Are we alone?

Life could be abundant in the Universe, but what about intelligence? Astronomers using radio telescopes have not yet detected messages from aliens, but the search continues.

Astronomers use radio telescopes to search for arti cial radio signals from alien civilisations – assuming that biological evolution elsewhere in the Universe has also led to intelligence. The Search for Extra-Terrestrial Intelligence (SETI) has been unsuccessful so far, but many people, including astronomers, find it hard to believe that we are the only sentient beings in this vast Universe. But even if we find another civilisation it will be almost impossible to visit them owing to the large distances in the Universe; even communication will only be possible with enormously long delays.

Aliens may never be able to visit Earth, but maybe we can listen to their radio signals. We can also send messages into outer space to let aliens know we are here. What would you ask an alien?