Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: Bruce Williamson on 12/04/2009 13:30:03

Title: Aren't measurements of the expansion of the Universe based on out of date data?
Post by: Bruce Williamson on 12/04/2009 13:30:03
Bruce Williamson  asked the Naked Scientists:
An elder friend that I hike with has been reading a lot and poses questions I cannot answer. I am beginning to think he has posed questions I have never seen answered. Here are some that started with him and we have discussed for some time without success:

1. Hubble looked out and noticed that the more distant the galaxy was from here the faster it was receding. But nowhere is it mentioned that he was observing 'old news'. Those distant galaxies he observed were sending that light 13 billion years ago and we have no information about their receding speed today? Could this not simply mean that galaxis WERE receding faster back then in time? Without ANY knowledge of what may be happening there currently, what can be honestly said about it?

2. When we see sketches of the cosmic sphere they are always football(rugby) shaped. Since they are the surface of last reflection (SLR?) in all directions, should they not be spherical?

3. If we can see back 13 billion years in one direction, lets say N, we can see galaxies as they existed long long ago and when we get to the SLR we cannot see farther because the light that started from there cannot overcome the speed of recession or something. We can also look S and see as far as we can. Now  the question. If an observer is present, today, on the most distant galaxy to our N and they look this way, I imagine they will not be able to see past us anymore than we can see past them. So they do not see all the stuff we see to our South. But what do they see when they look away from us? Do they see galaxies that we can never see? Or do they see the exact same galaxies that we see but from a different perspective? In other words, when they look away from us do they see the same stuff we see when we look away from them. Both of our views in that direction ending just before we see the duplicate of the other galaxy that we see in our mutual direction as the "last one"?

Would love to hear from you.
Bruce Williamson

What do you think?
Title: Aren't measurements of the expansion of the Universe based on out of date data?
Post by: Vern on 12/04/2009 17:25:33
As far as I can tell, the observations are valid. The more we study galaxies at the far reaches of the universe, the more we find that they look like the galaxies close by. We used to think that young galaxies would develop their magnetic fields slowly over billions of years. However, recent observations show that the most distant galaxies have magnetic fields similar to those close by.
Title: Aren't measurements of the expansion of the Universe based on out of date data?
Post by: lyner on 12/04/2009 19:09:30
Bruce, you have to be correct that what we see from distant objects is old light. The possibility must exist that, since the light was emitted, the speed has changed. However, one can infer that  most things were probably not too different then because the structure of the spectral lines emitted suggests that the 'Physics' was the same - at least as far as the small scale QM situation. Hubble gives the simplest explanation of why the red shift is what it is.
If we don't assume the principle that basic physical laws are the same everywhere and everywhen, then life becomes much harder for Cosmologists and the rest of us, It's the best we can do, I think. (
Title: Aren't measurements of the expansion of the Universe based on out of date data?
Post by: yor_on on 13/04/2009 12:15:47
You know, I'm not sure why the universe is depicted as a 'baseball' thinking about it. It could have to do with map coordinates transfered from a essentially 'flat' universe to a 'globe'? Just as a image of our Earth becomes distorted when you transfer it to a chart?

Or it could be as simple as our universe being described through a 'fisheyed' lens?