| From: W.D.Irwin | 27/08/99
20:13:24 |
| Subject: Universe expansion | post id:
33302 |
| I was reading a book some years
ago that stated that all the galaxies looked at so far seem to be red
shifted, in other words moving away from us. This has stuck in my mind all these years and I wonder if this is still true today. Surely in a random explosion such as the in the BIG BANG theory there must be some galaxies moving towards us or moving at the same speed as us. I think something else could be causing the red shift in their instruments. Could this be so???????? | |
| From: spud | 27/08/99
20:17:31 |
| Subject: re: Universe expansion | post id:
33304 |
| I have also read that some
scientist think the universe is not moving or is going backwards, ie.
shrinking??? I am not exactly sure myself? But also wouldn't the scientist
observing the universe be looking 100's millions of years in the past??
| |
| From: David Brennan | 27/08/99
21:17:07 |
| Subject: re: Universe expansion | post id:
33322 |
| Well assuming we are not on the
edge of the universe and it is expanding, you would expect most of what
you see to be receding from you. I use the term 'edge' here in the loose sense. the fact that the universe seems to be receding any way you look was actually used as evidence that the universe is expanding, rather than the other way around. Cheers, David | |
| From: James Richmond (Avatar) | 27/08/99
22:35:18 |
| Subject: re: Universe expansion | post id:
33346 |
| The Big Bang was not an explosion
in space, but an explosion of space. This is an important
distinction. The matter in the universe (stars, galaxies and so on) is not
expanding outwards from some central point. Instead, the space between
galaxies is stretching. The universe has no centre. The galaxies all move
away from each other, not away from a common point in space. One popular way to visualise the expansion of the universe is to imagine the surface of a balloon with dots drawn on it to represent galaxies. The universe is represented by the surface of the balloon, so the centre of the balloon is not a part of the universe. As the balloon is blown up, the dots all move away from each other, but there is no central point in the universe (i.e. on the surface) which can be said to be the centre of the expansion. In a similar way, one picture of our universe is that the space we see is like the surface of a higher dimensional space (or manifold). The centre of the expansion can be pinpointed in this higher space, but not in our visible 3 dimensional space. In the same way that the surface of a balloon has no boundaries (or edge), it is likely that our universe also has no edge. JR | |
| From: MikeE | 28/08/99
0:01:34 |
| Subject: re: Universe expansion | post id:
33350 |
| Did the particles undergo similar
expansion as did the space between them -- i.e. were they also "expanding
balloons"? | |
| From: Chris (Avatar) | 30/08/99
9:00:06 |
| Subject: re: Universe expansion | post id:
33636 |
No. At the particle scale you won't see an expansion - other interactions are far stronger (eg e/m, strong nuclear force, etc). Chris | |
| From: MikeE | 30/08/99
11:47:29 |
| Subject: re: Universe expansion | post id:
33701 |
| But surely if space is expanding
so is everything else along with it -- viz painted dots on the surface of
the analogous balloon? (otherwise this is not such a good analogy -- or is
it that the expansion theory is a bit
wonky?) | |
| From: Chris (Avatar) | 30/08/99
12:13:47 |
| Subject: re: Universe expansion | post id:
33715 |
Expansion theory is right - the analogy is limiting. Perhaps a more subtle analogy would be to stick spots of superglue on the balloon instead of drawing dots. The stuck spots would stay the same size as the balloon expands precisely because the force holding them together is stronger than the expansion. So the spaces between the spots get bigger but the spots themselves don't. Hope this helps! Chris | |
| From: MikeE | 30/08/99
13:41:53 |
| Subject: re: Universe expansion | post id:
33734 |
| So the space within the structure
of an object such as the Earth does not expand along with the space
between the Earth and the Moon, or between the Sun and Alpha Centauri, or
between the Milky Way and our neighbouring
galaxy? | |
| From: spOOk | 30/08/99
13:49:58 |
| Subject: re: Universe expansion | post id:
33738 |
| MikeE - The "space" between things that make up atoms is controlled by energy bands that lie in discrete quanta. You require energy to pull these things apart and release energy when combining them. Energy is required to move from one band to another and once achieved, interesting things happen. On a small scale you may see a photon or free an electron. On a larger scale you may get a chain reaction and make a big explosion and create lots of heat and radiation. | |
| From: Chris (Avatar) | 30/08/99
13:55:52 |
| Subject: re: Universe expansion | post id:
33739 |
No, it doesn't. The expansion only shows up at extra-galactic scale. Cooperstock et al showed that the influence of the cosmological expansion on the Earth's orbit around the Sun amounts to a growth by only one part in a septillion over the age of the Solar System. Another more readable and entertaining (although still informative) explanation can be found here. Hope this helps! Chris | |