The Supergravity Concept



Overview:

Supergravity is a concept intended to explain the gravitational force. It deals specifically with:
  • Its relatively weak strength.
  • Its independence from the other three fundamental forces.
    • Four forces are identified by modern physics: weak, strong, gravitational and electromagnetic forces
  • How a gravitational force is transmitted. (Source 1)


Definition and explanation:

In classical Newtonian physics, gravity is enforced through some unseen gravitational field. It is described as
affecting matter without direct contact, constantly. However, the standard model and Einstein's theory of general
relativity forbid this sort of behaviour. They determine that nothing can move at a speed greater than that light
attains in a vacuum. This speed is about 299 792 458 meters per second.

At great distances, gravity attracts masses more consistently over distance than either the strong or weak
forces. However, it is not as powerful at distances shorter than about 10^-15 meters. For this reason, it is most
detectable at distances above this femtometer scale.
The electromagnetic and weak forces have been proven to be aspects of a singular electroweak interaction. The
strong and gravitational forces have not been related to the other forces, though this newfound theory promised
to address the latter.

Firstly, Einstein's famous equation E=mc² means that energy may be freely converted into mass (and vice-versa),
and thus immediately start influencing other matter through gravity. If this field was created at the instant that energy
became mass, the field could affect far-away masses before light: it would mean something could move faster than light.

Secondly, gravity vortices such as in black holes exert a force on surrounding mass. This is known to be capable of
moving matter at a speed greater than that of light, violating Einstein's conclusion. Theorists looked through numerous
possibilities to explain the seemingly instantaneous influence of gravitational fields. Eventually, an explanation that did
not ignore this 'speed limit' was found.

Supergravity relies heavily on two concepts:
  • a theoretical particle/wave, known as the graviton.
  • multiple dimensions (originally eleven, now uncertain).

There has been no direct observance of these gravitons, which are said to form the gravitational field. The gravitons
would be massless; since they are emitted by matter that has mass, gravitons with mass would themselves emit
gravitons. Gravitons, as particles or as waves, must travel at a finite speed; if they are massless, they have no inertia.
Therefore, they'd either travel at the fastest possible speed, or be stationary.

The dimensions in which gravity operates have been a subject of contention. Simply put, gravity is supposed to work
across all dimensions of space and in one of time. Around a black hole, those dimensions usually hidden are opened,
and supergravity causes matter to be attracted toward the mass (thought to be a collapsed star) that created the rift.
The intense gravitational pull of such a mass is said to be present across all (or most) of the extra dimensions,
allowing interdimensional forces to be exerted.




Sources:


  1. English Wikipedia at http://en.wikipedia.org/
    1. The Wikipedia page pertaining to Supergravity was used for the overview: http://en.wikipedia.org/wiki/Supergravity
    2. The Wikipedia page detailing the Weak force was used to compare the various fundamental forces throughout: http://en.wikipedia.org/wiki/Weak_force
  2. Stephen Hawking's masterpiece, The Universe in a Nutshell, ©2001. The 'Shape of Time' chapter was particularly useful.




Comments:


Sam Edwards - What makes hidden dimensions open around a black hole?
>>I just added some more info. to the last paragraph. Simply put, the intense forces involved make these dimensions open.

Sonia Bansal- What is the practical application of supergravity?
  • Supergravity is designed to explain how gravity works - an application is yet to be found. But come on, who wouldn't
  • want to know why mass attracts more mass?
William Chan - How does this effect people on Earth?

>>On Earth, people shouldn't normally be affected greatly by supergravity - but the prospect of gravity on a greater scale
>>could have an effect on long-distance space travel.

Greg Sturm - So energy can be turned into mass, and have a gravitational field? Does that mean that radiation from
  • > > > > > > something like a star would create its own gravitational field, even if it is extremely small?

>>Indeed, as long as the radiation itself had mass. However, in the case of photons and other small particles, this is
>>mainly relativistic mass, and thus subject to change as its speed changes due to the acceleration of gravity - in other
>>words, just about constantly changing. This might apply to background radiation, but I have yet to find scientific proof.

Robert Lopez - What could supergravity be used to find once the mystery of it is discovered?

>>At the moment, any matter that may exist in other dimensions (i.e. about 93% of all matter thought to exist) or as
>>'black matter' cannot be detected directly. This theory has led to a few hypotheses: perhaps there is not as much matter,
>>and the effect seen is just that of gravitons from long-gone stars.

Brandon Siegenfeld- If gravity travels faster than light according to this theory wouldn't other forces like the strong force or no?

>>That's quite possible, though it's hard enough to measure the strong force as it is. That only really has an impact at the
>>nuclear scale, so large amounts of matter would need to be concurrent for such high speeds. It's quite possible that the
>>only barrier to this is the probability of such a situation.

Kevin Norris - Why isn't there much research on gravitons (everyone seems to be occupied by the Higgs Boson)?

>>Well, the Higgs boson is supposed to be detectable. Gravitons would be considerably more difficult to find: no mass, no
>>charge, a half-life based on its creator's mass. The Higg's particle, however, is supposed to have a very high mass, and
>>had a much better press secretary (c.f. 'The God Particle').

James Song- What would be the consequences on Earth if gravitons were to be discovered?

>>I refer you to Chan's answer. Consequences would be nearly undetectable outside the M-theory enthusiast groups.

Douglas Chin - Do gravitons travel freely between interdimensional spaces then?

>>Sorry to take so long - yes, gravitons travel through all dimensions. Mind you, modern physics assumes that just about
>>any number of dimensions could exist, so 'interdimensional spaces' aren't very well defined.