Gravity verses electromagnetic attraction

pulsar28

Weve seen how particles in zero gravity form clumps through electro magnetic attraction, and that these clumps will then develop gravitational forces. Isnt then gravity merely the same as this electro magnetic attraction only on a larger scale?

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lzkelley

Although many if not most hold onto the hope that some time (most likely long from now) all of the fundamental forces will somehow be unified... according to our understanding, gravity and E&M are very different.
For instance, E&M forces don't act on things without charge (i.e. neutral sums of charged particles or neutrinos(?) ).
Similarly, gravity doesn't effect massless particles (i.e. photons).
The details of the differences aren't too important, but another one of the main things, is that gravity is about a billion times weaker than the E&M forces.

malawi_glenn

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Gravity does indeed affect massless particles, see 'gravitational red shift' etc.

Nabeshin

Also, gravity is strictly an attractive force, whereas electromagnetism can work to attract or repel.

malawi_glenn

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electromagnetism can be "sheilded", gravity can not, since there is no such things as "negative" mass

lzkelley

Gravity does indeed affect massless particles, see 'gravitational red shift' etc.
You are absolutely correct that the presence of gravity does change the observational nature of massless particles; but at the same time i think its worth noting that its not gravity that is causing such a change (for instance redshift) - but the bending of space due to gravitational fields (to my knowledge)... this is really semantics - but i think it does illustrate an important conceptual different.

NerfMonkey

Also, gravity is strictly an attractive force, whereas electromagnetism can work to attract or repel.
In some cases gravity can be repulsive instead of attractive. But in every day circumstances you're right.

Wallace

You are absolutely correct that the presence of gravity does change the observational nature of massless particles; but at the same time i think its worth noting that its not gravity that is causing such a change (for instance redshift) - but the bending of space due to gravitational fields (to my knowledge)... this is really semantics - but i think it does illustrate an important conceptual different.
The 'bending of space' is simply a qualitative description of how gravity effects the motion of particles. It is not something different from gravity, it is gravity, if it is anything.

Nabeshin

In some cases gravity can be repulsive instead of attractive. But in every day circumstances you're right.
Elaborate. I am mystified.

malawi_glenn

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You are absolutely correct that the presence of gravity does change the observational nature of massless particles; but at the same time i think its worth noting that its not gravity that is causing such a change (for instance redshift) - but the bending of space due to gravitational fields (to my knowledge)... this is really semantics - but i think it does illustrate an important conceptual different.

Gravity IS bending of space, according to the theories of Einstein

W3pcq

Maybe it is like the difference between a wave and a current in water in a way?

malawi_glenn

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Maybe it is like the difference between a wave and a current in water in a way?
The theory of both EM and gravity is well known, and it is nothing like what you are trying to ascribe.

W3pcq

What I was trying to say is that maybe they are both different types of the same thing. By the way, what is "the theory of both EM and Gravity"? It is my impression that science still does not know exactly what EM is, or what the cause of gravity is. We know how to measure it and make predictions, but linking them would require a better understanding of what they are.

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malawi_glenn

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Ooop I should have written the "theories" ;-)
Unification of EM and Gravity is not done yet.

"Maybe it is ... " (What is 'it' referring to?)
"... that maybe they are both ... (What is 'they' referring to?)

W3pcq

Gravity, and EM is what I am referring to. If they can be unified, they must be linked somehow. The same way E=mc2, maybe gravity and em are phenomena of the same fundamentals. Comparing EM to a current, and G to a wave is to me an interesting way of looking at it because EM is a current of photons yet gravity is not a current of particles but instead it is a change in the structure of space just as a wave is not a current but instead it is a change in the structure, or a curvature of the ocean.

malawi_glenn

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Have you done "Classic Electrodynamics" in collage / university yet? I am referring to "because EM is a current of photons "

unifying all physical theories into one, has always been a goal. String Theories are the candidates for this task today, even though their reasoning are quite a bit more intricate than yours.

W3pcq

Even if they come up with the right series of 1's or whatever they are trying to do, what will they understand after the math works?

malawi_glenn

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How to unify Gravity with Quantum field theories.

W3pcq

Even if they do that, there will still be room for interpretation of what it all means. They will be able to do a whole new level of predictions which will allow huge advances in science which is totally awesome. That doesn't mean that no one can wonder what the findings mean philosophically.

nuby

Has it been proven or shown how mass creates a gravitation field? Where does the "gravity" come from within an atom? Do neutrons have something to do with gravity?

malawi_glenn

Homework Helper
W3pcq: I concern physics. The OP asked a physics related question and he should get the answer from contemporary physics, not just speculations from laymen non-physicists (see the forum rules), they you may keep to yourself or post elsewhere.

nuby: All mass generates gravity, just not the neutron.

nuby

Everyone knows mass generates gravity. But how can mass do it?

malawi_glenn

Homework Helper

Well a simple answer would be: Mass bends space-time, which is gravity (bending in space time).

Redbelly98

Staff Emeritus
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In some cases gravity can be repulsive instead of attractive. But in every day circumstances you're right.
I'll repeat Nabeshin's request for an explanation here.

Nabeshin

Lol thank you redbelly. That claim was thrown out there but nobody wants to take up the task of explaining it? :P

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