Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: Jeff Wedgwood on 23/10/2008 10:43:35

Title: Would we notice a swap in the higher dimensions?
Post by: Jeff Wedgwood on 23/10/2008 10:43:35

Jeff Wedgwood  asked the Naked Scientists:

In some forms of cosmological theory, including string theory (I think), they postulate that there are more than the usual 3 space dimensions and time dimensions. Usually they mention a total of 10 or 11 dimensions.

The most popular metaphor I've heard to help understand why we don't see or experience these other 6 or 7 dimensions is that they are "curled up" and thus we cannot see them.  The usual example I've read is that of an ant walking along a hose (the hidden dimension is the circumference of the hose).  However, the circumference is so small that the ant experiences the hose as a single dimension, a string. Thus it is not aware of that extra dimension.

What would happen if one of these hidden space dimensions was swapped with a space dimension in our reality? Would we notice any change at all?

Thanks for a very stimulating podcast (http://www.thenakedscientists.com/HTML/podcasts/), I look forward to it every week.

Jeff
Washington state, USA

What do you think?

Title: Would we notice a swap in the higher dimensions?
Post by: DoctorBeaver on 23/10/2008 16:09:39

If 1 of the compactified dimensions suddenly enlarged and 1 of our 3 compactified, then everything within our dimension would also be compactified. That probably wouldn't be a particularly healthy thing to happen to us. We'd get a bit squished.

Title: Would we notice a swap in the higher dimensions?
Post by: LeeE on 23/10/2008 17:09:22

I think it would be problematic for us, but I'm not sure the issue would be about one of our spatial dimensions getting compactified and another dimension, which we currently do not occupy, enlarging.

This depends though, on what is meant by compactification - does the compactified dimension just get very small, but otherwise remain consistant e.g. imagine a balloon deflating, with the original atom and molecule counts and relationships remaining unchanged, or does it mean that the dimension is collapsed, equivalent to all the atoms and molecules in the balloon collapsing into a single particle?

There are two issues that I think would cause problems with dimensions being swapped though.  One is the nature of the propagation of the swap - how does the swapping between the two dimensions propagate through our universe?  Would it be instantaneous or would it occur at the speed of light?  An instantaneous propagation would seem to be less problematic to me as a swap that propagated through the universe at light-speed would mean that bits of it would be in one set of dimensions while other bits would be in another.

The other issue is how whatever exists in one set of dimensions migrates to the other set.  It's difficult to imagine how this could occur and I suspect (on no current scientific basis) that everything that existed, as matter at least, would breakdown in to energy.

Title: Would we notice a swap in the higher dimensions?
Post by: DoctorBeaver on 23/10/2008 17:36:27

LeeE - the molecule counts & relationships could not remain the same if 1 of our dimensions were suddenly compactified. Compactification is generally thought to involve the dimension being at the Planck scale. That means that even atoms would be too big to fit and would have to break down.

When a balloon deflates, air is released. Therefore the atom & molecule count inside the balloon is reduced.

Title: Would we notice a swap in the higher dimensions?
Post by: LeeE on 24/10/2008 13:39:00

Hi DrBeaver - thanks for the clarification on compactification i.e. the dimension is shrunk but it's contents are not.  In the example of the balloon I was just considering the balloon itself, not it's contents, just as with the example of using an inflating balloon with spots on it's surface, representing galaxies, to illustrate the effects of the expansion of the universe.

Title: Would we notice a swap in the higher dimensions?
Post by: DoctorBeaver on 24/10/2008 14:53:40

OK, I misunderstood your comment about the balloon.

Title: Would we notice a swap in the higher dimensions?
Post by: LeeE on 24/10/2008 14:58:49

np

Title: Would we notice a swap in the higher dimensions?
Post by: Soul Surfer on 27/10/2008 19:04:22

It is now seriously being suggested that this is what is happening behind the event happening inside the event horizon as matter collapses inside a black hole as some dimensions collapse others expand and the "universe" inside the horizon turns itself "inside out".  look at the article in the October Scientific American for a bit more detail.

Title: Would we notice a swap in the higher dimensions?
Post by: LeeE on 28/10/2008 14:48:00

Haven't read the article but is it anything along the lines of these couple of paragraphs from something I posted in topic 14416?

Quote from: LeeE on 19/09/2008 17:06:19

<snip...>

If we go along with this idea of a pre-existing dimensional super-set we could then postulate that an (unknown) event and mechanism within that super-set caused the isolation of the region forming our universe from the rest of the super-set.  It's difficult to imagine what such an event could be, especially from our point of view within our sub-set, but as this is an issue of hierarchy we might find a lower order example of this mechanism within our own universe.  For example, if we think of our four-dimensional space-time universe as being an isolated region of four-dimensional space-time within a five dimensional space-time universe, perhaps we should look for the formation of isolated three-dimensional regions of space-time within our four-dimensional universe.

One possible candidate for this phenomenon occurring in our universe could be the formation of Black Holes.  In the current model of Black Holes (from our four-dimensional space-time point of view) the rate of time becomes zero at the Schwarzchild radius/Event Horizon, effectively removing one of the dimensions and leaving an isolated three-dimensional region of space(/time?) within our four-dimensional space-time universe.  Now because no events can occur without a time dimension, which is required to allow the necessary before/after states that define the occurrence of an event, the implication would seem to be that if a new universe is created within a BH, and starts when the BH is formed, it'll only have two spatial dimensions but be spatially unbounded (not only in terms of it's shape but also because there's infinite two dimensional area within a three-dimensional volume).  At the same 'time' it's time dimension would be entirely new, 'current' time having been zeroed at the EH.  A pleasing aspect of this model is that we could hypothesize that the energy and matter we see falling into a BH results in the expansion of the three-dimensional universe within it, although such a universal expansion would have to be non-constant and varying over time, due to the varying stream of in-falling energy & matter from our universe.  Ultimately, such a universe is likely to evaporate due to Hawking radiation.

Title: Would we notice a swap in the higher dimensions?
Post by: yor_on on 07/11/2008 00:45:48

It all falls back to what we mean by dimensions.
Spacetime I see as a 'whole'.
So 'taking away' a dimension from it would take away spacetime.

What we have is an experience of movement in space and time inside spacetime.
That we experience and prove through our observations (consciousness:)
Times arrow is what makes it hang together (cause and effect)

On the other hand that doesn't prove a thing.
There might not be any motion at all in spacetime.
Just as a black hole seen from the inside might have an infinite space to it.
What we have is localized phenomena belonging to our 'spacetime'.
and the further we investigate the stranger our world becomes:)