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Gravity: It's What Keeps Us Together


Image using color to show gravity concentration on the surface of the Moon.
This gravity map of the Moon was made by Lunar Prospector in 1998-1999; the red areas show gravitational anomalies due to mass concentrations beneath the lunar mare. The new GRAIL mission will provide much more detailed information about the Moon's gravitational field. Credit: A.S. Konopliv in Icarus.

Gravity is the powerful force that glues our universe together. Gravity helped form our solar system, the planets, and the stars. It holds the planets in orbit around the Sun, and moons in orbit around the planets. The gravitational pull of the Sun and Moon creates the tides on Earth. Far beyond our solar system, the irresistible force of gravity is collapsing stellar cores into amazing - and bizarre - objects in our universe--neutron stars and black holes.

Pushing the Moon Away
Our Moon is moving farther away from Earth!
The energy transferred from gravitational tides
is causing the Moon to move away at almost
4 cm a year, and slowing the Earth's rotation!
Color image of the moon rising over the limb of the Earth.

This fundamental force of gravity will help scientists model the interior of our Moon, Earth, and other planets, and measure the masses of distant stars and galaxies. NASA's GRAIL mission is studying the Moon's gravitational field, which will give scientists a better picture of the lunar interior.

The GRACE mission is still making detailed measurements of our home planet's gravity field while providing a unique tool for monitoring the Earth's natural systems. Gravity Probe B, a mission that has now ended, measured predictions of Einstein's general theory of relativity to verify the fundamental effect of gravity on time and space. Observatories on the ground are trying to observe the gravitational waves rippling through our universe to study distant black holes and the early evolution of the universe.

Check out this topic's activities in Classrooms and Organizations and Clubs to explore tides, your weight on other worlds, and orbits of moons and comets. It's a weighty topic; join us to tackle it together!

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Last Updated: 12 Sep 2014