Simple chemistry shows these gases should not co-exist for long, and yet on Earth they do, offering a clear sign for any watchful alien astronomers that something lives and breathes on this particular pale blue dot. (scientificamerican.com)
To spot the tint of Earth, alien astronomers from Andromeda might measure light shimmering off the surface of a planet, as sunlight reflected from our planet's vegetation reaches their telescopes. (sciencedaily.com)
Alien astronomers in a galaxy 100 million light - years away would see us whizzing in the opposite direction at 1,400 miles per second. (discovermagazine.com)