IS ANYONE OUT THERE
So far, the only place in the universe known to support life is Earth. However, out galaxy probably contains billions of planets that we cannot see; and there are billions of galaxies in the Universe. Many astronomers think it is very unlikely that Earth could be the only planet that has life. There is even a faint possibility that life might exist within our Solar System, under the icy surface of Jupiter's moon Europa, for example. Whether we will ever discover intelligent life forms is another matter. If alien civilizations do exist, they are probably too far away to visit.
MARTIAN MICROBES
In 1996, NASA scientists shocked the world with a remarkable discovery. They had found what looked like the remains of tiny life forms in a meteorite from Mars. The worm-like structures were 100 times thinner than a hair. However, after closer inspection, many scientists decided these "fossils" were just patterns on the rock.
EAVESDROPPING ON ALIENS
If alien civilizations exist, perhaps they use radio waves to communicate or to broadcast TV and radio programmes. If so, we might be able to "eavesdrop". Astronomers involved in SETI (Search for Extra Terrestrial Intelligence) use powerful radio telescopes to scan the sky for alien signals. Apart from some false alarms, SETI astronomers have so far found nothing. Meawhile, our own radio and TV signals are spreading into space and may one day give us away.
MESSAGE IN A BOTTLE
As you read this, four space probes are heading out of our Solar System and into deep space. Each carries a message for any aliens that happen to find them. The two Pioneer probes carry engraved metal plates showing a man and woman and Earth's position in the Solar System. The two Voyager probes carry records that are gold-plated to protect them from space dust.
GOLD DISKS
The Voyager space probes carry old-fashioned records with recordings of Earth sounds, from Beethoven's music to greetings in 56 languages. More than 100 photographs are encoded on the records. Each probe also has a stylus for playing the records.
SEARCHING FOR ALIEN WORLDS
There may be billions of planets in our galaxy that support life, but modern telescopes are not powerful enough to see any of them. To search for new worlds beyond the Solar System, astronomers hope to build new telescopes. The telescopes would work from space, orbiting Earth as Hubble does.
THE ARECIBO MESSAGE
In 1974, scientists used the Arecibo radio telescope to send a radio message into space in the hope that intelligent aliens will detect it. The message translates into some simple pictures about life on Earth.. It was beamed towards a cluster of half a million stars called M13. Unfortunately, M13 is so far away that we will have to wait at least 48,000 years for a reply, if one ever comes.
ARECIBO
Arecibo has the largest telescope dish in the world. It is 305 m (1,000 ft) wide, and lies in a natural bowl in the hills of Puerto Rico. The curved dish reflects radio waves onto a detector/transmitter held overhead. The detector can be moved to aim
