"In 1961, Frank Drake wrote down an equation for the probability of a contactable alien civilization living on another planet in the Milky Way. This is known as the Drake equation. It tells us that there is a chance that we may coexist with another civilization but the probability is still quite ...

"Chatting with his colleagues over lunch in 1950, Fermi supposedly asked, 'Where are they?' our own galaxy contains billions of stars and there are billions of galaxies in the universe, so that is trillions of stars. If just a fraction of those anchored planets, that's a lot of planets. If a frac...

"How would you go about searching for signs of life? The first way is to start looking for microbes within our solar systems. Scientists have scrutinized rocks from the Moon, but they are inanimate basalt. It has been suggested that meteorites from Mars might contain the remnants of bacteria, but...

"The detection of life elsewhere in the universe would be the greatest discovery of all time. Physics professor Enrico Fermi wondered why, given the age and vastness of the universe, and the presence of billions of stars and planets that have existed for billions of years, we have not yet been co...

Cameras on spacecraft and landers have scouted the surfaces on Mars, asteroids and now even a moon in the outer solar system -- Titan, orbiting Saturn. But the Martian surface is dry and Titan's surface is drenched in liquid methane, though so far devoid of life. Jupiter's moon Europa may host se...

"But microbes are not going to call home. Now that individual planets are being detected, astronomers are planning on dissecting the light from them to hunt for chemistry that could support or indicate life. Spectral hints of ozone or chlorophyll might be picked up, but these will need precise ob...

"More than half a century after Fermi asked his question, we have still heard nothing. Despite our communication systems, no one has called. The more we explore our local neighborhood, the lonelier it seems. No concrete signs of any life, not even the simplest bacteria, have been found on the Moo...