Re: what is the ratio of the weak force to the strong force?

Thierry,

I'll admit your question set me back. I've studied physics for over fifty years and knew well that the strong interaction was the greater of the two nuclear forces. I have seen many tables that compared the forces, gave examples and compared effective ranges. What I have never done is internalize those statements to a real understanding because I never needed to.

Your observation prompted me to do a Google search of the topic and I have determined that they are both correct and both wrong. In a fraction of a second, I was able to see thousands of references to your question. There were dozens of different answers within the range you quoted. More to the point, I should say that they are equally inappropriate to quote out of the context of their origin.

I am familiar with Wichmann and have read most of Richard Feynman's work. My comments will not be a contradiction of either author's work. Rather, I'll try to show that under different conditions, other ratios would also change.

Let's consider the need for a "strong force" in the first place. Two protons are asked to remain in the nucleus of a helium atom. Why do the two positive charges remain so close together and not repel the two particles apart? We say it's because of the strong force. At close distances, that attraction is greater than the EM repulsion. However, for two protons wandering in a bubble chamber, they will be deflected from each other before they get within an atomic diameter because the EM force is greater. From these two examples, we can't determine which force is greater much less know by how much.

Another example might be to compare the EM force and gravity. If we were to calculate the ratio between two protons at some distance, we would determine that the repulsion was greater than the attraction and know the ratio. Place two electrons at the same distance and we find that the repulsion is the same, but the attraction is now much less : a different ratio. So what do we conclude about the relative strength of charge repulsion and mass attraction? Why do they seem different? Maybe you'd like to do that set of calculations for the two particles at a separation of an angstrom.

Distance of separation plays such a large part in all four forces; but they do not play by the same rules. EM forces and gravity are inverse square related and seem to extend over very great distances. The nuclear forces are MUCH more short ranged. Furthermore, the strong and weak interactions involve different particles and different events. This makes comparisons that much more difficult.

I hope my discussion helps you resolve this apparent conflict.

Gene Ewald