General relativity is a theory of gravitation that was developed by Albert Einstein. According to general relativity, the observed gravitational attraction between masses results from the warping of space and time by those masses. Before the advent of general relativity, Newton's law of universal gravitation had been accepted. Experiments show that Einstein's description accounts for several effects that are unexplained by Newton's law. Some general relativity predictions have been confirmed by experiment, while others are the subject of ongoing research. General relativity has developed into an essential tool in modern astrophysics. It provides the foundation for the current understanding of black holes and of the standard Big Bang model of cosmology. Although general relativity is not the only relativistic theory of gravity, it is the simplest such theory that is consistent with the experimental data. Nevertheless, a number of open questions remain: the most fundamental is how general relativity can be reconciled with the laws of quantum physics to produce a complete and self-consistent theory of quantum gravity.

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

_______________________________ Today's selected anniversaries:

1025:

Bolesław I Chrobry became the first King of Poland. http://en.wikipedia.org/wiki/Boles%C5%82aw_I_Chrobry

1506:

Construction of the current St. Peter's Basilica in Vatican City, to replace the old St. Peter's Basilica built in the 4th century, began. http://en.wikipedia.org/wiki/St._Peter%27s_Basilica

1906:

A major earthquake and resulting fires devastated San Francisco, killing at least 3,000 people and leaving more than half of the city's population homeless. http://en.wikipedia.org/wiki/1906_San_Francisco_earthquake

1942:

World War II: Sixteen B-25 Mitchell bombers from the aircraft carrier USS Hornet carried out the Doolittle Raid, the first Allied attack on the Japanese home islands. http://en.wikipedia.org/wiki/Doolittle_Raid

1983:

A suicide bomber destroyed the United States Embassy in Beirut with a car bomb, killing over 60 people. http://en.wikipedia.org/wiki/1983_United_States_Embassy_bombing

1996:

Israeli forces shelled Qana, Lebanon, during Operation Grapes of Wrath, killing over 100 civilians and injuring over 110 others at a UN compound. http://en.wikipedia.org/wiki/1996_shelling_of_Qana

_____________________________ Wiktionary's word of the day:

cicatrise (v): 1. To heal a wound through scarring (by causing a scar or cicatrix to form). 2. To form a scar http://en.wiktionary.org/wiki/cicatrise

___________________________ Wikiquote quote of the day:

I believe that music can be an inspirational force in all our lives — that its eloquence and the depth of its meaning are all-important, and that all personal considerations concerning musicians and the public are relatively unimportant — that music come from the heart and returns to the heart — that music is spontaneous, impulsive expression — that its range is without limit — that music is forever growing — that music can be one element to help us build a new conception of life in which the madness and cruelty of wars will be replaced by a simple understanding of the brotherhood of man. --Leopold Stokowski http://en.wikiquote.org/wiki/Leopold_Stokowski