The climate changes dramatically when you cross the equator.

The celestial equator has the same tilt as the Earth's equator.

Observing the movement of the celestial sphere is a fundamental part of astronomy.

Earth is one of the planets in the solar system.

In chemistry, we use projections to represent the shape of molecules.

There is a new projector in my office.

He prayed to the heavens.

Ancient people looked up at the sky and observed the movement of the stars.

Ancient people looked up at the sky and observed the movement of the stars.

When I looked up at the sky, a beautiful blue sky was spread out.