The Roche limit is the distance within which an object (typically a satellite in orbit) near a celestial body (typically a moon, planet or star) and held together only by its own gravity will start to disintegrate due to tidal forces exceeding the satellite's gravitational self-attraction. Within the Roche limit the net forces experienced by opposite ends of the satellite, gravity acting more strongly on the side closest to the body orbited and less strongly on the far side, are stronger than the force holding the satellite together, the satellite's own gravitational attraction. The term is named after Édouard Roche, the French astronomer who first discovered this theoretical limit in 1848.

Read the rest of this article: http://en.wikipedia.org/wiki/Roche_limit

Today's selected anniversaries:

1469 Ferdinand II of Aragon married Isabella of Castile. Their marriage led to the unification of Aragon and Castile into a single country, Spain. (http://en.wikipedia.org/wiki/Ferdinand_II_of_Aragon)

1604 Kepler's Star: German astronomer Johannes Kepler observed that an exceptionally bright star had suddenly appeared in the constellation Ophiuchus. This 'new star' turned out to be the last supernova observed in our own galaxy, the Milky Way. (http://en.wikipedia.org/wiki/SN_1604)

1989 Loma Prieta earthquake: The largest earthquake to occur on the San Andreas Fault in California since 1906, struck the San Francisco Bay Area at 5:04 pm local time and measured 7.1 on the Richter scale. (http://en.wikipedia.org/wiki/Loma_Prieta_earthquake)

2003 The pinnacle was fitted on the roof of Taipei 101, a 106-floor skyscraper in Taipei, allowing it to surpass the Petronas Twin Towers in Kuala Lumpur by 50 meters (165 feet) and become the World's tallest building. (http://en.wikipedia.org/wiki/Taipei_101)

Wikiquote of the day:

"Nothing endures but change." ~ Heraclitus (http://en.wikiquote.org/wiki/Heraclitus)