cosmology - expanding universe
marks...@yahoo.com
Universe is expanding rather than galaxies moving within a static
Universe. ?
Desertphile
wrote:
> In simple terms if possible how do astronomers determine that the
> Universe is expanding rather than galaxies moving within a static
> Universe?
If the universe did not expand, there would not be any place where
"moving galaxies" could move in to.
--
http://desertphile.org
Desertphile's Desert Soliloquy. WARNING: view with plenty of water
"Why aren't resurrections from the dead noteworthy?" -- Jim Rutz
aganunitsi
> effect).
>
> Astronomers can observe precisely what sort of "light" (its spectrum)
> is emitted by cosmic objects. Due to other things that i don't
> personnaly know exactly now, they have quite good model of what they
> should observe.
>
> The observations match very well the calculations for galaxies that
> are not too far away from ours, but, the farther the galaxy are, the
> bigger a strange difference between those happens : a shift to "lesser
> frequencies" (a shift toward the red side of the light spectrum).
>
> meaning that the galaxies are apparently moving away from us, and the
> farther they are, the faster they seem to go away. This exactly what
> would appear if all the universe was expanding. (you can imagine a
> balloon : before inflating it, put several marks on it with some felt-
> tip pen, and then inflate it : from any point , the other points seem
> to go away from each other the same manner). My example is not very
> good because the surface of the balloon is only in two dimensions, but
> the idea is the same. And all the shifts are compared with the known
> or estimated distance of those galaxies, and it match a consistant
> model.
And note that by "the universe is expanding", cosmologists are
referring to those areas low in mass/energy - the "empty" spaces
between the galaxies. The presence of mass/energy binds local space.
The distance between your ears isn't expanding like the space between
the Milky Way and Andromeda Galaxy, for example. Pagano, Backspace and
Nando are special cases, on account of the virtually empty space
between their ears. The size of their heads will someday reach
galactic proportions. And because their sensory organs are constantly
expanding away from their tiny minds, they are always seeing red.
Boikat
I think nando's mind is shrinking.
Boikat
Vend
> meaning that the galaxies are apparently moving away from us, and the
> farther they are, the faster they seem to go away. This exactly what
> would appear if all the universe was expanding. (you can imagine a
> balloon : before inflating it, put several marks on it with some felt-
> tip pen, and then inflate it : from any point , the other points seem
> to go away from each other the same manner). My example is not very
> good because the surface of the balloon is only in two dimensions, but
> the idea is the same. And all the shifts are compared with the known
> or estimated distance of those galaxies, and it match a consistant
> model.
I don't think this answers the question.
Vend
I don't think so.
If I understand correctly (and probably I don't) the expansion of the
space is a consequence of general relativity, which, simply speaking,
says that geometry follows mass (and mass follows geometry, I suppose
one has to do the math in order to understand this properly, and I
didn't).
BURT
I think you can go to the 4th spatial dimension in math. Einstein's
closed universe is an hypersphere math with the universe on its
expanding surface.
Mitch Raemsch
marks...@yahoo.com
OK, thanks for the comments.
Victor Eijkhout
> If the universe did not expand, there would not be any place where
> "moving galaxies" could move in to.
It could be infinitely big and mostly empty?
Victor.
--
Victor Eijkhout -- eijkhout at tacc utexas edu
Robert Carnegie: Fnord: cc talk-origins@moderators.isc.org
1. I don't know the details, but apparently Einstein's relativity
implies that the the actual space of the universe (a) is expanding, or
(b) is contracting, or (c) possesses a "cosmological constant"
balancing factor against a or b. Since his earliest work was at a
time when at least it wasn't definitely established that some of the
more fuzzy lights in the sky are separate galaxies as large as our
own, he initially went with c.
2. I think some galaxies apparently are receding faster than the speed
of light. Again according to Einstein, that can't be what's really
happening.
3. In recent results, the expansion of the universe appears to go
faster as time passes. I'm not sure if this counts, but maybe modern
theorists are happier to talk about a mysterious force that expands
space than one that pushes galaxies apart.
Vend
orig...@moderators.isc.org" <rja.carne...@excite.com> wrote:
> marks542...@yahoo.com wrote:
> > In simple terms if possible how do astronomers determine that the
> > Universe is expanding rather than galaxies moving within a static
> > Universe. ?
>
> 1. I don't know the details, but apparently Einstein's relativity
> implies that the the actual space of the universe (a) is expanding, or
> (b) is contracting, or (c) possesses a "cosmological constant"
> balancing factor against a or b. �Since his earliest work was at a
> time when at least it wasn't definitely established that some of the
> more fuzzy lights in the sky are separate galaxies as large as our
> own, he initially went with c.
Not really.
The cosmological constant, AKA dark energy, is an hypothetical long-
distance repulsive effect.
At Einstein time it was believed that the universe was essentially
static: galaxies were supposed to stand still respect to each others.
This causes a problem for general relativity: starting from a still
galaxies state, it predicts that galaxies will attract each other and
eventually collapse. So Einstein introduced a repulsive effect to
balance attraction.
Then Hubble discovered that the galaxies were not still, rather they
were moving away from each others. Then the cosmolgical constant was
no longer needed (since the universe was expanding, initially very
fast, and gravity was merely slowing the expansion down), and Einstein
defined it his greatest error.
Then cosmologists calculated better estimates of the expansion rate
and the mass of the universe and decided that maybe there is a
cosmological constant after all, albeit very small.
> 2. I think some galaxies apparently are receding faster than the speed
> of light. �Again according to Einstein, that can't be what's really
> happening.
No. Relativity says that the speed of light can't be locally exceded,
that is, it's not possible that an object passes right next to you
faster than the speed on light. But far object can appear to move
faster than the speed of light.
> 3. In recent results, the expansion of the universe appears to go
> faster as time passes. �I'm not sure if this counts, but maybe modern
> theorists are happier to talk about a mysterious force that expands
> space than one that pushes galaxies apart.
Indeed, the cosmological constant. Or some other form of dark energy.
Or maybe general relativity breaks down at universal scale.
Stuart
orig...@moderators.isc.org" <rja.carne...@excite.com> wrote:
> marks542...@yahoo.com wrote:
> > In simple terms if possible how do astronomers determine that the
> > Universe is expanding rather than galaxies moving within a static
> > Universe. ?
>
> 1. I don't know the details, but apparently Einstein's relativity
> implies that the the actual space of the universe (a) is expanding, or
> (b) is contracting, or (c) possesses a "cosmological constant"
> balancing factor against a or b. �Since his earliest work was at a
> time when at least it wasn't definitely established that some of the
> more fuzzy lights in the sky are separate galaxies as large as our
> own, he initially went with c.
