Donate SIGN UP
Gravatar

Answers

41 to 60 of 67rss feed

First Previous 1 2 3 4 Next Last

Best Answer

No best answer has yet been selected by Marshwarble. Once a best answer has been selected, it will be shown here.

For more on marking an answer as the "Best Answer", please visit our FAQ.
D***! Nanny has edited out my double and triple spaces, making a nonsense of my attempt to render expansion graphically, as I'd intended.

“It didn't so much occupy less space, it consisted of less space.”

So what was beyond the space it consisted of less of, OG? I cannot get to grips with the notion of “nothing” – not even space. If it ends or if it is “bound” or whatever other term you use, beyond that end or boundary there must be something else. The idea of infinity I can just about grasp – albeit uncomfortably. The idea of “nothing” (when “something” comes to an end) I cannot.

Anyway, this is my theory. There has always been an infinite amount of space. Always has been, always will be. It goes on forever no matter what direction you travel. In that space is an amount of matter. It may be finite, it may be infinite, I don't have a view. My leaning is towards an infinite amount (simply because there is infinite space and there’s no reason to believe the bit we can observe is any different to any other bit). Either way presents problems. An infinite amount of matter in an infinite universe sounds OK until you start trying to calculate the average density. A finite amount of matter in an infinite universe likewise. But no matter. In either case, the distribution of that matter has varied across time (which I believe also extends backwards infinitely and will do so likewise into the future). We are just witnessing the merest blink in all that.

All aspects of my theory present various problems, I know. But so does any other theory. The advantage of mine is that it is far easier to grasp (and probably just as plausible) as anything else. And equally unlikely to ever be proved right or wrong.

We could share tonight’s jackpot, OG (or is £25m not enough for you?) :-)
Yours may be easier to grasp, but it is certainly not more plausible. Notably less so, for various reasons. Seems to me for starters that it falls foul of Olbers' Paradox (an infinite universe that has been around for infinitely long would be bright in all directions), so straightaway the idea of matter extending infinitely in all directions is blown out of the water; ditto the age point. And then it seems to be postulating a universe in which time and space and matter are all disjoint concepts, functioning completely independently of one another -- another idea that was ruled out as plausible long ago, first with special relativity (time and space are combined) and then with General relativity (and both space and time are shaped by matter).

So in summary what you are suggesting isn't even remotely plausible, contradicted by a century of theory and experiment, and to put it on the same platform as the current orthodoxy is mistaken. Of course, the current scientific models for the Universe are also wrong -- but wrong in a rather different way, because they are right, so far as they go.

"...beyond that end or boundary there must be something else."

Why? This assertion is quite simply unsupported. There may well be something else, of course. But there doesn't need to be.
To my simple mind, as I said at the start, if the universe is expanding then it must presumably be expanding into the "not-universe" for want of a better turn. And if there is a "not universe" then the universe cannot be infinite.

Infinity is surely in any case only a theoretical concept. What we get when we divide by zero. of think of where two parallel lines meet. Or that the last number is. Perhaps what some people mean by "infinite" is actually never ending. So the universe could be said to be expanding infinitely, but is that also thought not to be likely? (Over to Jim :-) )
Oh lor...

The problem is that people are, quite naturally, tied down to what they can experience or easily imagine. So if someone says that the Universe is expanding then most people might think of a balloon (and indeed often that's used as an analogy), that certainly does expand "into something". This is not really the case (or at least, it doesn't have to be). Instead the Universe creates its own spacetime as it expands, and the net result is that objects can be measured as further apart than they were previously.

There is no perfect analogy to what is going on. The best I can do is return to the 2D humans on earth. Being two-dimensional, they need two dimensions to measure their position on their Earth. If they explore it all, they will soon learn that at least one (and in fact both) of these two dimensions is closed -- which is to say that you can describe every point in their Universe using a finite range of numbers -- say, 360 degrees of latitude, and 360 of longitude, and Every point on earth will be covered. In their world, then, someone sitting at 365 degrees latitude, measured from a starting point, would be on top of someone at 5 degrees latitude. So what is beyond 360 degrees? Nothing. Literally nothing. Again, it doesn't make any real sense to ask the question -- all you can do is start describing the same space again with a new set of numbers, but this set is redundant.

This is the kind of situation we are talking about. The closure of space-time in the Universe would imply that you eventually stop needing more numbers to describe your position in the Universe, because you just end up redescribing the same point you were at before. What, then, is beyond? It isn't even a valid question.

The only way it might make sense is if you found -- as our Earth-people might -- that there is some entirely new dimension, extending beyond the confines of the observable Universe. In this analogy, that direction would be up, as opposed to North and East.

Asking what is "Beyond" the Universe, then, only makes sense if either:

i) the dimensions that describe the Universe are bigger than the Universe itself (ie you run out of Universe before you run out of numbers in a certain direction)
ii) there are more dimensions than just three spatial and one temporal direction.

The first is actually true -- so far as we know, at least -- with respect to time. Although the Universe has an apparent beginning, it doesn't necessarily have an end, and may continue to exist forever. We'll have to wait a near eternity to find out though.
There is nothing beyond the space for this universe. The space in the universe is all there is. I think the concept of "nothing" is just something one needs to accept as one can not show "nothing". All we can get to is inside the universe and then that's "something".

