It's all pale green
From Mr Michael Smith Sir Paul Johnson asks (And another thing, 12 January) whether light is the natural state of the universe. The answer is yes, and the colour is green. The conventional cosmology story is as follows.
Until the Big Bang there was utter void — no matter, no radiation; indeed, no space and no time. All these things arose instantaneously 15 billion years ago as the result of a quantum fluctuation in the void. This early cosmos, a hot, inflating fog of atomic particles and radiation, expanded and cooled for the next 300,000 years until the temperature dropped to the point where the free particles could coalesce into atoms. At this moment the opaque cosmos became transparent and light burst through in an immense flash still visible today (to radio telescopes) as cosmic background radiation. This discovery won the Nobel prize in 1965.
After the flash the universe went dark again. For the next billion years matter accreted under gravitational attraction into lumpy regions of higher density. As these regions grew, enormous gravitational forces eventually ignited nuclear fusion, and a star was born. Other stars switched on from time to time throughout the cosmos, like candles being lit on a Christmas tree. This process of star formation continues today.
A recent project by Johns Hopkins University astronomers has found that to the human eye the overall colour of the universe is pale green. They analysed the visible light from some 200,000 galaxies as a representative sample for the entire universe. Then, using ophthalmic methods, the net effect on the human eye was derived. They announced the results in a recent meeting of the US Astronomical Society. Their finding was a surprise, since no individual green star or galaxy has ever been seen.
So, returning to Paul Johnson's question, if he were able to see the universe from afar, he'd see a glowing aquamarine globe
floating in the void, with a myriad of tiny points of light within.
Michael Smith Bangkok, Thailand
From Mr Edward Smith Sir: Paul Johnson's article about darkness and light has reminded me of Wittgenstein's condensation of Genesis:
In the beginning there was nothing. And God said, 'Let there be Light.' And there was Light. And there was still nothing, but you could see it better.
Edward Smith
Toronto. Canada
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