Is there intelligent life on Earth? When NASA's Galileo spacecraft was forced to slingshot around Earth, Carl Sagan had an idea -- and we're only just realising how genius it was.

The article discusses comments by astronomer Carl Sagan on using the Galileo spacecraft to search for signs of intelligence life on Earth. Topics include the significance of the presence of methane, and green pigment covering the Earth's surface, and the detection of narrow-band radio transmissions. The significance of the experiment for research on exoplanets is noted.