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I read on a post

Big Bang and Cosmic microwave background radiation?

We detect light from another 13 billion years ago does this mean that one billion years ago we could only detect light from about 12 billion years ago.

If so why and is the same true for the inverse

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up vote 4 down vote accepted

The current age of the universe is estimated to be 13.75 billion years. Obviously we can't detect light from before the beginning of the universe, because there wasn't any, so the oldest light we could possibly detect would be 13.75 billion years old.

However for the first 380,000 years the universe was opaque to light so we can't detect any light older than about 13.4 billion years. The cosmic microwave background is this age (in fact it dates from the moment that the universe stopped absorbing all light) so it's the oldest light we can observe.

A billion years ago the universe was only 12.75 billion years old, so the oldest light we could observer (i.e. the CMB) would be about 12.5 billion years old.

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With a more exact device can the age be increased or is there a maximum effective detection. – Argus May 8 '12 at 7:26
During the first 380,000 years the universe was so hot that all the atoms were ionised. This means the universe was full of free electrons, and free electrons scatter light very strongly. The CMB dates from the time when the ions and electrons recombined and the universe stopped strongly scattering light. Because of this there is no way we'll ever see light older than 380,000 years no matter how good our equipment. See for more details. – John Rennie May 8 '12 at 7:36
@Argus the CMB is the oldest light that is still around. There really isn't a way to look at older light if there isn't a way to find any! – tmac May 8 '12 at 7:37
Very good observation. What about detecting the rate that the light was scattered. Might not be possible due to the high heat. – Argus May 8 '12 at 13:53

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