now?
> ...
> Soon.
*chuckles*
Ludicrous speed......GO!
[rest snipped]
--
#191, ewi...@earthlink.net -- insert random Spaceball 1 here
Mike Varney
You are standing around in a physics groups making stupid comments. Go
away.
Laurel Amberdine
> "Laurel Amberdine" <lau...@sff.net> wrote in message
> news:aspgrd$t9u7f$1...@ID-45790.news.dfncis.de...
<snip>
>> (Apologies for my imprecise newbie answer, but this is what I
>> understand.)
>>
>> Basically, everything moves at the same total "speed" in spacetime,
>> which has four dimensions (three spatial + time). We move so slowly
>> that we do most all of our motion in time.
>>
>> However, a photon moves at maximum spatial speed, so it doesn't move in
>> time at all. (This is that special relativity thing where more motion
>> in space means less motion in time: time contraction.)
>>
>> For a really good explanation, you might want to read chapter two of
>> _The Elegant Universe_ by Brian Greene.
>
> Yes, everything can be thought of as having a vector with a magnitude of c.
> Of course, c is a constant so every vector for everything has the same
> magnitude. The difference is in the direction of the vector as oriented in
> spacetime. Did Brian Greene illustrate his point with vectors?
Right. I knew there was some better way to state things. :) Brian Greene
explains by analogy, using an example with a race car which travels the same
east-west distance but with varying amounts of north-south (diagonal)
movement, and thus, takes more time to cover the same distance at the same
speed. His book is meant for a general audience, so he doesn't use terms like
"vector".
-Laurel
Randy Poe
> This thread asked for it on a silver plate... :)
>
> What the hell am I looking at? When does
> this happen in the movie?
> Now. You're looking at now, sir. Everything
> that happens now, is happening now.
> What happened to then?
> We passed then?
> When?
> Just now. We're at now, now.
> Go back to then.
> When?
> Now.
> Now?
> Now.
> I can't.
> Why?
> We missed it.
> When?
> Just now.
> When will then be now?
> ...
> Soon.
Ah, a fan of the epic ground-breaking Science Fiction thriller
masterpiece "Spaceballs", I see.
- Randy
Galen
> Right. I knew there was some better way to state things. :) Brian Greene
> explains by analogy, using an example with a race car which travels the
same
> east-west distance but with varying amounts of north-south (diagonal)
> movement, and thus, takes more time to cover the same distance at the same
> speed. His book is meant for a general audience, so he doesn't use terms
like
> "vector".
>
>
> -Laurel
That's a good analogy. I'll have to remember it. Thanks.
Galen
concept of a present that could separate a past from a future. The concept
of a present seems to have as little to do with time itself as color has to
do with light." -H. D. Zeh
The "present" or the "right here, right now" is not a problem for physics.
It is an "illusion of consciousness" associated to temporal vertigo.
When an astronomers says "the light from that star is 1,500 years old," what
they really mean is that the star emitted the light at time t1 and it
reached Earth at time t2, and that the difference between t1 and t2 is 1,500
years. "Now" or the "present" never need enter the equation.
"Beacon" <openm...@mydeja.com> wrote in message
news:ojGH9.33277$zX3....@news.indigo.ie...
> http://csep10.phys.utk.edu/astr162/lect/cosmology/lightspeed.html
> says:
> Because light travels at a large but finite speed, it takes time for light
> to cover large distances. Thus, when we see the light of very distant
> objects in the universe, we are actually seeing light emitted from them a
> long time ago: we see them literally as they were in the distant past.
> For example, Supernova 1987a occurred in a "nearby" galaxy called the
Large
> Magellanic Cloud (adjacent figure). Its light was observed on Earth in
1987,
> but the distance to the Large Magellanic Cloud is about 190,000 light
years.
> Thus, we normally say that Supernova 1987a occurred in 1987, but it really
> happened about 190,000 years earlier; only in 1987 did the light of the
> explosion reach the Earth! If we want to know what the Large Magellanic
> Cloud looks like "now", we will have to wait 190,000 years.
>
> In comparison, the Sun is only about 8 light-minutes away. So the light we
> see from the Sun represents what the Sun looked like 8 minutes ago, and we
> must wait another 8 minutes to see what it looks like "now".
>
> [end quote]
>
> The problem I have with this is that "now" is when we see it. What is the
> significance of saying that we are looking at the a sunset but the sun is
> "really" under the horizon. Surely the Sun is where we see it now?
>
> I am also aware that the cosmic background radiation gives us ideas about
> how the universe evolved "in the past" . But what does this "in the past"
> mean?
>
> When I hear astronomers say "the light from that star is 1,500 years old"
> that irks me since to me the light is current and to attribute some
> significance to the fact that it is 1,500 light years away is only valid
if
> we could be here and there at the same time.
>
> Maybe I am not being clear about this. Is it a locality/ privileged
> observer/ action at a distance problem? Can anyone understand the problem
I
> have? I feel something is funny here. Something worth explaining to the
> public. Why do I feel that? Is it a problem with the word "now"? With what
> an event is?
>
Beacon
>
>
> You are standing around in a physics groups making stupid comments. Go
> away.
you crossposted the replies which I pick up in one of the other groups. If
it is ot relevent then don't crosspost and I will not reply.
And please produce some evidence to back up your "stupid comment" argument.
Beacon
>
[snip]
> > > > >
> > > > > Yes, here we all go where very young children and most
> > > > > animals can't go. It takes a critical amount of intelligence.
> > > >
> > > > Ad hominem does not assist your position.
> > >
> > > But it was not ad hominem. It was ad some life form that asks
> > > questions and then awaits the replies with its fingers in its ears.
> > >
> >As I stated: Ad hominem does not assist your position.
>
> As I stated, due to absentia hominis it cannot have been
> ad hominem.
You are being disingenuous. What did you mean by a "critical amount of
intelligence" if it was not a personal atack?
What do you mean by suggesting I have my fingers in my ears?
What do you mean by accusing me of not being a person i.e. " absentia
hominis" ?
Now when you finish with that please focus on the problem and not the
person.
Mike Varney
You already have provided the evidence for me by simply making the stupid
comments.
Go away.
Galen
concept of a present that could separate a past from a future. The concept
of a present seems to have as little to do with time itself as color has to
do with light." -H. D. Zeh
The "present" or the "right here, right now" is not a problem for physics.
It is an "illusion of consciousness" associated to temporal vertigo.
When an astronomers says "the light from that star is 1,500 years old," what
they really mean is that the star emitted the light at time t1 and it
reached Earth at time t2, and that the difference between t1 and t2 is 1,500
years. "Now" or the "present" never need enter the equation.
"Beacon" <openm...@mydeja.com> wrote in message
Dirk Van de moortel
"Beacon" <openm...@mydeja.com> wrote in message news:iPcI9.33629$zX3....@news.indigo.ie...
>
> "Dirk Van de moortel" <dirkvand...@ThankS-NO-SperM.hotmail.com> wrote
> in message news:0W2I9.37$fo6.4...@news.cpqcorp.net...
> >
> [snip]
[UNSNIP]
> > > > >> > > On top of that, the light you see is 8 minutes old.
> > > > > > >
> > > > > > > Here we go again.
> > > > > >
> > > > > > Yes, here we all go where very young children and most
> > > > > > animals can't go. It takes a critical amount of intelligence.
> > > > >
> > > > > Ad hominem does not assist your position.
> > > >
> > > > But it was not ad hominem. It was ad some life form that asks
> > > > questions and then awaits the replies with its fingers in its ears.
> > > >
> > >As I stated: Ad hominem does not assist your position.
> >
> > As I stated, due to absentia hominis it cannot have been
> > ad hominem.
>
> You are being disingenuous. What did you mean by a "critical amount of
> intelligence" if it was not a personal atack?
> What do you mean by suggesting I have my fingers in my ears?
I unsnipped something that you conveniently snipped
away.
> What do you mean by accusing me of not being a person i.e. " absentia
> hominis" ?
>
> Now when you finish with that please focus on the problem and not the
> person
What person?
The only thing I see here, is a little weasel.
Dirk Vdm
Martin Hogbin
"Beacon" <openm...@mydeja.com> wrote in message news:fA2I9.33506$zX3....@news.indigo.ie...
>
> "Martin Hogbin" <sp...@hogbin.org> wrote in message
> news:aspq4u$eov$1...@venus.btinternet.com...
> > Physics does not attempt to say what
> > is 'really' happening it tries to produce a consistent and useful
> > mathematical model.
> Yes. But the map is not the territory.
In physics no on knows what the territory is. All we have is a selection of
maps.
> > The theory of relativity tells us that no physical
> > object or information can travel faster than the
> > speed of light (in a vacuum).
> > Thus, if we take two events, say a flare on a distant star and the
> > observation of that flare on earth, it is not possible for any effects
> > of that flare to be detected on Earth before the flare is observed. In
> > terms of relativity, the spacetime interval between the two events is
> > zero.
