question about the speed of light
Kostas Mavroeidis
reality
I cannot understand this. Please tell me what is wrong with the following:
Imagine a train going one direction at 0,7*c speed and another train going
to the exact opposite direction with the same speed.
The relative speed of each train against the other sould be 1,4*c right?
The speed of the particles (that produce the image we see) in any old
fahioned television is more than half the speed of light. If you put two tv
sets facing one another the same question. What is their relative speed?
Kostas
Jamieson Christie
The relative speed will always be less than c. There is a good explanation
of this at http://www.weburbia.demon.co.uk/physics/velocity.html
Jamieson Christie
Trevor Morris
news:be0fra$93a$1...@ulysses.noc.ntua.gr...
> In school they say that the speed of light cannot be exeeded in the
current
> reality
That seems to be correct for any known form of matter or radiation: the
speed of light in vacuum seems to be an upper limit. Note that elementary
particles such as electrons can move faster than light in transparent
materials (glass, water, Perspex etc, in which light is slowed down compared
to its speed in a vacuum). You then get a kind of optical "shock wave"
effect - a blue glow called Cerenkov radiation.
> I cannot understand this. Please tell me what is wrong with the following:
>
> Imagine a train going one direction at 0,7*c speed and another train going
> to the exact opposite direction with the same speed.
>
> The relative speed of each train against the other sould be 1,4*c right?
That is correct for someone standing at the side of the tracks. Note that
it is just the sum of two numbers: the distance between the trains is
changing at that rate for the track-side observer, but no single object is
really moving at 1.4*c. To get the relative speed *as it will be measured*
by observers on the trains, you have to use the relativistic formula you
have learned at school, and the answer will always be < c. The same applies
to your other example.
> The speed of the particles (that produce the image we see) in any old
> fahioned television is more than half the speed of light. If you put two
tv
> sets facing one another the same question. What is their relative speed?
>
> Kostas
Trevor Morris
kenseto
current
> reality
>
> I cannot understand this. Please tell me what is wrong with the following:
>
> Imagine a train going one direction at 0,7*c speed and another train going
> to the exact opposite direction with the same speed.
>
> The relative speed of each train against the other sould be 1,4*c right?
Right from the third party point of view. However, from the observers A and
B in the trains each will caculate their approaching speed to be less than
c. Why?? Because light is used as carrier of information and light moves in
space at a max speed of c.
Actually the train each observer can made his measurement agrees with the
third party observer measurement of 1.4 c if he takes the observed doppler
shift into account as follows:
A is the observer and B is approaching A
Vab=Vc(Fab/Faa) =1.4c
Where Vab= the true approaching speed between A and B
Vc=the speed of B approaching A as calculated by A using the
SR formula
Fab=frequency of a standard light source in B's frame as
measured by A
Faa=frequency of a standard light source in A's frame as
measured by A
Ken Seto
John Anderson
Kostas Mavroeidis wrote:
No, it is not their relative speed in the theory of relativity. Theyare
approaching each other at 1.4*c in the frame that you describe,
but that isn't the velocity of a single object in that frame.
The velocity of the other object in the rest frame of one of them
in special relativity is
((0.7 + 0.7)*c)/(1 + (0.7)*(0.7))
which is less than c. This is the velocity of a single object in
a given reference frame.
Look at the FAQ for this newsgroup for more information.
John Anderson
Peter K.
> Actually the train each observer can made his measurement agrees with the
> third party observer measurement of 1.4 c if he takes the observed doppler
> shift into account as follows:
> A is the observer and B is approaching A
> Vab=Vc(Fab/Faa) =1.4c
>
observer regardless of frame of reference (And to the inertial
observer (third party C=.7 for both but in opposite direction).
Thus for both observers C= perhaps C or .7
Velocity (or resolution of spacetime/wave always constant) and only
frequency and wavelength vary proportionally.
frequency = velocity / wavelength
Thus velocity always constant or equal to maximum (C) and only
frequency and wavelength vary accordingly (thus no longer wave of
light but gamma ray etc... from doppler effect).
Minor Crank
news:be0fra$93a$1...@ulysses.noc.ntua.gr...
> In school they say that the speed of light cannot be exeeded in the
current
> reality
>
> I cannot understand this.
Warning: the sci.physics and sci.physics.relativity newsgroups are filled
with crackpots, and you have been answered by several of them. Ken Seto is a
well known crackpot, and Peter K., with his incoherent babblings, is a new
addition to the crackpot ranks.
