Earth’s orbit is nearly circular.

The motion of Earth around the Sun is Earth’s rotation.

As Earth revolves, it always tilts toward the Sun.

The Sun produces energy through nuclear fusion.

Day and night are caused by Earth’s rotation.

The equator is warmer than the poles because the Sun’s energy is more concentrated at the equator than at the poles.

Seasons take place because the tilt of Earth’s rotation axis relative to the Sun stays the same during the year.

On the December solstice, the north end of Earth’s rotation axis continues to point away from the Sun, but it does so less and less.

A day when Earth’s rotation axis is leaning along Earth’s orbit, neither toward nor away from the Sun, is called an equinox.

When the southern hemisphere is experiencing summer, the northern hemisphere is experiencing summer.

The light energy absorbed by a surface depends on

A beam of light becomes more spread out as

Energy is carried to Earth in

Some energy is absorbed by Earth’s surface when

Energy is less concentrated near

Less energy reaches the poles because

Earth is warmest at the equator because

Earth is coldest at the poles because

Surface temperature depends on the amount of

The surface of Earth

Less energy is received in regions where

A beam of light

Earth is warm at the equator and cold at