> Great! I thought I was on my own and being labelled as an unscientific
> crackpot. It is sensible then.
It is sensible in a way. The proper time between two events that
a light beam passes through is zero. The time measured in any
coordinate system is not zero. The relationship between proper
time and coordinate time is what relativity is about.
Martin Hogbin
The Ghost In The Machine
<Hm2I9.33502$zX3....@news.indigo.ie>:
>
> "The Ghost In The Machine" <ew...@sirius.athghost7038suus.net> wrote in
> message news:9ql5c-...@lexi2.athghost7038suus.net...
>> In sci.skeptic, Beacon
>> <openm...@mydeja.com>
>> wrote
>> on Thu, 5 Dec 2002 10:58:22 -0000
>> <ojGH9.33277$zX3....@news.indigo.ie>:
>> > http://csep10.phys.utk.edu/astr162/lect/cosmology/lightspeed.html
>> > says:
>> > Because light travels at a large but finite speed, it takes time for
> light
>> > to cover large distances.
>>
>> Depends on how one looks at it.
>
> Oops! Relativity rears its head.
It tends to do that at high relative speeds.
>
>>If you work it out, from
>> the viewpoint of the light quanta it takes no time at
>> all to traverse the Universe from end to end.
>
> This was mentioned above and I asked when the commentator last interviewed a
> photon or if what a photon "really " was could be answered ?
> Flippancy aside we can measure such effects. Maybe I am assuming an "at
> rest" reference frame which I can not show to be as such?
You're not only assuming it, it's easily proven. Every
reference frame is at rest -- relative to itself.
One fairly classical experiment:
You're in an elevator car, enclosed, no windows, but air,
some lighting, maybe some muzak, etc. The elevator car
is either standing at rest on the Earth's surface,
or being smoothly accelerated by some sort of rocket.
Absent issues such as acceleration variations because of
bad rocket fuel, hitting space debris, planet curvature, etc.,
can the occupant of said elevator car determine which
situation he's in?
If you prefer, you can be in free-fall, orbit, or in deep space.
Similar issues ensue.
>
>> Of course
>> from our viewpoint it will take 15 or so billion years
>> from the Big Bang to our eyeballs -- or, more accurately,
>> a piece of microwave equipment.
>>
> [snip]
>
>> >
>> > The problem I have with this is that "now" is
>> > when we see it. What is the significance of saying
>> > that we are looking at the a sunset but the sun
>> > is "really" under the horizon. Surely the Sun is
>> > where we see it now?
>>
>> Yes and no.
>
>
>
>> Bear in mind that the Sun isn't really moving
>> (at least, not in a fairly conventional reference), but
>> the Earth is rotating, which means the person is going
>> from the light side to the shadow side of the Earth.
>> It gets even weirder since the atmosphere bends the light
>> as well; in a sense, the Sun has already set when one sees
>> it go behind the mountains. (This also explains why the
>> setting Sun might look slightly squished.)
>
> Okay on a "flat" rotating Earth (or mush less massive Earth sized object)
> without atmosphere then?
Well, if you want we can shift our vantage point to a conveniently
orbiting satellite. (Bear in mind that looking directly at
the Sun can damage one's retina.) One such satellite is SOHO,
which as it turns out is orbiting the Sun. I'd have to look
precisely where but it's probably at one of many Lagrange points.
So this satellite is observing something happening on the Sun.
When did it happen? The answer is: when it was observed, relative
to the satellite anyway. Fortunately for us, light is much
faster than the solar wind, so (Sun->satellite + satellite->Earth),
even were the satellite observing the Sun from somewhere else
in Earth's orbit, is plenty fast enough.
But OK, we'll go with the idea of a flat, spinning disc. This
disc, which could be any size -- let's say it's the size of
the space station on _2001_ just for the sake of argument;
that's probably a few hundred meters in diameter -- will of
course rotate at some rate. We'll stand on its edge and
watch the Sun. Well, now there's the little problem that
the Sun is moving relative to us in a circular fashion.
This is fine, but does complicate its observation a bit.
Let's assume once an hour for the sake of argument.
(A real space station would probably have to rotate
much faster to have any useful centripetal/"centrifugal"
gravity.) An event happens on the Sun. The disc rotates
48 degrees during the objective light transit time from
Sun to disc, according to theoretical computations.
But there's no elegant method by which to determine that
short of shooting a laser at a mirror near the Sun and
watching for photons coming back. (A variant of this
method can be used to measure the distance to the Moon,
using a special reflector set up for such experiments.
The transit time and back is a little more than 2 seconds.)
Were we to shoot a "perfect laser" at a "Sun-mirror",
the disc would have rotated about 96 degrees when the
laser beam comes back, assuming the observer could see
it (lasers aren't *that* good yet). Variants of this
experiment can easily measure the speed of light, and have
the advantage that the light originates in the observer's
frame of reference, not some distance away.
So we could hypothesize that, if an event occurs on the
Sun that we can see, the disc is 48 degrees turned from a
hypothetical time-point; this rotation would be half of
a 96 degree rotation necessary to fire a laser from the
spinning disc at the sun to create an observable event,
assuming such was possible anyway.
What does that time-point mean? Not much, really.
At best, it's a convenient fiction for the purposes of a
quasi-Newtonian viewpoint, where light has infinite speed,
velocities add v' = v+w instead of (v+w)/(1+vw/c^2),
and the Lorentz-Fitzgerald contraction is nonexistent.
We might be able to use this fictional time-point to
determine when we will receive a signal from the SOHO
satellite observing the same event (since we know where
both SOHO and the Sun is, relative to us). However, a
better method from a conceptual standpoint might simply be
to take a laser beam and fire it at SOHO, and have SOHO
relay it back to the Sun, have SOHO observe the impact
on the Sun, and get that info back to us, and take half
the time-value. (Actually SOHO can't relay laser beams anyway
so it would be kind of pointless to perform this experiment
in actuality.)
>
>
>> >
>> > I am also aware that the cosmic background
>> > radiation gives us ideas about how the universe
>> > evolved "in the past" . But what does this "in
>> > the past" mean?
>> >
>> > When I hear astronomers say "the light from that
>> > star is 1,500 years old" that irks me since to me
>> > the light is current and to attribute some significance
>> > to the fact that it is 1,500 light years away is only
>> > valid if we could be here and there at the same time.
>>
>> In fact, the light is fresh and new.
>
> As far as the light is concerned. I haven't asked it
> recently but this does help.
Heh.
I'll admit I'm not entirely certain how one can, say, measure
the degradation of, say, an electron moving at a certain
velocity, but my understanding is that an electron "wavicle"
will flatten out in a well-defined fashion. But light does
not flatten out.
Or one can look at unstable particles moving at relativistic
speeds. A particle at time t0 is there, and at time t1 is
now a bunch of other particles, which we can identify by
the tracks they leave in, say, a cloud chamber. The
problem is we're not in the particle's frame of reference,
but some distance away, in a different (and stationary, as
far as we're concerned) frame of reference. So t0 and t1
are measured from our frame, and differ depending on how
fast the particle's moving. Again, this is expected from
relativity and provides nice evidence for relativity's
utility as a theory, as opposed to Newton's theories which
are OK for crashing cars into barriers but not useful
at relativistic speeds.
>
>>Work it out,
> [snip ]
> I have thought about that before but not tied it to
> the idea fo the observer waiting 15Ga for it to arrive.
>>
>> So light can't be 1,500 years old anyway. At best,
>> we can state with some qualifications that an event is
>> 1,500 light-years away, 1,500 years away (remember that
>> the invariant is x^2 + y^2 + z^2 - c^2*t^2, and that c,
>> the speed of light, is equal to 1 light-year per year),
>> or a combination of both.
>
> Yes while a spacetime geodeisic describes its path the
> light as it arrives is "unchanged" or "new" or "now".
> Indeed It might not even be aware of all that distance in between.
It's not, as far as our computations show. Of course there's
no elegant method by which one can interview a massless boson.
CNN reporters are good -- but not *that* good. :-)
>>
>> >
>> > Maybe I am not being clear about this. Is it a
>> > locality/ privileged observer/ action at a
>> > distance problem? Can anyone understand the
>> > problem I have? I feel something is funny here.
>> > Something worth explaining to the public. Why do
>> > I feel that? Is it a problem with the word "now"? With
>> > what an event is?
>>
>> Yes, there's a massive problem with "now", mostly because
>> it's subjective no matter what one does with it. We are
>> here, at point (0,0,0) (the coordinate system is slightly
>> arbitrary but we're defining it so why not? :-) ).
>> They are over there, at point (+1500ly,0,0,0). We see
>> something in the direction of that point. What can we
>> conclude, absent such things as gravitational lensing,
>> the Moon getting in the way, etc? Not a lot beyond the
>> fact that something interesting happened over there some
>> time back and we get to see it "now". (This is assuming
>> we even have the length accurate, of course.)
