Today on Crash Course Astronomy, Phil explains comets. Comets are chunks of ice and rock that orbit the Sun. When they get near the Sun the ice turns into gas, forming the long tail, and also releases dust that forms a different tail. We’ve visited comets up close and found them to be lumpy, with vents in the surface that release the gas as ice sublimates. Eons ago, comets (and asteroids) may have brought a lot of water to Earth -- as well as the ingredients for life.
To determine the true age of the Earth, geochemist Clair Patterson developed the uranium-lead dating method to make an unprecedented discovery - calculating Earth's age of 4.5 billion years. But Patterson's groundbreaking discoveries were just beginning. Patterson made it his mission to draw public attention to the detrimental effects of lead in the environment and dedicated his career to fighting against the petroleum and chemical industry, eventually achieving public health's biggest victory of the 20th century.
Black holes are the least understood places in the universe, where the rules of physics collapse. We go inside the supermassive black hole in the center of the Milky Way to uncover terrifying secrets about parallel universes, wormholes, and space-time.
43m • 2015 • How the Universe Works
Wanderers is a vision of humanity's expansion into the Solar System, based on scientific ideas and concepts of what our future in space might look like, if it ever happens.
Cassini-Huygens has given us a more detailed account of Saturn than we could have ever imagined. Breathtaking images of Saturn and its sparkling rings, a massive 6-sided polar storm, and 62 moons - including the most bizarre worlds in our Solar System -- we have seen them all thanks to Cassini.
21m • 2016 • Space Probes
Neil deGrasse Tyson sets off on the Ship of the Imagination to chase a single comet through its million-year plunge toward Sol. Later, Tyson visits the birth-place of Sir Isaac Newton and retraces the unlikely friendship between Newton and brilliant polymath Edmond Halley. It was Halley's patience and generosity which allowed Newton to conquer his fear of isolation and find the courage to publish his masterwork, "Principia Mathematica" which launched a scientific revolution.