# Extra neutrons in heavy atoms and Gravity

1. Oct 11, 2008

Question:
The postulate that mass attracts mass is present in both the classical description of gravity and GR. My question is related to the extra nuetrons in heavy atoms, if there is experimental evidence that these extra neutrons are also part of the equation.
I wish to read about experiments that confirm that gravity is not related to paired nucleons, p-n pairs. Any suggestions?

br, nl

2. Oct 11, 2008

### mathman

I can't quite understand what you are looking for. However it is safe to say that gravity has no role in holding the particles in nuclei together. Off hand I don't know exactly how many orders, but gravity is very many orders of magnitude less than the strong force between quarks (nucleon constituents).

3. Oct 12, 2008

### blechman

I believe the typical ratio of strong:gravity is $10^{-39}$ (that might be electromagnetism, not strong - strong:EM is $10^{-2}$) - point being, this is VERY small, and far beyond our ability to measure on top of the strong nuclear force!

There IS some attempts to study graviational effects in particle physics systems, but they're very ambitious! For example: there are some people who are proposing to study antiprotons to search for "antigravity" - this looks VERY hard, to me, and I don't understand it. But look at the antiproton working group at the "Project-X report" (I'm not sure the link, but you can start on www.fnal.gov; or just try google).

4. Oct 13, 2008

### malawi_glenn

however, in Neutron stars, nuclei and nucleons are held togheter by gravitation to a very large extent:-)

5. Oct 13, 2008

Sorry guys. Must have misled you. I want to read about experiments whereby it is shown that if a fixed mass M5, made up entirely of p-n pairs [nuclei with same number of protons and neutrons] and another mass also of M5 but made up of heavy atoms [nuclei contains more neutrons than protons] will have the same 'pull'.
According to Newton's law for gravitation F=G.m1.m2/r2 the pull is the same. My question is where can I find research comparing these two types of nuclei in the real world.

Posted it here because you are the experts for Nuclear physics and I've read elsewhere that, quote
"the nucleus is the little heavy place that knows everything there is to know about gravity" (Man from Kibish)

6. Oct 13, 2008

### malawi_glenn

You are funny, what is a "man from kibish" and what has that to do with anything relevant?

Are you saying that you want to compare a heavy Z = A/2 nucleus gravitational "pull" compared to another nuclei with same A?

I can tell you that the effects of gravity in the subatomic world is totaly neglectable in the subatomic world - you CAN'T measure the effect of gravity. And certainty not in the nuclear physics field, where you have the "so called" Strong force. (also see post #3).

btw WHY should not n-p paris have gravitational effect? n-p is just deutrons. Also the pairing force is between identical nucleons in a nucleus...

7. Oct 14, 2008

### genneth

I seem to remember a series of experiments where torsion balances with different materials attached at the ends were made to resonate with the gravitational forcing caused by the rotation of the earth. They were extremely precise, and confirmed that mass of all kinds, including energy, gravitates the same to something like 1 in 10^10. I thought they were done by Dicke, but google seems to return no relevant results. Will Clifford's Living Review article on GR experiments might not be a bad place to start.

8. Oct 15, 2008