>
> Well this is exactly my point. I couldn't have put it better.
> Thanks. I now (no pun intended ) feel a lot more comfortable.
You're welcome. I'll admit to having exactly this
problem in explaining the "twin paradox". Undoubtedly
you've heard of it; Person A climbs into rocket which
blasts off and accelerates to near-lightspeed. Person B
waits for A to come back. A comes back -- but A is now
younger than B. I'm working out how A and B interrelate
(I'm assuming a communications system using light beams)
and am running into some issues because of this problem of
pseudo-Newtonian simultaneity among other things; Newton's
theories have to be abandoned at some point because they
simply do not work.
>
>>
>> Someone over at (0,+1500ly,0) will probably see things
>> similarly but would be unable to throw that info our way
>> that we'd see for an additional 2,100 years or so.
>
> Yes that is a I view it (no pun) also. So I wasn't unscientific.
>
>> (Assuming they even could; terristrial lasers can be
>> reflected from the Moon but we might get a few paltry
>> photons back. Perhaps we need better mirrors on the ends
>> of the excitation rods -- or longer rods.)
>>
>> Someone on a rocket ship moving near the speed of light
>> towards "there" would see things even more weirdly.
>> However, I'd have to look up the specifics.
>
> Well I was considering light "funnelling" of "tunelling"
> (not in a quantum sense ) in that 90 degrees to straight
> ahead would be dark i.e. no info from there.
Hmmm...an interesting thought, that. Of course a light
beam traverses the universe in 0sec anyway (subjective)
-- there's no time for it to absorb info from the side.
A rocket at near-lightspeed would see UV at its head,
and infrared at its tail and, to a lesser extent, infrared
from its sides.
I'm going to have to find my copy, but one other
experiment -- mentioned by Einstein himself --
is a setup with a straight train track with two
light-posts, and a mirror arrangement in between.
The lights flash "simultaneously", as observed
by the ground observer (this can even be engineered
by having him press a button that conducts a current
to the lights; since he's halfway in between, the
current and the light take the same time to both
lights).
Now add a fast-moving train with a similar mirror
arrangement and another observer, bearing in mind that the
observers can't compare notes immediately. If the first
observer sets up a mechanism whereby he can automate the
light flashes by cleverly positioning another device to
fire the flashes at some point before the moving observer's
mirror pair reaches the stationary observer's mirror pair,
so that the light reaches the moving observer's mirror
pair at just the right point -- does the moving observer
also see simultaneous light flashes?
I for one would want to set up this problem very
carefully, mostly because there's also the other
coordinate to consider (the mirror-pairs cannot be
physically coincident). I might even have to drag in a
z-coordinate, depending on whether I want to place the
lights on poles next to the track, or on overhead trusses.
I'll have to work it out and get back to you, but I suspect
the answer will be "no", even if the engineers are
very clever about when the lights fire.
--
#191, ewi...@earthlink.net
The Ghost In The Machine
<jamesga...@sbcglobal.net>
wrote
on Fri, 06 Dec 2002 22:12:56 GMT
<Ih9I9.1980$Il7...@newssvr19.news.prodigy.com>:
> "...physics does not even offer any conceptual means for deriving the
> concept of a present that could separate a past from a future. The concept
> of a present seems to have as little to do with time itself as color has to
> do with light." -H. D. Zeh
>
> The "present" or the "right here, right now" is not a problem for physics.
> It is an "illusion of consciousness" associated to temporal vertigo.
>
> When an astronomers says "the light from that star is 1,500
> years old," what they really mean is that the star emitted
> the light at time t1 and it reached Earth at time t2, and
> that the difference between t1 and t2 is 1,500 years.
> "Now" or the "present" never need enter the equation.
Ah, but t1 and t2 are from *different* frames of reference. In
a sense, t1 and t2 are both the same!
Let me illustrate this rather odd-looking point.
Suppose two star systems A and B are stationary to each other.
(A moving relative to B would introduce additional complications.)
These star systems are 1,500 light-years apart. Now something
happens on both A and B, happening at the same time (as determined
by another star system C which happens to be conveniently placed
right between the two and is also stationary).
But A won't see it that way. "Oh, look, our Sun is turning an
odd shade of orange for an instant." But they won't see B's
sun turning green for 1,500 years.
B won't, either. "Oh, gosh, our Sun is turning an odd shade
of green for an instant." But they won't see A's Sun turning
orange for 1,500 years.
So are the two events simultaneous? The answer is "mu".
At best we can state that D = dx^2 + dy^2 + dz^2 - c^2*dt^2
is invariant between the two events, no matter what the
reference frame. We can compute a D value for event pairs
without too much difficulty.
So A sees things this way:
Ea Eb
x 0 +1,500 ly
y,z 0 0
t 0 +1,500 y
D 0
(remembering that c is 1 light-year per year)
or, if one has an alternative calendar:
Ea Eb
x 0 +1,500 ly
y,z 0 0
t +200y +1,700 y
D 0
This is one reason why D must refer to pairs of events;
just computing two D values on single events and then
subtracting them isn't going to work.
B sees things this way:
Ea Eb
x -1,500 ly 0
y,z 0 0
t +1,500 y 0
D 0
Now our man in the middle C sees things this way:
Ea Eb
x -750 ly +750 ly
y,z 0 0
t +750 y +750 y
D 0
OK, this is getting weird. Let's create another star system.
This one will be star system 'E', and be 2,000 light years
from A off at a 90-degree angle, just to make the computations
a little easier. So, from E's point of view:
Ea Eb
x 0 +1,500 ly
y +2,000 ly +2,000 ly
z 0 0
t +2,000 y +2,500 y
D 0
Star system 'F', positioned 1,000 ly away from C in a
similar fashion, will see things this way:
Ea Eb
x -750 ly +750 ly
y +1,000 ly +1,000 ly
z 0 0
t +1,250 y +1,250 y
D 0
The difference is *still* invariant!
We could introduce Wowbagger the Infinitely Prolongued
into this discussion, moving him at .96 of lightspeed. [*]
From his point of view, assuming he's insulting someone
on star system A at just the right time (we'll assume
the insults take 0 time) then traveling to star system
B, it will take him 437.5 years to get to star system
B (subjective); of course star system B will welcome
(?) his arrival 1,562 1/2 years after the event on A.
In order for D to come out at the same value (namely, 0),
he'll have to see the event Eb 420 years into his journey.
Of course this is assuming the conclusion anyway in this
case; I'm not entirely certain how to show Wowbagger's
viewpoint properly without a little more work. It's clear,
though, that Wowbagger's viewpoint is a little bit warped,
and not just because of his self-imposed mission to insult
everyone in the Universe in alphabetical order. :-)
Ea Eb
x 0 +420 ly
y,z 0 0
t 0 +420 y
D 0
[rest snipped for brevity]
[*] one of the odder Pythagorean triplets:
7^2 + 24^2 = 25^2. Therefore, .96c = 24/25 c
works for this sort of thing reasonably well.
Henri Wilson
wrote:
>"...physics does not even offer any conceptual means for deriving the
>concept of a present that could separate a past from a future. The concept
>of a present seems to have as little to do with time itself as color has to
>do with light." -H. D. Zeh
>
>The "present" or the "right here, right now" is not a problem for physics.
>It is an "illusion of consciousness" associated to temporal vertigo.
>
>When an astronomers says "the light from that star is 1,500 years old," what
>they really mean is that the star emitted the light at time t1 and it
>reached Earth at time t2, and that the difference between t1 and t2 is 1,500
>years. "Now" or the "present" never need enter the equation.
'Now' occurs simultaneously throughout the whole universe.
Information about what happens in the 'now' takes varying times to reach
different observers throughout the universe.
The fact that humans rely on EM for communication has no effect on what
happens instantaneously.
Arfur Dogfrey
"It depends on what your definition of 'is' is." -WJC.
> > I am also aware that the cosmic background radiation gives us ideas about
> > how the universe evolved "in the past" . But what does this "in the past"
> > mean?
> >
> > When I hear astronomers say "the light from that star is 1,500 years old"
> > that irks me since to me the light is current and to attribute some
> > significance to the fact that it is 1,500 light years away is only valid
> if
> > we could be here and there at the same time.
> >
Is the fact that Los Angeles is 3000 miles away or so from New York only
valid if we could be in both Los Angeles and New York at the same time?
Hmmmm.
> > Maybe I am not being clear about this. Is it a locality/ privileged
> > observer/ action at a distance problem? Can anyone understand the problem
> I
> > have? I feel something is funny here. Something worth explaining to the
> > public. Why do I feel that? Is it a problem with the word "now"? With what
> > an event is?
Read Einstein's popularization "Relativity: the Special and General Theories"
up to the operational definition of "simultaneity" This tells you what "now"
means in physics.
