Gravity inside and outside a spherical shell @animations

Uploaded January 2025 | Updated September 2026, 2 weeks ago

This silly and somewhat buggy little video shows some physics that i found very interesting once upon a time when I was a physics student.

A spherical shell with homogeneous mass distribution obeys the same Newtonian gravitational force as if all the mass was centered in the sphere. Close to the surface, normal projectile (parabolic) motion can be observed as we see close to Earth's surface. However, inside the shell the gravitational force exactly vanishes. That is, if earth would be hollow, then upon drilling a hole on the surface, we would experience normal gravity on the outside and zero gravity if daring jumping down the hole.

The sphere is here depicted in two dimensions for visual purposes. Further, the effect of the hole is ignored, i.e., the ball moves as if there was a shell where the hole is placed.

More info of this concept here: http://hyperphysics.phy-astr.gsu.edu/hbase/Mechanics/sphshell2.html

Beautiful music by @gpcbass and Rogge. It's a Bach reproduction. Full version and more info here: youtube.com/watch?v=1LUzDOIIFO0

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Gravity inside and outside a spherical shell

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