1 A2 aliens

CHAPTER 1 Little Green Men IS THERE INTELLIGENT LIFE BEYOND EARTH? SCIENTISTS ARE TRYING TO FIND OUT. Do you think there are aliens that live on other planets in the universe? What do you think they look like? In science-fiction books and Hollywood movies, the aliens are often "little green men" with long, thin bodies, very large eyes, and hands with only three long fingers. They travel in "flying saucers." In some movies, like E.T. the Extra-Terrestrial, the alien is very kind and friendly. In other movies, like The War of the Worlds, the aliens are dangerous. They want to kill everyone on Earth.

No one knows what aliens really look like— or if they really do exist. However, some scientists think that the universe is so big that intelligent life must exist beyond our world. But scientists are not waiting for aliens to come to Earth in flying saucers. They think that the first contact with aliens will be with messages. So scientists are trying to find messages from aliens— and at the same time, they are sending messages. They hope that their messages can be the beginning of communication with aliens. The scientific way to say "aliens" is "extraterrestrial intelligence." Extra means "out" and terrestrial means "of Earth." So extraterrestrial intelligence means any intelligent life-form that lives outside of Earth. Do you think aliens will receive our messages? Will they communicate with us in words or in another way, like musical sounds? That's what the aliens did in the movie Close Encounters of the Third Kind.

CHAPTER 2 SETI COMMUNICATING WITH EXTRATERRESTRIAL LIFE-FORMS IS NOT JUST SCIENCE FICTION. IT IS REAL SCIENCE. In the 1997 movie Contact, a scientist is trying to find proof that extraterrestrial life exists. She uses a special radio to listen for messages. One day, she hears messages from a far away star. The messages tell her how to build a machine that will let her travel to that star. Does this sound like a strange story? Well, it's based on the work of real people at a real organization that wants to make contact with extraterrestrial life-forms.

It's called the SETI Institute. SETI stands for "Search for Extraterrestrial Intelligence." SETI has many important scientists. They are trying to find out if there is life in the universe beyond Earth. The SETI Institute was started in 1984 in California, USA. But the search for extraterrestrial intelligence started earlier. In 1960, a young radio astronomer named Frank Drake started the first search for signals from other solar systems. He used a 26-meter antenna, but he didn't hear anything. Many other scientists, however, were interested in his research. In 1974 the famous Arecibo Message was sent from a 305-meter antenna. It was the strongest message ever sent. The message was a simple picture. Scientists think prime numbers may be easier for aliens to understand, so the picture is 73 lines of 23 characters per line (73 and 23 are prime numbers). The picture shows a person, our solar system, DNA, and some of the chemicals of life.

Ten years later, a group of scientists started the SETI Institute. Today, SETI does many different kinds of research. One part of SETI uses radio to listen for messages from other intelligent life-forms. Why radio? People started sending radio signals into space about 100 years ago. We do it every time we turn on a radio, a TV, or use radar. So, maybe, other intelligent life-forms send out radio signals, too. Maybe one day we will hear alien radio programs! The SETI Institute also uses telescopes to look for extraterrestrial intelligence. What do they look for? Short but strong lights that are not natural. They think these lights could show that aliens are trying to send signals to us.

Another part of SETI, the Carl Sagan Center, studies astrobiology, which is the study of life in the universe. They want to answer these questions: Where did we come from? Are we alone? The Carl Sagan Center also researches habitability— if and how people can live in a place. They study different kinds of habitability on Earth, in very difficult places like the Arctic, Antarctica, the highest mountains, and the bottom of the ocean. They also research habitability in other places in our solar system. They want to find out if there are other planets where people could live. To do this, scientists from the National Aeronautics and Space Administration (NASA) fly into space, and they also use the world's best telescopes to look into space.