> >
> > I just get upset at the idea of an explosion 190,000 years ago since to me
> > the explosion was 16 years ago, just like the sun is on the horizon at
> > sunset.
This is an issue of psychology then. All you need to do is calm youself down
and not get upset at the idea.
"A train leaves Podunk and travels at 60 miles per hour. It reaches
Sawtooth, which is 300 miles away from Podunk at noon. When did the train
leave Podunk?"
This is a typical 6th grade math problem that probably doesn't bother you.
"A light signal leaves the Andromeda galaxy and travels at one light year
per year. It reaches Earth, which is 2 million light years away from
the Andromeda galaxy, in the year 2002 AD. When did the light signal
leave the Andromeda galaxy?"
This is the identical problem with only the input numbers changed to
different values. This problem upsets you. So it's not a question
of physics or mathematics. It's a question of psychology. Why does
one version of a problem upset you while another version doesn't?
Arf!
Arfur
Beacon
i.e. "This is a physics group. No philosophy is allowed here. Physics is
self contained and explains the universe"
Mike by the way posted quotes from a philosopher of science. Okay Mike if
you whis stay loked up in your physics group with you "safe" belief that
those outside do not deal with reality the way that physics does and that
you can assume that the rest of society will keep supplying you with budgets
just because you can call them stupid.
Beacon
>
> "Beacon" <openm...@mydeja.com> wrote in message
news:iPcI9.33629$zX3....@news.indigo.ie...
> >
> > "Dirk Van de moortel" <dirkvand...@ThankS-NO-SperM.hotmail.com>
wrote
> > in message news:0W2I9.37$fo6.4...@news.cpqcorp.net...
> > >
> > [snip]
>
> [UNSNIP]
>
> > > > > >> > > On top of that, the light you see is 8 minutes old.
> > > > > > > >
> > > > > > > > Here we go again.
>
>
> > > > > > >
> > > > > > > Yes, here we all go where very young children and most
> > > > > > > animals can't go. It takes a critical amount of intelligence.
> > > > > >
> > > > > > Ad hominem does not assist your position.
> > > > >
> > > > > But it was not ad hominem. It was ad some life form that asks
> > > > > questions and then awaits the replies with its fingers in its
ears.
> > > > >
> > > >As I stated: Ad hominem does not assist your position.
> > >
> > > As I stated, due to absentia hominis it cannot have been
> > > ad hominem.
> >
> > You are being disingenuous. What did you mean by a "critical amount of
> > intelligence" if it was not a personal atack?
> > What do you mean by suggesting I have my fingers in my ears?
>
> I unsnipped something that you conveniently snipped
> away.
And now folks the actual words : i.e. "Here we go again " were PRECEEDED by
a SNIP by ad hominem Dirk
The preceedin words were :
On top of that, the light you see is 8 minutes old. [actually closer to
eight an a half but i do not agree as the light I see is to me "new"]
i.e. Here we go again was in response to "On top of that, the light you see
is 8 minutes old."
The last question i asked himn before that was : "Is it somewhere eight and
a half light
minutes away which you can imagine being in at the same time as here? "
And the last comment before it was : "Dont get silly. If it was below the
horizon you would not see it."
In other words "here we go again" is a continuation of the various times
that I have stated that in my opinion we can not be here and eight and a
half light minutes away. It is silly to assume we can but sayint "don't be
silly" is not a personal attack.
A personal attack is calling someone an animal as we will see below. An
argument based on a personal attack is called AD HOMINEM.
> What do you mean by accusing me of not being a person i.e. " absentia
> > hominis" ?
> >
> > Now when you finish with that please focus on the problem and not the
> > person
>
> What person?
> The only thing I see here, is a little weasel.
As I stated: Ad hominem does not assist your position.
As I also stated please answer the question or as you seem to be avoiding an
answer please do not try to pretend you are answering by insulting me. you
only make yourself look bad in the eyes of your collagues. Bith in terms of
bad manners and inability to answer a simple question related to physics.
Beacon
> In sci.skeptic, Beacon
[snip]
> You're in an elevator car, enclosed, no windows, but air,
> some lighting, maybe some muzak, etc. The elevator car
> is either standing at rest on the Earth's surface,
> or being smoothly accelerated by some sort of rocket.
> Absent issues such as acceleration variations because of
> bad rocket fuel, hitting space debris, planet curvature, etc.,
> can the occupant of said elevator car determine which
> situation he's in?
Yes he can since "at rest" he is not accelerating. If you mean "at rest"
means accelatering on the Earth's surface then no he can't. But if "at rest"
then means accelerating in the first place.
>
> If you prefer, you can be in free-fall, orbit, or in deep space.
> Similar issues ensue.
But in "free fall" you are accelatering also.
>
> >
> >> Of course
> >> from our viewpoint it will take 15 or so billion years
> >> from the Big Bang to our eyeballs -- or, more accurately,
> >> a piece of microwave equipment.
> >>
> > [snip]
> >
> >> >
> >> > The problem I have with this is that "now" is
> >> > when we see it. What is the significance of saying
> >> > that we are looking at the a sunset but the sun
> >> > is "really" under the horizon. Surely the Sun is
> >> > where we see it now?
> >>
> >> Yes and no.
> >
> >
> >
> >> Bear in mind that the Sun isn't really moving
> >> (at least, not in a fairly conventional reference), but
> >> the Earth is rotating, which means the person is going
> >> from the light side to the shadow side of the Earth.
> >> It gets even weirder since the atmosphere bends the light
> >> as well; in a sense, the Sun has already set when one sees
> >> it go behind the mountains. (This also explains why the
> >> setting Sun might look slightly squished.)
> >
> > Okay on a "flat" rotating Earth (or mush less massive Earth sized
object)
> > without atmosphere then?
>
> Well, if you want we can shift our vantage point to a conveniently
> orbiting satellite.
How convenient! No really that is a good ides.
[snip the usefull advice]
The answer is no. Put the other way around with a light in the center of the
carriage. Without the maths - since the train is moving the man on the track
"sees" the "back" door catch up and teh "leading " door move away from a
flash in the middle of the carriage. Thus since the speed of the beams are
finite (an assumption you make) the back door gets "hit" by the light before
the front door. but to the guy in the carriage since a his constant speed he
must witness the same effect as at rest (anopther assumption made) then both
ends of the carriage get struck at the same time.
You could change the assumptions and assume varying speeds of light and no
principle of equivalence.
Beacon
> In sci.skeptic, Beacon
[snip]
> some lighting, maybe some muzak, etc. The elevator car
> is either standing at rest on the Earth's surface,
> or being smoothly accelerated by some sort of rocket.
> Absent issues such as acceleration variations because of
> bad rocket fuel, hitting space debris, planet curvature, etc.,
> can the occupant of said elevator car determine which
> situation he's in?
Yes he can since "at rest" he is not accelerating. If you mean "at rest"
means accelatering on the Earth's surface then no he can't. But if "at rest"
then means accelerating in the first place.
>
> If you prefer, you can be in free-fall, orbit, or in deep space.
> Similar issues ensue.
But in "free fall" you are accelatering also.
>
> >
> >> Of course
> >> from our viewpoint it will take 15 or so billion years
> >> from the Big Bang to our eyeballs -- or, more accurately,
> >> a piece of microwave equipment.
> >>
> > [snip]
> >
> >> >
> >> > The problem I have with this is that "now" is
> >> > when we see it. What is the significance of saying
> >> > that we are looking at the a sunset but the sun
> >> > is "really" under the horizon. Surely the Sun is
> >> > where we see it now?
> >>
> >> Yes and no.
> >
> >
> >
> >> Bear in mind that the Sun isn't really moving
> >> (at least, not in a fairly conventional reference), but
> >> the Earth is rotating, which means the person is going
> >> from the light side to the shadow side of the Earth.
> >> It gets even weirder since the atmosphere bends the light
> >> as well; in a sense, the Sun has already set when one sees
> >> it go behind the mountains. (This also explains why the
> >> setting Sun might look slightly squished.)
> >
> > Okay on a "flat" rotating Earth (or mush less massive Earth sized
object)
> > without atmosphere then?
>
> Well, if you want we can shift our vantage point to a conveniently
> orbiting satellite.
How convenient! No really that is a good idea. Especially for teaching a
class. Though SOHO was lost.
[snip the usefull advice]
The answer is no. Put the other way around with a light in the center of the
carriage. Without the maths - since the train is moving the man on the track
"sees" the "back" door catch up and teh "leading " door move away from a
flash in the middle of the carriage. Thus since the speed of the beams are
finite (an assumption you make) the back door gets "hit" by the light before
the front door. but to the guy in the carriage since a his constant speed he
must witness the same effect as at rest (anopther assumption made) then both
ends of the carriage get struck at the same time.
You could change the assumptions and assume varying speeds of light and no
principle of equivalence.
>
Beacon
> In sci.skeptic, Beacon
[snip]
> some lighting, maybe some muzak, etc. The elevator car
> is either standing at rest on the Earth's surface,
> or being smoothly accelerated by some sort of rocket.
