Empirical Earth · Gravity, Buoyancy & the Air

Why nobody falls off the bottom — “down” is local

The claim

“On a globe, wouldn’t people on the bottom be upside down and fall off into space?”

What is measured

Gravity pulls toward Earth’s center everywhere, so “down” is local and space has no absolute up or down. People in the Southern Hemisphere stand upright on their own ground, a plane’s floor turns with it around the underside, and there is no edge to fall off. The “upside-down” worry assumes a universal “down” that does not exist.

What would show this is wrong

demonstrating a universal, fixed “down” direction in space independent of local mass, such as objects in the Southern Hemisphere falling “up” away from Earth’s center, or a plane’s occupants becoming inverted as it crosses the underside.

Sources

  1. Why nobody falls off: gravity points to the center. Gravity pulls every mass toward Earth’s center, so “down” is local everywhere and space has no absolute up or down; people in the Southern link
  2. “True down” is toward the center. A physicist notes that “true down” is always toward Earth’s center; even a flat disc’s gravity would pull toward its own center, so those away from the midd link
  3. Deflection of the vertical. Geodesy defines the deflection of the vertical as the angle between the local plumb line, which is the direction of gravity, and the normal to the reference ellip link
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