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Dec18-07, 06:58 AM
Sci Advisor
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Roughly speaking, it can be said that space itself is expanding (when actually it is the metric - the way we measure distances - of space time that is expanding). Borrowing an analogy from Hawking's Brief History of Time, imagine a huge balloon so that if we were to stand on the balloon it appear locally flat. Now suppose that we draw several spots on the surface on the balloon and for the purpose of this analogy suppose that we can only measure distance across the surface of the balloon, that is in two dimensions. Now, imagine taking a tape measure and measuring the distance between two spots; then we inflate the balloon and repeat the measurement; you will find that the distance between the two spots has increased. So the measured distance between the spots has change although locally, they are not moving. So you can see that if we inflate the balloon rapidly enough, the spots on the balloon can appear to be moving apart faster than the speed of light.