What is current scientific thinking regarding the size of the universe? Is it infinite or is it limited but expanding or something else…
[Carnac the Magnficent]
Size of the universe. [Opens envelope. Reading.] Johnny L.A.'s ego.
[/CtM]
Finite in size, with no boundaries, and expanding.
Until you can tell me what’s outside of the Universe, my money’s on Infinite.
From what we know today it is definitely not infinite in size.
It started at a finite point in the past and is expanding since then. Definitionally that makes it finite (note this only deals with our universe…there may be something “more”, a multiverse if you like, but that is speculation and sci-fi at this point).
Candyman74 is right but to give it some explanation:
Imagine the Earth is a smooth ball. It is clearly finite in size but you could walk around it forever and never find an end or edge.
The surface of the Earth is 2D and the Universe is 3D but that gives you the sense of it. You could travel around the universe forever and while finite in size you would never run into a wall or reach an edge or whatever.
The observable universe–the parts we can see on some spectrum out to the cosmological event horizon–is spherical and about 92 billion lightyears in diameter. Whether it is bounded or overlaps is not known for certain, but WMAP survey data doesn’t show any sign that any segment of the sky is repeated at any other point, so we assume that it is a simply connected finite region without interior boundaries.
The area beyond the observable universe, which barring some kind of indistinguishable-from-magic hyperfloople drive technology is and has always been beyond our ability to experience, may be finite or infinite. The general assumption is that the overall universe is infinite and unbounded because it makes calculations about initial expansion easy, but there is really no way to determine based upon current cosmological data and models.
Stranger
IANAPhysicist but I always thought infinities in their calculations were deal breakers. If you can’t squeeze out an infinite number from your equation the result was screwed.
For example I thought this was the main problem in merging QM with Relativity. They get infinities in the equations/answers that ruin getting any sensible answers. I also thought this was one reason for ongoing interest in String Theory since it avoids these infinities.
So, how is it here that plugging in “infinity” to your equation makes it work? More, while it may make the calculation simpler is there any reason to believe that is the right way? Never thought physicists would rest an equation on laziness. That they’d go with “X” equation merely because it was simpler than the alternative.
Contrary to popular depictions of the Big Bang, the universe did not necessarily start as a finite point. The chunk of space that would expand to become the *observable *universe was certainly very tiny at the moment of creation, but the entire universe might have been of infinite size even then.
At the exact moment t = 0, the size of the Universe is undefined. At any moment after that, though, it’s presumed to be infinite. Certainly, it never went from being finite to infinite, nor the other way around.
Quoth Whack-a-Mole:
That depends on where the infinity is. The entire Universe is not observable, so it’s OK for that to be infinite. All of the things that matter, though, like the density, are finite.
Thanks for that.
I assume the 92 billion l.y. figure (as opposed to 27 billion l.y. one might expect given an age of 13.5 billion years for the Universe) is because of the Universe’s expansion. Would it be possible for you to show here how the actual value of 92 billion is derived, (please ignore this request if the math and calculations are too complex to summarize here)
I’ve always found this page to be really helpful in getting a layman’s head wrapped around the size of the universe issue. Has a little animation too which I think is helpful. It is not long and think it is a good start for this.
That is a great page, thanks! And the site itself - Atlas of the Universe - looks awesome. Much obliged.
Space is big. Really big. You just won’t believe how vastly hugely mind-bogglingly big it is. I mean, you may think it’s a long way down the road to the chemist, but that’s just peanuts to space.
So that means that the universe is about 3.453 × 10[SUP]71[/SUP] m[SUP]3[/SUP]? That seems pretty big. . . .