The border of the universe?

[gugglebum]

We have all heard the theory that the universe is expanding - which has always made me think: Expanding into what?

If the universe is supposedly all there is, how could it be expanding? Something without a border can't really expand, can it?

Also, if it's expanding, into what is it expanding? There must be something on the other side into which the universe is expanding.

Sorry I know this isn't very scientific and probably very misinformed but I've always wondered what the latest research and theories on this are? Anyone care to enlighten me? In layman's terms if possible, I'm not much of a scientist!

 

[vegan]

the universe could very well already be infinite
expansion would then just mean things are getting further away from each other in an already infinite space

or it could be closed, and expand as the surface of a ballon that you're blowing into (same idea with 2 more dimensions)

or the universe could be finite, and create space to expand into as it does

or...

 

[knight_marshall]

i remember once reading about negative matter, and i got the idea that this surrounds our universe. The only problem, what is beyond the negative matter.

I believe that our universe does have a border, but beyond it is simply another universe, probably pushing against ours as ours pushes against it, like two balloons being blown up next to each other. Of course they're is probably that negative matter in between holding us apart with an anti-vacuum effect.

 

[L2R]

Space bends and stretches. There seem to be phenomena that influence the shape of space. Objects of large mass seem to distort the space in and around them.

The expansion of space is not only unstopping but it's also accelerating. This would seem to indicate some sort of pulling drive on the boundaries of space. Some think that there is a repelling force somewhere in the universe causing this acceleration, but i don't buy that, what with my almost complete lack of knowlege on the subject.

 

[gugglebum]

Wow I'm even more confused by all this now

"the universe could very well already be infinite
expansion would then just mean things are getting further away from each other in an already infinite space"

But how can something infinite stretch? I mean, if there's no borders, how can you measure it stretching? It can't get bigger if it's already infinite...

"or it could be closed, and expand as the surface of a ballon that you're blowing into (same idea with 2 more dimensions)"

But what's outside of this surface of said balloon? If there's a border, this means there's something on the other side.

"or the universe could be finite, and create space to expand into as it does"

But what does it create this space from?

"or..."

Or ... I just hope my children will live long enough to learn about this. I'd love to one day find some reasonable answers, but I guess I won't live long enough. At least I've stopped smoking I guess that increases my chances of one day finding an explanation for all this!

This is probably the most interesting things human will ever find out - how far does the universe go, and what is there after it? Is there a wall to it? Or is there a point where anything that goes past it just ceases to exist.

The idea of something being infinite just strikes me as impossible - there's always a start and an end. Maybe the universe IS the only things that absolutely infinite, but I'm afraid humans won't find this out, ever.
Our only chance is finding (or being found) by some highly evolved alien life-form that teaches us about this, but until those little green men come down, I'm afraid all our answers are gonna be shots in the dark!

Or maybe Men in Black was right and our whole universe is just the size of a little ball some huge aliens play with

Ps. Vegan, no busco que me respondas a estas preguntas, solo queria plantearlas para ver si alguien sabe de alguna teoria

 

[SmC]

I am confused, how can the universe expand?That doesn't make any sense.

 

[knight_marshall]

light travels in all directions, granted affected by gravitational pulls, but it escapes these too. The edge of our universe is the point furthest away from the center of our universe to which light has travelled. But light continues to travel in the direction away from the center, in all directions... at the speed of light. As nothing can move faster than the speed of light, to attempt a measurement of this space with any means would only allow the light to travel further, thus making our measurement incorrect. We can't measure infinite, because infinite is this distance that grows so fast we cant measure it.

Space is infinite, infinite is a finite size, but an impossible size to measure... theoretically this measurement would have to be in the smallest element of space... light. And theoretically the moments in time (time taken for light to move the space of itself, and therefore smallest fraction of time possible) may outnumber the number of this smallest element... perhaps they are equal... buts thats a whole other discussion.

 

[redeemer]

Check out this thread. It has some pretty cool explanations by zorn.

 

[mr_p]

the universe could very well already be infinite
expansion would then just mean things are getting further away from each other in an already infinite space

or it could be closed, and expand as the surface of a ballon that you're blowing into (same idea with 2 more dimensions)

or the universe could be finite, and create space to expand into as it does

or...

or this universe we inhabit is a cell for a giant magical 7 headed slimey space being and that universe is the molecule for our elementary particles

 

[Cyrus]

I KNEW I WASN'T THE ONLY ONE THAT THOUGHT THAT! (well, something along those lines. that we are actually a cell in a larger being, thats a cell in a larger being.... and so on)

 

[Raw Evil]

You mean like a fractal? I like fractals...

 

[Smyth]

I think it is expanding in the sense that if it is xxxxxxxxxxxxxxxx miles to another planet now, in 1000 years time it will be xxxxxxxxxxxxxxxx + 1 miles. So although the rate is very small, it is nevertheless still expanding.

But u wont be able to ever measure anything really cosmic, humans just dont have the capabilities. It has been considered theoretically possible based on quantum mechanics to do far out crazy stuff like warp space into the fourth, 5th, 6th and 7th dimensions - but this is beyond human capabilities.

I know this because a guy was doing work on 'worm holes' for his undergraduate research project. He says that it can be done if u have a strong enough electromagnet but that even the strongest electromagnets can only make a fraction of the cosmic energy required to open up a worm hole.

Maybe if someone is suicidal enough to drive a space rocket down a blackhole, they might just kill themselves or they might find their way into an alien planet.

 

[complexPHILOSOPHY]

Think of space-time as an infinite rubber sheet. Conceptualize yourself sitting down on what you percieve is the center of the rubber sheet. In all directions you see an infinite rubber sheet extended into an horizon.

