Higher Dimensions - Possibility or Requirement?

[Hypercube]

I have come to notice that not many people take the idea of higher dimensions seriously, mainly because they can't grasp the fact that just because they can't see it doesn't mean that it's not there. Higher dimensions might not be just a possibility, they might be a requirement.

 

When I was reading a book called "Beyond Einstein" by Michio Kaku, I made several realizations that back up the idea that the universe exists in more than four dimensions. One of which is that - at least for the first three dimensions - each lower dimension is physically impossible without a higher one. Think about it; if an object was truly one dimensional, it would have a width and depth of 0, hence it couldn't physically exist. The same rule applies for every dimension up to four, so it is logical to assume that it might also apply to every higher dimension up to the number of dimensions that the General Unified Theory - not that we have made one yet - exists in. In other words, the universe might not be able to physically exist in only four dimensions.

 

That being said, if we assume that that there are higher dimensions, it would also explain one of the biggest mysteries in modern astrophysics; the universes missing mass. Most physicists think that the explanation is some kind of matter that doesn't emit light, it's generally referred to as Dark Matter. But what if the reason that most of the universes mass seemes to be missing is because it exists in higher dimensions, it would explain why we have never detected it, since our 3d vision cannot view higher dimensions.

 

For all I know, my theory could be complete nonsense, but who knows?

[ajb]

If you take string theory seriously then you have to believe in extra dimensions, it is a formal requirement of superstring theory that in order to be quantum mechanically consistent then it must be formulated in 10 dimensions.

 

In string theory gravitons, Kalb-Ramonds and Dilatons are states of the closed string and so can propagate in the "bulk", that is they are not restricted to start and finish on branes.

 

I do not know of any other closed string states. I guess they are all of spin higher than 2 and so there low energy effective interactions are inconsistent (Witten-Weinberg theorem).

 

So I guess (but I am no expert in string theory) that it is difficult to imagine other particles propagating in the bulk.

[Severian]

When I was reading a book called "Beyond Einstein" by Michio Kaku, I made several realizations that back up the idea that the universe exists in more than four dimensions. One of which is that - at least for the first three dimensions - each lower dimension is physically impossible without a higher one. Think about it; if an object was truly one dimensional, it would have a width and depth of 0, hence it couldn't physically exist. The same rule applies for every dimension up to four, so it is logical to assume that it might also apply to every higher dimension up to the number of dimensions that the General Unified Theory - not that we have made one yet - exists in. In other words, the universe might not be able to physically exist in only four dimensions.

 

This is bogus reasoning. You only classify objects with less than 3 spatial dimensions as 'impossible' because you have never seen one. But the reason you have never seen one is because you live in 3 spacial dimensions.

 

That being said, if we assume that that there are higher dimensions, it would also explain one of the biggest mysteries in modern astrophysics; the universes missing mass. Most physicists think that the explanation is some kind of matter that doesn't emit light, it's generally referred to as Dark Matter. But what if the reason that most of the universes mass seemes to be missing is because it exists in higher dimensions, it would explain why we have never detected it, since our 3d vision cannot view higher dimensions.

 

It is technically possible for extra dimensions to predict the right amount of Dark Matter, but to do this, the extra dimensions have to be of the scale of an inverse TeV and you have to invent some new parity to keep the Kaluza-Klein excitations stable. (And the reason we have not detected the extra dimensions is not because we have 3d vision - it would be either that photons are not allowed to travel in the extra dimension, or more likely, that the extra dimensions are curled up really small.)

 

Incidentally, the scientific community does take extra dimensions very seriously, as you can see from the number of papers on the subject:

http://www.slac.stanford.edu/spires/find/hep/www?rawcmd=FIND+title+extra+dimensions&FORMAT=www&SEQUENCE=

[foodchain]

I have come to notice that not many people take the idea of higher dimensions seriously, mainly because they can't grasp the fact that just because they can't see it doesn't mean that it's not there. Higher dimensions might not be just a possibility, they might be a requirement.

 

When I was reading a book called "Beyond Einstein" by Michio Kaku, I made several realizations that back up the idea that the universe exists in more than four dimensions. One of which is that - at least for the first three dimensions - each lower dimension is physically impossible without a higher one. Think about it; if an object was truly one dimensional, it would have a width and depth of 0, hence it couldn't physically exist. The same rule applies for every dimension up to four, so it is logical to assume that it might also apply to every higher dimension up to the number of dimensions that the General Unified Theory - not that we have made one yet - exists in. In other words, the universe might not be able to physically exist in only four dimensions.

 

That being said, if we assume that that there are higher dimensions, it would also explain one of the biggest mysteries in modern astrophysics; the universes missing mass. Most physicists think that the explanation is some kind of matter that doesn't emit light, it's generally referred to as Dark Matter. But what if the reason that most of the universes mass seemes to be missing is because it exists in higher dimensions, it would explain why we have never detected it, since our 3d vision cannot view higher dimensions.