> Absent issues such as acceleration variations because of
> bad rocket fuel, hitting space debris, planet curvature, etc.,
> can the occupant of said elevator car determine which
> situation he's in?
Yes he can since "at rest" he is not accelerating. If you mean "at rest"
means accelatering on the Earth's surface then no he can't. But if "at rest"
then means accelerating in the first place.
>
> If you prefer, you can be in free-fall, orbit, or in deep space.
> Similar issues ensue.
But in "free fall" you are accelatering also.
>
> >
> >> Of course
> >> from our viewpoint it will take 15 or so billion years
> >> from the Big Bang to our eyeballs -- or, more accurately,
> >> a piece of microwave equipment.
> >>
> > [snip]
> >
> >> >
> >> > The problem I have with this is that "now" is
> >> > when we see it. What is the significance of saying
> >> > that we are looking at the a sunset but the sun
> >> > is "really" under the horizon. Surely the Sun is
> >> > where we see it now?
> >>
> >> Yes and no.
> >
> >
> >
> >> Bear in mind that the Sun isn't really moving
> >> (at least, not in a fairly conventional reference), but
> >> the Earth is rotating, which means the person is going
> >> from the light side to the shadow side of the Earth.
> >> It gets even weirder since the atmosphere bends the light
> >> as well; in a sense, the Sun has already set when one sees
> >> it go behind the mountains. (This also explains why the
> >> setting Sun might look slightly squished.)
> >
> > Okay on a "flat" rotating Earth (or mush less massive Earth sized
object)
> > without atmosphere then?
>
> Well, if you want we can shift our vantage point to a conveniently
> orbiting satellite.
How convenient! No really that is a good idea. Especially for teaching a
class. Though SOHO was lost.
[snip the usefull advice]
> >
>
The answer is no. Put the other way around with a light in the center of the
carriage. Without the maths - since the train is moving the man on the track
"sees" the "back" door catch up and teh "leading " door move away from a
flash in the middle of the carriage. Thus since the speed of the beams are
finite (an assumption you make) the back door gets "hit" by the light before
the front door. but to the guy in the carriage since a his constant speed he
must witness the same effect as at rest (anopther assumption made) then both
ends of the carriage get struck at the same time.
You could change the assumptions and assume varying speeds of light and no
principle of equivalence.
>
Beacon
> In sci.skeptic, Beacon
[snip]
> some lighting, maybe some muzak, etc. The elevator car
> is either standing at rest on the Earth's surface,
> or being smoothly accelerated by some sort of rocket.
> Absent issues such as acceleration variations because of
> bad rocket fuel, hitting space debris, planet curvature, etc.,
> can the occupant of said elevator car determine which
> situation he's in?
Yes he can since "at rest" he is not accelerating. If you mean "at rest"
means accelatering on the Earth's surface then no he can't. But if "at rest"
then means accelerating in the first place.
>
> If you prefer, you can be in free-fall, orbit, or in deep space.
> Similar issues ensue.
But in "free fall" you are accelatering also.
>
> >
> >> Of course
> >> from our viewpoint it will take 15 or so billion years
> >> from the Big Bang to our eyeballs -- or, more accurately,
> >> a piece of microwave equipment.
> >>
> > [snip]
> >
> >> >
> >> > The problem I have with this is that "now" is
> >> > when we see it. What is the significance of saying
> >> > that we are looking at the a sunset but the sun
> >> > is "really" under the horizon. Surely the Sun is
> >> > where we see it now?
> >>
> >> Yes and no.
> >
> >
> >
> >> Bear in mind that the Sun isn't really moving
> >> (at least, not in a fairly conventional reference), but
> >> the Earth is rotating, which means the person is going
> >> from the light side to the shadow side of the Earth.
> >> It gets even weirder since the atmosphere bends the light
> >> as well; in a sense, the Sun has already set when one sees
> >> it go behind the mountains. (This also explains why the
> >> setting Sun might look slightly squished.)
> >
> > Okay on a "flat" rotating Earth (or mush less massive Earth sized
object)
> > without atmosphere then?
>
> Well, if you want we can shift our vantage point to a conveniently
> orbiting satellite.
How convenient! No really that is a good idea. Especially for teaching a
class. Though SOHO was lost.
[snip the usefull advice]
> >
>
The answer is no. Put the other way around with a light in the center of the
carriage. Without the maths - since the train is moving the man on the track
"sees" the "back" door catch up and teh "leading " door move away from a
flash in the middle of the carriage. Thus since the speed of the beams are
finite (an assumption you make) the back door gets "hit" by the light before
the front door. but to the guy in the carriage since a his constant speed he
must witness the same effect as at rest (anopther assumption made) then both
ends of the carriage get struck at the same time.
You could change the assumptions and assume varying speeds of light and no
principle of equivalence.
>
Dirk Van de moortel
"Beacon" <openm...@mydeja.com> wrote in message news:h4KI9.33782$zX3....@news.indigo.ie...
As I stated: due to absentia hominis it cannot have been
ad hominem. This was a clear-cut case of ad mustelam.
Dirk Vdm
Happy Dog
> > some lighting, maybe some muzak, etc. The elevator car
> > is either standing at rest on the Earth's surface,
> > or being smoothly accelerated by some sort of rocket.
> > Absent issues such as acceleration variations because of
> > bad rocket fuel, hitting space debris, planet curvature, etc.,
> > can the occupant of said elevator car determine which
> > situation he's in?
>
> Yes he can since "at rest" he is not accelerating. If you mean "at rest"
> means accelatering on the Earth's surface then no he can't. But if "at
rest"
> then means accelerating in the first place.
That's a bit garbled. There is no way for a person, or anything else for
that matter, to distinguish between being inside an object, that prohibits
any contact with the outside environment, at rest on the earth's surface and
inside one that is in a 0g environment being accelerated at a rate of 1g.
If you really want to make things interesting, when the object reaches
relativistic speeds, shoot a beam of light through it.
moo
The Ghost In The Machine
<_zKI9.33787$zX3....@news.indigo.ie>:
>
> "The Ghost In The Machine" <ew...@sirius.athghost7038suus.net> wrote in
> message news:4049c-...@lexi2.athghost7038suus.net...
>> In sci.skeptic, Beacon
> [snip]
>> You're in an elevator car, enclosed, no windows, but air,
>> some lighting, maybe some muzak, etc. The elevator car
>> is either standing at rest on the Earth's surface,
>> or being smoothly accelerated by some sort of rocket.
>> Absent issues such as acceleration variations because of
>> bad rocket fuel, hitting space debris, planet curvature, etc.,
>> can the occupant of said elevator car determine which
>> situation he's in?
>
> Yes he can since "at rest" he is not accelerating.
> If you mean "at rest" means accelatering on the Earth's
> surface then no he can't. But if "at rest"
> then means accelerating in the first place.
A bit nitpicky, but if you want me to be more precise, I
can say that one possibility is that the elevator car is
not moving relative to the Earth's surface (which is of
course moving relative to the Earth's center because the
Earth is rotating). It is of course being accelerated by
the Earth's warpage of space in that case, however.
The other is that a rocket is pulling the car through
free space in such a matter as to impart a constant
acceleration on the car, as measured by instruments
within the car.
>
>>
>> If you prefer, you can be in free-fall, orbit, or in deep space.
>> Similar issues ensue.
>
> But in "free fall" you are accelatering also.
Correct. However, the acceleration is such that the net force
on the craft is in fact zero. To an outside observer, of course,
it looks like the craft is imparting a "centrifugal force" [*] to
its contents. But because space is actually warped, it's not.
How does one prove space is warped? Good question. The simplest
method is to pass a light beam through it and see if the light
beam bends, moving the apparent target. Then shoot a light beam
through it when the mass has moved. We've done this for the Sun
and the light beam does shift by a fraction of an arc-second
(1 arc-second = 1/3600 of a degree). It's barely discernible
with current equipment.
Another example was a rather impressive picture of a free-floating
black hole acting as a gravitational lens. Unfortunately, I'm
not entirely sure what to search for (the picture was part of a
show I saw regarding astronomy some time back).
Your original idea IIRC was to attempt to understand why
is it that the Sun is not at the point at which we are
observing it. At best I've probably confused the issue --
but the issue is itself confusing as all we can discern
about the Universe is that we can passively look at it
as it shoots things our way (mostly photons of various
wavelengths, but we do get neutrinos and charged particles
from the Sun).
BTW: SOHO appears to be operating normally.
Not a bad analysis; however, I have to assume that all physical
laws apply equally to all reference frames, and one of those
laws is that the speed of light is a constant.
Bear in mind that the train appears squished
(Lorentz-Fitzgerald again) to the stationary observer;
however, that won't affect your argument as it is squished
uniformly.
