Learn what scientists say about aliens, Bigfoot, fortune tellers, ghosts, monsters, UFOs, and other strange things.

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In a nutshell: Some people say that creatures from other planets have landed on Earth. They say they've seen them and been on their spacecraft. Some say that aliens have made drawings on rocks, on the ground, on pottery, and on ancient buildings. Some say aliens taught ancient peoples on Earth how to build monuments. Some say aliens have carved patterns in wheat and corn fields. Some say that aliens have crash landed here. Even so, the science doesn't favor the likelihood that any creatures from other star systems have made their way to our planet.

Aliens are creatures from other planets. Do they exist? Most scientists think so. Since there are billions of galaxies and each has billions of stars, and we know that many stars have planets, it seems likely that some other planets out there have living creatures on them.

What are those alien creatures like? We have no idea. Some might be like creatures on our planet, but some might be unlike anything we've ever seen. Creatures evolving on planets like ours might be very much like the creatures on Earth, but creatures might evolve on planets that are not like ours at all.

Is there intelligent life on other planets? It seems likely. We know intelligent life evolved on our planet after about four billion years. To get some idea of how long ago that was, think of this: if you were born four billion seconds ago, you would be more than 125 years old. To get some idea of how old the visible universe is, if you were born about 12 billion seconds ago, you'd be about 400 years old today.

If there are other planets in the universe that are like ours, then there are probably other planets with intelligent life on them. It seems pretty likely that there are many other planets in the universe like ours. There are probably some other stars that give just the right amount of energy to planets that are just the right age, size, and distance from their suns for life to evolve and thrive, including intelligent life.

signs of intelligent life

monkey at NascaMany people believe that some aliens have come to Earth in flying saucers or UFOs (unidentified flying objects) from planets outside our solar system. Some think that aliens had a civilization on an island called Atlantis and then destroyed themselves with nuclear bombs or some other very powerful device. Some people think aliens helped build the pyramids in Egypt and Mexico thousands of years ago. Some think aliens made the geometric line clearings in the Peruvian desert known as the Nazca lines. The picture of the monkey seen here was taken from an airplane. The drawing was made by scratching away the surface dirt and is called a geoglyphsound icon. You could fit two football fields end to end and not reach all the way across this geoglyph.

Some say that aliens created stones in Ica, Peru, with pictures of men riding dinosaurs scratched into them. Dr. Javier Cabrera Darquea runs the Engraved Stones Museum (Museo de Piedras Grabadas) in Ica. He thinks the stones were engraved by aliens from the Pleiades who came to Earth one million years ago. (The Pleiades is a small group of stars about 440 light years from Earth. If you could ride on a beam of light [a photon], the fastest thing in the universe, it would take you 440 years to get to the Pleiades. Many scientists think that the stars in the Pleiades are too young for life to have evolved on any planets that might be there. It took something like 4 billion years for intelligent life to evolve on our planet. Our solar system is 40 times older than the Pleiades.) Anyway, the Ica stones are not ancient. They were created by local farmers who either tricked Dr. Cabrera or were in cahoots with him.

Ica stone rider on dino?

crop circleSome say aliens have landed on Earth and are using designs in corn fields to let us know they're here. Some of these so-called "crop circles" are quite beautiful.

Some say aliens crash landed in Roswell, New Mexico, in 1947, and that our government recovered some alien bodies and took them to a place in Nevada known as Area 51 (more about that later). And some say that aliens have been attacking our cattle and taking humans to their spaceships.

Of course, saying something doesn't make it true. What do scientists think of all these claims about aliens?

Have the aliens landed?

Despite the problems that would face anyone on any planet from traveling to other star systems or galaxies, it is not impossible. (For more on some of these problems, see the entry on UFOs.) Maybe there are intelligent creatures who can travel at very fast speeds and have the technology and the raw materials to build spaceships that can travel here from other solar systems. Did such creatures come here to help people build pyramids and glyphs of large animals in the desert and then leave? Have more of these obviously intelligent creatures come here in recent years to make signs in corn fields, fly around but not make contact, take people into their ships, hurt cattle, carve stones, and crash in New Mexico?

