The third planet from the Sun and the largest of the four inner, or terrestrial, planets. The Sun is an average-sized, middle-aged star situated...

Earth-approaching asteroids (in 'Asteroid' article)
Apollo, Amor, and Aten asteroids are of special interest, particularly because they stand a chance of striking the Earth. Indeed, Meteor Crater (Arizo

Near-Sun and near-Earth comets (in 'Comet' article)
Most comets are observed under so-called normal circumstances; that is, the comet is between 0.5 and 1.5 AU from the Sun and a few tenths of an AU fro

Rotation of the Earth (in 'Earth rotation and orbital motion' article)
Historically the rotation of the Earth has been an essential part of timekeeping. It was assumed that the rotational speed of the Earth was essentiall

Orbit of the Earth (in 'Earth rotation and orbital motion' article)
A large number of astronomical observations of the positions of the Sun and other solar system objects have been made and are being made continuously.

Motion over Earth's surface (in 'Eclipse' article)
The Moon's shadow travels at approximately 2100 mi/h (3400 km/h) through space. The Earth rotates in the same direction that the shadow is traveling;

Appearance from Earth (in 'Saturn' article)
The nearly circular ring system looks like an ellipse whose appearance changes with the relative positions of Earth and Saturn (Fig. 2). The maximum o