Since for all you know, I myself may be as crackpotty as the above, I don't
think you should necessarily believe anything I say, either. Instead, I
recommend that you check the Physics FAQ.
The originating site for the Usenet Physics FAQ is
http://hermes.physics.adelaide.edu.au/~dkoks/Faq/
Since you are in Greece, you may get better connections from the German
mirror:
http://www.desy.de/pub/www/projects/Physics/
or possibly the Netherlands mirror:
http://www.xs4all.nl/~johanw/PhysFAQ/index.html
The USA mirrors are:
http://math.ucr.edu/home/baez/physics/index.html
http://scope.joemirando.net/faqs
http://www.obscure.org/physics-faq
In Taiwan:
http://www.phys.ncku.edu.tw/mirrors/physicsfaq/index.html
Finally, there is the Canadian site, which uses a different format and thus
tends to be somewhat behind in its updates:
http://www.stillmoving.ca/physics/usenetFAQ.php
Minor Crank
Minor Crank
news:vofNa.9067$Ix2.2714@rwcrnsc54...
Kostas -
For some reason Trevor Morris doesn't show up in this thread on my regular
news server, but I spotted him on Google. He's also a crackpot, but less
obvious than the others. Basically, Kostas, unless you already have a pretty
good knowledge of physics and can recognize the crackpots, these newsgroups
are not a good source of information about relativity.
Read the FAQ, study your textbooks, do problems from the textbooks, and ask
questions of your professors in school.
An excellent book is Spacetime Physics: Introduction to Special Relativity
by Taylor and Wheeler. Don't be put off by the style...it may -look- "dumbed
down" but it actually has an extraordinary wealth of insight, lots of
examples, and plenty of exercise problems. Do the exercises!
Minor Crank
Trevor Morris
> Kostas -
>
> For some reason Trevor Morris doesn't show up in this thread on my regular
> news server, but I spotted him on Google. He's also a crackpot, but less
> obvious than the others.
Thanks, Minor Crank. Is there anything wrong with what I told Kostas? Why
not reply to me direct instead of calling me names to others?
[...]
Minor Crank
news:105732891...@despina.uk.clara.net...
Had to go back to google to double-check your post. Nothing really wrong
with what you said, except you present relativity as if it could be
understood by a simple application of a magic formula: "...To get the
relative speed *as it will be measured* by observers on the trains, you have
to use the relativistic formula you have learned at school..."
Your problem shows up at a higher level than when answering basic freshman
physics questions. You never did show how you could derive LET from your two
postulates, which both Bilge and I agree are horribly weak. Your first
postulate deals -only- with fields propagating at the speed of light, and
your second postulate is pretty much just a step function.
But that's really for another thread. Right now, our purpose to direct
Kostas towards reliable sources of information presented at a level
appropriate to his degree of understanding.
Minor Crank
Trevor Morris
> "Trevor Morris" <ted...@DELETEfreeuk.com> wrote in message
> news:105732891...@despina.uk.clara.net...
> > "Minor Crank" <blue_whal...@comcast.net> wrote in message
> > news:bfgNa.9192$Ix2.1538@rwcrnsc54...
> > > "Minor Crank" <blue_whal...@comcast.net> wrote in message
> > > news:vofNa.9067$Ix2.2714@rwcrnsc54...
> > >
> > [...]
> >
> > > Kostas -
> > >
> > > For some reason Trevor Morris doesn't show up in this thread on my
> regular
> > > news server, but I spotted him on Google. He's also a crackpot, but
less
> > > obvious than the others.
> >
> > Thanks, Minor Crank. Is there anything wrong with what I told Kostas?
> Why
> > not reply to me direct instead of calling me names to others?
>
> Had to go back to google to double-check your post. Nothing really wrong
> with what you said, except you present relativity as if it could be
> understood by a simple application of a magic formula: "...To get the
> relative speed *as it will be measured* by observers on the trains, you
have
> to use the relativistic formula you have learned at school..."
I just wanted to answer his question as directly as possible.
> Your problem shows up at a higher level than when answering basic freshman
> physics questions.
Thanks again.
> You never did show how you could derive LET from your two
> postulates, which both Bilge and I agree are horribly weak. Your first
> postulate deals -only- with fields propagating at the speed of light, and
> your second postulate is pretty much just a step function.
You seem to have missed my replies on all of that - I suggest you look at
the "Re: More on LET" thread via Google. E.g. around:
http://groups.google.com/groups?q=g:thl3857312330d&dq=&hl=en&lr=&ie=UTF-8&selm=1057085429.20721.0%40iris.uk.clara.net
[...]