A
>
> 2. I think some galaxies apparently are receding faster than the speed
> of light. �Again according to Einstein, that can't be what's really
> happening.
False.
cassandra
This is one of the many things about cosmology I don't understand.
Exactly how far must a "far object" have to be before it can appear to
travel faster than light? Why does distance even make a difference?
Of course, I can ask the same question by its complement: Exactly how
close can a "far object" get before it stops appearing to travel
faster than light?
bpuharic
pick up the latest scientific american. there's a great article by
tamara davis of the u. of new south wales on this exact question.
turns out, according to relativity, there's little difference between
the 2 ideas.
johnbee
"cassandra" <cassand...@gmail.com> wrote in message
news:3cf1ef90-91b8-485f-bf06->
> This is one of the many things about cosmology I don't understand.
> Exactly how far must a "far object" have to be before it can appear to
> travel faster than light? Why does distance even make a difference?
>
OK, you are about to find out.
For the sake of understanding, let us assume that each kilometre of space
expands 1 millimetre per year. That is, however far apart two objects are,
a year later they are a millionth further apart.
Obviously objects 1000 kilometres apart will be 1000 millimetres further
apart after a year. Object a million km apart will be a million mm further
apart after a year, and objects a billion km apart will be a billion mm
further apart after a year i.e. a km further.
I expect you can see where this is going, because space is big and a billion
km is peanuts. One light year (much less than the distance to the nearest
star), is 10 trillion km. One of them gets a million km bigger every year.
The universe is known to be a lot bigger that 10 billion light years across
so that much expands by 10 million billion km each year. That is bigger
than a light year, so the universe is expanding by more than a light year
every year. In that sense, it expands faster than light - but the things
that far apart are not actually moving apart, it is the space that is
expanding.
The limitation on speed assumed that space was not expanding.
Please note that actually space expands a bit slower than this, not a lot
but a bit, but I simplified it for the sake of explanation. I could go a
bit further with this, but the football has started.
odin
> On Jun 18, 6:34 pm, marks542...@yahoo.com wrote:
>
> effect).
>
> Astronomers can observe precisely what sort of "light" (its spectrum)
> is emitted by cosmic objects. Due to other things that i don't
> personnaly know exactly now, they have quite good model of what they
> should observe.
>
> The observations match very well the calculations for galaxies that
> are not too far away from ours, but, the farther the galaxy are, the
> bigger a strange difference between those happens : a shift to "lesser
> frequencies" (a shift toward the red side of the light spectrum).
>
> farther they are, the faster they seem to go away. This exactly what
> would appear if all the universe was expanding. (you can imagine a
> balloon : before inflating it, put several marks on it with some felt-
> tip pen, and then inflate it : from any point , the other points seem
> to go away from each other the same manner). My example is not very
> good because the surface of the balloon is only in two dimensions, but
> the idea is the same. And all the shifts are compared with the known
> or estimated distance of those galaxies, and it match a consistant
> model.
There are other possible ideas on the red shift other than universal
expansion. For example it may be that physics itself changes as you go
further from the observer.
-snorri
odin
wrote:
> On Fri, 18 Jun 2010 09:34:13 -0700 (PDT), marks542...@yahoo.com
> wrote:
>
> > In simple terms if possible how do astronomers determine that the
> > Universe is expanding rather than galaxies moving within a static
> > Universe?
>
> If the universe did not expand, there would not be any place where
> "moving galaxies" could move in to.
Nope. What if space started off big?
-snorri
odin
Why would the space between your ears not be expanding identically to
the space between galaxies? Of course, with uniform expansion, the
absolute rate of change of separation would be proportional to the
distance involved. So your ears are not flying apart at the same
relative velocity as that with galaxies. But there is no fundamental
difference between the expansions in the two cases.
-snorri
odin
Yes. Its been a black hole for as long as I can recall.
cassandra
> "cassandra" <cassandra99...@gmail.com> wrote in message
An excellent explanation to my question. Thank you. I hope your team
wins.
cassandra
>
> - Show quoted text -
As aganunitsi pointed out, cosmic expansion happens only in regions of
low mass/energy. Local effects overwhelm the expansion at least up to
clusters of galaxies.
Robert Carnegie: Fnord: cc talk-origins@moderators.isc.org
If the space between my ears has been expanding for 13.7 billion years
and is still comfortable, it's unlikely to become a medical issue in
my remaining lifespan.
Mike Dworetsky
Various observations have shown that whenever these "alternate physics"
ideas are put forth, they don't work out. For example, the fine structure
constant remains constant to within tight observational limits, as do
phenomena such as supernova explosions. "Tired light" redshift explanations
do not work because they do not account for the observed GR time dilation
effects in supernova light curves. The only remaining small doubt is over
so-called MOND theories to explain "dark energy" and even here there are
difficulties.
--
Mike Dworetsky
(Remove pants sp*mbl*ck to reply)
Desertphile
Then it would have to be older than it's age.
Robert Carnegie: Fnord: cc talk-origins@moderators.isc.org
wrote:
> On Sun, 20 Jun 2010 11:44:58 -0700 (PDT), odin
>
> > On Jun 18, 11:34 am, Desertphile <desertph...@invalid-address.net>
> > wrote:
> > > On Fri, 18 Jun 2010 09:34:13 -0700 (PDT), marks542...@yahoo.com
> > > wrote:
>
> > > > In simple terms if possible how do astronomers determine that the
> > > > Universe is expanding rather than galaxies moving within a static
> > > > Universe?
>
> > > If the universe did not expand, there would not be any place where
> > > "moving galaxies" could move in to.
> > Nope. What if space started off big?
>
> Then it would have to be older than it's age.
But that's all right. Empty space is a vacuum, and so it stays cold.
And because it's cold, it stays fresh. So it doesn't matter how old
it is. It's like food in the freezer.
cassandra
> On Fri, 18 Jun 2010 09:34:13 -0700 (PDT), marks542...@yahoo.com wrote:
> >In simple terms if possible how do astronomers determine that the
> >Universe is expanding rather than galaxies moving within a static
> >Universe. ?
>
> pick up the latest scientific american. there's a great article by
> tamara davis of the u. of new south wales on this exact question.
>
> turns out, according to relativity, there's little difference between
> the 2 ideas.