[i]One of my occasional reflections is thinking about why there can be anything other than "nothing". Why would "something" be the default state rather than "nothing" ? Is it not more comfortable to think "something" needs to cause "something" to exist, whilst "nothing" needs "nothing" to exist ?[i]

There is not a "not-universe" to expand into. Unless one thinks of other dimensions and branes (thus the pun earlier) there is nothing more than the universe you are in for you. (And one brane doesn't expand into another but may collide :-) )
Darned lack of italics :-(
"...beyond that end or boundary there must be something else."

Why?

Because you can’t have “nothing”, jim. You must have something – even if it’s completely empty space. And if and where something ends something else will begin.

I think there are explanations to Olber’s paradox which accommodate an infinite universe including, of course, that in the expanding universe we seem to be witnessing at present the “red shift” exhibited by distant stars reduce their ability to illuminate vast regions. So a star beyond the edge of the observable universe would be receding at such a rate that its energy would be diminished towards distant observers.

I’m only a simple grammar school lad, jim, and I certainly don’t have all the answers. But it strikes me that the issue is being unnecessarily complicated.
Anyway, all by the by. As I said, my theory is fraught with difficulties but no more so than most of the others. And I’m comfortable with mine. But I do appreciate you taking the time to share your knowledge even if I my feeble brain cannot quite grasp the theories and principles involved. :-)
Because you can’t have “nothing”, ***. You must have something – even if it’s completely empty space. And if and where something ends something else will begin.

This has kept me awake from time to time, i.e how can the universe end but then how can it not as there would need to be something the other side and where would the other side end?.
That's exactly what is being discussed OL. A thing can be unbounded yet still be finite. In which case the question of what is the other side of the boundry isn't a valid one. The surface of a ball is unbounded: move over it and you never reach a place where it ends. But the surface is still not infinitely large. No end, no boundary, and thus no other side.
When I've gone I'll let you all know.
Question Author
Wormholes, parallel universes, string theory, Heaven, Hell, Purgatory, dreamstates, places stuck in time.

Some of these might be c***, of course!
@jim360

Why did Hubble reverse-extrapolate to a pinpoint starting condition? Why not any other shape?

If space is expanding between pockets of matter as of now, could we end up with the familiar microwave background map from any old starting shape or only that pinpoint?

"The surface of a ball is unbounded: move over it and you never reach a place where it ends. But the surface is still not infinitely large. No end, no boundary, and thus no other side."

Agree 100% OG.

The trouble is there are things beyond the ball.
Jim 360 said somewhere that as the universe expands it creates spacetime at it's expanding edge. Which is how I understand it. So there can be nothing, not even time, beyond the universe.
"The trouble is there are things beyond the ball."

Then again, from the perspective of the [surface of the] ball, these other things exist only in a higher dimension -- which is to say that both these things are not part of the ball, but also that they aren't necessary for the ball to exist.

It's a very difficult thing to conceive and it's completely reasonable to struggle with it. Imagine something asks you to picture a circle. Then you'd probably imagine one that had been drawn on a piece of paper, or maybe somehow floating in mid-air -- at any rate, it's essentially impossible to visualise the circle entirely on its own. Even if you did, you would presumably have to be standing somewhere in the distance in order to be looking at it. All of this, though, is baggage. It isn't a part of the circle, and it would certainly be possible for the circle to exist without you needing to stand somewhere outside to look at it.

When discussing what lies "beyond" the Universe you have to try to shake off all of this extra stuff. You have to allow for the fact that the shape of the Universe anyway can't be visualised properly -- it is a four-dimensional hypersurface, and humans just can't cope with that. Too, you need to allow for the fact that dimensions aren't necessarily infinitely long straight lines -- the geometry of the universe is far more complex, and allows for closure in a manner similar to defining your position on a circle or the surface of a sphere. You have to allow for a whole host of other things besides, but these first two are the killers. It is literally impossible to picture the Universe accurately.

The key point, though, is that whatever is "beyond" our Universe is certainly part of a higher dimension, or indeed several. Incidentally, invoking extra dimensions still would lead to the same conceptual problem, because once you've exhausted all those dimensions then beyond *them* there would again be literally nothing. The only way to resolve your dilemma is not if space is infinite, but if the number of dimensions needed to define your position is.

Anyway, there's nothing beyond the Universe (possibly), because the question doesn't even make sense (unless there are more dimensions (which there might be)).

* * * * *

To answer hypo -- I'm not totally sure that Hubble's done any extrapolating itself. I may be mistaken on that, but most of what we know about the shape of the early Universe should be due to studying the Cosmic Microwave Background. From that you basically see that the Universe is (almost) the same in all directions, which implies that it should have started off as sphere-like. On the other hand, there has been some interesting work testing the idea that the universe has or had other shapes, or is even smaller than it appears. So far as I know, none of this has led anywhere particularly, but it's certainly worth further testing.
I promise I won't make any more contributions to this thread :-) :-)
Jim, //Anyway, there's nothing beyond the Universe (possibly), because the question doesn't even make sense (unless there are more dimensions (which there might be)). //

Back to square one. You don't know - and neither does anyone else.
the fact is that not one of you know. not even mr hawkins.
Nobody knows! Jim has done a great job of explaining it. If he can't visualise what the universe "actually" looks like then I don't feel too bad that I can't.
I've been thinking about this for years. It's a fascinating topic. Will we ever know?

41 to 60 of 67rss feed

First Previous 1 2 3 4 Next Last

Do you know the answer?

Is This All There Is?

Answer Question >>