Is the Universe Infinite?

#1

Is the Universe Infinite?

Health Warning: This thread may or may not cause your mind to blow up and has driven some people insane just thinking about it

The Universe is it infinite or does it have an end?

I was watching this program last night about infinity and it blew my mind. It’s a debate that has baffled and divded many scientists and mathematicians

So firstly if the Universe is infinite that means that any infinite amount of possibilities are playing out, meaning there would have to be another Earth out there somewhere with another you, living the same life, reading exactly what I’ve written and believing that you are the only “you” reading this. The odds of that happening are quite unbelievable but if the universe is infinite even if there’s a 1 in 1 billion chance it can happen, it’s happened because the universe is infinite

But if the Universe is not infinite and it has an end, a point similar to that on Earth where we end up back where we started, then surely that should mean there is an end number. A number can only really be considered a number when we use it in a formula or a total. So even though this number may indeed be huge, if the universe is not infinite then numbers can’t be. It would have a to be an unbelievably large number, beyond our imagination, but upon reaching that number we would just go back to zero, that is the last possible number

So based on this do you believe the universe is infinite or just massive? And which would you personally perceive as the most unbelievable?

#2

Well, I can’t be sure if the universe is infinite or not, but I’ll post something here.

To be more precise, there wouldn’t have to be another Earth exactly like this one, but the probability of that happening would be 1 (or 100% if you rather). No, the two things aren’t the same. For instance, if you sort a number in the interval [0,1], there are infinite possibilities, so the probability of the sorted number to be 1 is 0, but nothing says it won’t be.

But, yes, I see your point, and you are right, if the universe was proven to be infinite than there should have infinite Earths exactly like this one. Unless, of course, there is some unknown law of physics that impeaches that from happening.

This philosophy is called Ultrafinitism, and it fails completely to convince me. Numbers are abstract entities, they don’t exist the same way matter exists. They only exist in logic.

#3

My mind = blown

#4

From what i understand from documentaries 'bout the universe it grows constantly because the galaxies drift away from eachother.

#5

Just because the area of the universe may be infinite, doesn’t mean that it’s contents are.
For example, in theory if I had a bathtub of infinite size, and threw a rubber duck in there, it doesn’t mean that there is another rubber duck somewhere in the tub because the tub is of indeterminate size. You can’t extrapolate contents of a certain area to the infinite area if there is uneven distribution.

#6

This presents me with issues. lol, many a night I have sat up thinking about this. The key point as I see it, is that there is more than one infinity, some infinities are larger than others. https://en.wikipedia.org/wiki/Aleph_number explains it a bit.

If it is not infinite, then let me propose a thought experiment for you. Let us assume you are capable of superluminal travel. Let us also assume that either a)Your life expectancy is prolonged indefinitely, or b)There are sufficient people on your craft that will allow future generations to exist indefinitely. Now if you were to pick a direction and head in that direction at a speed which is greater than the expansion of the universe. What happens when you reach the edge of the universe?

Indeed as an extension of the above experiment, what is the universe expanding into.

That blows my mind.

#7

isn’t there already a thread called The Size of the Universe?

#8

We are reflecting here on “infinity” and discussing whether or not “infinity” truly exists

So for this bathtub to accurately portray the universe there would be an infinite number of people standing away from you throwing in other ducks. These other people to you would be what stars, other suns, represent to us in our universe. Meaning that if this bath was infinite, many people, not just you, would be throwing ducks into the bath, so it’s very likely that one of the ducks they throw in, despite the odds, will be exactly the same as the duck you’ve just thrown in, because its infinite, it can go on forever

If the universe is not infinite then in theory when you reach the end of the universe you should end up straight back were you started

#9

There is absolutely no difference between the universe being finite or its contents being finite. It is just a definition of what universe is, if the nothingness is part of it or not. So, when the OP said about the universe being infinite, I took that as the contents of the universe being infinite. Otherwise it is just an irrelevant and useless question.

In any case, thinking about it again, it doesn’t make sense to me that the universe is infinite if the big bang originated what we know as universe. So what, there would be infinite big bangs everywhere causing infinite sets of galaxies everywhere you go? Or it is just the big bang the wrong theory here?

Those kind of infinite do not make difference in the case of the universe. The universe being infinite means you can go as far as you want in any direction and there will be still universe in front of you. Set cardinalities can’t have an interpretation here.

You can’t travel in a greater speed than the light speed, and the first thing that the big bang emitted was light. But, if you can travel faster than light speed and reach the border, you are causing the universe to expand.

It doesn’t need to expand into anything. It is just expanding indefinitely.

#10

Again you are assuming the contents of the universe have the the matter concentration that we have in our area of the universe. Just because the universe is infinite doesn’t mean that there is infinite stars. There can be blank empty space you know.

#11

The universe is like 90% nothing with 10% (anti-/dark-)matter, so yeah I think that an infinite amount of nothingness is entirely within the realm of possibility :stuck_out_tongue:

#12

I can’t get my silly engineers brain round some of this shit lol.

I think the problem I have most is understanding the concept of it not having to expand into anything, that it just expands indefinitely. Bah I’m too rooted in the physical. Is there anywhere I can read in a bit more depth in this, without needing a PhD in theoretical physics?

#13

“Space” is defined by gravity. If there is no matter then there is no gravity, so the concept of an infinite “empty” universe is irrelevant.

The universe is all the space there is. Everything that is under the effects of gravity. Everything within a certain distance of matter.

So, while the universe has a finite size, it does not have a border, in the same way earth doesn’t have a border. Someone else explained it much better in the other universe thread, though.

#14

Hmmm reminds me of boundary layer theory. Boundary layers have no end, but when the boundary velocity is 99% of free stream velocity you assume it’s effect is negligable.

I like thinking about this stuff. Maybe I should go do an undergrad degree in theoretical physics. Hell if I wait a couple of years the university may even let me do it for free.

A little off topic, but the entire thing could be a rather moot point

#15

You do realize that the force of gravity is related to distance right? So the force of gravity can become infinitely weak, but never reach zero.
For example when you graph the effects of gravitational force you will find it never reaches zero, it simply approaches zero. Thus by your definition the universe IS NOT finite.

When talking about space this sort of approaching zero mathematical outlook is important because in many cases there is so much distance separating masses that the effects of gravitational force are so small, they can hardly be said to exist at all. But they most certainly do.

#16

This whole thing is a moot point because, infinite or not, humanity is almost definitely not going to explore that much of our universe even with the most conservative predictions of size.

#17

True dat.

#18

interesting, I was watching exactly that same program.

#19

Nope. It’s like in pacman, when you get to one end, you spawn at the other one.

#20

I remember when I was very small, I was sitting thinking about existence, and I got so deep into it, that I forgot I existed.

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