Also, why is the weak interaction force $10^7$ times smaller than the strong nuclear force?
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5$\begingroup$ Relevant self-promotion: physics.stackexchange.com/a/127010/50583 $\endgroup$– ACuriousMind ♦Commented Dec 15, 2014 at 16:05
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2$\begingroup$ Physics does not answer "why" questions. At most we could answer a question like "What's the mechanism that causes gravity at the GeV scale to be much weaker than the other forces?". The honest answer to that would be, that currently nobody knows. Many theorists have made very detailed suggestions for the mechanisms that may be behind this phenomenon, but we have no way of knowing which one of these explanations is correct (if any). After reading ACuriousMind's answer I gave him an upvote and I would give another, if I could. He is spot on. $\endgroup$– CuriousOneCommented Dec 15, 2014 at 16:08
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$\begingroup$ @CuriousOne I think the question is "what does such a comparison mean ?". I think the question is thus about the Coupling constant. $\endgroup$– TZDZCommented Dec 15, 2014 at 16:15
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$\begingroup$ @TZDZ: The comparison is quite naive. It's just the ratio between the force of gravity AS CALCULATED using Newtonian theory at nuclear distances relative to the order of magnitude of measured electroweak and color force. The actual force of gravity has never been measured at that distance and it could be quite a bit larger without perturbing our current dataset in nuclear and high energy physics. The best experiments we have can measure gravity at the scale of 0.1mm, I believe, and at that distance it seems to be perfectly Newtonian. What happens between 0.1mm and 1e-15m we don't know! $\endgroup$– CuriousOneCommented Dec 15, 2014 at 16:20
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3$\begingroup$ Zade, I think it's time you stopped posting a deluge of naive questions and took the time to go off and read some physics texts if you're really interested in this stuff. $\endgroup$– Carl WitthoftCommented Dec 15, 2014 at 16:49
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2 Answers
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The Anthropic answer to this question is that if gravity were a lot stronger, then the evolution of the universe would have proceeded in a different way, it would have collapsed just after the Big Bang. One can speculate that all possiblities really exists, but we can obviously only find ourselves in those universes with laws of physics that are compatible with our existence. Moreover, the laws of physics will appear to be fine tuned to maximize the probability of our existence. In reality there is no such fine tuning, it's all an observer selection effect.
answered Dec 15, 2014 at 17:55
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There is no reason we humans can tell why gravitational force is so weak. We did not create it. We just measured it and found it was too low.
