The speed of light in vacuum, denoted c, is a physical constant that is exactly equal to 299,792,458 metres per second (approximately 186,282 miles per second, or one foot per nanosecond). According to standard modern physics, visible light and all other electromagnetic radiation moves at this constant speed in vacuum, and c is the fastest speed at which matter, energy or any signal carrying information can travel through space. Ole Rømer first demonstrated in 1676 that light does not travel instantaneously by studying the apparent motion of Jupiter's moon Io (diagram shown). In an 1865 paper, James Clerk Maxwell proposed that light was an electromagnetic wave, and therefore travelled at the speed c. According to the theory of special relativity, which interrelates space and time, all observers will measure the speed of light as being the same, regardless of the inertial reference frame of the observer or the velocity of the object emitting the light.
Read more: https://en.wikipedia.org/wiki/Speed_of_light
_______________________________ Today's selected anniversaries:
1942:
The Holocaust: During the deportation of Jews from Slovakia, President Jozef Tiso gave a speech describing Jews as "parasites" and "the eternal enemy". https://en.wikipedia.org/wiki/Jozef_Tiso%27s_speech_in_Holi%C4%8D
1945:
The Stanley Internment Camp in Hong Kong was liberated following the announcement of the surrender of Japan in World War II. https://en.wikipedia.org/wiki/Stanley_Internment_Camp
1962:
The English rock band the Beatles fired their drummer Pete Best, replacing him with Ringo Starr (pictured). https://en.wikipedia.org/wiki/Ringo_Starr
1986:
Typhoon Wayne formed over the South China Sea, going on to become one of the longest-lived tropical cyclones in the north-western Pacific, lasting 21 days. https://en.wikipedia.org/wiki/Typhoon_Wayne_%281986%29
_____________________________ Wiktionary's word of the day:
catapeltic: 1. (military, weaponry, archaic) Pertaining to a catapult or catapults. 2. (military, weaponry, obsolete, rare) A catapult. https://en.wiktionary.org/wiki/catapeltic
___________________________ Wikiquote quote of the day:
Take heed of doing irrevocable acts in thy passion, As the revealing of secrets, which makes thee a bankrupt for society ever after: neither do such things which done once are done for ever, so that no bemoaning can amend them. Sampsons hair grew again, but not his eyes: Time may restore some losses, others are never to be repaird. Wherefore in thy rage make no Persian decree which cannot be revers'd or repeald; but rather Polonian laws which (they say) last but three dayes: Do not in an instant what an age cannot recompence. --Thomas Fuller https://en.wikiquote.org/wiki/Thomas_Fuller