Daniell, John Frederic (1790-1845), an English scientist. He was born in London, and in 1831 was made professor of chemistry at King's College, London. He invented the dew-point hygrometer, which measures relative humidity; a pyrometer (a type of thermometer); and an electric cell called the Daniell cell. He wrote Meteorological Essays (1823) and other scientific works.
He's ventured to the abyss of black holes, wagered on the information paradox and floated around in zero gravity. Meet the man, the legend, the super scientist: Stephen Hawking.
He is famous for a phrase he never said, for wearing turtlenecks and for hosting the original 'Cosmos' TV series. As enthusiastic about the stars as he was about marijuana, Carl Sagan led a very surprising life. Here are 10 cool facts.