# How big is the universe?

Well I’ve just been thinking… Since the Big Bang theoretically occurred 15 billion years ago, and nothing travels faster than the speed of light, shouldn’t the universe only be under 30 billion light years wide? And another thing: how do Astronomers tell if something is small or if it’s just far away… aren’t telescopic images only 2-d?

Just thought there’d be a science nut in this forum that could answer these questions:p

I welcome any theories:)

Haha surprisingly that’s the movie that got me thinking these questions. Small world:rolleyes:

Did you know scientists argue all matter, when compressed, is as big as a golf ball?
Of course, there’s lot’s of space between everything… the space between quarks, protons neutrons, electrons, atoms, molecules… and eventually planets, solar systems, galaxies… Thanks to all of that space we can make one VERY heavy golf ball
My theory is that before the big bang, there was another universe with the exact same matter and energy that makes up our universe, but it expanded too much and collapsed. After collapsing, the amount of energy and mass in such a small space became too much and exploded and is now expanding until that happens again and again and again.
To answer your question: the universe keeps on getting bigger, until one day we’re goners and all starts anew. So how do scientists measure distances when looking at 2D images? Maths, my friend and chemistry and physics too. It’s too complex for me to grasp so I can’t explain

Darn you animatinator! I was in the middle of posting the exact same thing…

Darn you animatinator! I was in the middle of posting the exact same thing…

Yup, fastest type in the West:D

Heh…The speed of light…Who can say that this is a defined constant? Human physics…

Well, if matter didn’t travel as energy first, and if it actually expanded in a spherical shape, and if the big bang really occured 15 billion years ago…then yea, I guess you could say that the “diameter” of the universe would be somewhere under 30 billion light years.

However I think your question would best be answered by an “area” estimate.

So wait basically we just can’t see anything beyond 15 billion lightyears away? since the light didn’t reach us it’s like there is just darkness all around us, so how far can a telescope theoretically see??

Well assuming the universe IS spherical and not curved or flat, what could be beyond a 15 billion light year distance? Just empty space? Or another universe?

I’m doing cosmology right now so I can answer some of these questions…

Firstly, you have several different “horizons” beyond which there is a Universe with matter in it but we can’t see it.

• There is the light horizon that you mentioned - approximately 30 billion light years across if you ignore the event of last scattering. This is because light has a fixed speed using the equivalence principle.

• That said the Universe is bigger than that and there is mass beyond this horizon. The reason is that space itself expands rapidly (this does not violate special relativity but puts things out of causal contact even if they were in causal contact initially).

• There is another horizon when then Universe was “opaque” in a time when everything was plasma. Light could not cross the Universe without being scattered. This means that if you look far back enough, you see “fog”.

• According to inflation, the Universe we can actually see relative to everything there is can be roughly contrasted as what a grain of sand is to the entire Earth!

So the Universe is big.
Very very big.

As for what is beyond it, current theories suggest that if spcae closes in on itself (so there is no “beyond that”) then the Universe has to be unspeakably huger than what I have just mentioned.

Koba

Let’s start colonizing space, shall we?
The scales in the universe are so enormous that it sometimes scares me. The speed of light is a lot worse than a snail’s pace if you want to just cross the entire universe, never mind visiting every one of it’s notable features.
So what if there is more than one universe? Like how there are multiple atoms that make up molecules which make up matter which makes up planets, and stars which make up solar systems which make up […] you get the point.
Conclusion: let’s forget about space and concentrate on Blending, shall we?

Conclusion: let’s forget about space and concentrate on Blending, shall we?

Umm, can you forgive me at the moment? I have a very large ham, stabbed with cloves, covered with pineapple and cherries and brown sugar and a bit of mustard cooking in the oven, and quite frankly, the smell is driving me crazy!

I once read somewhere (not sure where) that the universe is like the surface of a sphere. That means it has a fixed size, but if you walk around it long enough, you’ll end up back where you started. Don’t quote me on that one, because I’m not completely sure…

Um… Albert Einstein I think, along with many other well-defined scientists…

[quote=Popsy;770873]I once read somewhere (not sure where) that the universe is like the surface of a sphere. That means it has a fixed size, but if you walk around it long enough, you’ll end up back where you started. Don’t quote me on that one, because I’m not completely sure…/quote]

Some scientists have claimed that the universe can have either of the following shapes:

• Flat
• Bended (a bit like the sphere thingy, where you end up where you started were you to travel in a straight line)

After an interesting explanation, they concluded there’s not enough energy and matter to bend the universe (including dark energy & matter) BUT there wasn’t enough to keep it flat either :eek:
So what does that mean?!
Don’t ask me for any details, though. I saw it on National Geographic.

I think it’s pretty obvious that no one KNOWS how big the universe is. We simply do not have that information. There’s a few guesses, but it’s more like a man tied to a chair on top of a mountain trying to figure out how big the world is. Well, he can look at the obvious (the horizon). And if he’s really smart, he might use the curvature or the horizon to help him figure out how big it is, but what if the earth was a cylinder shape with half-spheres for caps. Well, he’d never really know unless someone told him (and he believed him) or until he travelled around it himself.

My apologies to cosmologists, (I love reading all the theories), but they certainly don’t KNOW the answers. They suppose things based on other supposed things. Are they lying? no, they’re theorizing, but a “reasonable” theory is certainly not fact, nor is it evidence.

Isnt the universe doughnut shaped? mmmm…

You can’t give the size of the universe as its constantly expanding. Approximately 3x10^8 metres/second(speed of light) in every direction.

What you should be asking is what is the meaning of life & everything else. And no the answer is not 47.

I think it’s pretty obvious that no one KNOWS how big the universe is

What does it matter in the end anyway? A human will have difficulty grasping the size of the Earth, nevermind eanything else. In the end the best we can do is get a number - the number of zeros doesm’t make any difference to what we can grasp with our minds.

Koba

I think I have a pretty good handle on the size of the earth. I’ve been in every time zone! the earth is 24 hrs big. See, I know. seriously though, google earth really helps give a perspective on the size of the earth. Someone should make “google universe” that would be cool

Yeah it’s 42:p