How many alien civilizations are out there?
Let's try to guess.
Our galaxy, the Milky Way, has about 100 billion stars.
If they all sent us radio signals at once, it might sound like this.
Here's a picture of a galaxy like the Milky Way.
Each green star represents a star with intelligent life.
|Frank Drake invented Drake's equation. He's one of the first SETI researchers.||In 1960 Drake used an 85-foot radio telescope in Green Bank, West Virginia, to listen for alien radio signals.|