Physicist: Probably nothing. We do know that the universe doesn’t need anything to expand into, and we haven’t seen any evidence that there is anything outside of the universe. But there has still been some speculation.
In the last hundred years physics has gotten pretty weird, and defining “universe” has become a little tricky. So, in what follows I’m defining the universe as “all the places that could be connected to one another by a sufficiently long rope” (never mind how the rope got there).
Having never been outside of the universe, it’s hard to discuss it with any certainty. Most of the theories about the outside of the universe fall into the “I can’t say you’re wrong for sure” category.
We can say that space isn’t “made of anything”, and that it doesn’t need any kind of “higher space” to exist in. If space did need some other kind of space to live in, you find that the question just gets pushed back. After all, what’s outside of that space?
In a conversation about spacetime often as not you’ll have some unpleasant and unrepentant jackass drawing parallels to rubber or sheets or something else material. It’s not that these metaphors are misleading (although they are a little) it’s that they reinforce the quiet, underlying assumption that space is made of something, and that it needs somewhere to be. About the best definition of space is “Space is nothing more and nothing less than what rulers measure”. If you think about some of the properties of space, as described in relativity (both general and special), you find that it has all kinds of properties that a material can’t have.
For example, there’s no difference whatsoever between moving and being stationary. So, it’s impossible to meaningfully talk about “moving through space”, when you may as well be motionless. Even worse, you can fit an arbitrarily large amount of space within any volume (as measured from outside that volume). Think: Dr. Who’s TARDIS. Or, if that’s not your thing: the diameter of a circle drawn around the volume can be arbitrarily great, while the circumference stays finite.
Point is: space isn’t stuff. And the universe doesn’t need anything to expand into.
When you picture the universe as a whole it’s almost impossible not to think of a fish bowl or a bubble.
The Universe: Nothing like this.
Implicit in that picture of the universe is an outside. However, that outside is defined in terms of space, and all of space should be inside the universe. When you try to talk about the outside of the universe you find yourself asking questions like “okay, where are you?” or “how far from the universe are you?”, you know, the types of questions that really rely on some notion of position and space.
That all being said, there are some theories that do talk about things outside of the universe. There are some proponents of M-theory who claim that the universe could be a sheet floating in a higher dimensional space, and that there are other universe-sheets floating along side us, just a tiny distance away. Although the other sheets act exactly like what almost everybody would call “other universes”, it’s would be slightly more accurate to say that the collection of sheets and the higher space they float around in are all part of the same “super-universe”. They’re still at least a little connected to each other.
Aside: Btw, when physicists want to talk about more than three dimensions they (being born and bred here) like to knock off dimensions to help picture things. So, if you want to imagine the universe in a higher dimensional space, just get rid of a dimension. The universe goes from a 3-D volume to a 2-D “sheet”.
The universe may also have “bubbled off” of some other larger universe, or spontaneously started, or who knows. If there are truly other universes, or any other stuff outside of our universe, it’ll be “causally separated” from everything going on here (or that has or ever will go on here). Rather than thinking of other universes as being “somewhere else” it’s better to think of them as “in every way independent”. You can’t even sensibly talk about “going there”.
Science (and more generally: everything we can know), being based on observation, inference, and experience, can’t say much about things entirely outside of the universe. We can infer, and make some spectacular guesses, but that’s about all. In another 20 years or so our entire approach to the nature of the universe will have completely changed (it always seems too).
It’s funny that you posted this today, with the example of explaining gravity in terms of rubber as xkcd posted a comic about this today.
Clearly, someone around here is psychic!
sorry to bug you guys again, but what other options do we have to define stuff in besides space?
“In” implies space. So the options are kinda limited.
well, um there has to be a start of the universe, which means there was an OUTSIDE of the universe right? there can’t just be NOTHING its impossible…
Based on our way of thinking one would surmise that there would have to be an outside to the universe. But at the same time one must wonder what this outside would look or feel like; and how possible is it for this outside to continue on indefinately. The number “0″ has a value of nothing, but it is still something… it’s property is still “zero.”
Yep, whilst this remains a enigma the major Faiths have every right to hold on to the Old testament God.
The eternal is one,that belief has never changed,but physics moves the goal posts on a whim.?
Lincoln was right,about intelligent foolers,
The universe did not emerge into an empty void , it brought the void with it and we call that void spacetime
The answers to these and other questions are often overlooked because humans tend to apply rules when seeking answers to the unknown. Who says the unknown follows rules?
I think Knook has hit it on the head it is very unlikely that the unknown, that we are such a very small part of would follow the rules our scientists logically discover, no matter how great their scientific achievements are because we think and reason logically while the unknown just acts.
If the universe came into existence after big bang , where did the big bang took place and what was there before big bang . where is are universe ? this is biggest question in my mind.
There was an article recently claiming there might be proof that the universe is a computer simulation and we’re all living in it. Wouldn’t in that case the space be a function of software, an abstract ‘space’ accessible inside the program, while anything outside it would be unknowable (though still abstract)?
If we define the universe as something that contains everything that exists (space, time & matter) the answer to the question of what exists out side of the universe is ´not the universe. Its the same answer as to what exists out side of your self. The notion of ´you contains everything that you are made of, and is limited to the outmost extent of ‘you. Everything out side of that boundary is, in fact, ‘not you.
Interesting topic. I think not only should we be studying the forces of physics but also how our minds work and how we perceive the commotion going on around us. What we “feel” to be the truth out there will never be verified. We will only get an idea of how things work by studying what we possibly can observe. Everything else is part of the answer that we can never piece together. For there is no answer. “Laws” change Infinitely as we reach a limit of observation. Imagine how large an atom would be without any one there to observe it. The very fact that we exist and give things “size” and label things is part of the problem.
There is another theory known as “The big rip” where basically, the expansion of the universe will accelerate to a point where ever atom in it will split and explode. What if this is just the same universe recycling itself over and over and the big bang is just the explosion of the atoms ripping?
I’m certainly no physicist and I don’t have much knowledge on this sort of thing. Im just a curious 12 year old.
This universe or big bang, is nothing more than a local event in an infinitely large universe.