Okay, M-theory proponents, can you enlighten me on this brane business?

[derby378]

I had somehow come to think that a "brane" in M-theory was the same as a dimension, which would make ours a 4-brane universe. But I've been sitting through all these shows on Science Channel that suggest a brane is something more fundamental than a spatial dimension. Can you help me out here without telling me to just read Wikipedia? Thanks.

[cliffordu]

1. I don't have the branes to figure stuff like this out...

which should be obvious from this attempt at grantcart-like humor.

[derby378]

2. Bwaah!

I'll give you points for catching me off guard. :hi:

[grantcart]

11. on the road - so just saw this - very funny

[silverweb]

3. Sure.

I read it for you.

"A membrane, or brane, is a multidimensional object, usually called a P-brane, with P referring to the number of dimensions in which it exists. The value of 'P' can range from zero to nine, thus giving branes dimensions from zero (0-brane ≡ point particle) to nine - five more than the world we are accustomed to inhabiting (3 spatial and 1 time). The inclusion of p-branes does not render previous work in string theory wrong on account of not taking note of these P-branes. P-branes are much more massive ("heavier") than strings, and when all higher-dimensional P-branes are much more massive than strings, they can be ignored, as researchers had done unknowingly in the 1970s."

Here's an artistic representation of a multidimensional brane:
Understand now? Me either! :D

On Edit: Now that I've read this over a couple more times, seriously and without the wise-ass attitude, it does make a certain amount of sense -- despite the fact that I'll never have sufficient smarts to really understand this stuff, fascinating as it is to me.

[derby378]

5. Actually, that's a big help

It's along the lines of what I thought a brane was in the first place. So our universe with length, width, height, and time is what we observe to be a 4-brane universe, and to hear some physicists talk, it might even be shaped like a donut. Mmmm, donuts...

[cliffordu]

6. WElll....

donuts...
:rofl:

[silverweb]

7. I'm glad it helps.

You might want to note the addendum to my original post, as well.

I remember getting all excited when string theory first hit popular science literature -- then quickly got discouraged trying to understand it because it was just so far over my head.

The P-brane description really does help clarify a bit.

[RandomThoughts]

8. I question the existence of the time dimension

for it to exist every point in time would have to be stored or still exist in some form, leading to concepts of time travel.

The relativistic different rates of time passing for objects moving at different speeds still does not take anyone out of Now, and without time travel, the only point on the time dimension is now.


However perspective and belief can add new dimensions, in that type of thought time could be a dimension, since it really is a construct of memory of past, or thoughts of what will be future.

Just like when a persons perspective on any event creates a new dimension. In this two people with different perspectives live in different dimensions since they live in different worlds.

When 'how a person sees the world' changes, his entire world changes, so it can almost be seen as a dimension in the same way time is seen as a dimension, since both are based on some thought.

It is possible to think of every perspective and every belief on every thought to be a new dimension, and as your perception changes you slide to dimensions that exist in parallel that match that thought.

However this is just a way to think about it and is not an assumption of real space, however it puts some doubt into being able to really call time a dimension, based on the way that calling perspective a dimension is also a thought exercise.

[mike_c]

4. wikipedia has a discussion....

http://en.wikipedia.org/wiki/M-theory#M-theory_and_membranes

...which I pass on simply as a courtesy-- I don't even pretend to have the conceptual background to understand or discuss string theory. I'm a biologist, and we have enough problems with our own theories, thank you very much....

[silverweb]

9. And speaking of M-theory (aka string theory)...

Here's an interesting TED talk on the subject:

http://www.ted.com/talks/brian_greene_on_string_theory.html

[Ready4Change]

10. Branes are not dimensions.

My highly inexpert understanding.

A pencil line is not a sheet of paper. It exists ON a sheet of paper.

In the same way, branes are not dimensions. They exist WITHIN dimensions.

We say we exist within 4 dimensions. Call them length, width, height and time. If I hop a lot, you could say I am 'vibrating' in a single dimension. (Height.)

Branes exist in more than 4 dimensions. They can 'vibrate' in some of those extra dimensions in ways we don't have a natural feel for, but which physicists say they can describe mathematically, and those vibrations are thought to have effects on what we see as our universe.

[derby378]

12. That would help explain one of the Big Bang theories...

It's the theory that two multidimensional branes intersected each other - "collided," if you prefer - and the resulting interaction took the form of a singularity which quickly lost stability and inflated into the universe we inhabit today.

Purely hypothetical at this point, but the idea that we're a "baby universe" spawned from two larger multidimensional realities is interesting.