 

For all I know, my theory could be complete nonsense, but who knows?

 

I would think that if our 3+1 dimensions can physically interact with the other dimensions posed, and that the other dimensions posed are needed for the universe to function, then anything you would do or take for instance would be a interaction with, and a portal to if you will, these other dimensions then. This would apply on any level then physically and be a constant function, the interaction with these other dimensions.

 

What I mean is the electron seems to be some natural entity that gives off basically various physical realities of reality really, and it exists, we have found it, named it and study it as such, so then how do they do this with string theory physically? Far be it from me, but sure I could believe that an electron might have hundreds of thousands of smaller particles that make it up, I can say that all I want, but I would have little to no idea how to test such, or even if technology today even permits any way to really study for such, or if science even has enough of understanding how to go about it. I don’t understand how science can really test string theory really. I mean giving the idea that a great many questions at the QM level have no lasting answers yet, or a full picture even, is string theory sort of jumping the gun possibly?

[theCPE]

String theory is losing support, and for reason. Its a mathematical game.

 

I only mention string theory because it is the most popular multi-dimensional theory which has varied from 26 to 11 to 7 to etc etc.....

 

A few comments on dimensions.

 

1) Seeing with our eyes is not a good way at all to determine the number of dimensions. Instrumentation is of course the way to do it, after all we don't base any scientific theories hardly anymore off of 'empirical' evidence gathered with our eyes.

 

2) The whole Abbott Flatland analogy is outdated and not very useful IMO. Sure it creates an interesting perspective that allows someone to think for a second, "wow, my imagination really is the limit", but that is about it. Why beings of different dimensions can't interact? Lets pretend there is some fundamental particle we haven't discovered yet that makes everything. Well, this particle not only builds objects in our universe, it builds the dimensions OF our universe as well. Anything existing within the said universe is therefore built of these fundamental particles. THerefore, it follows that everything would be equally dimensional.

 

3)Curled up, microscopic, useless, unobservable dimensions sound like the ether too me......

[ajb]

String theory is losing support, and for reason. Its a mathematical game.

 

 

Losing support from who and why?

 

What I might accept is that string theory may be losing support from the theoretical physics community as a possible unification scheme, but that does not mean that string theory is useless. Quite the contrary, string theory is getting back to it's roots as a description of strong physics and this makes it very interesting and useful.

 

This new look at the possibility of describing strong physics by a string theory is the AdS/CFT correspondence which relates a gravity theory to a gauge theory. One is able to do gauge theory calculations using gravity! This is one of the great properties of string theory, it allows one to geometrically construct gauge theories. (You can construct gauge theories by stacking branes and conneting them with strings).

 

One issue so far is that the gauge theories are supersymmetric and as of yet do not quite reflect physical gauge theories. This is all work in progress by many people and the out look it good.

 

Other areas of interest include twistor string theory and MHV amplitudes, integrability of N=4 super Yang-Mills and the AdS/CFT corrspondence, D-Brane Dynamics and Gauge Theories and many other things...

 

So string theory is not dead and is far from being useless in phsyics. Woit is wrong!

[someguy]

I see what you mean about spacial dimensions necessitating the higher dimension to exist. I'm not sure if that is completely true i can't fathom a one dimensional object, or at least i can't understand how such an object could exist.. but that doesn't necessarily mean it is impossible i guess. I can certainly imagine three dimensions without the 4th though, not very exciting but i don't think that lacking the 4th dimension would cause an object to cease to exist. the 4th dimension is necessary for how our universe is has become and will be but I think in order to qualify for existing you don't need the 4th dimension. though i suppose that depends on your definition of existing.

 

Using higher dimensions in a theory could easily explain many things.. pretty much anything since no one can know what a higher dimension would be like. But I still have yet to see a reason for believing they exist. Using God in your theory could explain just as much just as easily, we could use god to explain the lack of mass in the universe just as easily. I have yet though to see a reason why we need a God to exist. That alone though is not enough to say that they don't but i prefer to first find reasons for needing stuff to exist before saying they are because that way i won't conjure things that don't exist. Superstring theory from what i know uses mathematical postulations in order to suggest multiple dimensions and many other things about superstring theory. and from what i understand the only reason they made those postulations is because it made the math tidy and simpler. But nature doesn't really necessarily tend to be neat and nice mathematically it just is whatever it is. Pi is not a nice and neat number yet it is such a simple part of nature.

[ajb]

Superstring theory from what i know uses mathematical postulations in order to suggest multiple dimensions and many other things about superstring theory. and from what i understand the only reason they made those postulations is because it made the math tidy and simpler.

 

NO!

 

Multiple dimensions are necessary in string theory. For superstrings you need d = 10 and for the bosonic string you need d = 26. These dimensions are not postulated to make things simpler but are needed.

