If our universe is only 14 billion years old, and since nothing can travel faster than the speed of light?

Question

How is it possible that from one edge of the visible universe to the other the two edges are nearly 28 billion light years apart and our universe is only 14 billion years old?

Answer 1

The rule that "nothing can travel faster than the speed of light" only applies to objects that are near each other.

Distant parts of the Universe can, and do, move much faster than the speed of light with respect to each other. There is nothing in logic or physics that forbids this, and it does not cause the "causal paradoxes" that interacting faster-than-light objects can cause. (Paradox example: in rest frame object A, event 1 occurs before event 2; in rest frame of object B, event 2 occurs before event 1; but suppose event 1 "causes" event 2?)

Distant parts of the sky in opposite directions from us are not in causal contact. We can see both of them, each of them can see us, but they can't see each other, because they are over each other's "event horizon". So there is no problem that they are traveling nearly twice the speed of light with respect to each other. To themselves, they seem "at rest" (with respect to the Cosmic Microwave Background), just as we seem to ourselves to be "at rest" (nearly). Those distant places are the same in their average conditions as we are.

In fact, our Universe is almost certainly much, much larger than 28 billion light years across. Our event horizon prevents us from seeing more than 14 billion light years away, but each day we see one light-day further.

How it got that way is generally thought to be due to "early inflation" in the big bang, but that's another story.

Answer 2

There is an answer here that says 14*2 (the diameter of the universe) = 28 billion, which wouldn’t be correct because that would place the centre of the universe right here on earth if the big bang actually exploded equally outward in a directions. Even if it didn’t, we’ve proven that we live on the outer edge of a galaxy, in a fairly random area of space.

But this answer helps to determine what is not right about our universe. If we can see everything in our visual universe in all direction out to 14 billion light years, then we can easily prove that the universe is much larger than we think.

Draw a circle and call it the Theoretical Universe. Make this circle about 28 cm across (the representation of the size we think it is). Then make a tiny dot anywhere away from the centre (since we know that we are not the centre of the universe).

Now using a compass, draw another circle 14 cm away from the dot (28 cm in diameter). Call this circle the Visual Universe.

You will immediately note that part of the visual universe doesn’t actually lie in the theoretical universe. If this were true, then we’d have actually discovered the edge of the universe on one side of it.

But we haven’t, and since we can visually see this missing part, it must mean that the Actual Universe is bigger than the Theoretical Universe.

As scientists tend to do, you can increase the size of the theoretical universe until you create a better telescope…only to discover of course, there’s more universe out there!

Answer 3

Mike's previous answer was a good one - and he's one of the nicer guys in this category who knows things you didn't get any of the real assholes. Space can expand faster than light - there is nothing to restrict this. It isn't "just written", it is the result of decades of observations being formulated into a scientific theory. The theory fits the data, the theory effectively predicts new data points which we have then observed - it's a good theory. Not a fact or a law, it may yet be proven falsifiable, but a damn good theory. Just because you don't buy into it, does not mean that it is any less valid - it just means that you either have a better theory that outperforms it, or you don't understand it and cannot make an informed decision. Science doesn't make things up - science seeks to explain observations. When an explanation fails to explain new observations, then it gets revised. There has been nothing to indicate that this particular concept is in need of a revision. We didn't start at a central point. Expansion happened (and is happening) everywhere. It isn't something you can visualize, and it is hard to pull your mind away from the concept of a typical explosion or expansion which does come from a central point. Without a much more extensive background in the math and physics (more than being "well read", whatever that means), you're not going to understand this beyond the analogies like the rubber band. EDIT: Apparently you didn't know that this is BY FAR the angriest category on this website. It is easier to wind these people up than even categories like religion or parenting. Why do you think people troll here so often?

Answer 4

Nobody knows the exact size of the universe. A quick google search will show you many conflicting answers to this. All we know that is we can see up until the particle horizon of the observable universe and that's it. Anything happening beyond the particle horizon hasn't had enough time for the light being emitted there to reach us here on Earth. This is one of the ways that we know the universe is expanding.

I personally beleive that the speed of light is not a boundary. Prior to 1947 people thought that the speed of sound was a barrier.

Answer 5

Our universe is infinitely large. That galaxy you see 14 billion light-years to your right, they can't yet see the galaxy you see 14 billion light-years to your left. But both those galaxies can see you (well, theoretically, at least). Likewise there are galaxies farther than 14 billion light-years away that we can't see yet, but other galaxies can.

Answer 6

I think that you may have your facts confused. I believe that the cosmos is approximately 15 Billion LY in 'diameter'? In other words, it is approximately 15 Billion LY from one 'end' to the opposite. Evidently, though, it is expanding rapidly.

Answer 7

28 / 2 = 14.

Next question.