Today Edmond Halley is known as the scientist whose comet returns every 75 years or so. But he was a man of many talents who did much more than make a prediction about a comet that happen to appear during his time. Probably Halleys biggest impact on history was from an idea for finding the distance to the sun. After viewing a transit of Mercury across the suns face during a starmapping trip to the southern hemisphere, Halley hit on the idea of timing a transit of Venus in different parts of the world as a way of discovering the distance to the sun. Halleys scheme would eventually send Captain James Cook on his first voyage into the South Pacific aboard Endeavour years after Halleys death. Halley himself made several scientific trips to southern waters. His aim was to investigate the earths magnetic field, but he was also charged with attempting to discover new lands in the South Atlantic. Beyond a scrap of land many miles off the coast of Brazil, he found nothing new in the way of land. But measurements of the earths magnetism gave support for his ingenious theory of how the earth is put together. Adventurer Halley also gained fame as an early underwater explorer. He developed a diving bell and a diving helmet and used them under the waters of the English Channel, intending eventually to hunt for sunken treasure. Halley was surely the 17th centurys most active promoter of science, serving for years as editor for publications of the influential Royal Society. He is acclaimed for encouraging the reluctant Isaac Newton to publish his ideas about motion and gravity. Altogether, Halley gave the world much more than a name for a speedy comet.