John Ambrose Fleming (November 29, 1849 - April 18, 1945) was an English electrical engineer and physicist. In 1904, he invented the two-electrode vacuum-tube rectifier, which he called the oscillation valve. It was also called a thermionic valve, vacuum diode, kenotron, thermionic tube, or Fleming valve. This invention is often considered to have been the beginning of electronics, for this was the first vacuum tube. Fleming's diode was used in radio receivers and radars for many decades afterwards, until it was superseded by solid state electronic technology more than 50 years later. He also contributed in the fields of photometry, electronics, wireless telegraphy (radio), and electrical measurements. He coined the term Power Factor to describe the true power flowing in an AC power system. Fleming was a devout Christian and in 1932, along with Douglas Dewar and Bernard Acworth, helped establish the Evolution Protest Movement. Having no children, he bequeathed much of his estate to Christian charities, especially those that helped the poor. He was an accomplished photographer and, in addition, he painted watercolors and enjoyed climbing in the Alps. He died in 1945 at the age of 95.