Why is the Earth habitable today but Venus and Mars not? This lecture
explores the question of planetary habitability from the perspective of
the stability of liquid water on the surface of planetary bodies. We
will see how the amount of sunlight and the greenhouse effect in the
atmosphere combine to create a classic Goldilocks problem: whether or
not a p ... Show More
Nov 2009
Lecture 29: The Children of Saturn
Among the 61 known moons of Saturn, two stand out: Enceladus and Titan.
Giant Titan is the only moon in our Solar System with a substantial
atmosphere, composed of nitrogen and methane, dense enough to maintain a
weather cycle with methane analogous to the water cycle on Earth, e ... Show More
46m 10s
Nov 2009
Lecture 28: The Galilean Moons of Jupiter
The four large Galilean Moons of Jupiter seem unlikely places to look
for life; at first glance they should be cold, dead, icy worlds.
Instead we find tremendous geological diversity, and two big surprises:
volcanically-active Io, and icy Europa. Io is the most volcanically
activ ... Show More
44m 57s
Nov 2009
Lecture 27: Is There Life on Mars?
Is there life on Mars? We begin with a brief historical survey of the idea of inhabitable Mars, from Herschel to Lowell, and look at how the idea of Mars and Martians is deeply embedded in the popular culture. We then turn to spacecraft explorations of Mars, and how they have cha ... Show More
47m 4s
Mar 2022
Comment calculer l'âge d'une étoile ?
La durée de vie d'une étoile peut nous renseigner sur sa composition et sur l'existence éventuelle de la vie dans le cosmos. mais, en dehors du Soleil, il est assez difficile de déterminer l'âge d'une étoile.
L'importance de la masse
En évaluant, grâce à la radioactivité, l'âge d ... Show More
1m 58s