• Question: Do we know how large / old the universe is? If so, how did we measure that?

    Asked by anon-267385 on 9 Nov 2020.
    • Photo: Sam Geen

      Sam Geen answered on 9 Nov 2020:

      The most recent answer I could find was 13.77 billion years, give or take 40 million years: https://www.livescience.com/universe-expansion-atacama-hubble-constant-measurement.html

      The way we find this out is to look at the “Cosmic Microwave Background” – this is a faint glow of microwaves coming from the early universe shortly after the Big Bang. Because light travels at a fixed speed, the further away things are, the older they are. Light from the Sun is about 8.3 minutes old by the time it reaches us, and light from the nearby Andromeda galaxy is 2.5 million years old.

      Because the Cosmic Microwave Background isn’t exactly the same temperature, we can compare it to our theory about how the universe expands and find out which numbers work best in the theory. We can then figure out how old the universe is.

      I don’t think we know how big the universe is (correct me if I’m wrong!). The Cosmic Microwave Background is about 45 billion light years away – remember the universe is expanding, so light that started 13.77 billion years ago came from a place that is further away now. However, there could be more universe beyond that, and we need more advanced ways of understanding the universe to know for sure if it has a limit or if it’s infinite.

    • Photo: Daisy Shearer

      Daisy Shearer answered on 9 Nov 2020:

      How large: The observable universe is about 13.8 billion light-years in every direction. This means that astrophysicists can use their telescopes to look back 13.8 billion years into the past when they look at the most distant stars!! But the word ‘observable’ is important here– we don’t actually know how big the whole universe is (or what shape it is). It could be infinite or it might not be. There are plenty of theories out there about this but we don’t know for sure.

      How old: Cosmologists think that the universe is 13.8 billion years old. They’ve calculated this both from observing the most distant stars and using something called the ‘cosmic microwave background’.

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