# Gravity as simply being the cumulative effect of atomic particles?

1. Apr 1, 2013

### juniorcarty

If atoms clump together through the interaction of electrons, protons and neurons to form matter, why can't gravity ( of the Earth for example),be simply described as just being the wholesale cumulative effect of all those electrons, protons and neurons of which the mass of the Earth consists, pulling and attracting the the respective electrons, protons etc. of which, for instance, the moon consists?

2. Apr 1, 2013

### Staff: Mentor

In Newtonian physics, the gravitational force between two bodies is indeed the sum of the (individually minuscule) gravitational forces between each and every particle making up the two bodies. We don't calculate the gravitational force that way because it would be intolerably cumbersome in practice, but there's nothing wrong with it in principle. So not only could gravity be that cumulative effect... It is.

But be aware that the force that causes atoms to clump together to form matter is not gravity. It takes a truly enormous number of atoms to generate a significant gravitational force; any chunk of matter less massive than a good-sized asteroid is going to be held together by intermolecular forces generated by electromagnetic interactions between nearby electrons and atomic nuclei. It's really hard to tear a steel sheet apart, and that has nothing to do with gravitational attraction between the atoms in the steel; that's all electromagnetic forces between them.

3. Apr 3, 2013

### juniorcarty

I am now more confused than I was previously. You recognise that the cumulative effect of a 'truly enormous number of atoms' , can 'generate a significant gravitational force'. ie. the gravitational force of the Earth for instance. 'It is....... (gravity)'. However, you go on to state that the 'gravitational force between each and every particle' ie, the subatomic electromagnetic force, 'is not gravity'. This indicates that you hold with the universally accepted model which regards the subatomic electromagnetic force and the force of gravity as being distinctly separate. What confuses me is where the distinction begins?

For instance we know that the Earth initially originated and was formed from particles of dust and gas which clumped together due to the influence of the subatomic electromagnetic forces within the said particles. The first 'attractive' force in the universe was that of electromagnetism. No latter, no matter. At what point or stage in the increasing burgeoning bulk of the fledgling Earth could it legitimately be stated that local matter in space, ( be it either dust particles or asteroids), were alternatively drawn to Earth, not by the influence of the electromagnetic force, but by the force of 'gravity' ? When do we begin to describe the former as being the latter.

It always appears to me that any attempt to explain the force of gravity is always from a top down perspective instead of from the bottom up. I don't see why it would be 'intolerably cumbersome' to simply describe Earth's gravity as being the cumulative wholesale effect and outward extension of the electromagnetic force/attraction as contained within the mass of the planet ? Perhaps in doing so, particle physicists may not be required to spend as much as they do, looking for gravitons?

4. Apr 3, 2013

### Bandersnatch

The point was that these are two distinct forces that act at the same time. One is much stronger than the other, but easy to cancell out, the other is weaker but always attractive.
That's why gravity dominates large-scale attraction, while electromagnetic forces dominate smaller scales(and nuclear forces take over in the >really< small scales).

Once again, electromagnetism does not emerge from gravitation, nor vice versa.

5. Apr 3, 2013

### ZapperZ

Staff Emeritus
You are trying to assert that gravity is nothing more than the resultant electromagnetic force from all the constituents. This is incorrect on more than one grounds. For example, something can be neutral (no net electrostatic field), and can still assert gravitational field. So already this is something inconsistent here.

Secondly, the repulsive force that is present in electromagnetic interaction is missing in the typical gravitational field that we observe (neglecting exotica in General Relativity and Cosmology).

However, it is certainly true that the sum of all the gravity of these individual particles would be equal to the gravity of the macroscopic object. This, however, is different than equating their electromagnetic property to the gravity of the macroscopic object.

Zz.

6. Apr 3, 2013

7. Apr 3, 2013

### ZapperZ

Staff Emeritus

8. Apr 3, 2013

### DrewD

So far you're right. Every particle with mass exerts an attractive force on every other particle with mass.

There is still gravity down there. As far as I know, gravity is expected to behave the same way down to the size of nuclei (beyond that realm I don't know anything) but nobody ever bothers to talk about it because the effect is incredibly small in comparison to the electromagnetic forces. It is still there, but the effect is drowned out by EM forces.

Nope. Matter can still exist without EM forces. Maybe it wouldn't clump together in quite the same way, so yes, the two completely separate forces do effect each other indirectly, but there is no (at least on the energy scales that we can observe) fundamental connection between the two forces.

9. Apr 3, 2013

### juniorcarty

Neutrinos participate only in the weak decay of nuclear particles and have no role to play in the strong force binding nuclei together.However, (and confirming your comments), Fermilab DID confirm in 2006 that neutrinos do indeed have mass. This is significant with regard to the fact that Neutrinos CAN exert gravitational effects. ( and therefore may have some significance in the formation of dark matter.)

10. Apr 3, 2013

### ZapperZ

Staff Emeritus
But you are neglecting what this contradicts in your assertion that matter must have EM interaction! That's the whole point of us bringing up the neutrinos.

BTW, Fermilab did NOT confirm that neutrinos have mass. The first confirmation came out of detection at Kamiokande in Japan of neutrino oscillation.

Zz.

11. Apr 3, 2013

### Staff: Mentor

There is no stage that gravity 'takes over'. Gravity constantly pulled the dust together. It is only once it began to clump in large lumps that the attractive force started to have noticeable effects at a small scale. And the EM force did not bring the dust together, it merely caused it to stick together upon collisions with each other.

And no, the first attractive force in the universe was not the EM force. It was gravitation.

It's not intolerably cumbersome to describe gravitation as an extension of the EM force. It's just plain wrong. The two forces behave very differently when you look at the details.

No, we don't. And your logic doesn't make any sense. If you have less and less gravitational force when the mass of the object is reduced further and further, when do you ever hit zero? Not until you have zero mass. A single particle still has mass and exerts gravitational force on other objects.

If you believe this, then show the math.