2006-11-19 14:30:04 · 9 answers · asked by Chase 4 in Science & Mathematics ➔ Astronomy & Space
The expansion was first predicted theoretically in Einstein's equations of gravity (although he initially changed them to disallow that result). The expansion was first observed using the doppler effect from nearby galaxies. For things moving towards us, light is shifted to be more blue and for things heading away from us, it is shifted to be more red. It was found that the further away galaxies are from us, the faster they are moving away (except for a few close to us whose 'peculiar' motion is large enough). This pattern is maintained to the farthest distances we have been able to see. It also agrees with the theoretical predictions.
It should be pointed out that even pictures taken a hundred years ago would not be able to show this expansion. The galaxies are simply too far away for speeds of 100 km/sec to have any noticeable effect on the images!
It should also be pointed out, like one previous poster did, that every galaxy would see the same type of expansion. In other words, if you were in galaxy A that is 500 million light years away from us, you would still see all the galaxies as moving away from you in such a way that the farther they are away, the faster they go.
2006-11-20 02:47:04 · answer #1 · answered by mathematician 7 · 1⤊ 0⤋
At the moment we think the universe is expanding. A few statistics here or there tell us that the universe is expanding relative to our current position in the universe. If we where located in another part of the universe or at the center of our galaxy we would have a different point of view. We only have had the current view of our universe for less than 100 years. Actually the knowledge we have gained in the last 100 years makes our 40,000 years or so of our existence a waste of time. I think we need a larger sample to come to the conclusion that the universe is continuing to expand. Our sample is to small at the moment to say whether it is continuing to expand or slowling down. The information we have only tells us that it is expanding, it does not tell us nothing about the rate of change in the past or future. Our old view of the sky, by looking at drawings of the sky in the past is not extensive enough to give is a rate of expansion say a 1000 years ago versus the present. Also as some think we are in a massive black hole that might give us a false sence of the truth.
2006-11-19 20:33:29 · answer #2 · answered by G Constant 2 · 0⤊ 0⤋
Scientists and Astronomers use the general analysis of the annual NASA Space report that provides yearly details of the positions of various objects in space relative to each other.
The addition of the Doppler Shift Effect input records further confirm the idea of a Self-Expansive Universe. The radio signals emitted by stars and planets are gathered over many years and fed into a digital anagraph that provides a computerised display of an expanding universe.
The fact that the distance between galaxies today are more than that measured in 1901, 1956 and 1984 prove that the Universe is Expanding at its own pace
2006-11-19 19:13:57 · answer #3 · answered by Santhosh S 5 · 0⤊ 0⤋
Just to add to the answer involving type A1 supernovas, the supernovas the the red shifts are observed in occur in other galaxies. These exploding stars are so bright that we can see them even in very distant galaxies; that single star's explosion outshines the other billion or so stars in it's galaxy for a brief time. So, when we see a supernova in a distant galaxy, we can see that the light is shifting towards the red end of the spectrum, meaning it's moving away from us.
Another interesting tidbit is that all galaxies are moving away from each other. This is hard to picture, but imagine using a marker to put dots on a balloon and then blowing the balloon up; every dot will move away from every other dot.
2006-11-19 15:14:10 · answer #4 · answered by Jason 3 · 0⤊ 0⤋
From looking at the light from type A1 supernova. the farther away a star is, the more redshift is seen in the light coming from it. Since all type A1 supernova produce the same 'brightness' we can tell how far away it is by a shift in its color toward the red spectrum.
We also know that this expanding universe is accelerating too.
2006-11-19 14:36:16 · answer #5 · answered by GlooBoy 3 · 1⤊ 0⤋
Red Shift
2006-11-21 04:12:10 · answer #6 · answered by Ramsees II- the Great One 5 · 0⤊ 1⤋
it appears to be expanding,
i believe it will shrink again later and cycle like a wave ...
expand, contract, expand, contract,
that's the way everything else seems to work
2006-11-19 14:33:57 · answer #7 · answered by Anonymous · 0⤊ 0⤋
The doppler shift when we look at stars
2006-11-19 14:31:58 · answer #8 · answered by clayzer08 1 · 0⤊ 0⤋
guys smarter than we are tell us.
i believe they're called scientists.
2006-11-19 15:39:20 · answer #9 · answered by Joey Joe, yo 5 · 0⤊ 0⤋