The Royal Institution Christmas Lectures
Carl Sagan: The Planets
What exists beyond Earth? Over six Lectures presented in 1977, American astronomer and cosmologist Carl Sagan explores the vast expanse of space that surrounds the third planet from the Sun.
Where to Watch The Royal Institution Christmas Lectures • Carl Sagan: The Planets
6 Episodes
- The Earth as a PlanetE1
The Earth as a PlanetIn his first Christmas Lecture, American astronomer and cosmologist Carl Sagan explores planet Earth and the place, scale and geometry of the “pale blue dot” in the Solar System. Sagan provides a unique insight into the history of our knowledge of the third planet from the Sun, formed 4.5 billion years ago. Using images and models of the planets in our Solar System, Sagan reveals how the heliocentric model of our universe, in which the Earth and planets revolve around the Sun, came to replace the earlier Aristotelian idea that our planet was at the centre and everything orbited around it. - The Outer Solar System and LifeE2
The Outer Solar System and LifeFrom ancient organisms to the plants and animals we see today, our planet showcases a spectacular array of life. But beneath such diversity lies an underlying unity. All life on Earth is based on two molecules (the proteins and the nucleic acids) and the origin of these molecules in the early stages of our planet’s development is inextricably linked to the origin of life. - The History of MarsE3
The History of MarsCold, arid, and tens of millions of miles away from Earth, Mars has intrigued scientists for centuries. The existence of liquid on its surface was confirmed by NASA’s flyby mission, Mariner 4, in 1965, but the question of whether life exists on our neighbouring planet has remained a subject of much speculation. - Mars Before VikingE4
Mars Before VikingObserving the planets in our solar system from Earth provided limited scope for astronomers wishing to explore them in more detail. To get a better understanding of planets such as Mars, astronomers needed to get a closer look through the use of unmanned space probes which could beam data back remotely. In this Lecture, Carl Sagan explores the surprising discoveries made by Mariner 9, the first unmanned space probe to orbit another planet. This mission went on to provide scientists with a glimpse at Mars that was wildly different from their expectations. Sagan explores the features of Mars as uncovered by Mariner 9, including the formation of craters, presence of volcanoes, polar regions and the significance of its winding sinuous valleys and tributaries. These findings point towards a planet that has undergone considerable climate change, with early evidence that it might once have been conducive to terrestrial life. - Mars After VikingE5
Mars After VikingIn his fifth lecture, Carl Sagan takes a look at the design, launch and accomplishments of the Viking mission, a major chapter in the history of planetary exploration. After Mariner 9s remote orbital inspection of Mars, the Viking program finally allowed scientists to study the Martian surface in detail. The photography of the terrain, the chemical analysis of the soil and testing for microbiological life yielded stunning, yet enigmatic results. Results returned from the microbiology experiments gave signs consistent with life, however the search for organic molecules in the Martian soil turned up completely negative. The conflict between these results suggested either the presence of microbiological life or a non-biological, inorganic process occurring within the Martian soil. Four decades later – following the success of subsequent Mars rovers – the question concerning life on Mars is one that still remains unanswered. - Planetary Systems Beyond Our SunE6
Planetary Systems Beyond Our SunTheoretical work on the origin of solar systems suggests that planets are a frequent, if not invariable, accompaniment of stars. If there are billions of planets, if the origin of life occurs readily under general cosmic conditions, and if there are many worlds much older than the Earth for evolution to work upon, why shouldn’t the galaxy be brimming over with life?