 

If you quantise a string you will see that in order be be consistent, that is free of anomalies you require d=10 or 26 depending on the theory. In no way are these dimensions put in by hand, the mathematics requires these dimensions. You should not that this does not depend on the quantisation scheme you use, you will always get these dimensions but using slightly different arguments.

[Hypercube]

Severian, you missed the point of my theory. What I said was that I believe that we actually live in a universe that is made of more than 4 dimensions and the only reason that we think it is made of only 3 is because our brains cannot process information in more than three dimensions.

 

And believe it or not, there is some indirect evidence of higher dimensions; virtual particles. They are particles that appear out of nowhere in a vacuum, and then just as fast disappear. And I remember reading that some scientists believe that they come from higher dimensions through quantum tunneling.

[Severian]

Severian, you missed the point of my theory. What I said was that I believe that we actually live in a universe that is made of more than 4 dimensions and the only reason that we think it is made of only 3 is because our brains cannot process information in more than three dimensions.

 

But then you need to explain why our brains cannot process information in more than 3 dimensions. If we truely existed in more spatial dimensions and there was not some physics reason we couldn't access them (such as compacification or restriction to a brane etc) then one would expect us to evolve to be aware of them.

[theCPE]

Severian, you missed the point of my theory. What I said was that I believe that we actually live in a universe that is made of more than 4 dimensions and the only reason that we think it is made of only 3 is because our brains cannot process information in more than three dimensions.

 

And believe it or not, there is some indirect evidence of higher dimensions; virtual particles. They are particles that appear out of nowhere in a vacuum, and then just as fast disappear. And I remember reading that some scientists believe that they come from higher dimensions through quantum tunneling.

 

It doesn't matter if we can imagine, conceive, or work conceptual problems in more or less than 3 dimensions, if our instrumentation that observes, interacts, and manipulates matter on what we know as the fundamental level does not provide the emperical evidence of more dimensions than it is boogus.

 

Again and this seems like a lost concept but:

 

If there is something more fundamental that we are currently unaware of how ever many dimensions it has is how many dimensions ALL of the Universe will be made of.

 

Can you construct different dimensional things from legos of X dimensions?

 

That being said, if any version of string theory were right the fundamental particles of the verse would have that many dimensions and therefore we would have that many as well.

[someguy]

NO!

 

Multiple dimensions are necessary in string theory. For superstrings you need d = 10 and for the bosonic string you need d = 26. These dimensions are not postulated to make things simpler but are needed.

 

If you quantise a string you will see that in order be be consistent, that is free of anomalies you require d=10 or 26 depending on the theory. In no way are these dimensions put in by hand, the mathematics requires these dimensions. You should not that this does not depend on the quantisation scheme you use, you will always get these dimensions but using slightly different arguments.

 

my bad. it sounds like what i was talking about is what you're talking about and i probably misunderstood. But i don't really understand the theory well enough to know exactly what you mean. I realize it's very mathematical and would take me too long to understand well enough. But where did they get the equations they used to plug in those values that are necessary for there to be no anomalies? It seems like the dimension thing was a necessary mathematical conclusion to string theory. But what i'm wondering then i guess is why superstring theory was ever considered in the first place. wasn't it just math? I don't think anyone can argue with math but not all physicists agree with string theory so there must be something somewhere.

[ajb]

String theory has a well documented history. If you are interested then look it up.

 

Initially, string theory was developed as a model for the strong interaction. As we have fermions in nature string theory needed fermionic degrees of freedom and hence superstrings. It was things like the d=10 than made it difficult to apply to the strong force and then QCD took over.

 

What "saved" string theory is the fact that it includes the graviton in it's spectrum. We can say that the biggest prediction of string theory is gravity.

 

If you are interested pick up Barton Zwiebach's book.

[someguy]

thx, i may do that. how does that book approach the subject? And how much do i need to know before reading it?

[ajb]

thx, i may do that. how does that book approach the subject? And how much do i need to know before reading it?

 

Part I chapter 1 is "just words" and explains the "why strings".

 

The rest of the book is suitable for anyone with some undergrad physics, like classical and quantum mechanics.

[merlin wood]

Who knows? One day physicists will give up the attempt to develop an experimentally testable string theory and realise that, without the needto develop any theory of quantum gravity, there is evidence in quantum physics for the existence of a cause acting from large scale higher or extra dimensions of space

[merlin wood]

...and so you can insist that the quantum theory of the standard model does not explain how matter as atoms and molecules can exist or persist given the known action of the forces.

 

But rather, such an explanation requires enough detals to be suffiently justified and described of a cause of quantum wave, spin and entanglement behaviour from its effects upon objects in motion. While the evidence of quantum physics indicates that to produce this quantum behaviour a cause would need to act non-locally and thus could not be described as surrounding objects in 3D space.