|Hyperdimensions||Explore a 4D Hypercube|
|The Hierarchy Problem||Scale Anisotropy|
|Quantum Physics vs. General Relativity||Scale Anisotropy|
|Cold Dark Matter - the Missing Mass||In another dimension?|
|The Myth of Magnetism||A Relativistic Electro-Dynamic Force|
We currently know of four forces[3.4.1] From strongest to weakest, these are: Strong, Electromagnetic, Weak, Gravitational. The mystery here is why are their relative strengths so enormously different?
|EMF||1||infinity||10^-14 - 10^-20|
|Weak||0.00001||10^-18m||10^-8 - 10^-13|
Look at the other forces relative to the Electromotive force (EMF). The Strong
(nuclear) force is only 100 times as strong as the electric. This is exactly
the difference between a TNT (or dynamite) explosion and the blast of a nuclear
weapon. Now notice the difference with regard to Gravity:
0.000000000000000000000000000000000001 to 1.
Gravity is not very strong, even in relation to the Weak force. On a scale of 100 billion billion to one, gravity would be so weak compared to the other forces as to be undetectable. The reason that Gravitation feels stronger than EMF is because the electric +'s and -'s cancel each other out, while the gravity (i.e. the Earth, Moon, Sun) each adds up to a large number. Lucky for us. That is why a little refrigerator magnet can hold itself up against the pull of the entire Earth! (Need a picture).
There is a huge desert between gravity and all the other forces. Physicists are not used to this sort of discrepancy in our Universe. A physicist looks at this and says "There's something wrong with this picture. Here is a big clue to the way gravity works, if I could just figure it out."
(Then you have that spooky coincidence of gravitational mass and inertial mass equivalence. - more later)
Contemporary physicists Arkani-Hamed, Dimopoulos, & Dvali (ADD), have suggested that this discrepancy is due to additional dimensions, called the bulk. Only gravity can travel in the bulk. Particles and the other forces are 'stuck' to a 3D membrane called a 3-brane, floating in the bulk. Thus, at small distances, gravity falls off at a rate greater than r-2, e.g. r-(d-1) (where d is the number of dimension) for the first few fractions of a millimeter as the force spreads out in d dimensions. This high-attentuation distance could be as small as a femtometer, 10-15m - a range similar to that of the strong force (note - physicists are often suspicious of coincidence such as this simularity in the range of the strong force and the range of high-attentuation gravity). The result is that beyond this small distance, all that is left of gravity is a tiny fraction of its original strength that now falls off at r-2, like the other forces. Randall and Sundram (RS) advanced a theory that the bulk is warped, again addressing the hierarchical problem in the domain of Large Extra Dimensions (LXD).
There are other theories. But these are interesting to us because they include hyperdimensions, and that is what this site is about.
This is the classical conundrum trying physicists souls since the early twentieth century. Please note that there are two theories of Relativity: Special Relativity and General Relativity, both developed by Albert Einstein.
Special Relativity (SR) is simply a description of the result of a finite limitation on the speed of light and the assuption that the speed-of-light must be identical to all observers. If the electro-magnetic force (light) does not communicate instantaneously, then the SR outcome immediately follows (see the section on Magnetism).
The Theory of General Relativity (GR) states that matter curves space, and space moves matter. Somewhere within these two theories is the famous matter-energy relationship:
E = mc2
General Relativity readily explains cosmic phenomenon - those events that occur at great distances and great energies. GR explains gravity, predicted black holes, and other astronomical and cosmological observations of the twentieth century.
On the other hand, Quantum Physics is the science of the minute - events that occur at subatomic scales. It explains interactions that occur between and within the nuclei of atoms such as beta decay and electron-photon energy exchanges.
SR and Quantum Physics work well together and explain a great many experimental results that could not be explained otherwise.
However, GR & Quantum Mechanics are at opposite ends of the scale - GR is cosmological - QM is subatomic. GR is about billions of years, QM is about billionths of a second. GR is about gravity, QM is about the Electro-weak and the Strong forces.
QM's main problem is gravity. Gravity is so weak (see the Hierarchy Problem) compared to the the other forces, that it is very difficult to measure experimentally at subatomic scales. While it is possible to develop theory from no data, it is much more difficult to prove a theory with no data. We do not know how gravity works at subatomic scales - i.e. less than 0.8 mm which is a great deal larger than the 10^-15m of nuclei radii.
QM is characterized by probability distributions - nothing is black & white - it is all fuzzy. .
QM wants gravitons, but it can't find them.
GR wants scale isotropy, but can't prove it.
This Dark Matter section is obsolete - Google for Dark Energy to get up-to-date.
We know the way gravity works at local and planetary distances. We therefore assume isotropy of scale, and observe the motions of the galaxies. The galaxies revolve as if there were 10 times the mass within them that we can detect with our astronomical instruments.
This has led some scientists to wonder of gravity works the same at cosmological distances as it does at planetary distance. It has caused others to suspect that there is a huge amount of mass that we can't detect for some reason - black holes, neutron stars, brown dwarfs. Some suggest that there is another form of matter, a non-baryonic type, in the Universe that we have not yet detected (most of the matter we encounter is made of baryons, i.e. - protons & neutrons - atoms).
But there is another school that suggests that this missing matter is in a number of adjacent parallel Universes. These parallel universes are called Branes from "3D membranes" which was shortened to "D-branes" and again shortened to "branes". We cannot see beyond our 3D brane because photons, leptons & baryons are stuck to the brane. Only gravity can spread beyond our 3D portion of the Universe to the multi-verse beyond (figure of parallel branes). This also conveniently explains why gravity is so weak (see The Hierarchy Problem).
Another suggestion is that our 3D brane folds over on itself, so that we are feeling the mass from galaxies beyond the curve of the universe (provide a figure of warped universe).
Relativity In Action
This analysis, is based upon Griffiths' discussion in his Introduction to Electrodynamics [3.3].
Essentially, Griffiths states that the (magnetic) force on a moving charged particle near a long, straight wire is identical to the force experienced by the particle due to the relativistics effects of the motion of the charges within the wire in relation to the motion of the particle. The section is reprinted as a PDF here.
This can be interpreted to mean that the term magnetism is short-hand for relativistic electro-dynamics.
Hence, refrigerator magnets are a kitchen demonstration of relativity in action.