[.sigsnip]
[*] Centrifugal force is a bit of an illusion. If a ball is
swung around one's head, the ball is accelerating because
the string is imparting a *centripetal* force on the ball.
If the ball happens to be hollow, anything within the ball
will continue in a straight line until it hits the side
of the ball, in which case the ball will impart a force
on it.
Were the string to snap, the ball would no longer have
this force. The ball would fly off in as straight a
line as local gravitational conditions will allow.
Anything within the ball would fly along as well.
Mike Varney
>
> "Mike Varney" <var...@collorado.edu> wrote in message
> news:asrm1g$8cj$1...@peabody.colorado.edu...
> >
> > "Beacon" <openm...@mydeja.com> wrote in message
> > news:hPcI9.33628$zX3....@news.indigo.ie...
> > >
> > > "Mike Varney" <var...@collorado.edu> wrote in message
> > > news:asqtc1$jql$1...@peabody.colorado.edu...
> > > >
> > >
> > > >
> > > > You are standing around in a physics groups making stupid comments.
> Go
> > > > away.
> > >
> > > you crossposted the replies which I pick up in one of the other
groups.
> If
> > > it is ot relevent then don't crosspost and I will not reply.
> > >
> > > And please produce some evidence to back up your "stupid comment"
> > argument.
> >
> > You already have provided the evidence for me by simply making the
stupid
> > comments.
> > Go away.
>
> i.e. "This is a physics group. No philosophy is allowed here. Physics is
> self contained and explains the universe"
>
> Mike by the way posted quotes from a philosopher of science.
www.google.com "How to use google"
www.google.com "Feynman"
Beacon
Your reply does not assist me Mike. I do not like to indulge in ad hominems.
I really think that getting annoyed does you no good and being dismissive
does nobody else any good.
I suggest you ask someone like Nauenberg or John Price if my question is
cocktail philosophy and if Physicists have a duty to bridge gaps and
communicate with the public.
As for Feynman. I would remind you that oppenheimer in the going away
address at los alomos stressed the importance of duty to the wider community
Mike Varney
>
> "Mike Varney" <var...@collorado.edu> wrote in message
> news:at0bvu$pj1$1...@peabody.colorado.edu...
> > >
> > > Mike by the way posted quotes from a philosopher of science.
> >
> > www.google.com "How to use google"
> >
> > www.google.com "Feynman"
>
> Your reply does not assist me Mike.
That is your problem, not mine. You are the one that needs to work on your
reading comprehension skills.
> I do not like to indulge in ad hominems.
> I really think that getting annoyed does you no good and being dismissive
> does nobody else any good.
You stand around making stupid comments, you get what you deserve.
> I suggest you ask someone like Nauenberg or John Price if my question is
> cocktail philosophy and if Physicists have a duty to bridge gaps and
> communicate with the public.
I am certain they would consider you an intellectual moron.
> As for Feynman. I would remind you that oppenheimer in the going away
> address at los alomos stressed the importance of duty to the wider
community
Go away, cocktail philosopher.
Beacon
"Henri Wilson" <HW@..> wrote in message
news:l546vukc9c8nsqh1e...@4ax.com...
> On Fri, 06 Dec 2002 22:12:56 GMT, "Galen" <jamesga...@sbcglobal.net>
> wrote:
>
> >"...physics does not even offer any conceptual means for deriving the
> >concept of a present that could separate a past from a future. The
concept
> >of a present seems to have as little to do with time itself as color has
to
> >do with light." -H. D. Zeh
> >
> >The "present" or the "right here, right now" is not a problem for
physics.
> >It is an "illusion of consciousness" associated to temporal vertigo.
> >
> >When an astronomers says "the light from that star is 1,500 years old,"
what
> >they really mean is that the star emitted the light at time t1 and it
> >reached Earth at time t2, and that the difference between t1 and t2 is
1,500
> >years. "Now" or the "present" never need enter the equation.
>
> 'Now' occurs simultaneously throughout the whole universe.
> Information about what happens in the 'now' takes varying times to reach
> different observers throughout the universe.
>
> The fact that humans rely on EM for communication has no effect on what
> happens instantaneously.
Here we go. This is exactly my problem. I entirely disagree with this
definition of "now". Relativity would tell us that time is a strange beast
as regards similtaneous things happening "now". Quantum people may beg to
differ. I do not.
Similtanous events are not similtaneous.
Beacon
"Arfur Dogfrey" <dogs...@dog.com> wrote in message
news:b8a07d3f.02120...@posting.google.com...
> >
> > "Beacon" <openm...@mydeja.com> wrote in message
> > news:ojGH9.33277$zX3....@news.indigo.ie...
> > > http://csep10.phys.utk.edu/astr162/lect/cosmology/lightspeed.html
> > > says:
> > > [end quote]
> > >
> > > The problem I have with this is that "now" is when we see it. What is
the
> > > significance of saying that we are looking at the a sunset but the sun
is
> > > "really" under the horizon. Surely the Sun is where we see it now?
> > >
>
> "It depends on what your definition of 'is' is." -WJC.
Good point. What is is what is here now to me. the Universe may be
everything but that "is not the case". Not until I witness it.
>
> > > I am also aware that the cosmic background radiation gives us ideas
about
> > > how the universe evolved "in the past" . But what does this "in the
past"
> > > mean?
> > >
> > > When I hear astronomers say "the light from that star is 1,500 years
old"
> > > that irks me since to me the light is current and to attribute some
> > > significance to the fact that it is 1,500 light years away is only
valid
> > if
> > > we could be here and there at the same time.
> > >
>
> Is the fact that Los Angeles is 3000 miles away or so from New York only
> valid if we could be in both Los Angeles and New York at the same time?
> Hmmmm.
Yes in a way it is. I sometimes listen on the net to the radio. But I also
have a radio beside me. Or try watching the same match on two different
channels. Actually I watched a match really but prefer radio commentary. I
had to give up since the radio was about one second ahead. so Whenever a
score was about to happen the audio reality hit me before the visual
suspense had been resolved. Ruined the whole experience.
in any case I didn't state that the points couldn't be light years apart
only "so what"? The idea that light form them is say "1500 years old" really
is a meaningless concept to me. Or maybe it is just lost on me. I do not
tend to say wow to such comments.
>
>
> > > Maybe I am not being clear about this. Is it a locality/ privileged
> > > observer/ action at a distance problem? Can anyone understand the
problem
> > I
> > > have? I feel something is funny here. Something worth explaining to
the
> > > public. Why do I feel that? Is it a problem with the word "now"? With
what
> > > an event is?
>
> Read Einstein's popularization "Relativity: the Special and General
Theories"
> up to the operational definition of "simultaneity" This tells you what
"now"
> means in physics.
It is observer dependent okay. But the simplest of ideas sometimes hit me
out of the blue or from the side (pun intended but out of the red would be
more correct).
>
> > >
> > > I just get upset at the idea of an explosion 190,000 years ago since
to me
> > > the explosion was 16 years ago, just like the sun is on the horizon at
> > > sunset.
>
> This is an issue of psychology then. All you need to do is calm youself
down
> and not get upset at the idea.
True. But I meant upset in the confused way not the redundant way.
>
> "A train leaves Podunk and travels at 60 miles per hour. It reaches
> Sawtooth, which is 300 miles away from Podunk at noon. When did the train
> leave Podunk?"
>
> This is a typical 6th grade math problem that probably doesn't bother you.
>
> "A light signal leaves the Andromeda galaxy and travels at one light year
> per year. It reaches Earth, which is 2 million light years away from
> the Andromeda galaxy, in the year 2002 AD. When did the light signal
> leave the Andromeda galaxy?"
I accept that the context does seem different but the same physics applies.
I also accept the light left 2 million or so years ago. What bothers me is
that the light is "2 million years old" or that it is presented as having
some signifigance to as if that was connected to early man or something from
the history of this planet.
>
> This is the identical problem with only the input numbers changed to
> different values. This problem upsets you. So it's not a question
> of physics or mathematics. It's a question of psychology. Why does
> one version of a problem upset you while another version doesn't?
But that was my initial question you thief! Okay thanks for that anyway.
>
> Arf!
> Arfur
I am presented with a paradox which suggest that to resolve it the same is
true of teh Podunk train. But then again the Podunk train shares a history
which relates to events which happened here. andromeda does not.
Beacon
>
> "Beacon" <openm...@mydeja.com> wrote in message
news:fA2I9.33506$zX3....@news.indigo.ie...
> >
> > "Martin Hogbin" <sp...@hogbin.org> wrote in message
> > news:aspq4u$eov$1...@venus.btinternet.com...
>
> > > Physics does not attempt to say what
> > > is 'really' happening it tries to produce a consistent and useful
> > > mathematical model.
>
> > Yes. But the map is not the territory.
>
> In physics no on knows what the territory is. All we have is a selection
of
> maps.
Instrumentalist! So do you believe atoms "really" do not exist and are just
a handy construct? Don't answer that it is off topic.
