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How old is the universe?
Answer 1:

The Big Bang created the universe 14 billion years ago, so it would be impossible to see anything farther than 14 billion light years away, because nothing existed- not even space or time. The most distant thing we can see is the fading fireball of the Big Bang itself, a bit less than 14 billion light years away. We can't see the first instant of the Big Bang, because the universe was too hot and dense- it only became transparent when it cooled to a few thousand degrees. We see the fireball in any direction we look, because the Big bang occurred everywhere- even here. This is because space itself has expanded. At the time of the Big Bang, space was a single point, so everywhere in the universe was all the same place (sounds like a garbled sentence- but the wording is correct!) The expansion of space has "redshifted" the fireball far down the electromagnetic spectrum- down past red and infra red, all the way to microwaves- so its now called the "cosmic microwave background". Redshifting is similar to the reduction of a sound's pitch as the source speeds away from you. If not for this phenomenon the fireball would still be bright, like a sun covering the entire sky. Nothing in space could be colder than the fireball, so the temperature of space would be a few thousand degrees. Thanks to the extreme redshift, we receive only a small fraction of the fireball's original heat. It is possible for objects in dark, empty space to cool down to about -415 degrees Fahrenheit, or 5 degrees above absolute zero. This is the temperature of space!


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