My subscripiton has expired, so I have to wait until my next visit to
the library. OTOH my online search found this:
http://www.scientificamerican.com/article.cfm?id=where-is-the-universe-exp
Hopefully, this will also help answer marks542's question.
As an aside, I found it interesting the author wrote that GR is
"conceptually distinct" from Newtonian physics, which is a point
several posters disagreed with when I mentioned it in an earlier topic.
aganunitsi
<quantum snip>
> > And note that by "the universe is expanding", cosmologists are
> > referring to those areas low in mass/energy - the "empty" spaces
> > between the galaxies. The presence of mass/energy binds local space.
> > The distance between your ears isn't expanding like the space between
> > the Milky Way and Andromeda Galaxy, for example. Pagano, Backspace and
> > Nando are special cases, on account of the virtually empty space
> > between their ears. The size of their heads will someday reach
> > galactic proportions. And because their sensory organs are constantly
> > expanding away from their tiny minds, they are always seeing red
>
> Why would the space between your ears not be expanding identically to
> the space between galaxies? Of course, with uniform expansion, the
> absolute rate of change of separation would be proportional to the
> distance involved. So your ears are not flying apart at the same
> relative velocity as that with galaxies. But there is no fundamental
> difference between the expansions in the two cases.
>
I'm no cosmologist, or quantum physicist, I just look the shit up
online. Hell if I understand the math behind it. It has something to
do with inertia.
http://en.wikipedia.org/wiki/Metric_expansion_of_space
Getting back to Mark's original question, I think what he was going
for is "what observations have been made that point to an expanding
universe"? There's a summary of observational evidence on the link
above. What it leaves out is "how do we know if a certain wavelength
of light is more red than it should be?"
There is a book I read once on the development of scientific
measurements. The book is aptly name "Measuring the Universe". It was
damn easy to read.
http://www.amazon.com/Measuring-Universe-Historic-Quest-horizons/dp/0802713513
A lot of what the observed redshift comes down to is simple
comparison. For example, comparing similar objects that should all be
emitting similar wavelengths of light. The more varying these similar
objects are in their distance from earth, the more their observed,
emitted wavelengths vary. The further the distance from us, the more
the energy of this wavelength is weakened (longer wavelength, weaker
energy). This is called "redshift" even if the originating wavelength
in question is already weaker than that of red light - a microwave,
for example.
cassandra
> On Jun 20, 11:53 am, odin <odinoo...@yahoo.com> wrote:
> <quantum snip>
>
>
>
>
>
> > > And note that by "the universe is expanding", cosmologists are
> > > referring to those areas low in mass/energy - the "empty" spaces
> > > between the galaxies. The presence of mass/energy binds local space.
> > > The distance between your ears isn't expanding like the space between
> > > the Milky Way and Andromeda Galaxy, for example. Pagano, Backspace and
> > > Nando are special cases, on account of the virtually empty space
> > > between their ears. The size of their heads will someday reach
> > > galactic proportions. And because their sensory organs are constantly
> > > expanding away from their tiny minds, they are always seeing red
>
> > Why would the space between your ears not be expanding identically to
> > the space between galaxies? Of course, with uniform expansion, the
> > absolute rate of change of separation would be proportional to the
> > distance involved. So your ears are not flying apart at the same
> > relative velocity as that with galaxies. But there is no fundamental
> > difference between the expansions in the two cases.
>
> > -snorri
>
> I'm no cosmologist, or quantum physicist, I just look the shit up
> online. Hell if I understand the math behind it. It has something to
>
> Getting back to Mark's original question, I think what he was going
> for is "what observations have been made that point to an expanding
> universe"? There's a summary of observational evidence on the link
> above. What it leaves out is "how do we know if a certain wavelength
> of light is more red than it should be?"
>
> There is a book I read once on the development of scientific
> measurements. The book is aptly name "Measuring the Universe". It was
>
> A lot of what the observed redshift comes down to is simple
> comparison. For example, comparing similar objects that should all be
> emitting similar wavelengths of light. The more varying these similar
> objects are in their distance from earth, the more their observed,
> emitted wavelengths vary. The further the distance from us, the more
> the energy of this wavelength is weakened (longer wavelength, weaker
> energy). This is called "redshift" even if the originating wavelength
> in question is already weaker than that of red light - a microwave,
> for example
My understanding of Mark's original question is he makes a distinction
between objects that move away from you while space remains static,
and objects that move away from you because spacetime expands. Both
cases cause redshift. Can you tell the difference between them?
Paul J Gans
>http://www.scientificamerican.com/article.cfm?id=where-is-the-universe-exp
"Conceptually different" depends on your point of view. Certainly
Newtonian physics flows from GR in the proper limits of small
distances and slow relative motions. On the other hand, the
philosophical bases for the two are very different.
The problem is a common one. When folks in a field talk, they
assume that all of them share a common knowlege base, so what
is said is taken relative to that common knowlege base.
--
--- Paul J. Gans
aganunitsi
Even trickier. The wiki article states that the theory of the Milky
Way sitting at the center of a static (metric wise) universe, with all
other galaxies traveling away from it, wasn't ruled out until 10 years
ago! The nail in the coffin for this theory was observations of the
cosmic background radiation. Not that I understand the math - so the
observations were a nail for someone else, and a "hmmm, interesting -
I'll take your word on it" for me.
BURT
> cassandra <cassandra99...@gmail.com> wrote:
> >On Jun 20, 1:15 pm, bpuharic <w...@comcast.net> wrote:
> >> On Fri, 18 Jun 2010 09:34:13 -0700 (PDT), marks542...@yahoo.com wrote:
> >> >In simple terms if possible how do astronomers determine that the
> >> >Universe is expanding rather than galaxies moving within a static
> >> >Universe. ?
>
> >> pick up the latest scientific american. there's a great article by
> >> tamara davis of the u. of new south wales on this exact question.
>
> >> turns out, according to relativity, there's little difference between
> >> the 2 ideas.
> >My subscripiton has expired, so I have to wait until my next visit to
> >the library. OTOH my online search found this:
> >Hopefully, this will also help answer marks542's question.
> >As an aside, I found it interesting the author wrote that GR is
> >"conceptually distinct" from Newtonian physics, which is a point
> >several posters disagreed with when I mentioned it in an earlier topic.
>
> "Conceptually different" depends on your point of view. Certainly
> Newtonian physics flows from GR in the proper limits of small
> distances and slow relative motions. On the other hand, the
> philosophical bases for the two are very different.
>
> The problem is a common one. When folks in a field talk, they
> assume that all of them share a common knowlege base, so what
> is said is taken relative to that common knowlege base.
