Hubble discovered that the further stars and galaxies are, the more red shifted the light is. One possible cause of red shift is the Doppler effect that we discussed in Puzzle Piece 5: The Doppler Challenge. This effect is the one that is usually mentioned in discussions about the Big Bang – even though it is not the one that is actually assumed to be the cause anymore.
This seems like a very reasonable assumption, and that’s how the idea of the expanding universe came about.
As you may know, the problem with this is that the red shift happens to be symmetrical around earth. So if it was really the standard Doppler effect, then it would mean that earth is at the center of the universe, which is of course not very realistic.
The energy of a photon is E=hv, where v is the frequency. When photons get red shifted, it means they lose energy. Hence any process, by which photons lose energy, results in a red shift. There several dozen possible explanations of how photons can lose energy and thus be red shifted (See Marmet’s paper on this) . Some include absorption by dust or electrons (Thompson scattering), another is one is due to gravity, yet another one is an intrinsic red shift of objects, interaction with the plasma of space etc, and yes, one of them is the idea of the expansion of “space time”.
The last one seemed to fit nicely with the (mainstream) interpretation of general relativity (the space-time interpretation), and so this is the one and only cause that is simply assumed to be true.
What did Hubble have to say about “his” discovery and the idea that space is supposed to be expanding?
“Astronomer Edwin P. Hubble says that after a six-year study, evidence does not support what we now call the Big Bang theory, according to the Associated Press. “The universe probably is not exploding but is a quiet, peaceful place and possibly just about infinite in size.””
Halton Arp has observed several highly red shifted quasars that appear in front of close by galaxies… so then it seems that the red shift of at least some quasars does not necessarily indicate distance (or space expansion)… (and if that is the case, not only are quasars not very distant, enormously large and bright objects, but this raises the question about the red shift interpretation in general).
Even if space expansion is real, then an obvious question is: how much of the observed red shift is due to space expansion, how much is due to galaxies/stars actually literally moving (Doppler), and how much is due to other causes? The fact that light travels billions of years through space makes me think that the idea that light just might be losing a bit of energy during such a long trip does not sound entirely unreasonable, and should be seriously investigated. After all, the entire Big Bang idea rests mainly on the red shift interpretation…
Ok, let’s be positive about this, and assume that indeed, the red shift is due to space expansion, at least part of it. Then how would that work, exactly?
Let’s picture a part of space, indicated with a grid, and a light wave traveling through it.
If we expand this piece of space, and if light is “attached” to that piece of space, then yes, the light wave will be red shifted (at least in this picture – relative to an outside observer…):
But wait a minute: if the light wave is literally stretched because it is somehow “attached” to space, just like a drawing on a balloon is stretched as it expands, then not only would the light wave expand, then it seems to me matter would also have to expand the same way.
If we use the usual assumption that there is no absolute space, then light in that model of course cannot be “attached” or connected to this (non-existent) absolute space, then why would the expansion of that space affect light in any way at all? Simply increasing the distance that light has to travel does not affects its wave length. Let’s consider a typical space-time diagram. For this example, let’s assume neither earth nor that star is moving (note, earth does not exist yet when the star emits the light).
There is no red shift. Now, let’s add some space, and assume that neither light nor matter is *attached* to space. So the only thing that changes is the distance. The gray area indicates the amount of space added:
Since the sun was not moving when the light was emittd, and the planet is not moving when the light arrives… there is no Doppler effect and no red shift.
So it seems that this only works if light and matter is in fact somehow “attached” to space and thus stretched by the space expansion. In the space-density model, this is obvious, as light and matter are oscillations of space, so there clearly, any stretching of space would indeed affect light - and matter:
Let’s consider a small “particle”, indicated by a wave in the “medium space”.
Does expansion mean that space is stretched (left)? Well in that case, if light is stretched by this, then matter would also have to be stretched, and all atoms, and molecules would get larger over time. That of course essentially means we would not be able to notice anything different at all. If the entire universe, including matter in it, would increase in size proportionally, then all distances would never change relative to each other, and we would not observe a red shift either.
If expansion means that space is somehow “added” – even in the case where matter is in fact attached to space, neither light nor matter would be stretched. If light is just moving through more space, then all it means it takes light longer to travel.
Even if this were the case, then where exactly is that new space added? Is it added just between atoms? Then it would mean that the distance between atoms, including within a molecule, a star, within a galaxy etc. would be increasing. (And where would this new space be coming from)?
So the only way that light could be affected by the expansion of space is:
- if space is stretched (no new space)
- if light is somehow attached to space (like in the elastic solid model)
- => but then matter would also be affected the exact same way, resulting in no relative net effect
This is just one of many question – many more are discussed in numerous places elsewhere (see links below). To me, these were some of the question that started my doubt, because nobody was ever able to answer it…
Next Puzzle: Big Bang Puzzle Piece 2: Older than Legally Allowed
- Hubble and red shift: http://www.science20.com/eternal_blogs/blog/hubble_eventually_did_not_believe_big_bang_associated_press-85962
- Is the Universe Really Expanding: http://arxiv.org/PS_cache/arxiv/pdf/1107/1107.2485v2.pdf
- Causes of red shift: http://www.plasma-universe.com/Redshift
- Other causes of red shift: http://qedradiation.scienceblog.com/11/redshift-by-cosmic-dust-trumps-hubble-and-tired-light-theories/
- Tired Light: http://www.lyndonashmore.com/
Big Bang Problems: