I picked up five stones in the river.

He lives in a stone-built house.

He is strong like a stone.

I am an Earthling.

We are searching for extraterrestrial life.

The process of terraforming is part of transforming other planets into a habitable environment for humans.

Earth science is an important field of study for unraveling the mysteries of nature.

The diagonal elements of this matrix are all 1.

Global warming is a big issue that affects all of us.

He is an expert in geophysics.