Does the science support any of these claims about aliens? The short answer is "no." Even so, about one in three Americans believe aliens have landed on our planet.

It's true that many people claim to have seen aliens. Most of the timealien by J. Ruhe they describe the aliens as being small and bald or white, gray, or green. They have big craniums, small chins, large slanted eyes, and pointed or no ears. How do we explain the fact that so many claims are alike? The stories and descriptions are alike because they are based on the same movies, the same stories, the same television programs, and the same comic strips (like the 1930 comic adventure, Buck Rogers in the 25th Century).

Scientists have no doubt that ancient humans built their own civilizations. Ancient Egyptians and Mayans planned and built large tombs and temples. They created large art projects. They did these things without help from space aliens. Erich von Däniken spread the idea that aliens were here thousands of years ago. He has been caught trying to trick people into thinking he had proof aliens were here. He had pottery items with aliens climbing into spaceships made by local artisans and burnt to make them look old.

Von Däniken said the Nazca drawings were to guide alien ships when landing, but there is no evidence that the area was ever used as an airport. In fact, some of the drawings are on hillsides, not a good place to land a spaceship. There is much evidence that the local Nazca people did the drawings of giant lizards, spiders, monkeys, llamas, dogs, and hummingbirds. Some of the same designs have been found on Nazca people's weaving and pottery. Why they created the large geoglyphs is uncertain, but it may have had something to do with water or religious rituals. The Nazca lived without science but they had to have water for their crops. They may have turned to magic and superstition to help them with their need for water.

mummies of NazcaThe Nazca people, like most of us, were worried about death. Mummies litter the Nazca desert, left there by grave robbers. Was this a place for rituals aimed at helping the dead live forever? We don't know for sure, but the claim that this was a landing ground for aliens has no basis.

Others also claim that aliens were on Earth thousands or millions of years ago. L. Ron Hubbard, the founder of the Church of Scientology, wrote that aliens came here 75 million years ago. Hubbard wrote that their leader, Xenu, dumped billions of aliens into volcanoes and dropped bombs on them. Most people think this story is science fiction.

Crop circles have been created by many humans as pranks and hoaxes. There's no evidence that any of them have been created by aliens.

The so-called "cattle mutilations" done by aliens have been studied by scientists. Their conclusion is that dead animals sometimes look strange when found because insects, vultures, or other animals have eaten some of the softer parts. There is no evidence that aliens have harmed any animals on our planet.

Nobody has been able to prove that anyone has actually been picked up by aliens and taken to any spaceship going around the Earth. That doesn't mean it's impossible, but until there is some good evidence to believe such stories we should hold off taking them as true. When the only proof we have for something is a belief that isn't backed up by physical evidence (like a spaceship or an alien tool) or any other kind of evidence, maybe the belief is a trick of the brain.

The UFO sightings are just that: sightings of unidentified flying objects. So far there has been no strong evidence that any UFO is an alien spacecraft, not even any of those flying saucers you may have heard about.

Finally, it is generally agreed among scientists that no alien spacecraft crash landed in Roswell, New Mexico, or anywhere else on the planet. No aliens or alien spacecraft have been taken to Area 51 in Nevada. The debris found at Roswell was from U.S. Air Force high-altitude balloons that blew apart in a thunderstorm. Area 51 is an off-limits government location that may be used to dump poisons. Several former workers at Area 51 and widows of former workers have filed lawsuits against the government for injuries or death resulting from illegal hazardous waste practices.

You may hear many scary stories about aliens. But so far the scientific evidence does not favor the idea that aliens have landed on our planet.

further reading

Bringing UFOs Down to Earth by Philip J.Klass (Prometheus Books, 1997).

Last updated 21-Aug-2011

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