E.g. why do we experience gravity all the time, but on an atomic scale, the gravitational forces are so small?
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1$\begingroup$ Because it is absurdly weak compared with other forces but always attractive. So large numbers of particles which are electrically neutral in bulk become very dominated by gravity. $\endgroup$– user107153Commented May 17, 2016 at 10:42
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3$\begingroup$ The difference between the diameter of the smallest atom and the entire Universe is about 10 to the 36th power. That means that if you measured the gravitational attraction between the electron and proton in a Hydrogen atom it is about the same amount of force as the electromagnetic attraction of an electron and a proton at opposite sides of the Universe! Gravity is 'really weak! $\endgroup$– drvrmCommented May 17, 2016 at 11:27
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$\begingroup$ gravitational force is dependent on the mass of a particle, whereas other forces such as the electric force is independent of mass, and also much larger than the gravitational force as described above. In the case of the electric force, you have opposite charges that cancel out so on the larger scale mass can continue to increase while the electric force is zero. $\endgroup$– Peter RCommented May 17, 2016 at 14:04
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$\begingroup$ Have a look at comparative forces strength hyperphysics.phy-astr.gsu.edu/hbase/forces/funfor.html $\endgroup$– anna vCommented May 17, 2016 at 15:01
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$\begingroup$ Possible duplicates: physics.stackexchange.com/q/24314/2451 , physics.stackexchange.com/q/4243/2451 , physics.stackexchange.com/q/153443/2451 , and links therein. $\endgroup$– Qmechanic ♦Commented May 17, 2016 at 21:23
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If you see the expression of gravitational force:
$$F=G\frac{m_1m_2}{r^2}$$
it has a coefficient, two mass terms and one distance term.
Now,
$G$ (gravitational constant) $\approx 6.6\times10^{-11}$ SI Units
$m_1$ & $m_2$ (suppose mass of an electron) $\approx 9.1\times10^{-31}\ \mathrm{kg}$
$r$ (distance between two electrons) $\approx 10^{-12}\ \mathrm m$
Gives us force in range of $10^{-47} - 10^{-46}\ \mathrm N$ which is very very less.
And there are other forces working at those distances like Electrostatic Forces, which have magnitude of $1 - 10\ \mathrm N$
Because gravity is dependent on mass at atomic level where mass of atoms and particle become very little magnitude of gravity also becomes very little. Thats why at atomic level gravity has such insignificant effect.
