Why is gravity stronger than other forces at the macroscopic level, yet weaker than other forces at the quantum level? Is there an explanation?
Answer
The gravitational constant at the quantum level leads to a very much smaller force than the forces the elementary particles see in their vicinity, in order of strength:
The weak and the strong are short range forces, their effect disappears when the sizes grow larger than a nuclear radius, order of a fermi. They cannot build up into one strong component that can appear macroscopically.
The electromagnetic force is a long range one like the gravitational force, and stronger, BUT . It has two opposite charges that attract, same charges will repel. This means that mass agglomerates will be mainly neutral, assuming equal positive and negative charges were created at the Big Bang.
Gravity, in contrast is only attractive and can and does build up to the forces we see controlling the space around us, the galaxies and clusters. It is the one that survives at long distances, because of its 1/r collective potential and its attractive only character, so it cannot be masked as the electromagnetic one can be and is.
As an aside, in space the electromagnetic force can be quite evident as a state of matter called plasma which carries magnetic fields and creates storms in space starting from sun explosions. Still the collective effects of massive bodies give gravity the lead macroscopically.
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