Beacon
>
> [snip]
> >
> > As I stated: Ad hominem does not assist your position.
>
> As I stated: due to absentia hominis it cannot have been
> ad hominem. This was a clear-cut case of ad mustelam.
>
Dirk I am having none of your weasel words :)
Beacon
"Happy Dog" <happydog@hello_kitty.sympatico.arf> wrote in message
news:wiOI9.1257$281.1...@news20.bellglobal.com...
> "Beacon" <openm...@mydeja.com> wrote in
> > "The Ghost In The Machine" <ew...@sirius.athghost7038suus.net> wrote in
> >> > You're in an elevator car, enclosed, no windows, but air,
> > > some lighting, maybe some muzak, etc. The elevator car
> > > is either standing at rest on the Earth's surface,
> > > or being smoothly accelerated by some sort of rocket.
> > > Absent issues such as acceleration variations because of
> > > bad rocket fuel, hitting space debris, planet curvature, etc.,
> > > can the occupant of said elevator car determine which
> > > situation he's in?
> >
> > Yes he can since "at rest" he is not accelerating. If you mean "at rest"
> > means accelatering on the Earth's surface then no he can't. But if "at
> rest"
> > then means accelerating in the first place.
>
> That's a bit garbled. There is no way for a person, or anything else for
> that matter, to distinguish between being inside an object, that prohibits
> any contact with the outside environment, at rest on the earth's surface
i.e accelerating at one g.
> and
> inside one that is in a 0g environment being accelerated at a rate of 1g.
i.e. also accelerating at one g.
My point is that "at rest" means accelerating at one g.
Beacon
> In sci.skeptic, Beacon
> <openm...@mydeja.com>
> wrote
> on Sun, 8 Dec 2002 16:38:17 -0000
> <_zKI9.33787$zX3....@news.indigo.ie>:
> >
> > "The Ghost In The Machine" <ew...@sirius.athghost7038suus.net> wrote in
> > message news:4049c-...@lexi2.athghost7038suus.net...
> >> In sci.skeptic, Beacon
> > [snip]
>
>>
> How does one prove space is warped? Good question. The simplest
> method is to pass a light beam through it and see if the light
> beam bends, moving the apparent target. Then shoot a light beam
> through it when the mass has moved. We've done this for the Sun
> and the light beam does shift by a fraction of an arc-second
> (1 arc-second = 1/3600 of a degree). It's barely discernible
> with current equipment.
So the old eclipse measurement (was it 1919 ish -and Eddington?) was a "get
up" and inconclusive was it?
Is this a get up?
http://arxiv.org/PS_cache/quant-ph/pdf/9605/9605030.pdf
>
> Another example was a rather impressive picture of a free-floating
> black hole acting as a gravitational lens. Unfortunately, I'm
> not entirely sure what to search for (the picture was part of a
> show I saw regarding astronomy some time back).
i believe I have seen several of galaxies acting as grav lenses. I had a
hard time trying to understand why the lens showed four "originals" and not
a continuous ring around the center where the massive object was.
[snip]
> >>
> >> Well, if you want we can shift our vantage point to a conveniently
> >> orbiting satellite.
> >
> > How convenient! No really that is a good idea. Especially for teaching a
> > class. Though SOHO was lost.
>
> Your original idea IIRC was to attempt to understand why
> is it that the Sun is not at the point at which we are
> observing it. At best I've probably confused the issue --
Not to me.
> but the issue is itself confusing as all we can discern
> about the Universe is that we can passively look at it
> as it shoots things our way (mostly photons of various
> wavelengths, but we do get neutrinos and charged particles
> from the Sun).
>
> BTW: SOHO appears to be operating normally.
No it was lost in the past. Hint to other readers : I really do believe in
the past.
But this to me is a mathematical interpretation. In reality to me it relates
to what one calls an event. In other words the points at either end of a
meter stick are really events in spacetime. The contraction effect is to me
a consequence of how you define the "now" of two ends of a stick.
> however, that won't affect your argument as it is squished
> uniformly.
Thats one way of looking at it :) The other being it isnt changed but time
is.
[snip]
Happy Dog
> > > > Absent issues such as acceleration variations because of
> > > > bad rocket fuel, hitting space debris, planet curvature, etc.,
> > > > can the occupant of said elevator car determine which
> > > > situation he's in?
> > >
> > > Yes he can since "at rest" he is not accelerating. If you mean "at
rest"
> > > means accelatering on the Earth's surface then no he can't. But if "at
> > rest" then means accelerating in the first place.
> >
> > That's a bit garbled. There is no way for a person, or anything else
for
> > that matter, to distinguish between being inside an object, that
prohibits
> > any contact with the outside environment, at rest on the earth's surface
>
> i.e accelerating at one g.
>
1g.
>
> i.e. also accelerating at one g.
>
> My point is that "at rest" means accelerating at one g.
No it doesn't. The point is that, absent reference cues, the effect of
constant 1g acceleration is indistinguishable from the effect of gravity on
the earth's surface. "At rest" has little meaning on its own. That's why
we say "on the Earth's surface". Acceleration maens a change of rate of
velocity (or change of velocity WRT time). How do you see this happening to
an object which is "at rest"?
erf
Galen
"The Ghost In The Machine" <ew...@sirius.athghost7038suus.net> wrote in
message news:im89c-...@lexi2.athghost7038suus.net...
Vis Mike
> definition of "now". Relativity would tell us that time is a strange beast
> as regards similtaneous things happening "now". Quantum people may beg to
> differ. I do not.
>
> Similtanous events are not similtaneous.
I am really trying to understand your point of view, but it has to be a
joke. It's not funny anymore. Did you not read the fireworks explanation?
If you hear the fireworks two seconds *after* the event, did it not happen
until I heard it? Of course not! Light is just a little (ok, a lot) faster
than sound. Now in philosophical sense, it is true that what you see is
what you interpret as 'now'. When I look at the sky, I just see the stars
and don't always think about their light. And everybody perceives this old
light as 'now'. But in reality, it's just an old transmission, like reruns
from an old sitcom. :)
PS and please get a spell checker. Although that could be intentional?
Mike
"Beacon" <openm...@mydeja.com> wrote in message
news:MQSI9.33910$zX3....@news.indigo.ie...
Galen
is important during an experiment to include an initial state and a final
state and perhaps a simultaneous state, however, it is never an issue to
clarify when "now" is. As far as we know, "now" is completely subjective and
has no place in physics. There is no single equation or law that has
anything to do with "now."
Yours is an interesting philosophical opinion, but that is all it is. How
long does your "now" last? What is its exact duration? How quickly does it
go from being one "now" to another "now" and by what mechanism does this
transition occur? How can we demonstrate these properties of "now" in an
experiment? What would an experiment look like with "now"s and without
"now"s?
There are many states which could be described as simultaneous. How do we
objectively demonstrate which one is "now"? We can't, because "now" is
subjective.
"Henri Wilson" <HW@..> wrote in message
news:l546vukc9c8nsqh1e...@4ax.com...
Dirk Van de moortel
"Beacon" <openm...@mydeja.com> wrote in message news:q1TI9.33913$zX3....@news.indigo.ie...
>
> "Dirk Van de moortel" <dirkvand...@ThankS-NO-SperM.hotmail.com> wrote
> in message news:xHMI9.41917$Ti2....@afrodite.telenet-ops.be...
> >
> > [snip]
> > >
> > > As I stated: Ad hominem does not assist your position.
> >
> > As I stated: due to absentia hominis it cannot have been
> > ad hominem. This was a clear-cut case of ad mustelam.
> >
>
> Dirk I am having none of your weasel words :)
http://www.science.uva.nl/~robbert/zappa/files/jpg/Weasels_Ripped_My_Flesh.jpg
Dirk Vdm
Beacon
Great composer and not a bad lyricist. If you are comparing me to him then
modesty forbits me eating you.
Beacon
"Happy Dog" <happydog@hello_kitty.sympatico.arf> wrote in message
> "Beacon" <openm...@mydeja.com>
[snip]
> > > That's a bit garbled. There is no way for a person, or anything else
> for
> > > that matter, to distinguish between being inside an object, that
> prohibits
> > > any contact with the outside environment, at rest on the earth's
surface
> >
> > i.e accelerating at one g.
> >
> > > inside one that is in a 0g environment being accelerated at a rate of
> 1g.
> >
> > i.e. also accelerating at one g.
> >
> > My point is that "at rest" means accelerating at one g.
>
> No it doesn't.
Yes it does. I just showed you. Note the quote marks. The "at rest" in "at
rest on the Earth's surface" means accelerating.
>The point is that, absent reference cues, the effect of
> constant 1g acceleration is indistinguishable from the effect of gravity
on
> the earth's surface.
So what? I didn't disagree with that.
> "At rest" has little meaning on its own. That's why
> we say "on the Earth's surface". Acceleration maens a change of rate of
> velocity (or change of velocity WRT time). How do you see this happening
to
> an object which is "at rest"?
