A few days left to check this film out...

[CoxRox]

Thanks guys. I wish I knew all this stuff. I don't even know how to put smileys in the shout box??

[Edwardo Piet]

It was a good film. Thanks for informing me CR.

[CoxRox]

The bit that I was particularly interested in was the mathematician who had a theory of many dimensions and time always exisiting. It think it's to do with string theory. What he was proposing seemed to me to be going into the realms of 'imagination' for want of a better word. Very interesting though..

[Edwardo Piet]

You mean that, was it, french guy with the 'branes' thing? And that time has always existed? That was my favourite bit too. Very interesting.

[CoxRox]

Yes, him. I wish I understood the mathematics behind his theory? I love these kinds of films because I can just about understand the contents and Brian Cox is good with explaining things for the lay person.

[Darwinian]

You see, now you're talking my kind of language.

String theory, M theory, multiple universes, time as a dimension that we travel through at the speed of light..

I've always thought of time as a bit like one of those interactive books were if you make one decision you turn to page 10 and if you choose another, you turn to page 15, or whatever.

The quantum world suggests that every possible action that could ever take place is played out in one of these realities and that each universe, at the scale of the atom and smaller are linked with each other. It's not that particles necessarily wink in and out of existence from nowhere, it's simply that they are whizzing through the multiverse and we simply get a glimpse of them.

Also, the theory of multiple dimensions is very real. The trouble is that we only exist in three physical dimensions and no matter how hard we try, we simply cannot imagine where a fourth or fifth etc. would be. This does not mean they don't exist, in fact, if many branches of physics and mathematics are to make sense then they must.

The image below is a tesseract, or hypercube. And as my little sproglets will tell you (because I've drummed it into them) it's the 2D representation of a 3D shadow cast be a 4D cube.



The Universe itself is a case in point. The Universe, as far as can be determined, has no edge and no centre and yet is finite in scale. Also, the way that the Universe is expanding strongly suggests, to me anyway, that our three dimensions are acting in exactly the same way as the surface of a balloon that is being blown up.

On the surface of a balloon you can have no centre and no edge unless you travel through the 'mythical' third dimension.

ooh, I've found a balloon piccy..



And there's no reason why time could not have always existed. All we have worked out so far is what happened just after the big bang (if there was one ) and we know nothing of before.

[CoxRox]

Thanks Darwinian, very interesting. Love the hypercube. Do you think the 'space' that the universe is expanding into, is infinite and has always existed? Also, these other dimensions: what would you say is the biggest proof they exist? Do the sub atomic particles disappearing and then reappearing suggest these other dimensions or do they disappear into another universe or dimension, and it's actually a different particle that seems to reappear, which itself is coming from another dimension?

[Darwinian]

The only, sort of, evidence that I can think of right now to suggest the existence of multiple dimensions is gravity.

There are four forces in nature. The strong nuclear force, the weak, electro-magnetism and gravity. The first three are all explained very well but gravity is still a bit of a mystery. The problem with gravity is that it is so weak. You may think that it is strong as you fall down the stairs but you have to remember that you have the entire planet pulling you down.

Consider, on the other hand, how strong electro-magnetism is when you use a simple magnet to pick up a nail. The entire planet cannot compete with the magnetic pull of a little fridge magnet.

One of the suggestions that is widely held to explain the apparent weakness of gravity is that it is able to 'leak' away from our three dimensional universe through other dimensions and therefore what we experience is basically a diluted effect.

As for your first point. Strictly speaking, the universe isn't expanding into anything as it's space itself that is getting bigger and thus, things are getting further apart. It's only the local effect of gravity that stops galaxies and star system from being stretched apart, although, if the current theory for dark energy is anything to go by and the expansion continues to accelerate then not even gravity will be able to resist this expansion and eventually even matter itself will be ripped apart leaving just a cosmic soup. But that's another story

[CoxRox]

Maybe there are more forces than we are aware of (I'm not intending anything spiritual there, in case you wondered, although that's a thought..... ). The leaking thing sounds like conjecture. Why does it matter if gravity is so weak or rather why is that a mystery? Is gravity the same strength in the whole universe?

Also, how can the universe be expanding into nothing? Surely it's expanding into a space? My dad told me something recently about Einstein saying space has physical properties. I think it was 'space', can't remember now.

[Darwinian]

Because gravity should be just as strong as all the other forces. This is one of the problems with trying to come up with the theory of everything.

At the moment the two theories which explain the universe on the very large scale, general relativity and on the very small, quantum mechanics don't get on very well with each other and one of the main problems is that of gravity. It 'should' be just as strong as the other forces but it is not. That's the mystery.

NO, the universe is not expanding into space. I agree that it's a very tricky concept to get your head around but it is simply the space itself that is expanding. i.e. the distances between points that are getting larger. Space, by definition, cannot be expanding into anything as it is space itself.

It's easier to understand the other way around, in fact I put this theory on the science forums with no real objection. Instead of space expanding, imagine that all the matter in the universe is shrinking. So, from our point of view, everything is getting further and further away from everything else.