The path that an object takes around another object in space.

A group of stars that seem to form a picture in the night sky.

•As Earth rotates, one side of Earth faces the sun. This side of Earth has ___________.

The other side of Earth faces the sun. This side of Earth has night time.

•Earth ___________, or turns like a top. Earth’s rotation causes day and night.

•Earth rotates around an imaginary line called an axis, which runs through its center from the North Pole to the South Pole.

Earth completes two rotations every 24 hours.

•The sun, Earth, and the moon form a system in space. This system is held together by _______.

Earth revolves, or travels, around the sun. It takes Earth about 1 year and 365 days to complete one revolution.

While Earth revolves around the sun, the ______ revolves around Earth.

It takes about one month for the moon to complete one rotation.

The moon’s rotation and revolution take the same amount of time, the same side of the moon always faces Earth.

Hot, glowing gases, mostly helium and nitrogen

As Earth revolves around the sun, the direction of its tilted access does not change. The tilt of Earth’s axis and its orbit cause the seasons.

Earth is divided into halves called _______________.

When one of the hemispheres tilts toward the sun, it has _________________.

As Earth rotates on its axis, constellations seem to move across the night sky.

He suggested that Earth and the planets revolved around the sun.

His calculations showed that the planets revolved around the sun in elliptical orbits.