The cosmic microwave background radiation is the oldest light we can observe in the universe, originating from approximately 13.8 billion years ago, very close to the Big Bang. Since light takes time to travel through space, looking at distant objects means looking back in timeβwhen we observe something a billion light years away, we see it as it was a billion years ago. This principle allows astronomers to study the early universe by observing increasingly distant objects, with the cosmic microwave background representing the furthest point in time we can directly observe.
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Looking billions of years into the pastβ¦ πβ³ w/ Brian CoxAdded:
But the most distant light we can see is from the cosmic microwave background radiation. If you look at the Andromeda galaxy, which we can see with the naked eye, it's the most distant object you can see with the naked eye, and it's about 2 million light years away, which means the light took 2 million years to get to us. We can actually look so far out >> [music] >> that we can see almost back to 13.8 billion years ago, which is very close to the Big Bang. So, we can look to light that began [music] its journey before there were galaxies.
And that's the the oldest light in the universe. As you look further out into the universe, to more and more distant galaxies, you're looking further back in time. If you look at something that's a billion light years away, then the light took a billion years to get to us. So, you see it as it was a billion years in the past. But
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