Gravity

Factual Questions
1

I’m just wondering if there is any smallest unit of gravitational force, something that cannot be cut in 2…

(using my memory, may be wrong):
Length has Planck lengths. Time has Planck time. Is there anything of the sort for gravity?

Or does the gravititional of any object in the Universe have an affect if ever so little on any other object, irregardless of distance between the 2 objects?

2

Smart People have been pondering this for a while. There have been atomic (that is, indivisible, not made of atoms, which are not atomic) particles found for other forces, like the strong nuclear force, but no one has yet discovered a graviton.

And I don’t believe Planck length or time has ever been proven, but I don’t know. Quantum effects apply to energy, not measurements.

3

[Is] there is any smallest unit of gravitational force?

I’d say yes. Given that there is a Planck length and a Planck mass (the two variables in the gravitational force formula), I’d say there’s definately a quantum unit for gravitational force.

I was thinking of saying no, because of the energy required to hold nuclear particles together, as well as bundles of particles (atomic nucleii) is detected as mass in larger particles and structures. However, since E=mc[sup]2[/sup], c is a constant (in units of length over time, which both have Planck constants), and m is mass once again, energy is therefore also “quantumized”.

4

overall, it’s an unknown, but…

I suppose there might be since gravitational acceleration can be measured as length per time^2 (applying the Planck limits). Seems like this would be based on the view of gravity as curved space.

Also, Quantum Mechanics(?) speculates the existance of gravitons which would be the fundamental particle that carries gravity (the fundamental particle of spacetime?). If such a thing exists, then maybe they would define the smallest unit of gravity. (note: an atom is HUGE as compared to a graviton)

5

Physicists are scrambling madly to try to produce a quantized theory of gravity, but they’ve been trying ever since Einstein, and they haven’t found it yet (although the string theories may be getting close). Even if General Relativity (Einstein’s highly successful theory of gravity) is reconciled with the quantum mechanical Standard Model of particle physics, which is highly successful at explaining the other forces, this does not necessarily imply a lower (or upper) limit on possible gravitational forces. It might put constraints on gravity in particular situations, however, on on other aspects of gravity. For instance, in quantum mechanics, a particle in a bound state can only assume certain discrete energies, but there are no known restrictions on the possible energies of a free particle. Charge, on the other hand, is always strictly quantized, with all visible particles posessing a charge which is an integer multiple of that on an electron, and some of the invisible ones (quarks) being multiples of a third that charge. Maybe the gravitational field jumps between discrete values; we don’t know yet.

6

I’m no physicist here, but I thought the school of thought now was that gravity might be part of the electro-magnetic spectrum, like radio and microwaves, and that the graviton thing had been given up on.

7

Gravity is not in the electromagnetic spectrum. It isn’t carried by photons, and it can’t be defined as a wavelength. I might be corrected later on, but I’ve never come across this little theory before and I have no idea how it might work (photons have inertia as if they had mass, so they would push something they hit, not pull on it).

8

Well, there is such a thing as gravitational waves, which do have a wavelength, frequency, and all of those other wave properties, and they travel at the speed of light, but they’re not the same thing as light. If nothing else, the symmetries are different: In the particle view, this means that gravitons are spin-2 and photons are spin-1, and in the wave view, this means that the basis polarization vectors are perpendicular for light, but at a 45[sup]o[/sup] angle for gravity. Sorry, that’s probably TMI.

Photons do vector the electromagnetic force, which can either push or pull, sepending on the situation. It’s a bit more complicated than just “the photons push on the objects, and force them apart”. Unfortunately, I don’t think that there’s any simple layman’s analogy for how vector particles can cause an attractive force.