Richard Dawkins - The Magic of Reality

False memory syndrome helps us understand why at least some of the people who think they have been abducted by aliens claim to have such vivid memories of the incident. What usually happens is that a person becomes obsessed with aliens through reading stories in the newspapers about other alleged abductions.

Often, as I said, these people are fans of Star Trek , or other science fiction tales. It is a striking fact that the aliens they think they’ve met usually look very like the ones portrayed in the most recent television fiction about aliens, and they usually do the same kind of ‘experiments’ as have recently been seen on television.

The next thing that may happen is that the person is afflicted by a frightening experience called sleep paralysis. It is not uncommon. You may even have experienced it yourself, in which case I hope it will be a bit less scary the next time it happens if I explain it to you now. Normally, when you are asleep and dreaming, your body is paralysed. I suppose it’s to stop your muscles working in tune with your dreams and making you sleepwalk (though this does, of course, sometimes happen). And normally, when you wake and your dream vanishes, the paralysis goes and you can move your muscles.

But occasionally there is a delay between your mind returning to consciousness and your muscles coming back to life, and that is called sleep paralysis. It is frightening, as you can imagine. You are sort of awake, and you can see your bedroom and everything in it, but you can’t move. Sleep paralysis is often accompanied by terrifying hallucinations. People feel surrounded by a sense of dreadful danger, which they can’t put a name to. Sometimes they even see things that are not there, just as in a dream. And, also as in a dream, to the dreamer they seem absolutely real.

Now, if you are going to have a hallucination when you suffer sleep paralysis, what might that hallucination look like? A modern science fiction fan might well see little grey men with big heads and huge eyes. In earlier centuries, before science fiction came along, the visions people saw were different: hobgoblins, perhaps, or werewolves; bloodsucking vampires or (if they were lucky) beautiful winged angels.

The point is that the images people see when experiencing sleep paralysis are not really there but are conjured up in the mind from past fears, legends or fiction. Even if they don’t hallucinate, the experience is so frightening that, when they finally wake up, sleep paralysis victims often believe that something horrible has happened to them. If you are primed to believe in vampires, you might wake with a strong belief that a bloodsucker has attacked you. If I am primed to believe in alien abductions I might wake up believing that I was abducted and my memory then wiped clean by aliens.

The next thing that typically happens to sleep paralysis victims is that, even if they didn’t actually hallucinate aliens and gruesome experiments at the time, their fearful reconstruction of what they suspect may have happened becomes consolidated as a false memory. This process is often helped along by friends and family, who eagerly pump them for more and more detailed accounts of what happened, and even prompt them with leading questions: ‘Were there aliens there? What colour were they? Were they grey? Did they have big wraparound eyes like in the movies?’ Even questions can be enough to implant or cement a false memory. When you look at it like this, it is not so surprising that a 1992 poll concluded that nearly four million Americans thought they had been abducted by aliens.

My friend the psychologist Sue Blackmore points out that sleep paralysis was the most likely cause of earlier imagined horrors, too, before the idea of space aliens became popular. In medieval times people claimed to have been visited in the middle of the night by an ‘incubus’ (a male demon visiting a female victim to have sex with her) or a ‘succubus’ (a female demon visiting a male victim to have sex with him). One of the effects of sleep paralysis is that, if you try to move, it feels as though something is pressing down on your body. This could easily be interpreted by the terrified victim as a sexual assault. Legend in Newfoundland talks of an ‘Old Hag’ who visits people in the night and presses down on their chests. And there is a legend in Indochina of a ‘Grey Ghost’ who visits people in the dark and paralyses them.

So we have a good understanding of why people believe they have been abducted by aliens, and we can tie the modern myths of alien abduction in with earlier myths of rapacious incubi and succubi, or of vampires with long canine teeth who visit in the night and suck our blood. There is no good evidence at all that this planet has ever been visited by aliens from outer space (or, for that matter, by incubi or succubi or demons of any kind). But we are still left with the question of whether there actually are living things on other planets. Just because they haven’t visited us doesn’t mean they don’t exist. Could the same process of evolution, or even a very different process that perhaps resembles our kind of evolution only slightly, have got going on other planets as well as ours?

Nobody knows. If you forced me to give an opinion one way or the other, I’d say yes, and probably on millions of planets. But who cares about an opinion? There is no direct evidence. One of the great virtues of science is that scientists know when they don’t know the answer to something. They cheerfully admit that they don’t know. Cheerfully, because not knowing the answer is an exciting challenge to try to find it.

One day we may have definite evidence of life on other planets, and then we’ll know for sure. For now, the best a scientist can do is write down the kind of information that might reduce the uncertainty, might take us from guesswork to an estimate of likelihood. And that, in itself, is an interesting and challenging thing to do.

The first thing we might ask is how many planets there are. Until quite recently, it was possible to believe that the ones orbiting our sun were the only ones, because planets could not be detected by even the largest telescopes. Nowadays we have good evidence that lots of stars have planets, and new ‘extra-solar’ planets are discovered almost every day. An extra-solar planet is a planet orbiting a star other than the sun ( sol is the Latin for sun and extra is the Latin for outside).

You might think that the obvious way to detect a planet is to see it through a telescope. Unfortunately, planets are too dim to be seen at any great distance – they don’t glow in their own right but only reflect their star’s light – so we can’t see them directly. We have to rely on indirect methods, and the best method again makes use of the spectroscope, the instrument we met in Chapter 8. Here’s how.

When a heavenly body orbits another one of approximately equal size, they orbit each other, because they exert approximately equal gravitational force on each other. Several of the bright stars that we see when we look up are actually two stars – so-called binaries – in orbit around each other like the two ends of a dumbbell connected by an invisible rod. When one body is much smaller than the other, as is the case with a planet and its star, the smaller one whizzes around the larger one, while the larger one makes only little token movements in response to the gravitational pull of the smaller. We say that Earth orbits the sun, but actually the sun also makes tiny movements in response to the gravity of Earth.

And a planet as large as Jupiter can have an appreciable effect on the position of its star. These token movements of a star are too small to count as ‘going round’ the planet, but they are large enough to be detected by our instruments, even though we can’t see the planet at all.