Astronomers study a lot of gorgeous things, but nebulae might be the most breathtakingly beautiful of them all. Nebulae are clouds of gas and dust in space. They can glow on their own or reflect light from nearby stars. When they glow it’s usually predominantly red from hydrogen and green from oxygen, and when they reflect and scatter light it’s from massive hot stars, so they look blue. Stars are born in some nebulae, and create new ones as they die. Some nebulae are small and dense, others can be dozens or hundreds of light years across.
On a high plateau in a remote desert in northern Chile lies the largest observatory on Earth, ALMA, or Atacama Large Millimeter/Submillimeter Array. The name refers to a network of 66 massive radio telescopes, working in unison to observe the birth and death of stars and planets, and answer centuries-old questions about the origins of our universe. Witness the history of ALMA, the remarkable product of a 20-year global effort, and see how it is already changing our basic understanding of the cosmos, and astronomy itself.
2013 • Astronomy
Right now, we know there is water on the Moon. But how much water? Is water largely at the poles? These are Strategic Knowledge Gaps that scientists are working to fill in, and a Resource Prospector robot will be launched to the moon in the 2020's to look for the presence of water
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).