Wednesday, May 23, 2007

The death of cosmology?

This ties in with what I wrote recently, half-facetiously, about the expansion of the universe. In an article today in MSNBC, physicists predict that one day, in the far distant future, observers of the universe won't be able to observe anything except their own galaxies, which they will mistake for the entire universe since all the other galaxies have moved too far away. The article says:

The universe is rapidly expanding — perhaps not rapidly enough to rip to shreds, but enough that distant galaxies will eventually be moving away faster than the speed of light. This much has been known for decades.

Emphasis mine. How can anything move faster than the speed of light? Einstein's theory has placed c as the absolute maximum speed of anything as far as I know. Even if something moves away at the speed of light, its light still reaches us at the speed of light and I would think that would mean that we wouldnt detect any movement or expansion at that point. The galaxies will not 'blink out of existence.' Theyll just sit there, that is, moving away from us at the speed of light while their light reaches us at the speed of light.

It's either that or Einstein's theory has been debunked while I wasnt looking. The universe can expand faster than the speed of light relative to our galaxy and can blink out of existence away from an observer. If there are any physicists out there, can you explain this?

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