>
> --
>
> - Show quoted text -
The discovery of the expansion of the universe leads to an
hypersphere. Einstein called it a closed universe finite yet unbounded
curving in the 4th dimension.
Albert Einstein is the father of the hypersphere cosmology. His
closed universe was its beginning.
Mitch Raemsch
bpuharic
wrote:
>
>The discovery of the expansion of the universe leads to an
>hypersphere. Einstein called it a closed universe finite yet unbounded
>curving in the 4th dimension.
>
>Albert Einstein is the father of the hypersphere cosmology. His
>closed universe was its beginning.
and yet there's no proof the universe is closed.
>
>Mitch Raemsch
Paul J Gans
Please don't babble at me.
cassandra
Obviously, the finer points of cosmic expansion continue to elude me
as well.
On a related note, whenever I stop and think about how little was
known about the Universe until recent times, I am always taken aback.
It wasn't until the 20th century that we knew about other galaxies.
With the veil of Earth's atmosphere literally lifted from astronomers'
eyes, they are rapidly making up for lost time.
cassandra
> On Mon, 21 Jun 2010 16:26:43 -0700 (PDT), BURT <macromi...@yahoo.com>
> wrote:
>
>
>
> >The discovery of the expansion of the universe leads to an
> >hypersphere. Einstein called it a closed universe finite yet unbounded
> >curving in the 4th dimension.
>
> >Albert Einstein is the father of the hypersphere cosmology. His
> >closed universe was its beginning.
>
> and yet there's no proof the universe is closed.
So it's a 24/7 kinda thingie? Good. I need to order some takeout
from Betelgeuse.
BURT
what do you mean?
I don't even know who you are!
Mitch Raemsch
BURT
> On Mon, 21 Jun 2010 16:26:43 -0700 (PDT), BURT <macromi...@yahoo.com>
> wrote:
>
>
>
> >The discovery of the expansion of the universe leads to an
> >hypersphere. Einstein called it a closed universe finite yet unbounded
> >curving in the 4th dimension.
>
> >Albert Einstein is the father of the hypersphere cosmology. His
> >closed universe was its beginning.
>
> and yet there's no proof the universe is closed.
>
>
>
>
>
>
> - Show quoted text -
True. But then there would be spatial boundaries where there is no
longer space.
And that is an absurdity. Einstein saw it as that and made the most
spectacular leap. That space curves back on itself in the 4th
dimension. Hawking kept that. But Hawking is not the father of it. He
just brought it back.
Mitch Raemsch
cassandra
<snip>
> "Conceptually different" depends on your point of view. Certainly
> Newtonian physics flows from GR in the proper limits of small
> distances and slow relative motions. On the other hand, the
> philosophical bases for the two are very different.
I'm not necessarily disagreeing with you here, but I don't understand
what you mean, exactly. I hope I can explain my confusion without
tipping over another can of worms. By analogy, within limits, a Flat
Earth concept gives results similar to an Oblate Spheroid Earth
concept. For example, I can build a house and survey my property
with the simpler assumption, because my conceptual error is less than
my measurement error. I can even explain Focault's Pendulum and
spinning hurricanes with a rotating Flat Earth. As long as I keep my
experience within my conceptual error, I could live blissfully unaware
that my Flat Earth concept is simply wrong. Now, I realize that
Newtonian physics is a much closer approximation to reality than a
Flat Earth, but my analogy doesn't rely on this. That Newtonian
physics works well within a subset of conditions is the important
part. I think we both agree without qualification that a Flat Earth
is conceptually different than an Oblate Spheroid Earth. So why don't
you say without qualification that Newtonian physics is conceptually
different than General Relativity?
Garamond Lethe
In the post to which Paul replied, you had "conceptually distinct". Paul
misread that as "conceptually different", and you've copied that.
<q>
As an aside, I found it interesting the author wrote that GR is
"conceptually distinct" from Newtonian physics, which is a point
several posters disagreed with when I mentioned it in an earlier topic.
</q>
Not sure that it makes too much of a difference, but I do think
"distinct" is both distinct and different from "different".
cassandra
>
> - Show quoted text -
Oops. Sure is. Dis stinks.
Robert Carnegie: Fnord: cc talk-origins@moderators.isc.org
Oh, I see! Except that there is (for this purpose) no fourth
dimension. If you want to construct a manifold like that in Euclidean
n+1-dimensional space, then you need four dimensions - just as the two-
dimensional non-Euclidean Riemann geometry of the surface of a sphere
requires a three-dimensional Euclidean space - but the non-Euclidean
space can also be self-sufficient, i.e. doesn't need a larger
Euclidean space to live in. It just exists.
Likewise, attached doubtfully to the name of Einstein is a description
of how radio works. "The wireless telegraph is not difficult to
understand. The ordinary telegraph is like a very long cat. You pull
the tail in New York, and it meows in Los Angeles. The wireless is
exactly the same, only without the cat."
Riemann's geometry is like drawing diagrams on the surface of a
sphere, but once you are proficient you don't need the sphere. And if
you think of the space of the spacetime of relativity as contained
inside a larger space, you may be making a mistake. The larger space
may not be there, or may not be as you expect. What if it's non-
Euclidean as well?
Robert Carnegie: Fnord: cc talk-origins@moderators.isc.org
> On Fri, 18 Jun 2010 09:34:13 -0700 (PDT), marks542...@yahoo.com wrote:
> >In simple terms if possible how do astronomers determine that the
> >Universe is expanding rather than galaxies moving within a static
> >Universe. ?
>
> pick up the latest scientific american. there's a great article by
> tamara davis of the u. of new south wales on this exact question.
>
> turns out, according to relativity, there's little difference between
> the 2 ideas.
I am even sceptical of _Scientific American_ since they apparently
published a few years ago a complete and detailed explanation of the
nature and cause of autistic spectrum disorders, over several pages,
with brain diagrams. This apparently has failed to settle the matter.
Surely if space is not expanding but the material of the Big Bang is
expanding into a pre-existing Euclidean-ish empty space, then there's
a place in the universe where you can stand with your back to
everything facing the still-empty space. An edge. But there doesn't
seem to be an edge and we have mapped most of the universe now. The
cosmic background radiation, the red-shifted glow of the self-neon-lit
clouds of the early universe (if what we see /is/ that), isn't totally
smooth, but it isn't significantly brighter in this direction than in
that, so we aren't off-centre inside an expanding cloud of matter in
an infinite universe. There would remain the possibility that we /
are/ in the centre, but that seems to have been disposed of, too.
