Expert: Philip Stahl - 12/15/2008

Question
I was watching something on TV that said that we can only see 13 Billion light years in either direction, because light has been traveling 13 Billion years. But i thought that since the Universe was expanding faster than light, that there has to be a lot more space out there than people say there is. Also, since our light horizon is limited by the age of the universe, is there any way to see beyond it?

Answer
Hello,

Actually, that is "see 13.7 billion light years in either direction".

However, as noted in one special "cosmology" issue of ASTRONOMY magazine (May, 2007, p. 33), what is observed now in the cosmic microwave background emitted its light 13.7 billion LY ago but since condensed into galaxies, quasars etc.  On account of the expansion of space those galaxies are now 46.5 billion light years away.

Thus - the observable universe must be: 2 x (46.5) billion = 93 billion light years across.  So you are correct in saying there is a *lot more space* available.

As the article notes (ibid.) though everyone acknowledges the speed limit (c = 300,000 km/s) set by special relativity - this doesn't apply to the expansion of space itself. The "speed limit of c has few exceptions, but this is one of them" -to quote the article.

As to your question about 'seeing beyond the light speed horizon', yes - if you were to wait long enough. That's because as time goes on more of the currently hidden (e.g. beyond the light horizon) universe will enter our horizon and be revealed.

Of course, this difference is minuscule unless one possesses a life span of a billion years or more! And there is no way for puny humans to speed it up, or peek around the edge of the light boundary, so to speak!