Our Solar System
Science

The average distance between Earth and the Sun, about 150 million km, or 93 million miles
Astronomical unit
The average distance between Earth and the Sun, about 150 million km, or 93 million miles, is called an astronomical unit. An astronomical unit is a standard measurement used by scientists to describe distances in space.

The two days a year when the Sun is directly over the equator, making day and night equal
Equinox
The two days a year when the Sun is directly over the equator, making day and night equal. Equinox. An equinox is when the length of day and night are nearly the same because the Sun is directly above the equator.

One of the four rocky planets of the inner solar system, Mercury, Venus, Earth or Mars
Terrestrial planet
One of the four rocky planets of the inner solar system, Mercury, Venus, Earth, or Mars, is a terrestrial planet. A terrestrial planet is a planet made mostly of rock and metal with a solid surface.