With billions of planets in our galaxy, including small Earth-like worlds, the possibility of life out there is an exciting thought to many people. So, humans have set out to look for planets that might support life.
My friend Dirk Schulze-Makuch studies life in the universe as an astrobiologist at Washington State University. He explained that for life to exist on Earth it needs a few ingredients. It needs liquid water, just the right combination of elements, and a source of energy, such as our Sun. These are required for every living thing we know of, from bacteria to plants to intelligent life forms, like humans.
Intelligent life, said Schulze-Makuch, is especially rare.
“For 4.5 billion years, on our planet we’ve only had one species so technologically advanced,” he said. “That’s us.”