Last Watched

"Comet"  Sort by

Comet of the Century

   2013    Science
Comet ISON can well be the brightest and most spectacular comet for a generation. It appeared above the eastern horizon from December 2013 as a glorious streak across the sky. ISON has been travelling towards the sun for ten thousand years and will make only one orbit through its corona before disappearing off into the outer solar system.
But as well as providing a great spectacle, ISON's tail of vaporised gas and water, hundreds of millions of kilometres long, will give insights into some of the greatest mysteries of science; it will help explain the origins of the solar system, whether earth's water was delivered on comets and even whether we are alone in the universe.

One Voice in the Cosmic Fugue

   1980    Science
Sagan discusses the story of the Heike crab and artificial selection of crabs resembling samurai warriors, as an opening into a larger discussion of evolution through natural selection (and the pitfalls of intelligent design). Among the topics are the development of life on the Cosmic Calendar and the Cambrian explosion; the function of DNA in growth; genetic replication, repairs, and mutation; the common biochemistry of terrestrial organisms; the creation of the molecules of life in the Miller-Urey experiment; and speculation on alien life (such as life in Jupiter's clouds). In the Cosmos Update ten years later, Sagan remarks on RNA also controlling chemical reactions and reproducing itself and the different roles of comets (potentially carrying organic molecules or causing the Cretaceous–Paleogene extinction event).
Series: Cosmos

Comets: Frozen Wanderers

   2012    Science
We think of comets as beautiful glowing balls of light streaking across our skies with their long sweeping tails, yet comets are so much more than just a cosmic firework display. Comets have a uniquely important place in modern science. As time machines from the early universe, they could hold the key to unlock the secrets of the cosmos. Comets could even be the origin of life itself. We follow the incredible odyssey of a comet as it sails through the solar system, watching it's every move as it evolves from a dormant chunk of ice and rock into a tumbling, violently active nucleus engulfed in a gaseous haze. What we learn is a revelation; comets are even more mysterious and fascinating than we had ever imagined.
Series: How the Universe Works

Gravity

   2008    Science
Gravity is the most powerful and exacting force in the universe. It is pervasive and penetrating. Gravity binds us together, its reach hangs stars in the sky and its grip crushes light. Gravity holds planets together, and leashes them to their suns. Without gravity, stars, comets, moons, nebulae, and even the Earth itself would not exist. Explore how science and humanity discovered, overcame and utilized gravity. Learn what it takes to propel objects into the heavens, to ride a wave or to ski down a slope. Take a front row seat as an astronaut subjects himself to the weightless wonders of the specially modified aircraft used to train astronauts known as the "Vomit Comet."
Series: The Universe

Heaven and Hell

   1980    Science
Sagan discusses comets and asteroids as planetary impactors, giving recent examples of the Tunguska event and a lunar impact described by Canterbury monks in 1178. It moves to a description of the environment of Venus, from the previous fantastic theories of people such as Immanuel Velikovsky to the information gained by the Venera landers and its implications for Earth's greenhouse effect. The Cosmos Update highlights the connection to global warming.
Series: Cosmos
First Life
First Life

   2010    Science
Absolute Zero
Absolute Zero

   2007    Technology
Conquest of the Skies
Conquest of the Skies

   2015    Nature
Chemistry
Chemistry

   2010    Science
The Men Who Built America
The Men Who Built America

   2012    History
Planet Earth
Planet Earth

   2007    Nature
How to Grow a Planet
How to Grow a Planet

   2012    Science