When the cosmologists say the universe is flat, what does that mean?
If you could explain it briefly in layperson terminology, that would be great. Thanks!
2006-10-03 15:18:18 · 5 answers · asked by powhound 7 in Science & Mathematics ➔ Astronomy & Space
Briefly is not possible. But I think you can follow this.
Our universe is expanding now, pushed out by the big bang.
Gravity is trying to slow the expansion and pull it all back together.
Which will win? The force from the big bang or gravity? Astronomers have been asking this question for a long time. The answer is stated simply as a number called Omega. They try to measure Omega. If Omega is less than one the universe will expand forever. If it's greater than one the universe will collapse back. If it's exactly one, the universe will expand forever, but the rate of expansion will always be slowing down. After a long while it will almost stop.
If Omega is one, the Universe is "flat".
More info:
Omega is really really hard to measure. It depends on questions like "How much dark matter is there?" The current best value is somewhere around 1/3. But the measurement is so uncertain that could well be one. In fact scientists think that might be the case. They think that if Omega wasn't one we should get an answer like .00006, or 75,000,000. 1/3 is close to one compared to those numbers.
The reason they think that, if it wasn't one, Omega should be far from one, is that the theories of the big bang say that omega was set very early in the bang. And that, unless it was exactly one, it should keep changing over time. They used to be puzzled why it should be anywhere near to one. It was like Omega was balanced on one in a very unlikely way.
Then someone invented a slight modification of the big bang theory called "inflation". One reason people like inflation so much is that it says omega would have been set as exactly one by inflation, where it would stay.
So presently, astronomers think that Omega is exactly one, the universe will expand forever, but that the rate of expansion will always be slowing down. It's "flat".
More detailed information:
http://www.astro.ucla.edu/~wright/cosmo_03.htm
2006-10-03 18:55:20 · answer #1 · answered by Bob 7 · 0⤊ 1⤋
Flat Universe
In a flat universe, all of the local curvature and local geometry is flat. In general it can be described by Euclidian space, however there are some spatial geometries which are flat and bounded in one or more directions. These include, in two dimensions, the cylinder and the torus. Similar spaces in three dimensions also exist
2006-10-03 15:28:17 · answer #2 · answered by mysticideas 6 · 0⤊ 0⤋
Flat Univerise is achieved when the Universe stops expanding. In other words, the momentum of the expansion of the univerise, and the inward force of gravity, are equivalent, and thus, no movement is made. However, Scientists believe that the Universe is still expanding today.
2006-10-03 15:24:12 · answer #3 · answered by Xeel 1 · 0⤊ 1⤋
By flat, they mean everything is as linear, or straight, as it seems. A curved universe would eventually intersect with itself, even though everything would look straight to us. In other words, if you went far enough in a "straight" line, you could eventually find yourself where you started. Current theory says that is not the case.
2006-10-03 15:25:37 · answer #4 · answered by skepsis 7 · 1⤊ 0⤋
This would be the universe according to the Catholic Church in the old days. Cosmologists were russian sprit leaders that started the rumor.
2006-10-03 15:23:03 · answer #5 · answered by David T 2 · 0⤊ 1⤋