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Why is space dark?

Karen Fisher, Leicester

This is one of those ‘silly’ questions, which has an answer that’s anything but. It’s perplexed many astronomers since the time of Sir Edmond Halley, of comet fame, in the 17th century. That’s because although starlight gets fainter with distance, a simple calculation shows the fading is cancelled out by the ever-increasing numbers of stars with distance, and should therefore leave space ablaze with light.

Clearly, there’s something wrong with the simple calculation, and a big clue about what it is came in the 1920s when astronomers discovered that the Universe is expanding after exploding from a ‘Big Bang’ billions of years ago. As such, stars haven’t existed long enough to fill the Universe with their light, which is also stretched and weakened by the cosmic expansion. The result is a Universe as black as pitch.

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Submitted by Robert Matthews

Does that mean that over time

Thu, 2010-03-18 11:28
Guest

Does that mean that over time space will be 'ablaze with light'?

'ablaze with light'

Fri, 2010-03-26 18:31
Guest

It really depends on the future of the Universe. There were a number of epochs in the life of the Universe, and it looks like we have just entered another one - era of Cosmological Constant. Most of the 'current' research in astronomy points out that the Universe will expand forever thanks to one additional term in Einstein's fields equation - cosmological constant.

It would have been possible for the Universe to be filled with light, only if the Universe decelerated and then started contracting (what's called the 'Big Crunch'). Yet the observations show that the Universe's not only expanding but it is also accelerating at a certain rate. I believe someone coined the term 'Big Freeze' for this case.

There is a lot of research being done at present trying to verify the predictions and current observations, as well as trying to consolidate quantum mechanics and general relativity. I believe there are some issues between quantum mechanics and cosmology over the precise value of the cosmological constant.

Regards,
Vlad.