Walter Bushell
<e5df08ab-dd92-4b3e...@a40g2000vbl.googlegroups.com>,
cassandra <cassand...@gmail.com> wrote:
I here they have some killer bug juice made from the finest beetles.
--
All BP's money, and all the President's men,
Cannot put the Gulf of Mexico together again.
Walter Bushell
<d6159deb-aafc-47eb...@23g2000pre.googlegroups.com>,
odin <odin...@yahoo.com> wrote:
> On Jun 18, 12:02 pm, Blup Blip <usenetwande...@gmail.com> wrote:
> > On Jun 18, 6:34 pm, marks542...@yahoo.com wrote:
> >
> > > In simple terms if possible how do astronomers determine that the
> > > Universe is expanding rather than galaxies moving within a static
> > > Universe. ?
> >
> > one of the most convincing reason is the redshift (due to the doppler
> > effect).
> >
> > Astronomers can observe precisely what sort of "light" (its spectrum)
> > is emitted by cosmic objects. Due to other things that i don't
> > personnaly know exactly now, they have quite good model of what they
> > should observe.
> >
> > The observations match very well the calculations for galaxies that
> > are not too far away from ours, but, the farther the galaxy are, the
> > bigger a strange difference between those happens : a shift to "lesser
> > frequencies" (a shift toward the red side of the light spectrum).
> >
> > meaning that the galaxies are apparently moving away from us, and the
> > farther they are, the faster they seem to go away. This exactly what
> > would appear if all the universe was expanding. (you can imagine a
> > balloon : before inflating it, put several marks on it with some felt-
> > tip pen, and then inflate it : from any point , the other points seem
> > to go away from each other the same manner). My example is not very
> > good because the surface of the balloon is only in two dimensions, but
> > the idea is the same. And all the shifts are compared with the known
> > or estimated distance of those galaxies, and it match a consistant
> > model.
>
> There are other possible ideas on the red shift other than universal
> expansion. For example it may be that physics itself changes as you go
> further from the observer.
>
> -snorri
Or light decays as it travels. Or has that been disproven?
cassandra
I agree that if a non-expanding spacetime had an edge, the CMB would
almost certainly show anisotropy. But if non-expanding spacetime is
infinite, there is no edge and so no anisotropy. As I understand it
Hoyle had an explanation for CMB, but I'm not sure what it is. I
admit I am out of my element here, so when you show me wrong, please
be gentle.
Paul J Gans
I did read it that way. In my defense (not that you are in
any way attacking) I'd claim that if things are distinct, they
can't be the same. Hence they are different. Quantum mechanics
makes a big thing out of this.
Paul J Gans
><snip>
For several reasons. It depends on my sophistication and that
of the people I am talking with. You are sophisticated enough
to realize that Foucault's pendulum does not in itself prove
a spherical earth.
As you say, you can build a house and survey your property with
flat earth assumptions. Similarly you can use Newtonian mechanics
to explain many things. It is only when you take a wider view
that we understand that flat earth isn't sufficient and that
we understand that Newton isn't sufficient.
So I can say that spherical earth is correct and that flat
earth is simply a short distance approximation to it, but
since flat earth can be derived from spherical earth, their
foundations are the same.
In exactly the same manner, Newton follows from General
Relativity.
But I can take a different point of view and say that
flat earth does not encompass curved earth concepts
and so is conceptually different. Similarly I can say
that Newton does not encompass limits on velocities or
the constancy of the speed of light in any proper reference
frame and so is conceptually different.
So to me, concepts depend on your starting point.
As an example: Newton thought of fixed reference frames
and folks started using the "fixed" stars as just such a
frame. But it turns out that Newton's laws don't need that
at all. There is such a thing as Galilean relativity. To
quote from Wikipedia <http://en.wikipedia.org/wiki/Galilean_invariance>
"Galilean invariance or Galilean relativity is a principle of
relativity which states that the fundamental laws of physics
are the same in all inertial frames. Galileo Galilei first
described this principle in 1632 in his Dialogue Concerning
the Two Chief World Systems using the example of a ship travelling
at constant velocity, without rocking, on a smooth sea; any observer
doing experiments below the deck would not be able to tell whether
the ship was moving or stationary."
so *that* isn't the difference between relativity and Newton.
A physicist today would perhaps insist that Newton isn't even
the proper place to start with classical mechanics. Instead
he or she might insist that for any physical process the
"action" is either a maximum or a minimum and so among all
possible paths between the starting situation and the ending
situation, the one that takes place is the one that maximizes
or minimized the action.
The thing that matters in this case is a mathematical construct
called the Lagrangian (or its complement, the Hamiltonian).
This concept is useful in both quantum mechanics and in relativity
and so is perhaps more general than Newton's three (but really
two) laws of motion.
I'm sorry to go on at such length. This is an interesting subject.
Differing points of view cause most of the problems in discussions
on the internet as well as among scientists themselves.
One reason why it is so hard to talk to some of the troll-like
posters is that they use the sophisticated language of science
in a way that shows that they don't understand what they are
saying. And they get huffy if you point that out to them. It
is again a case of differing points of view. What they say
makes perfect sense to *them*...
Mike Dworetsky
Disproven. Unless somehow it can mimic time dilation of variable phenomena
such as supernova light curves and quasar oscillations such that the
frequency changes the same way as that of the red-shifted light.
cassandra
If I understand the above, you are saying that you consider the
relationship between Newtonian physics and GR as qualitatively similar
to the relationship between Flat Earth and Oblate Spheroid Earth, and
you would apply the same conditional qualifications to both
relationships. I can live with that.
I confess I am unfamiliar with these concepts. Yet more things to
catch up on.
> I'm sorry to go on at such length. �This is an interesting subject.
> Differing points of view cause most of the problems in discussions
> on the internet as well as among scientists themselves.
Thank you for helping me understand your POV better. I agree
differing POVs cause many problems, but differing POVs also generate
many solutions. At the very least, they keep life interesting.
> One reason why it is so hard to talk to some of the troll-like
> posters is that they use the sophisticated language of science
> in a way that shows that they don't understand what they are
> saying. �And they get huffy if you point that out to them. �It
> is again a case of differing points of view. �What they say
> makes perfect sense to *them*...
Isn't that obvious :-)
BURT
>
> - Show quoted text -
There is one higher dimension and is the 4th spatial dimension.
