✓ Sources checked · 10 September 2026 · View verification
Gravity connects falling objects with orbiting planets. Near Earth it gives objects weight; over astronomical distances the same interaction helps organize bound systems.
By Matan · Updated
Mass, distance and weight
Newton’s model gives F = GMm/r² for point masses or suitable spherical bodies, where r is centre-to-centre distance. Near Earth, weight is approximately mg. Mass and weight differ: changing location changes g and therefore weight without changing the object’s mass. [1]
Worked gravity above a planet
Take a model planet with surface gravity 9.8 m/s² and radius R. At a distance 2R from its centre, gravitational acceleration is 9.8/4 = 2.45 m/s². A 60 kg person would have gravitational force 147 N there, compared with 588 N at the surface. This point is one planet radius above the surface, not two.
Falling can continue around a planet
A satellite has sideways motion while gravity continually bends its path. Orbiting astronauts and their spacecraft fall together, which explains their near-weightlessness; gravity has not switched off. A gravity assist also depends on the motion of the encountered body, rather than being energy obtained from a stationary ramp.
Use analogies carefully
A trampoline picture illustrates curvature but relies on external gravity to pull balls down and is not a literal model of spacetime. General relativity gives a deeper description involving spacetime geometry. Tides depend on differences in gravitational acceleration across an extended body, not just one uniform upward bulge. [2]
Continue learning
- Why Things Fall Down
- Why is the equivalence between inertial and gravitational mass important in physics
- Six uses of gravity assists, with a velocity example
How this article was checked
Sources checked; calculations checked where shown. Main claims and model assumptions were checked against the references below. Example arithmetic and units were checked separately. Numerical examples are illustrative calculations, not experimental measurements.
Source checking and editing assisted by AI. No independent human scientific review is recorded for this revision. This record applies to the version dated 10 September 2026.
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Sources and further reading
Cite this article
Matan. “Gravity: The Universe’s Invisible Glue.” Your Physicist. Originally published 2026-06-11; updated 2026-09-10. https://your-physicist.com/gravity-the-universes-invisible-glue/
Revision history
10 September 2026: Added inverse-square altitude calculation and qualified trampoline, tide and gravity-assist analogies. Added references and a transparent verification record.
