The speed of light in a vacuum is exactly equal to 299,792,458 metres
per second (approximately 186,282 miles per second). This exact speed
is a definition, not a measurement, as the metre is defined in terms
of the speed of light and not vice versa. According to standard
modern physical theory, all electromagnetic radiation, including
visible light, propagates (or moves) at a constant speed in vacuo,
known as the speed of light, which is a physical constant denoted as
c. According to the theory of special relativity, all observers will
measure the speed of light as being the same, regardless of the
reference frame of the observer or the velocity of the object
emitting the light.
Read the rest of this article:
http://en.wikipedia.org/wiki/Speed_of_light
Today's selected anniversaries:
1787 Mozart's opera Don Giovanni received its first performance
in Prague.
(
http://en.wikipedia.org/wiki/Don_Giovanni)
1886 New York City office workers spontaneously "invented" the
ticker tape parade.
(
http://en.wikipedia.org/wiki/ticker_tape_parade)
1923 Mustafa Kemal Atat�rk became the first President of the
Republic of Turkey, a new nation founded from remnants of
the Ottoman Empire.
(
http://en.wikipedia.org/wiki/Kemal_Atat�rk)
1945 The first ballpoint pens went on sale at a department store
in New York City for US$12.50 each.
(
http://en.wikipedia.org/wiki/Ballpoint_pen)
1956 The Suez Crisis began: Israel invaded the Sinai Peninsula
and pushed Egyptian forces back toward the Suez Canal.
(
http://en.wikipedia.org/wiki/Suez_Crisis)
1998 The Truth and Reconciliation Commission presented its
report on Apartheid in South Africa.
(
http://en.wikipedia.org/wiki/Truth_and_Reconciliation_Commission)
Wikiquote of the day:
"We're just being ourselves and having fun playing baseball. The
biggest thing is when people look at our team, they can see that
we're having a lot of fun." ~ Johnny Damon
(
http://en.wikiquote.org/wiki/Johnny_Damon)