Mitch Raemsch
Jeffrey Turner
Immanuel Kant, who was a famous philosopher, was the first to suggest
around 1755 that the spiral nebulae were island universes.
http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/980417a.html
--
Love consists of overestimating
the differences between one woman
and another. --George Bernard Shaw
BURT
> wrote:
>
>
>
> >The discovery of the expansion of the universe leads to an
> >hypersphere. Einstein called it a closed universe finite yet unbounded
> >curving in the 4th dimension.
>
> >Albert Einstein is the father of the hypersphere cosmology. His
> >closed universe was its beginning.
>
> and yet there's no proof the universe is closed.
>
>
>
>
>
>
> - Show quoted text -
The Aether closes it.
Mitch Raemsch
Robert Carnegie: Fnord: cc talk-origins@moderators.isc.org
I'm out of my depth too, but if the big bang implies everything was in
the same place once, I don't like it somehow becoming infinitely
spread out.
bpuharic
wrote:
>On Jun 21, 6:38 pm, bpuharic <w...@comcast.net> wrote:
the universe is finite
your stupdiity is not. there is no 'ether'
Walter Bushell
And conversely if things are different they must be distinct.
Property was thus appall'd,
That the self was not the same;
Single nature's double name
Neither two nor one was call'd.
BURT
> On Tue, 22 Jun 2010 16:34:06 -0700 (PDT), BURT <macromi...@yahoo.com>
> wrote:
>
>
>
>
>
> >On Jun 21, 6:38 pm, bpuharic <w...@comcast.net> wrote:
> >> On Mon, 21 Jun 2010 16:26:43 -0700 (PDT), BURT <macromi...@yahoo.com>
> >> wrote:
>
> >> and yet there's no proof the universe is closed.
>
> >> >Mitch Raemsch- Hide quoted text -
>
> >> - Show quoted text -
>
> >The Aether closes it.
>
> the universe is finite
>
>
> - Show quoted text -
Einstein brough back the aether in the 1920's.
Miutch Raemsch
bpuharic
wrote:
>On Jun 22, 6:29�pm, bpuharic <w...@comcast.net> wrote:
no, he didn't.
Nick Keighley
wrote:
>
> >>> In simple terms if possible how do astronomers determine that the
> >>> Universe is expanding rather than galaxies moving within a static
> >>> Universe. ?
>
> ideas are put forth, they don't work out. For example, the fine structure
> constant remains constant to within tight observational limits, as do
> phenomena such as supernova explosions. "Tired light" redshift explanations
> do not work because they do not account for the observed GR time dilation
> effects in supernova light curves. The only remaining small doubt is over
> so-called MOND theories to explain "dark energy" and even here there are
> difficulties.
I thought MOND was a Dark Matter alternative?
Nick Keighley
wrote:
> Walter Bushell wrote:
> > In article
tired light gives relativity problems as well. Something moving at the
speed of light doesn't experience time. So it can't age or get tired
Nick Keighley
> On Jun 22, 6:29 pm, bpuharic <w...@comcast.net> wrote:
> > On Tue, 22 Jun 2010 16:34:06 -0700 (PDT), BURT <macromi...@yahoo.com>
> > >> On Mon, 21 Jun 2010 16:26:43 -0700 (PDT), BURT <macromi...@yahoo.com>
> > >> and yet there's no proof the universe is closed.
>
> > >The Aether closes it.
>
> > the universe is finite
>
> > your stupdiity is not. there is no 'ether'
>
> Einstein brough back the aether in the 1920's.
where from? Berne? Who'd moved it?
Nick: "The universe is a hard and cruel place"
cousin Cathy aged 10: "And you can't get milk there"
I think this conclusivly shows the universe *can* be closed
Nick Keighley
> On Jun 22, 7:03 am, "Robert Carnegie: Fnord: cc talk-
> orig...@moderators.isc.org" <rja.carne...@excite.com> wrote:
> > On Jun 20, 6:15 pm, bpuharic <w...@comcast.net> wrote:
> > > On Fri, 18 Jun 2010 09:34:13 -0700 (PDT), marks542...@yahoo.com wrote:
> > > >In simple terms if possible how do astronomers determine that the
> > > >Universe is expanding rather than galaxies moving within a static
> > > >Universe. ?
>
> > > pick up the latest scientific american. there's a great article by
> > > tamara davis of the u. of new south wales on this exact question.
>
> > > turns out, according to relativity, there's little difference between
> > > the 2 ideas.
<snip>
> > Surely if space is not expanding but the material of the Big Bang is
> > expanding into a pre-existing Euclidean-ish empty space, then there's
> > a place in the universe where you can stand with your back to
> > everything facing the still-empty space.
standing with you back to an expanding universe sounds damned
dangerous. Oi! mind that barred spiral! Could have had someone's eye
out.
> > An edge. But there doesn't
> > seem to be an edge and we have mapped most of the universe now. The
> > cosmic background radiation, the red-shifted glow of the self-neon-lit
> > clouds of the early universe (if what we see /is/ that), isn't totally
> > smooth, but it isn't significantly brighter in this direction than in
> > that, so we aren't off-centre inside an expanding cloud of matter in
> > an infinite universe. There would remain the possibility that we /
> > are/ in the centre, but that seems to have been disposed of, too.
>
> I agree that if a non-expanding spacetime had an edge, the CMB would
> almost certainly show anisotropy.
I didn't think he was saying that. I thought he was talking about the
case where space-time is infinite but matter (the galaxies) occupies a
finite but expanding volume of that space (which is what most lay-
people think "the expanding universe" means). In that case you'd also
get anisotropy.
> But if non-expanding spacetime is
> infinite, there is no edge and so no anisotropy.
so are the galaxies getting furthur apart? Are there an infinite
number of them? Why can we only see a finite number? Why is the sky
black?
> As I understand it
> Hoyle had an explanation for CMB, but I'm not sure what it is. I
> admit I am out of my element here, so when you show me wrong, please
> be gentle.
I have to be gentle I'm one of those people who doesn't know what he's
talking about
Walter Bushell
<fc2a176f-d14e-4302...@j4g2000yqh.googlegroups.com>,
"Robert Carnegie: Fnord: cc talk-o...@moderators.isc.org"
<rja.ca...@excite.com> wrote:
> Oh, I see! Except that there is (for this purpose) no fourth
> dimension. If you want to construct a manifold like that in Euclidean
> n+1-dimensional space, then you need four dimensions - just as the two-
> dimensional non-Euclidean Riemann geometry of the surface of a sphere
> requires a three-dimensional Euclidean space - but the non-Euclidean
> space can also be self-sufficient, i.e. doesn't need a larger
> Euclidean space to live in. It just exists.
