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Gravity

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.

Featured Images

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

HST image of thousands of galaxies

Galaxies Galore April 17, 2014

Hubble image of a galaxy cluster and the deduced location of its dark matter

Dark Universe August 5, 2013

GRAIL map of lunar surface gravity

Lunar Lumpiness April 14, 2013

Gravitational map of the Moon compiled by the GRAIL mission

Lunar Attraction December 15, 2012

Optical and X-ray image of the galaxy cluster Abell 383

Brilliant Darkness March 16, 2012

Map of the Moon's gravitational field

Lunar Lumpiness September 6, 2011

Radio Programs

Speed of Gravity Measuring the speed of gravity January 11, 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

On the Frontier Pushing the intergalactic frontier March 8, 2015