How can there be infinite space if there was a Big Bang?

Question

The average person tends to imagine the universe as a giant dome enclosing everything. This would suggest that if you traveled far enough in any direction, you would eventually reach a border you couldn't pass--the "end" of the universe.

I've read that scientists don't believe this is the case. They think one of the following bizarre possibilities: (1) If you travel far enough, you eventually come back to where you started (2) Space goes off infinitely in every direction.

I have the hardest time grasping that second possibility. And that's the crux of my question. How could the Big Bang have produced infinite space? Don't descriptions of the Big Bang suggest that the early universe had a definite size, and that it got bigger and bigger? If it's infinite, then it can't have a "size." And for those scientists who don't believe there are other universes, what IS this infinity of space? Is it just infinite nothingness in all directions? Or would there be galaxies and other "stuff" going on forever? If so, then how did that all get produced? It certainly couldn't have been a product of one Big Bang.

Answer 1

Let's forget for the moment the geometry of universe as it brings us into the nature of time and just confuses the issue.



For the sake of simplicity let's do a few things:

- Consider the universe to be a really really big ball.

- Assume that before the Big Bang, there was nothing.

- Assume that spacetime is flat (it isn't, but again just confuses the issue).



At the time of the Big Bang, matter was ejected in all directions. However more than matter was ejected, but also light.



As you know, nothing can travel faster than light. Therefore, the light that was ejected at the time of the Big Bang defines the borders of the universe.



Imagine this: Nothing exists except a single lightbulb. There is nothing else. Turn that lightbulb on. Light will begin to emit from that light bulb in all directions.



Let that lightbulb go for one second then we'll stop time. At this point, the universe is exactly 2 light-seconds in diameter.



As we travel around our time-stopped 2 light-second universe we are actually looking at the universe at various points in its short 1 second life. As we get closer to the light bulb, we see the lightbulb as it was very very recently. As we move away from the lightbulb, we see things as they happened closer and closer to the point where we turned the light bulb on.



When we get 1 light-second away from our lightbulb we see it just after it was turned on. But if we move just a little further away, we can't see the lightbulb anymore. Light from the lightbulb hasn't gotten there yet and therefore we are looking at a time before time began in our little universe. We are now outside our universe.



Now back to our own reality. Since nothing can travel faster than light and light expended at the time of the big bang is the furthest away, the size of the universe is bordered by that light.



Update for additional comments:

I don't believe anyone really is saying the universe is "infinite" by saying it has no bounds. In fact, there scientific community isn't arguing about whether or not the universe is infinite, but rather how big it is finitely.



One could say that it is functionally infinite because even if you could break pretty much every law of physics, go faster than the speed of light, and somehow pass beyond the original photons from the Big Bang, you'll have moved into a space of where nothing exists (yet), including time itself.



See this link for a better explanation: http://en.wikipedia.org/wiki/Cosmic_inflation

Answer 2

The Big Bang didn't happen at a point. The Big Bang started out hot and dense, and the stuff that is the current visible Universe started out perhaps the size of a proton. But the Universe at that time had to be at least as big as the currently visible Universe. Otherwise, the cosmic microwave background radiation wouldn't have reached us. It's been traveling in a straight line...



So, the current minimum size of the Universe is as much bigger than the currently visible Universe as the ratio of a proton to the currently visible Universe. It may be infinite in size. But it also may not be. It's certainly absurdly big.



There's not going to be a hard border at the end of the Universe. It may wrap around in some strange multi-dimensional topology. Then it could be finite in size but without an edge. Or it could just be expanding faster than you can possibly travel, so you'll never see an edge.



The Universe could be infinite in size and still expand. Twice infinity is still infinity. It just becomes less dense.



Since the Universe started dense everywhere, the rest of the Universe looks just like it does here, with galaxies, and so forth.



> How can the space have "already" been there, if the Big Bang was the beginning of time itself?



The trouble with the question is that it's thought that there was no time before the Big Bang. The initial event started with everything. There was no prior cause, no prior objects.

Answer 3

Great question. I'll take my best shot at it.



First off, nobody knows what causes the big bang. I say "causes" and not "caused" because the biggest misconception about that theory is that it's finished. It's not -- we're still expanding right now. (We're still mid-explosion, if you want to think of it that way).



The scientists who think that space is infinite are implying that there is infinite nothingness in every direction. This is because, as far as we know, the expansion we see from the big bang is a property of matter (or, more accurately, the space-time background that everything is fixed to).



Try to think of it in 2D, and it's simpler. Imagine yourself on a huge sheet of plain white paper that goes off forever in every direction. You're sitting there, and you decide, "I'm going to draw a grid on this paper." So you start drawing squares attached to each other. You work in a circle so as you go, there is this ever-expanding grid on what was once white paper. Someone behind you draws little galaxies and particles on the gridded part.



That grid is the space-time continuum, and the white paper beyond it is the infinite nothingness. The grid has a size, and that's what some scientists mean when they say "size of the universe." (Though there is some disagreement there too...). And the person behind you is drawing all the matter that (again, as far as we know) can only exist once the grid is set down.



Does that help?

Answer 4

i think that is the position they get the time period 'the only top frontier.' anybody can do i think, is speculate. i have continuously considered area as one of those infinite area with not something in it, and the universe as a collection of count number someplace in that nothingness. in this feeling, the large bang idea would not contradict infinite area in any respect, because at the same time as the easily universe isn't infinite, the universe isn't really 'area', and the enviroment of literal area itself the position that universe is residing can hypothetically flow on continuously. that is a rapidly ahead view, notwithstanding it type of feels incorrect someway... We for sure do not recognize all the solutions. I see you position this question interior the 'faith and spirituality' area. Universe and beginning idea might want to be scary i think, as maximum theories look to end in some bleak way, reminiscent of how the daylight will flow out, yet I have self belief God will make each and every thing all top interior the acceptable. He made this universe interior the first position. perhaps eventually we will get to the point the position we may be able to make certain for positive how the physics of the universe fairly function. P.S. And in all likelihood we'd want to be on the contained in the 'sphere,' because in the different case we does not be surrounded by technique of stars and count number, a.ok.a. the universe.

Answer 5

Well, I don't think the big bang produced the empty space, only that the infinite empty space was already there and the big bang was the start of this space being 'filled up'. I have no idea how something can extend for infinity though. Isn't the Universe wonderful? ^^

Answer 6

I can't explain this, nor can anyone else. To me, it's just funny how most scientists dismiss anything supernatural or anything of supernatural nature, even though almost every single theory describing how space began (even the Big Bang Theory) is of supernatural theory. Why is that? Well, it depicts things of unnatural nature occurring. Interesting oxymoron isn't it?





One thing about the Big Bang theory and its production of space:



The Big Bang Theory is basically stating that even though there currently exists matter, space is still exploding and everything that functions in our space today, is creating new energy (new matter). Therefore, space is currently infinite. However, if space were to ever cease from creating new matter, then space would be definite. Quite the clause, huh?

Answer 7

By definition, what lies outside the universe is unknown and never can be known. The expanding universe is essentially creating new space-time.

Answer 8

Exactly! Smarter than the average bear.



There have been no discovered infinities in reality, it is a concept, like perfect.