Pale Blue Dot

The Pale Blue Dot is earth but it comes from a photo of earth taken from a great distance. Sagan thinks the image shows us how insignificant we are.

Universe

For Sagan, a universe is a set of galaxies; we live in The universe, the only one we are aware of.

Cosmos

Sagan uses the word "cosmos" to refer to everything that exists, including anything beyond the universe.

The Solar System

The star system where the earth is located, along with seven other planets and the sun.

Voyager 1 and 2

Two robotic spacecraft launched in 1977 and 1978 respectively; they were intended to take pictures of far away planets and have done so successfully.

Rings

Jupiter, Saturn, Uranus and Neptune all have rings, but it is not clear why.

Moons

The only planet with no moons is Mercury. The gas giants all have many moons and Sagan talks...