But any mathematician and most physicists can embed it in a higher
dimensional space and will if it simplifies the problem he is working on.
aganunitsi
wrote:
I'm way out of my element on this one too. My understanding is based
solely on analogies, so when the analogy diverges from the underlying
math I'm screwed. Especially since I don't know when the analogy
diverges.
So my understanding of the CMB is based on the "ants on an expanding
balloon" analogy of the universe. As has been explained by others in
this thread, the velocity of two "stationary" ants receding away from
each other increases with their distance from each other. More distant
objects have a higher redshift.
So very, very, very distant objects will be redshifted all the way
into the microwave band - eventually into the radio band. The reason
we have a cosmic microwave background radiation, and not a cosmic
radio background radiation, points to the age of the universe. The
balloon hasn't been expanding long enough to create objects this
distant receding at such speeds. If the universe continues to expand
at the current rate, the dark areas of the sky will eventually appear
"empty" - they will fade to radio background radiation, and eventually
to no detectable radiation, because those objects will be receding
away from us at faster than light speeds.
So we *do* see light in every direction, it's just very weak light.
Assuming the ballon analogy is accurate, a portion of this CMB in
every direction originated a long, long time ago, from what was to
become the Milky Way galaxy. We are seeing a very weak signal from our
own past - light from our space, different time, that's made it all
the way around the expanding balloon.
If the expansion of the balloon slows down, we could have another
problem. The dark sky will start to get bright.
cassandra
wrote:
<snip>
> so are the galaxies getting furthur apart?
Of course. In this context I use non-expanding to distinguish the two
cases under consideration; expanding spacetime carrying galaxies
along, and galaxies moving uniformly through a non-expanding
spacetime.
> Are there an infinite number of them?
I don't know.
> Why can we only see a finite number?
> Why is the sky black?
I believe you are thinking of Olber's Paradox, the argument being that
any line-of-sight through an infinite Universe would eventually hit a
star, and the night sky should be very bright. Interestingly,
Einstein's Universe suffers the same question, as any line-of-sight
will wrap around indefinitely until it eventually hits a star. What
saves the night sky in both cases is that the Universe is expanding.
An expanding Universe redshifts starlight in proportion to distance,
thus making old distant galaxies fall off the visible spectrum, and
dumping the light's energy into the cosmic sink.
If the Universe had a beginning, there would be a temporal horizon
that we could not see beyond, because the speed of light is finite and
light from very distant objects would not have had enough time to get
to us. This doesn't mean there is nothing beyond that horizon. It's
roughly analogous to looking out in the middle of the ocean. At any
one time, you can only see a circular patch of water. As you move
forward, you see more of what's in front of you just as what's behind
you disappears.
Robert Carnegie: Fnord: cc talk-origins@moderators.isc.org
Wouldn't that be convenient at night? We can switch off street lights
and save on our limited energy resources.
One important detail: as described in
<http://en.wikipedia.org/wiki/Cosmic_microwave_background_radiation>
we think that our "universe" was once an opaque fog of hot glowing
hydrogen plasma, and that glow, redshifted, is the CMB - not
starlight.
And, the CMB /is/ in radio wavelengths as well - and, strictly,
microwaves /are/ radio. In fact, your cellphone, if you have one,
uses a microwave radio.
Mike Dworetsky
Oh. My slip. Yes.
Mike Dworetsky
Somehow I doubt that the advocates of TL worry over that little quibble.
Mike Dworetsky
At that time, Kant would have had very little observational evidence to go
on, other than the existence of the Milky Way and the existence of little
smudges of light that we call nebulae. In 1755 the spiral nebulae had not
yet been distinguished from other types as having obwervable sprial arms.
This was first done by the Earl of Rosse in the mid-19th C.
I think the specification of 20th century for the determination that spirals
(and ellipticals too) were other galaxies is correct.
It would be interesting to see what Kant actually said, and what evidence he
mustered. Remember, too, that this was well before William Herschel's
astronomical career.
aganunitsi
Per the article you linked to, the CMB peak is at 1.9 mm wavelength.
In the EM spectrum, this is traditionally referred to as a microwave,
not a radio wave: http://en.wikipedia.org/wiki/File:Electromagnetic-Spectrum.png
With changes in technology, of course now we have radios that can use
microwaves. That's what they get for naming a wave category after a
technological device. Radios can also communicate with infrared waves
(it's called a "remote control"), but that doesn't make infrared a
radio wave in the traditional EM spectrum.
I don't think I implied that CMB was from starlight, but OK -
important detail clarified. The first stars aren't far enough back in
space/time to have been shifted to the microwave band yet - they're
visible in the far infrared, though:
http://hubblesite.org/newscenter/archive/releases/1998/01/image/f/format/large_web/
http://hubblesite.org/newscenter/archive/releases/1998/01/image/a/
r norman
Searching my memory back to my ham operator days, traditionally
"radio" was categorized either as "long wave" or "short wave". The
long wave band was the AM broadcast band, up to about a couple MHz.
The 180 meter ham band was sort of long wave. Higher frequencies were
"short wave" and you needed a short wave radio to receive the signals.
That went down to about 1 meter wavelength or 300 MHz.
Anything higher (in frequency) or shorter (in wavelength) couldn't
really be done with "ordinary" electronic circuits because of strange
effects like the length of wires being a significant fraction of a
wavelength. So you needed special equipment like klystrons and
magnetrons and wave guides and such. This was the realm of microwave.
Because the technology was distinctly different, it wasn't ordinarily
viewed as "radio". The word "microwave" stood on its own so you had
longwave radio shortwave radio, and microwave.
cassandra
Yes. From ultra-low frequencies measured in seconds per cycle to
xrays and gamma rays and beyond, they are all part of a continuous
electromagnetic spectrum. DIvisions like radio vs microwave vs light
etc are partly historical and partly the consequence of physical
properties. As you say, different frequencies effect different
materials and processes differently. Humans eyes can see only a
narrow band, thus its distinction as "visible" light, but many animals
seel well into UV or IR. And some moths can "feel" light with their
antennae:
http://spie.org/x8540.xml?ArticleID=x8540
r norman
You are right to emphasize the unity of all electromagnetic radiation.
When you modulate an electromagnetic wave to send information, it is
pretty much all of a kind. However the distinction between
significantly different properties of different bands of radiation
make linguistic distinctions meaningful.
