I seem to be missing something when I read articles that refer to the immense pressures at Earth’s core. If the source of gravity is mass and there’s equal mass in all directions at the core, then the core should be suspended in zero gravity. It’s very frustrating for me to get this wrong.

Glenn T. Picard
Montebello, Calif.

Relax, you’re only half wrong. It’s true that the force of gravity drops to zero at the center of Earth. However, the pressure at any point within Earth is the sum of the pressures imposed by the material above it. Though weightless, an object at the center of Earth would be under pressure that’s about 3.6 million times that of the atmosphere at sea level. –S. Perkins