posted on Jul, 8 2005 @ 11:38 AM
Originally posted by siddharthsma
Many people argue that the Universe cannot expand faster then c, and when the rate of expansion reaches c, the Universe will begin to contract or
something like that. I just want to ask exactly why you say that.
Many people when considering the universe's expansion fail to consider that there is nothing against which to measure the rate. When we look at
distant galaxies, we see that the farther away they are, the faster they are moving away from us. If we look far enough, we will eventually see
galaxies moving away at a rate that is arbitrarily close to the speed of light (we cannot see any galaxies moving faster than this, the light from
them won't reach us - this is not exactly true, some galaxies are receding faster than light but we can still see them, their light left before they
achieved that speed.)
The point is, if anyone in those distant galaxies was looking at us, they would see us retreating from them at these high speeds. They would feel
that they are motionless, that it is we that are moving away from them. Additionally, if they looked the other direction, they could see all these
galaxies we cannot, being closer to these other galaxies means that the galaxies invisible to us are not moving away from them at such a high speed.
The idea here is that the rate of expansion of the universe need not approach lightspeed for it to result in most of the rest of the universe to
appear to be moving away from us at lightspeed.
The "dots on a balloon" example explains why further galaxies appear to be receding faster.
In any case, the rate of expansion of the universe need not be limited by c. As was stated earlier, c applies to objects with mass. The massive
objects contained in the universe are not being moved by the universe, the space between them is expanding.