MadSci Network: Physics |
Gravity is so weak a force that it has no noticeable effect on what happens in a nucleus. So far (!) there are four known forces in nature which can affect us, leaving aside questions of unification theories. They are: gravity, electromagnetism, the "strong" nuclear force, and the "weak" nuclear force. On a scale which assigns a strength of 1.0 to the electromagnetism between two protons in a nucleus, the "strong" force has a relative strength of 20, and the "weak" force has a strength of 10exp-7. However, both of those operate only over very short ranges, on the order of 10exp-12 centimeters, which is a typical separation between nucleons in a nucleus. The "weak" force is responsible for some types of radioactivity, and the "strong" force holds the nucleus together. Gravity on this scale has a strength of about 10exp-36, even though it has an infinite range like electromagnetism. The reason gravity can do the things we observe, such as make weights fall to the ground and the Moon orbit the Earth, is that the masses involved are so enormous compared to that of a nucleus.
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