CHAPTER 1 What Are Extraterrestrials For thousands of years people have wondered if there is life beyond Earth For more than 100 years scientists have been trying to answer that question People on Earth are terrestrials a word that comes from the Latin terra which means earth or land An extraterrestrial is a life form that exists beyond Earth Our Solar System Astronomers are scientists who study the stars planets and other aspects of space Some astronomers are searching for life beyond our planet Earth is one of eight planets in our Solar System This is a system in which planets orbit or travel around a star Earth’s star is the Sun Astronomers are studying these other planets and their moons but the search does not end there Our Solar System is part of a spiral-shaped galaxy called the Milky Way Our Solar System lies within one curved part of the spiral called the Orion Arm Earth’s Solar System belongs to a spiral galaxy or collection of stars similar to this galaxy M33 4
Radio telescopes scan space for signals that might be signs that intelligent life exists elsewhere in the universe There may be as many as 400 billion stars in the galaxy Many of these stars have at least one planet orbiting them This means that there are billions of possible places for scientists to look for life in the Milky Way alone There are billions of other galaxies in the universe and they also have billions of stars orbited by planets Extraterrestrial Experts Earth’s galaxy is so vast that many people believe that life must exist somewhere in it other than on Earth What kind of life could this be Extraterrestrials may take a form that we do not recognize Astrobiologists are scientists who are looking for extraterrestrial life They study the beginnings and future of life in the universe as well as its evolution and distribution or where it is found Astrobiology has become an important part of space science In 1998 the National Aeronautics and Space Administration NASA established the NASA Astrobiology Institute NAI to search for signs of life One part of astrobiology is the search for intelligent life Its scientists are looking for signs of thinking life forms in the universe In the late 1970s NASA began the Search for Extraterrestrial Intelligence SETI The SETI Institute founded in 1984 is a leading research center that works with NASA NASA and the SETI Institute are two leading U S organizations but the search for extraterrestrial life involves astrobiologists astronomers engineers and many others around the world Together they may find it 5
Early Explorations The idea of extraterrestrial life is not new More than 2,000 years ago the ancient Greek philosopher or thinker Epicurus wrote that there were infinite worlds both like and unlike ours He also believed that some form of life existed in these worlds Ancient peoples did not have the technology that we possess today They did not know that the Sun was a star or that Earth is part of a solar system In 1532 astronomer Nicolaus Copernicus became the first person to describe in a scientific way how Earth and the other planets orbited the Sun This suggested that if Earth could support life it seemed likely that other planets could too Lights and Mirrors In the 1800s people began to look for ways to send messages to extraterrestrials Carl Gauss a German mathematician had the idea of using a heliotrope A heliotrope was a device that used mirrors to reflect sunlight over long distances It was used to measure land Gauss believed a giant heliotrope could reflect sunlight to the Moon However Gauss never built the heliotrope By the 1900s the idea of Martians or beings living on Mars had taken hold of people’s imaginations and they began to develop more ideas for sending signals into space These included sending flashes of reflected electric light and putting mirrors on top of the Eiffel Tower in Paris France Nicolaus Copernicus’s theory that Earth orbited the Sun went against the previously held idea that the Sun and planets orbited Earth 6
Radio waves are a form of electromagnetic radiation They are invisible but transfer energy from one place to another Radio Waves Radio waves are disturbances that travel through space in the same way that waves travel through water in a series of up and down movements Many types of communications use radio waves from radios and cell phones to telescopes In the late 1800s Nicola Tesla and Guglielmo Marconi pioneered using radio waves to send messages In 1901 Tesla claimed to have picked up strange signals that he believed were a message from extraterrestrials Twenty years later Marconi also reported receiving signals from space In 1933 the U S astronomer Karl Jansky discovered that some objects in space do indeed produce radio waves The Sun for example produces radio waves Studying radio waves is called radio astronomy Today it is an important way to study space and search for extraterrestrials YOUR MISSION Many scientists believe that the chances of finding extraterrestrial life in the universe are high What arguments would you use to persuade people that a mission to find extraterrestrial life is worth pursuing 7