For imaging purposes, the tools to manipulate and focus the radiation
and the objects to be imaged must generally be larger than the
wavelength of the radiation. For human-type activities and
constructs, that generally means that hard microwave and above
(millimeter wavelength and less) is the only radiation good for
"seeing" things.
Other processes depend on the way that radiation interacts with
matter. Radio waves, long and short, generally don't interact much
and so pass right through us and our surroundings. They can produce
electric currents in relatively long conductors (antennae) but these
generally have too little energy to do much. Microwaves tend to cause
molecular rotations or torsions and so interact much differently with
matter. These and the molecular vibrations produced by infrared
generally produce heating but not much else. More energetic infrared
and visible light can break weak chemical bonds (van der Waals,
hydrogen bonds) orexcite electrons to higher orbitals induce some
chemical changes. UV can break chemical bonds and short UV and XRays
are ionizing radiation, capable of stripping electrons completely off
of atoms.
So these are the major reasons for categorizing the different types of
electromagnetic radiation.
As to what those moths are doing with their antennae, whatever it is
isn't "feeling". Animals have sensory structures of all sorts
scattered around their bodies. Scallops have visual receptors, eyes,
distributed along the edges of their mantle; flies have chemoreceptors
on their feet. Bats don't "listen" to their echoes -- they process
the information to form what you might call "images" of the world
around them and objects in that world. Many fish detect the electric
field in the water around them. Crayfish have light sensing cells
back in tip of their tails. Moths are reputed to detect infrared and
even microwave radiation with their antennae. What they "feel"
inwardly as they receive the information is something we can have no
notion about. But certainly it is not akin to the information they
receive from physical contant (feeling) an object.
cassandra
That's why I wrote "consequences of physical properties". You went
the long way 'round. OTOH FCC frequency assignments have as much to
do with politics as physics, and relates more to aganunitsi's point
IMO.
> As to what those moths are doing with their antennae, whatever it is
> isn't "feeling". Animals have sensory structures of all sorts
> scattered around their bodies. Scallops have visual receptors, eyes,
> distributed along the edges of their mantle; flies have chemoreceptors
> on their feet. Bats don't "listen" to their echoes -- they process
> the information to form what you might call "images" of the world
> around them and objects in that world. Many fish detect the electric
> field in the water around them. Crayfish have light sensing cells
> back in tip of their tails. Moths are reputed to detect infrared and
> even microwave radiation with their antennae. What they "feel"
> inwardly as they receive the information is something we can have no
> notion about. But certainly it is not akin to the information they
> receive from physical contant (feeling) an object.
I hoped my quotes made obvious my metaphor. You proved me wrong yet
again :-)
Robert Carnegie: Fnord: cc talk-origins@moderators.isc.org
> I don't think I implied that CMB was from starlight, but OK -
> important detail clarified. The first stars aren't far enough back in
> space/time to have been shifted to the microwave band yet - they're
Excuse me, but that seems to refer not to distant and ancient stars
directly, but to slightly warm intergalactic dust?
I thought it was warmer lately, I've been cycling to work without a
jacket...
Steven L.
"Paul J Gans" <gan...@panix.com> wrote in message
news:hvqogv$m57$1...@reader1.panix.com:
> cassandra <cassand...@gmail.com> wrote:
> >On Jun 21, 7:12 pm, Paul J Gans <gan...@panix.com> wrote:
>
> ><snip>
>
> >> "Conceptually different" depends on your point of view. Certainly
> >> Newtonian physics flows from GR in the proper limits of small
> >> distances and slow relative motions. On the other hand, the
> >> philosophical bases for the two are very different.
>
> >I'm not necessarily disagreeing with you here, but I don't understand
> >what you mean, exactly. I hope I can explain my confusion without
> >tipping over another can of worms. By analogy, within limits, a Flat
> >Earth concept gives results similar to an Oblate Spheroid Earth
> >concept. For example, I can build a house and survey my property
> >with the simpler assumption, because my conceptual error is less than
> >my measurement error. I can even explain Focault's Pendulum and
> >spinning hurricanes with a rotating Flat Earth. As long as I keep my
> >experience within my conceptual error, I could live blissfully unaware
> >that my Flat Earth concept is simply wrong. Now, I realize that
> >Newtonian physics is a much closer approximation to reality than a
> >Flat Earth, but my analogy doesn't rely on this. That Newtonian
> >physics works well within a subset of conditions is the important
> >part. I think we both agree without qualification that a Flat Earth
> >is conceptually different than an Oblate Spheroid Earth. So why don't
> >you say without qualification that Newtonian physics is conceptually
> >different than General Relativity?
>
> For several reasons. It depends on my sophistication and that
> of the people I am talking with. You are sophisticated enough
> to realize that Foucault's pendulum does not in itself prove
> a spherical earth.
>
> As you say, you can build a house and survey your property with
> flat earth assumptions.
Because the average residential lot is small.
And a sphere (or an oblate spheroid) is a two-dimensional manifold: On
a sufficiently small scale, it resembles the region of a plane.
> One reason why it is so hard to talk to some of the troll-like
> posters is that they use the sophisticated language of science
> in a way that shows that they don't understand what they are
> saying. And they get huffy if you point that out to them
Long ago, Martin Gardner listed the characteristics of a
pseudo-scientist. Among these were:
Egomania
Paranoia
Talking in neologisms
-- Steven L.
aganunitsi
orig...@moderators.isc.org" <rja.carne...@excite.com> wrote:
> On Jun 24, 3:32 pm, aganunitsi <ssyke...@mindspring.com> wrote:
>
> > I don't think I implied that CMB was from starlight, but OK -
> > important detail clarified. The first stars aren't far enough back in
> > space/time to have been shifted to the microwave band yet - they're
>
> Excuse me, but that seems to refer not to distant and ancient stars
> directly, but to slightly warm intergalactic dust?
>
> I thought it was warmer lately, I've been cycling to work without a
> jacket...
Did you actually read the link? "Seems to refer" according to who? You
really should cite if you're going to throw out one (incorrect)
contrarian observation after another.
From my link already provided:
"They illustrate the steps scientists used to find the cosmic infrared
background, which is a radiative fossil containing cumulative
starlight which now appears in the infrared due to the cosmic redshift
and by absorption and re-emission by dust in the universe since the
Big Bang."
Hell, just use wikipedia: http://en.wikipedia.org/wiki/Cosmic_infrared_background
Let's see... 50%-70% of the CIB is quoted as being from entire
galaxies...20%-30% from quasars... yep, "stars".
Paul J Gans
cassandra
Yes, that's exactly the point of my analogy.