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In the Standard Model of particle physics, we consider only three forces, my question is about the gravitation force why we ignore?

Qmechanic
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Nassrine
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    Related: https://physics.stackexchange.com/q/387/2451 and links therein. – Qmechanic Nov 30 '18 at 23:33
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    In point of fact, the SM fermion content is "just so" (magically) suitable to also cancel gravitational anomalies, thereby reassuring us the SM and gravity (and some type of quantum form thereof) are compatible and consistent. Gravity itself is so absurdly weak it could not influence the SM. – Cosmas Zachos Nov 30 '18 at 23:37

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Because gravitational forces are completely negligible in conventional particle physics. For example, the gravitational force between a proton and an electron is something like 0.0000000000000000000000000000000000000001 of the electromagnetic force!

And because quantizing General Relativity produces a “non-renormalizable” theory with various infinities that don’t make physical sense and can’t be dealt with in the same way that they get dealt with for the other three fundamental forces that are in the Standard Model.

A unified theory of all four forces is one of the unachieved goals of physics. Physicists are investigating how to do this but it is a very difficult problem.

In the meantime, the Standard Model is completely adequate for understanding (at least in principle) particle physics, nuclear physics, atomic physics, molecular physics, etc.

G. Smith
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