Perhaps the most dramatic, and potentially most important, of these paradoxes comes from the idea that the universe is expanding, one of the great successes of modern cosmology. It is based on a number of different observations.There's more at the link.
The first is that other galaxies are all moving away from us. The evidence for this is that light from these galaxies is red-shifted. And the greater the distance, the bigger this red-shift.
Astrophysicists interpret this as evidence that more distant galaxies are travelling away from us more quickly. Indeed, the most recent evidence is that the expansion is accelerating.
What’s curious about this expansion is that space, and the vacuum associated with it, must somehow be created in this process. And yet how this can occur is not at all clear. “The creation of space is a new cosmological phenomenon, which has not been tested yet in physical laboratory,” says Baryshev.
What’s more, there is an energy associated with any given volume of the universe. If that volume increases, the inescapable conclusion is that this energy must increase as well. And yet physicists generally think that energy creation is forbidden.
Baryshev quotes the British cosmologist, Ted Harrison, on this topic: “The conclusion, whether we like it or not, is obvious: energy in the universe is not conserved,” says Harrison.
Paradoxes in Cosmology
Two things we think we have very solid evidence for are an expanding universe, and the Law of Conservation of Energy and Matter. At least one has to go:
We have a lot of data about the conservation of mass and energy in our general neighborhood. We don't and can't have definitive information about the conservation of mass and energy in a universal sense. We often find that something we assumed was a universal law turns out to be a special case when we expand the frame of reference.
ReplyDeleteConservation of energy turns out to be a complicated beast. It won't look the same in different reference frames, for example.
ReplyDeletePlease don't ask me about "dark energy"
Okay, so I've always heard the expanding universe explained this way-
ReplyDelete"The first is that other galaxies are all moving away from us. The evidence for this is that light from these galaxies is red-shifted. And the greater the distance, the bigger this red-shift.
Astrophysicists interpret this as evidence that more distant galaxies are traveling away from us more quickly. Indeed, the most recent evidence is that the expansion is accelerating."
Now, here's the thing that popped into my head this time when I read it- Let's presume we're looking at galaxies 100 million light years away and 50 million light years away, and the red shifts indicate that the 100 mil. is moving faster- isn't it just as likely that the universe is decelerating as 100 mil. years ago (that's what we look at when we look at something 100 mil light years away!) things were expanding faster than at 50 mil years?
Physicists must have accounted for that somehow. Maybe I should just look that up...
Okay- a quick google search indicates that yes, travel time for light is factored into the equations- problem solved. I'll leave this comment just in case anyone else started wondering that!