Elevata

Meet Elevata, a lift passenger who floats when the whole lift is falling.

Mass shows up in two roles. Inertial mass sets how hard something is to accelerate. Gravitational mass sets how strongly gravity pulls on it. Every experiment so far finds them equal, so all objects fall with the same acceleration. Albert Einstein realised in 1907 that this means a person falling freely cannot feel their own weight, and he made this equivalence principle the starting point of general relativity.

In a freely falling lift, you and the floor accelerate together at g, so the floor pushes on you with zero force and a scale reads zero. Astronauts on the International Space Station float for the same reason. At about 400 km up, gravity is still roughly 9.81 × (6371/6771)² ≈ 8.7 m/s², about 89 percent of its surface value; they float because they are falling around Earth.

The equality of the two masses has been tested very precisely, most recently by the MICROSCOPE satellite, to about one part in 10¹⁵.

The principle is local: over large distances tidal effects show up, because gravity is slightly different at your head and your feet.