With an object "at rest" on the surface of the Earth? Well (In Newtonian
physics anyway ) it is moving around in a circle so it is accelerating. Of
course maybe it only thinks it is not moving or moving constantly in a
straight line and the space is curved. Where is this absolute reference
frame which something is "at rest" relative to? I thought Mach did away with
that?
Beacon
"Vis Mike" <visionary25@_nospam_hotmail.com> wrote in message
news:at1g7b$30k$1...@bob.news.rcn.net...
> > Here we go. This is exactly my problem. I entirely disagree with this
> > definition of "now". Relativity would tell us that time is a strange
beast
> > as regards similtaneous things happening "now". Quantum people may beg
to
> > differ. I do not.
> >
> > Similtanous events are not similtaneous.
>
> I am really trying to understand your point of view, but it has to be a
> joke. It's not funny anymore. Did you not read the fireworks
explanation?
> If you hear the fireworks two seconds *after* the event, did it not happen
> until I heard it? Of course not!
I didn't deny it didn't happen in the past. Just that it didn't happen in my
past and has no relevance. > Light is just a little (ok, a lot) faster
> than sound. Now in philosophical sense, it is true that what you see is
> what you interpret as 'now'. When I look at the sky, I just see the stars
> and don't always think about their light. And everybody perceives this
old
> light as 'now'. But in reality, it's just an old transmission, like
reruns
> from an old sitcom. :)
But the aliens at Mizar,the Mizarian's if they exist, are getting "Here's
Lucy" now. How is "The Dead Zone" relevant to them now? Are you saying "The
Dead Zone " is part of their reality?
>
> PS and please get a spell checker. Although that could be intentional?
Sometines it is. Mostly it isn't. But it does irk tidy and organised people
(and no that is not spelt with a "Z") which I envy and sometimes make
uncomfortable. I am biased in some way I suppose.
Beacon
"Galen" <jamesga...@sbcglobal.net> wrote in message
news:nxXI9.1795$BK5.72...@newssvr15.news.prodigy.com...
> You missed my point. Simultaneous events do not define "now." In physics,
it
> is important during an experiment to include an initial state and a final
> state and perhaps a simultaneous state, however, it is never an issue to
> clarify when "now" is. As far as we know, "now" is completely subjective
and
> has no place in physics. There is no single equation or law that has
> anything to do with "now."
Actulaay that was my point but if you made it at the same time then we are
in agreement on something?
>
> Yours is an interesting philosophical opinion, but that is all it is. How
> long does your "now" last?
An epoch
>What is its exact duration?
It doesn't have any.
>How quickly does it
> go from being one "now" to another "now" and by what mechanism does this
> transition occur?
Depends on whether you believe in spooky action at a distance or not. Let us
say not faster than c in a vacuum.
>How can we demonstrate these properties of "now" in an
> experiment?
Look at a star 1,500 light years away.
> What would an experiment look like with "now"s and without
> "now"s?
I don't understand the last question. I find it diffocult to comprehend
understanding something frozen without time flowing forward or backward as a
backdrop.
>
> There are many states which could be described as simultaneous. How do we
> objectively demonstrate which one is "now"? We can't, because "now" is
> subjective.
I completly agree. If it is then 1,500 year old light is also.
Spaceman
>With an object "at rest" on the surface of the Earth? Well (In Newtonian
>physics anyway ) it is moving around in a circle so it is accelerating.
Excuse my nitpickin'
when an object is "at rest on Earth"
it is not accelerating.
It is in constant angular motion.
Unless the Earth "changes" in spin rate are what you speak
of and if so,
Thje Earth both accelerates and deccelerates.
not just one.
but mostly.
at rest = (unchanging motion factors).
> Of
>course maybe it only thinks it is not moving or moving constantly in a
>straight line and the space is curved.
Space is not curved.
It "can not be" by definition.
distances are "straight"
space is "the distance between objects"
for correct "distance"
you do not measure the curves.
Where is this absolute reference
>frame which something is "at rest" relative to? I thought Mach did away with
>that?
The absolute frame is 1 of the frames you are relatively comparing.
but "not using "observation" but by using measurement devices.
and "triggers that are in that local space"
James M Driscoll Jr
Spaceman
http://www.realspaceman.com
Spaceman
>But the aliens at Mizar,the Mizarian's if they exist, are getting "Here's
>Lucy" now. How is "The Dead Zone" relevant to them now? Are you saying "The
>Dead Zone " is part of their reality?
In the future to them, it will be.
(if they actually had a TV to see Lucy already)
:)
but only if "nothing stops it from getting there"
The Ghost In The Machine
<2eTI9.33915$zX3....@news.indigo.ie>:
Hmm...perhaps we should call this one SOHO II, then?
Now I'm confused. However, this might be of some assistance....
http://sohowww.nascom.nasa.gov/operations/Recovery/brekke/
Evidently they got it back.
You don't. The ends are about 3 ns apart. :-)
>
>> however, that won't affect your argument as it is squished
>> uniformly.
>
> Thats one way of looking at it :) The other being it isnt
> changed but time is.
Both are equally valid.
>
>
> [snip]
The Ghost In The Machine
<E1XI9.1794$FG5.72...@newssvr15.news.prodigy.com>:
> In a sense, yes. But what does that have to do with my point?
Just that the phrase doesn't make that much sense. :-)
>
> "The Ghost In The Machine" <ew...@sirius.athghost7038suus.net> wrote in
> message news:im89c-...@lexi2.athghost7038suus.net...
>> In sci.skeptic, Galen
>> <jamesga...@sbcglobal.net>
>> wrote
>> on Fri, 06 Dec 2002 22:12:56 GMT
>> <Ih9I9.1980$Il7...@newssvr19.news.prodigy.com>:
>> > "...physics does not even offer any conceptual means for deriving the
>> > concept of a present that could separate a past from a future. The
> concept
>> > of a present seems to have as little to do with time itself as color has
> to
>> > do with light." -H. D. Zeh
>> >
>> > The "present" or the "right here, right now" is not
>> > a problem for physics. It is an "illusion of
>> > consciousness" associated to temporal vertigo.
>> >
>> > When an astronomers says "the light from that star is 1,500
>> > years old," what they really mean is that the star emitted
>> > the light at time t1 and it reached Earth at time t2, and
>> > that the difference between t1 and t2 is 1,500 years.
>> > "Now" or the "present" never need enter the equation.
>>
>> Ah, but t1 and t2 are from *different* frames of reference. In
>> a sense, t1 and t2 are both the same!
>>
>> Let me illustrate this rather odd-looking point.
[rest snipped for brevity]
Jacqueline Woodward
to take up valuable time. You are just aiming to be argumentative and you
do need to check your spelling. This is quite annoying and if you have a
problem with time, take it up with a shrink. Time exists, deal with it. If
you don't like the answers you are getting, then publish your own theory. I
get the impression you are an immature person who just wants to mess around
with some busy scientists' heads. Just take your problems elsewhere. This
is a metaphysics newsgroup, not a self-help newsgroup. Take into
consideration that your problem with time may never be solved. We all have
problems. I have a huge final exam tomorrow, but I don't whine about my
problem with it on an academic newsgroup. Find a mentor or someone who
actually WANTS to listen to your woes. I think I am speaking for more than
just me when I say...get over it!
"Beacon" <openm...@mydeja.com> wrote in message
news:xC1J9.33997$zX3....@news.indigo.ie...
Galen
put it. I played along with your version for fun where you toyed with the
idea of t1 and t2 being from different frames of reference and thus actually
being the same time (which is always true from the point of view of the
light "traveled" between two events), but I fail to see the relevance of
this to what an astronomer means when they say, "the light from that star is
1,500 years old."
"The Ghost In The Machine" <ew...@sirius.athghost7038suus.net> wrote in
message news:l5pec-...@lexi2.athghost7038suus.net...
Galen
Try reading up on "blocktime," and you may better understand such issues. I
highly recommend Huw Price's "Times Arrow and Archimedes' Point."
"Beacon" <openm...@mydeja.com> wrote in message
news:xC1J9.33997$zX3....@news.indigo.ie...
Happy Dog
> > we say "on the Earth's surface". Acceleration maens a change of rate of
> > velocity (or change of velocity WRT time). How do you see this
happening
> to an object which is "at rest"?
>
> With an object "at rest" on the surface of the Earth? Well (In Newtonian
> physics anyway ) it is moving around in a circle so it is accelerating. Of
> course maybe it only thinks it is not moving or moving constantly in a
> straight line and the space is curved. Where is this absolute reference
> frame which something is "at rest" relative to? I thought Mach did away
with
> that?
"moving around in a circle" is not necessarily accelerating. There has to
be a change in velocity over time. But you've been told this. And, I
haven't seen anyone refer to an "absolute reference frame". Have you?
erf