– How do astronomers know the universe is infinite?

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It’s said that the universe goes on forever but how do we know?

In: Earth Science

My understanding is that they don’t think its infinite and rather has a distinct boarder that is constantly pushing outwards. At some point that boarder will cease to expand and will spring inwards in an event they refer to as “the big crunch”. Then once everything is as tightly packed as it physics’lly (see what I did there?) can be into a single point this will trigger a big bang, and thus the cycle begins again bringing with it life and taxes.

They figured this out by kind of correlating or looking at many things like heat death and light travel and brightness and movement of particles and figured out that it was a system still in motion

Edit: wanted to add the term physics’lly

They don’t know that, and don’t claim to. All we know about is the *observable universe* – the distance around us that light has had time to reach us from, since about the start of the universe. Anything outside of the *observable universe* is simply too far away for light to have reached us, even in ~14 billion years.

Beyond that distance, astronomers make no claim about what exists – i’m sure people have their own guesses, but there’s just no data that could be taken about it, even hypothetically.

If the universe is infinite that would mean that there were an infinite number of particles. Would that mean that there were an infinite number of me’s out there? I think one of me is enough in the universe. I think that the astronomers aren’t sure if the universe is finite or infinite, but since infinity hurts my brain if I get a vote I vote for finite.

The same way we know anything else – by building models that explain what we observe while requiring the least assumptions.

In many contexts it makes sense to *model* the universe as infinite because that assumption alone predicts a number of other properties that we observe our universe to have (such as its flatness and its absence of any clear structures or boundaries even as you approach the “edge”).

It’s also a simpler model to work with because it means you don’t have to worry about what happens when you hit the edge. So assuming the universe is infinite makes a whole bunch of your calculations much easier to perform.

tl;dr we “know” the universe is infinite in the sense that an infinite universe is the *simplest* model consistent with the reality we see