What's the medium?

[the Jester]

(cross posted from the Circus)

I am getting no love over there, so I'm cross-posting here. Hope one of our resident physics folk can help me out!

I'm slightly familiar with brane theory, on the layman's level, but I have realized I have a major question about it. What is the 'medium' that the various branes are within? (Is there a medium at all?)

Thanks for any insight anyone can provide!

 

[Umbran]

If I recall correctly, just as a standard universe does not have to exist within something, same goes for branes. They just are.

 

[the Jester]

If I recall correctly, just as a standard universe does not have to exist within something, same goes for branes. They just are.

Do they have some kind of meta-location or something? How do they 'intersect' (which kind of thing, if I understand correctly, is possibly the trigger event for the Big Bang, right?)

 

[Umbran]

By the way, in some places here I may seem to equivocate - I say things like "not necessarily". This is not to be evasive. I say that when the various theories either don't all agree, or make no predictions on the matter.

Do they have some kind of meta-location or something?

Depends on which version of the theories you're working with. As I recall it, it is not necessary to define any other space (real or otherwise) in which the branes exist. Alternatively, they exist within our spacetime, and not outside it. Or alternatively, our spacetime is defined by the intersection of branes, and nothing (including the branes themselves) exists outside that intersection. Or, what we call spacetime is one entire brane, and material particles must be anchored to it so that they cannot move beyond it.

(which kind of thing, if I understand correctly, is possibly the trigger event for the Big Bang, right?)

Um, well, no, not in any human sense. It is one of the brain-benders of cosmology...

In order to talk about an "event", you have to be able to point to a place and time ans say, "it happened there". But, time and space were created in the Big Bang. There can be no event beforehand, for there was nowhere for the event to take place, and no time at which it might happen.

 

[paradox42]

In order to talk about an "event", you have to be able to point to a place and time ans say, "it happened there". But, time and space were created in the Big Bang. There can be no event beforehand, for there was nowhere for the event to take place, and no time at which it might happen.

This is certainly true, but I think the question about meta-locations raises an interesting possibility, given that branes are by nature multidimensional: the (presumed) 3-brane that is our spacetime might exist somehow within another, larger brane which is 4-D or even more, and if this is true then interaction with another brane could be defined as an event within that "higher" brane. Seem plausible?

On another note, why the intense curiosity on this particular question Jester? Just helping to wrap your brain around the ideas, or is this helping you to plan some kind of game campaign?

 

[the Jester]

On another note, why the intense curiosity on this particular question Jester? Just helping to wrap your brain around the ideas, or is this helping you to plan some kind of game campaign?

I am fascinated by physics, especially when it makes my brain hurt. I want to know. I want to plumb the darkest secrets of the universe- perhaps the multiverse.

 

[MavrickWeirdo]

This is certainly true, but I think the question about meta-locations raises an interesting possibility, given that branes are by nature multidimensional: the (presumed) 3-brane that is our spacetime might exist somehow within another, larger brane which is 4-D or even more, and if this is true then interaction with another brane could be defined as an event within that "higher" brane.

You are using an old edition, our spacetime is 3.5 brane

 

[Jdvn1]

is possibly the trigger event for the Big Bang, right?)

... It's really hard, if not impossible, to name the trigger for the Big Bang. The Laws of Physics just aren't designed to deal with that. There are only assumptions (though, pretty good ones) about what happened right after the big bang.

 

[Ferret]

I;m not well versed on the branes...but I thought they were the medium? If not could someone point me to a description of them, so I can learn more?

Also has anyone seen the theory that says that the whole space-time fabric that bends with masses (forget the name) that einstein theorized, was made up of loops (in the order of 10^-35 m across))? When the fabric scrunches up enough the loops uncurl or something and spring back, essentially creating a big band?

 

[Umbran]

This is certainly true, but I think the question about meta-locations raises an interesting possibility, given that branes are by nature multidimensional: the (presumed) 3-brane that is our spacetime might exist somehow within another, larger brane which is 4-D or even more, and if this is true then interaction with another brane could be defined as an event within that "higher" brane. Seem plausible?

Yes, plausible. But there are a couple of things to note -

1)This would nto be an "event" as we think of them. It is not along the dimension we call "time". So, it isn't that it happened "before" the big bang. It would be just as correct to say it happened to the left of the big bang.

2)Aside from this sort of accounting for the Big Bang, there is no cause to consider that our universe is ebedded in a larger space. There's no evidence of which I'm aware that we interact with such a space, and quite a few reasons to think that we don't. Interactions through larger spaces are a real headache in terms of causality. Occam's Razor applies - you don't go invoking spaces that are convenient, but which aren't actually necessary.