Trevor Morris
Minor Crank
"Trevor Morris" <ted...@DELETEfreeuk.com> wrote in message
> "Minor Crank" <blue_whal...@comcast.net> wrote in message
> > You never did show how you could derive LET from your two
> > postulates, which both Bilge and I agree are horribly weak. Your first
> > postulate deals -only- with fields propagating at the speed of light,
and
> > your second postulate is pretty much just a step function.
>
> You seem to have missed my replies on all of that - I suggest you look at
> the "Re: More on LET" thread via Google. E.g. around:
>
http://groups.google.com/groups?q=g:thl3857312330d&dq=&hl=en&lr=&ie=UTF-8&se
lm=1057085429.20721.0%40iris.uk.clara.net
You're right. I missed that thread...reading it over right now.
BTW, you can delete everything between the "groups?" and the "selm=" and
still get a valid link.
If anything shows up -after- the "iris.uk.clara.net" as a result of a
search, you can truncate it.
Minor Crank
Peter K.
> Since for all you know, I myself may be as crackpotty as the above,
Cranky you're one of us!!!
All I said here:
F= C/wavelenght where as C is constant
You're ego got thee best of thee Cranky! Howz Snow White?
Minor Crank
news:7f35df4b.0307...@posting.google.com...
> "Minor Crank" <blue_whal...@comcast.net> wrote in message
news:<vofNa.9067
> > Since for all you know, I myself may be as crackpotty as the above,
>
> Cranky you're one of us!!!
Kostas, who has little or no experience on this newsgroup, has no reliable
means of knowing which of us are crackpots and which are not. The safest
course for him is to dismiss us all as possibly nuts and to go to what are
obviously more trustworthy sources for information.
I daresay, however, that even a newcomer can tell that -you- are a crackpot.
Minor Crank
kenseto
> "Kostas Mavroeidis" <kos...@sparks.gr> wrote in message
> news:be0fra$93a$1...@ulysses.noc.ntua.gr...
>
> > In school they say that the speed of light cannot be exeeded in the
> current
> > reality
> >
> > I cannot understand this.
>
> Warning: the sci.physics and sci.physics.relativity newsgroups are filled
> with crackpots, and you have been answered by several of them. Ken Seto is
a
> well known crackpot, and Peter K., with his incoherent babblings, is a new
> addition to the crackpot ranks.
>
> Since for all you know, I myself may be as crackpotty as the above,
So what is wrong with what I said, Minor Crank? A third party can indeed
sees two objects approaching each other at speed greater than c. This is
allowed in SR.
Ken Seto
Bilge
What you said would have been fine if you had posted it to
alt.usenet.kooks.
HenriWilson
wrote:
Kostas, don't believe any of these people. They are all cranks.
The fact is the term 'speed' has no meaning, in itself. Speed can only be
calculated wrt another object. Effectively, all observers have ZERO velocity
and they can only consider the speeds of other objects wrt themselves.
If you are in a spaceship accelerating at .01c/sec^2, you can be pretty sure
you will have exceeded the speed of light wrt your starting point after 100
seconds. You starting point will not appear to be receeding at that speed
however. SR and aether theories both provide explanations - but I wouldn't
believe either.
The speed of charged particles in accelerators cannot be raised to beyond c
because the fields that accelerate them act at speed c. To put that another
way, "you can't make a boat travel faster than v by throwing rocks at it at v".
Even to get the boat up to v requires an increasing amount of energy per
'acceleration increment achieved'. It takes infinite energy to get it to v.
On the other hand, it is pretty clear that atmospheric muons produced in
(elastic) collisions between high energy cosmic rays and air molecules CAN and
DO exceed c wrt Earth's surface. Otherwise they would not live for sufficiently
long to reach the surface.
Relativity however is just a circular theory which describes
how the universe would appear if two-way light speed was made to always equal
one-way light speed BY DEFINITION. It is a blatant confidence trick that has
survived simply because, until now, clocks have not been sufficiently stable or
sensitive to measure differences between OWLS and TWLS. It has no connection
with reality and is a plain red herring that has hijacked physics for 100
years. Unfortunately it has now become a religion.
Henri Wilson.
The BIG BANG Theory = The creationists' attempt to hijack science!
But they didn't succeed!
See my animations at:
http://www.users.bigpond.com/HeWn/index.htm