This episode documents how gravity has an effect across the universe, and how the relatively weak force creates an orbit. We also see how a neutron star's gravity works. Finally, there is a look back at how research on gravity has enabled us to better understand the cosmos.
To land a human being on another celestial body will be the first step to living beyond our planet. The breathless pace and daring of the Apollo program sees NASA master previously unimagined tasks in the attempt to achieve the most incredible accomplishment in the history of human endeavor. From the ashes of tragedy on Apollo 1 emerges a determination that puts Apollo 8 in orbit around the Moon ahead of schedule. Apollo 9 and 10 each break bold new ground and pave the way for something few dared to believe was possible. When Neil Armstrong and Buzz Aldrin walk on the Moon and return safely to earth, the whole planet throws them a party.
Quantum theory, the best explanation of how atoms and anything smaller behave, is so weird even scientists who have mastered it find it baffling. But bit by bit scientists are finding maybe it's not so weird as comparable behavior is discovered in our every day world. It's just that no one noticed before.
Were "little green men" trying to contact us? Over 40 years ago, extremely constant pulses were detected reaching the Earth from outer space. It caused a great sensation. Using a radio telescope larger than a baseball field, scientists looked for the source of these signals and found - pulsars.
Today we’re rounding out our planetary tour with ice giants Uranus and Neptune. Both have small rocky cores, thick mantles of ammonia, water, and methane, and atmospheres that make them look greenish and blue. Uranus has a truly weird rotation and relatively dull weather, while Neptune has clouds and storms whipped by tremendous winds. Both have rings and moons, with Neptune’s Triton probably being a captured iceball that has active geology.
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).
Imagine a world where dinosaurs still walk the earth. A world where the Germans won World War II and you are president of the United States. Imagine a world where the laws of physics no longer apply and where infinite copies of you are playing out every storyline of your life. It sounds like a plot stolen straight from Hollywood, but far from it. This is the multiverse. Until very recently the whole idea of the multiverse was dismissed as a fantasy, but now this strangest of ideas is at the cutting edge of science. And for a growing number of scientists, the multiverse is the only way we will ever truly make sense of the world we are in. Horizon asks the question: Do multiple universes exist? And if so, which one are we actually in?