Gravitational field strength is a_g = GM/r², where r is measured from the centre of the planet, not its surface. Because r is squared, doubling your distance from the centre cuts the field to a quarter, not a half — at r = 2R the field is 1/4 of its surface value, at 3R it is 1/9, and at 4R it is 1/16. The field depends only on the planet's mass M and the distance r; the orbiting object's own mass never enters the equation.

Drag the satellite below to any altitude and watch it happen.

Switch the graph between a_g vs r and a_g vs 1/r². The second view straightens thecurve into a straight line through the origin whose gradient is GM — that is how you confirm an inverse-square law from data rather than assuming it. Use the orbit presets to test it against real spacecraft. At the ISS altitude of 420 km the field is still 88% of surface gravity. Astronauts float because they are in free fall — the station and everyone inside accelerate together, so nothing pushes up on them — not because gravity has vanished. At geostationary altitude (35786 km) the field is down to 2.3% of its surface value.

Change OBJECT MASS m and watch the weight F_g change while a_g stays fixed. That isthe whole point of a field: it belongs to the planet, not to the object sitting in it