Is there life outside the Earth and the solar system?
But if they're like us, they communicate using radio waves.
So the waves coming from space might
include a signal transmitted by an alien civilization
from another star.
Right now, the radio telescope at Arecibo is listening to radio waves from other stars. The data is being sent through the Internet straight to this computer!
You're listening to the radio signal from space.
What would an alien signal sound like? Click here to find out.
What is SETI?
Is there life outside the Earth? This is one of the greatest questions facing mankind. It is almost inconceivable that life has formed only on Earth. And yet we have no direct evidence of life outside our Solar System.
If there are other civilizations, we are separated from them by enormous distances. It would take thousands of years for light or radio waves from Earth to reach most other stars in the Milky Way galaxy, and equally long for their signals to reach us. So it's very unlikely that aliens have visited Earth in person. There is no evidence that UFOs exist.
Instead, SETI researchers are concentrating on detecting alien civilizations by their radio signals - "Radio SETI". If we detect such a radio signal, we may never be able to visit the aliens - or even reply to them - but at least we'll know they're there.