Now, let's place people at fixed points along the inifinite rubber sheet. If you asked each person from their vantage point, if they believed they were at the center, they would say, 'yes'.

Now we have an infinite rubber sheet with people sitting at fixed points, each one believing that they are at the center.

If we were to stretch the infinite rubber sheet, everyone would expand away from each other equally, each believing they are at the center of the infinite rubber sheet -- it's an optical illusion, nobody is at the center because there is no center but everyone percieves their position to be the center.

This is analagous to the stretching of space-time and why it's so difficult to pinpoint our position in relation to the universe.

Throw in the laws of physics and you have the highly ordered universe.

Asking someone to explain what lies beyond the edge of the universe is like asking someone how to go more northern than the north pole.

I posted this in another thread but I figured it pertains to here.

 

[PGTips]

Maybe if someone is suicidal enough to drive a space rocket down a blackhole, they might just kill themselves or they might find their way into an alien planet.

They might, but they'd make it there as their constituent particles after being shreded by tidal forces.

 

[complexPHILOSOPHY]

They might, but they'd make it there as their constituent particles after being shreded by tidal forces.

If someone offered me the opportunity to commit suicide via a blackhole, I'd do it in a second.

Speaking of which, I read somewhere about some Quantum Mechanical Suicide Machine -- I need to find the paper that discussed it.

 

[PGTips]

If someone offered me the opportunity to commit suicide via a blackhole, I'd do it in a second.

I can think of less painful ways of topping yourself than having your body stretched so that you are literally pulled limb from limb! Even if the view due to light bending was somewhat interesting.

 

[randomlily]

i remember my grandpa saying something about this stuff years ago, and he sayd the human brain simply cannot comprehend that the universe just keeps going and going...

but neway i rememba a documentry a while ago and they were talking about this expanding universe and such. from what iv learnt and remember the universe is expanding like the above rubber stretchy description, evrything is moving away from everything else.

from our point in the universe we are becoming more aware of objects (stars/planets n stuff) millions of galaxies away. for example these things may have existed for billions of billions of years, but because they are so far away the light from them (obviously traveling af the speed of light) takes billions of billions of years to reach us. when it finally does reach us we only see the light from whatever the object was all those billions of years ago, not what is is NOW. whatever it is NOW we wont know for more billions and billions of years when the now light reaches us). because there SO far away even with light traveling at the speed of light, the light takes all that time to reach us. what does that have to do with it expanding? i think thats more expanding in terms of what exists to us. we see more things further away being created, but actualy theyve existed for ages, and forever we will find this happening with even further-er away objects, again this is more expanding in terms of what we know to be the universe.

another idea is that there are all the millions of billions of galaxies n such, and and the universe (all these galaxies n matter in existance) is expanding outwards away from each other...what are they expanding into? past the universe stuff theres just infinate nothing.

oh n the other idea iv had in my head since i was a kid is that everything is kinda in a loop. like you go sooooo far in the universe u eventualy end up back where u started, no matter which direction u go. kinda like a sphere but in every single possible direction (again too much for human mind to comprehend)

im not saying i think any of these theories are correct their just ideas, either formulated from what iv heard or learnt or tried to figure out myself. and im really sorry if it doesnt make sense, its so hard to put things like this into words.

 

[PGTips]

i remember my grandpa saying something about this stuff years ago, and he sayd the human brain simply cannot comprehend that the universe just keeps going and going...

Certainly if you say to someone 'Imagine an infintiely large expanse' it's not going to happen but we most certainly have ways of describing infinitely large things. Huge chunks of cosmology and general relativity relate to 'asymptotics' where you consider quantities going to infinite. Truely sad though it may be, I've several space-time diagrams known as 'Penrose Diagrams' pinned on my wall (revision help) right now which relate to infinitely large asymototically flat space-time around certain types of black holes. They are one of many useful tools in cosmology.

from our point in the universe we are becoming more aware of objects (stars/planets n stuff) millions of galaxies away.

Actually the expansion means we're seeing less and less objects in the universe. True, the volume of space we can see if ever expanding, but more and more material is getting expanded away from us.

Eventually (if the universe continues indefinitely) we'd only be able to observe our logical super cluster, which is kept near us by gravity. Everything which isn't attracted to us enough by gravity will be carried away from us by the expansion.

another idea is that there are all the millions of billions of galaxies n such, and and the universe (all these galaxies n matter in existance) is expanding outwards away from each other...what are they expanding into? past the universe stuff theres just infinate nothing.

This is another area where sometimes mathematics is better than a physical idea in your head. There's plenty of differential geometry which covers infinitely large multidimensional entities but noone can get a mental image of. Why does space-time have to have an edge? It doesn't. Perhaps nowhere in the universe you can stand, point and say 'Over there it nothing, it is outside the universe'.

oh n the other idea iv had in my head since i was a kid is that everything is kinda in a loop. like you go sooooo far in the universe u eventualy end up back where u started, no matter which direction u go. kinda like a sphere but in every single possible direction (again too much for human mind to comprehend)

It's known as a closed universe. I think Einstein's example was "If you starred hard enough you'd see the back of your own head".

its so hard to put things like this into words.

Hence sometimes the mathematics makes things way easier. That is, once you've learnt the mathematics 8(

 

[doesntmatter]

maybe expanding is and outdated word.

everything is just moving.

 

[Akoto]

Eventually (if the universe continues indefinitely) we'd only be able to observe our logical super cluster, which is kept near us by gravity. Everything which isn't attracted to us enough by gravity will be carried away from us by the expansion.

If gravity could be strong enough to overcome expansion and maintain our supercluster, why not hold superclusters together?

Wouldnt there ever be a point where every particle is equaly spaced apart and unable to interact with eachother?