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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.

Featured Images

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

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

Neutron Stars Gravity wins the stellar battle March 20, 2013

Wobbly Clocks Listening for cosmic “ripples” May 10, 2012

Gravity Probe B Putting a spin on space itself May 9, 2012

General Relativity Albert Einstein “warps” the universe May 6, 2012

White Dwarfs II Stretching the light of a dead star February 1, 2012

Gravitational Waves V The “wavy” birth of a black hole January 26, 2012

Gravitational Waves IV Silencing the rumbling Earth January 25, 2012

Gravitational Waves III Lighting up ripples in spacetime January 24, 2012

Gravitational Waves II Tiny ripples from heavy objects January 23, 2012

Gravitational Waves Rippling across the universe January 22, 2012

Lumpy Moon Measuring the Moon’s “lumpiness” September 5, 2011

Apollo 15, Part II Putting Galileo to the test July 30, 2011

Urbain Leverrier A "calculated" planetary discovery... March 10, 2011