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The most feeble of the four fundamental forces in the universe that affect all matter. The magnitude of gravitational attraction depends directly on mass and inversely on distance squared. For instance, the gravitational attraction between you and Earth is much greater than that between you and the Sun, even though the Sun is 333,000 times more massive than Earth. The distance separating you from the Sun weakens the mutual gravitational attraction, so as you stand on Earth’s surface, Earth’s gravitational pull on you is 1,650 times greater than the Sun’s.

Radio Programs

Solar Lens A giant “lens” for imaging planets September 28, 2020

Hunting by Gravity Using gravity to track down planets July 24, 2020

Jupiter at Opposition The giant influence of a giant planet July 12, 2020

Time Machines Taking a trip into time September 20, 2019

Subatomic Astronomy Going small to study the universe January 31, 2019

Losing Weight A “global” weight-loss plan October 18, 2018

Round Earth Rounding off planet Earth September 3, 2018

Distant Planets Planets at the spout of the teapot August 29, 2018

The Great War, III The man who solved Einstein’s equations May 11, 2016

Gamma-Ray Bursts II A final gasp from dead stars April 19, 2016

Fingernail Moon Moving at the speed of a fingernail March 10, 2016

Featured Images

Artistic idea of a planet imaged through a solar gravitational lens

Long-Range Scanner September 28, 2020

Rippling Through Space February 19, 2019

gravity map of a portion of the Moon

Lumpy Moon June 22, 2018

Hubble Space Telescope view of a gravitational lens

Galactic Lens July 22, 2016

Hubble Space Telescope view of Abell 2744, a massive galaxy cluster

On the Frontier March 9, 2015