If you imagine yourself at the center of the earth your are floating since the pull is the same around you. But let us say you could turn up the gravity as much as you want. Why aren’t you pulled apart? The net forces are zero, sure. But wouldn’t the body experience tension?

Question

If we compare it to a rope pulled by two equal forces in each end. The net forces would be zero and you would have static equilibrium, but the rope would still break if pulled hard enough.

Additionally, wouldn’t a metal ball uniformly surrounded by powerful magnets be pulled apart as well?

I am not sure why I can’t wrap my head around this, when it comes to the center of the earth.

In: 83

Answer 1

Tension happens when different parts of an object are being pulled apart, and the internal binding forces of the object have to hold it together. When it happens with gravity, we usually call it a tidal force.

The thing is, when you’re inside a uniform spherical shell, there is exactly zero gravitational force from the mass in the shell. No matter where you are inside, each particle in your body will feel a net force of zero, so there’s nothing pulling it away from any other part of you.

So if you imagine the Earth as one or more uniform spherical shells that are outside you, and you’re living in a small cavity in the middle, there isn’t any gravitational force on you at all (from the Earth itself). So there’s no different force on different parts of you to pull you apart.

The shell thing is even cooler with electricity, because there are negative electric charges and they can move around. So you don’t even need a complete shell, or a net charge on the shell, and the charges in the shell can rearrange themselves to cancel out any field from anything else outside the shell too. This is called a “Faraday cage”