# Gravity - Do atoms orbit humans ?

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## Main Question or Discussion Point

If the Earth orbits the Sun due to the difference in their mass and their distance, then do atoms like air particles orbit humans due to the same reasons?

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Nugatory
Mentor
What do you think and why?

A good starting point might be to calculate the gravitational force between a human body (maybe 100 kg) and an atom (google will find a reasonable value for the the mass of an atom) at a given distance. What orbital speed does that correspond to? How does it compare to the other forces acting on the atom?

Dale
Mentor
How does it compare to the other forces acting on the atom?
And how does it compare to the normal thermal range of speeds for the atom.

hilbert2
Gold Member
A gravitational field does not produce a larger acceleration when acting on a very light object, unlike the electromagnetic force between objects of some given electric charge. I think this is the misconception in this case.

russ_watters
Mentor
If the Earth orbits the Sun due to the difference in their mass and their distance, then do atoms like air particles orbit humans due to the same reasons?
Things don't orbit really large objects due to mass difference, they orbit them because gravity is a weak force that acts best at large distances where other forces don't interfere.

For example, you can get a spacecraft to orbit a mountain sized asteroid in space. But even ignoring Earth's gravity you couldn't get something to orbit a mountain on Earth because the orbit would be so slow that wind would disrupt it!

Note that objects of equal mass can orbit each other, so mass difference means nothing. For example, Jupiter's mass fraction of the sun is about the same as a golf ball vs you.

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Mister T