A stretching force that is caused by the difference between gravitational forces on opposite sides of an object, such as a planet or moon. For example, because the Moon pulls on opposite sides of the Earth with different strengths, water on the Earth is pulled either toward or away from the Moon, resulting in the ocean tides. Elsewhere in the Solar System, the magnitude of gravitational force on Jupiter's moon Io is greatest on the side of Io that faces Jupiter and least on the back side. The difference between the two forces compresses and stretches Io, which in turn heats up Io's interior. As a result, Io is the most geologically active body in the solar system.


Earth We know our world as an abode for life. Earth is...

Radio Programs

Moon and Regulus Locking the Moon in position Tuesday, July 1, 2014
Moon and Spica Giant tides on giant stars Friday, January 4, 2013
Making Venuses A “stretchy” way to heat a planet Tuesday, April 3, 2012
Lake Tides Small waves on big ponds Saturday, September 10, 2011
Moon and Jupiter Diving into longer days Sunday, December 12, 2010
Palomar 1 The Milky Way destroys a star cluster Saturday, December 4, 2010


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