Trifid Nebula

Around many of the newborn stars in this photograph of the Trifid Nebula, there may be young planets. On some of those planets, life may exist now or in the future.

Creatures from other worlds – aliens – have us surrounded. In the movie theatre, on the television set, and from the shelves of every toy store, they grin and grimace and glower at us. Ugly, comical, fierce, and friendly – they come in every variety imaginable. All of them, though, have one important thing in common: they are totally make-believe.


No one has ever seen a real alien. Or, at least, if they have, no one has yet provided any firm proof that they have seen one. Despite many reports of unidentified flying objects UFOs and even of close encounters with space creatures, there is not one bit of evidence that aliens have ever visited us. The only living things we know about for sure are those that inhabit the Earth.


But look up at the sky on a clear, dark night. Each of the stars you can see is really a sun. Some of the stars are much bigger and brighter than our own Sun. Others are smaller and dimmer. With binoculars or a small telescope, you can locate about 50,000 stars, or 25 times more than with your eyes alone. A very large telescope shows millions upon millions.


Astronomers have already discovered several hundred planets circling around other stars. They expect to find thousands more in the years to come. On some of these faraway worlds, there may be life – perhaps life that is very different from that which exists on Earth. Even among the living things we do know about, there is a fantastic variety. It would be hard to imagine, for instance, anything more unlike than an ant and an oak tree, or a butterfly and a killer whale. It would be hard to imagine any creature stranger than the bug-eyed monsters of Hollywood movies. On planets of other stars, there may even be alien life forms that are much more advanced than human beings.


So, could you ever meet an alien? Scientists differ in their answer to this question. Some argue that there may be no intelligent creatures elsewhere in space. If such creatures exist, they say, then we should have found signs of them by now. Others point out that there are so may stars and probable planets that life, including intelligent life, almost certainly exists somewhere out there. According to this view, if we keep searching long enough, we will eventually find alien life forms.


Indeed, the search for life beyond Earth has already begun. With giant instruments, several groups of astronomers around the world are listening for radio signals that may be coming from intelligent races among the stars. Several probes have been launched carrying special plaques and even phonograph records describing life on Earth. These could provide information about our own planet to any aliens that ever came across them. Finally, two robot spacecraft have landed on the surface of our neighboring planet, Mars, and tested for simple life forms in the soil.


Today, scientists are striving to answer the question: Could you ever meet an alien? In what follows, we will consider the fascinating progress and the results they have achieved so far.