Andy Cohen details the extraordinary celestial phenomenon of a total solar eclipse, and when it will next occur. [3:47]

The students work in teams of two to discover the relative positions of the Earth, Sun and Moon that produce the different phases of the Moon. The students will be given a Styrofoam ball that they will attach to a pencil so that it looks...

A profile of the ancient Greek mathematician, geographer, and astronomer, Eratosthenes. Looks at his many accomplishments, including measuring the circumference of the Earth and the distance to the Moon and the Sun. Includes links to...

Enter our solar system to interact with the planets, moons, asteroids, meteors, and more. Investigate with NASA scientists and explore missions related to space exploration. Read facts, compare statistics, look through resources, and...

This site from Cornell University provides a discussion of how Aristarchus arrived at his conclusions of the distance from the Earth to the Sun and Moon. Also has his methods for determining the size of the Moon and the Sun.