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Transcript: Supernovae are rare because they represent the death stage of rare massive stars. On average, one occurs every fifty years in an entire galaxy. We might expect one in a human lifetime in the Milky Way, but a supernova might not be visible if it lies behind the dusty plane of the Milky Way. Ancient Chinese astronomers called them guest stars, and there’s good evidence that the star of Bethlehem was in fact a supernova. Perhaps the most famous supernova is the explosion that gave rise to the Crab Nebula. At the time it exploded it was visible in broad daylight for twenty-three days in July 1054 and at night for another six months afterwards. The Crab Nebula was recorded in Chinese, Japanese, and Islamic documents, and in Native American rock art. There have been fourteen supernovae in recorded human history, and in a sense we’re long overdue because the last one was nearly 400 years ago.
Transcript: A fundamental prediction of General Relativity is the fact that time slows down in strong gravitational fields. The ultimate test of this idea would be to observe someone falling into a black hole carrying a clock. In theory, the clock would slow down and come to a complete halt as...
Published 07/25/11
Transcript: Any change in a gravitational field or gravitational configuration causes ripples in space time to be emitted. These disturbances which travel at the speed of light are called gravity waves or gravitational radiation. Pulsars slow down slightly in their periods, and this corresponds...
Published 07/25/11
Transcript: If you throw an object up into the air it will eventually slow down and fall back to Earth. The object is losing kinetic energy by trying to climb out through the gravitational field of the Earth. Photons also lose energy as they climb out of the pit of gravity. This effect is...
Published 07/25/11