Nor was the voice of science silent on the matter: “I have heard from the lips of three witnesses to the most striking occurrences of this kind—The Earl of Dunraven, Lord Lindsay and Captain C. Wynne—their own most minute accounts of what took place. To reject the recorded evidence on this subject is to reject all testimony whatever, for no fact in sacred or profane history is supported by a stronger array of proofs.” So wrote Sir William Crookes, discoverer of the element thallium, inventor of the radiometer, and a pioneer in the study of electrical discharge in a vacuum.

This case has become an object lesson in the fallacy of trusting the reports of “people of standing” rather than the evidence. It concerned the thirty-five-year-old medium Daniel Home (rhymes with fume rather than foam), who, in December 1868, allegedly floated out a window at Ashley House in London, then back through the window of the next room. There were three witnesses: Viscount Adare (later the Earl of Dunraven) was twenty-seven years old; Lord Lindsay (twenty-one) was an astronomer, who later became a fellow of the Royal Society; and Captain Wynne (thirty-three) was an army officer stationed at the Tower of London.

Adare was the first to describe the event in print. He said: “Lindsay and Charlie (Wynne) saw tongues or jets of flame proceeding from Home’s head. We then all distinctly heard, as it were, a bird flying round the room, whistling and chirping.”

Two spirit voices spoke through Home to Wynne. Then Home got up, was “elongated” and raised into the air, and said: “On no account leave your places.” Adare heard Home go into the next room, “heard the window thrown up, and presently Home appeared standing upright outside our window.” Adare was baffled, and Home took him to the window in the next room and invited him to watch: “he told me to stand a little distance off; he then went through the open space, head first, quite rapidly, his body being nearly horizontal and apparently rigid. He came in again, feet foremost, and we returned to the other room.”

From that point on, in the words of the investigator Trevor H. Hall, “it is hard to understand why the witnesses, believing that they had been present at a miracle, were quite incapable afterwards of giving a coherent account of what occurred.”

Even the title of Adare’s account was wrong: “Séance at 5 Buckingham Gate, Wednesday 16th.” But Ashley House was not in Buckingham Gate: it was in Ashley Place. And the séance was held not on a Wednesday but on a Sunday. And the date was not the 16th, but the 13th. Lindsay introduced further confusion when he wrote: “I saw the levitations in Victoria Street.”

Adare wrote: “Outside each window is a small balcony or ledge, 19 inches deep, bounded by stone balustrades, 18 inches high. The balustrades of the two windows are 7 feet 4 inches apart. . . .”

Ashley House is no more, but there still exist photographs of it, and Trevor Hall arranged for his architect friend Peter Bond to calculate all the necessary measurements. The distance between the two windows was about four feet, two inches.

Lindsay said the window was eighty-five feet above the street. The true height was about thirty-two feet. He also said there were no balconies at all, but they are clearly visible in the photographs. The word balcony suggests places where one could stroll outside and take the air, but to my eye, they appear to be more in the nature of large window boxes for plant pots.

It was also Lindsay who “saw two spirits on the sofa, and others in different places.” He wrote: “The moon was shining full into the room.” But on that date, the moon was new, and besides, Adare had written: “It was so dark I could not see clearly how he was supported outside.” There is also the awkward fact that Lindsay was sitting with his back to the window and also, in Trevor Hall’s words, “managing by some miracle to be in both rooms at the same time, saw Home floating outside the window in the next room.”

There were many other discrepancies, and at this late stage, there is no way of sorting out exactly what happened, though even at the time, there were speculations about the method. Some people thought that maybe Home didn’t go outside at all, but simply crept back quietly into the room he had just left.

Nor was everyone charmed by his charisma and his claims to be in touch with the spirit world. When Home had first arrived in London from the United States, the poet Robert Browning attended one of his séances, and said he had never seen so impudent an imposture. When Home called on him, Browning threatened to throw “this dungball” down the stairs. Later he wrote a sarcastic poem about Home, titled “Mr. Sludge, ‘The Medium.’” (“I cheated when I could, rapped with my toe-joints, set sham hands at work. . . .”)

Even Charles Darwin was intrigued with reports of Home’s abilities, but he was too shrewd to take them at face value. “I cannot disbelieve Mr. Crooke’s statement,” he wrote, “nor can I believe in his result.” Unfortunately, he was too ill to accept an invitation to attend a séance—but what a fascinating diary entry that could have given us.

Unless you are prepared to reveal what happened on every spot on the earth since the beginning of civilization, there is no way to prove that extraterrestrials have not landed on the earth. This means that the question of whether such an event has occurred really boils down to asking whether or not there is compelling evidence of such visitation now, either in literature or in the remains of old civilizations. The ancient-astronaut arguments usually rely on both kinds of evidence, but I’d like to concentrate on just one—the evidence for ancient astronauts as revealed in the building technology of ancient civilizations.

The study of the history of technology has been a growing field for a long time, and we know a surprising amount about the way that things were done in ancient times. We can use this knowledge to set up a couple of guidelines that will help us evaluate the claims used by Von Däniken and others about extraterrestrial help to explain this or that technological advance.

One thing we know about technological change is that it is continuous, although it may proceed faster at one time than at another. Each step in the building of a technology makes use of previous steps. For example, our ability to put up skyscrapers depends on the development of structural steel, the harnessing of energy to run cranes and other large machines, the use of electricity, and countless other things.

To make this point clear, imagine what would happen if somehow all of the evidence of European civilization in North America were removed, so that the continent was returned to its pristine state, except for one thing. Suppose that whoever or whatever accomplished this task forgot to remove the Sears Tower in Chicago. Suppose then that some future anthropologist were to visit this building. He would see a structure which would have required a vast industrial backup system, but there would be no evidence of anything of the kind. In such a situation, he would clearly be justified in concluding that there was more to the situation than met the eye and that something like an ancient- astronaut hypothesis would be needed to explain what he saw.

Of course, this example is pretty extreme—the Sears Tower would be just as out of place in the Gay Nineties as it would be in 1600. There would be no tradition showing the Sears Tower as the culmination of a long period of development in which people learned to construct tall buildings, and in its own way, this sort of situation would be just as startling as if the building really existed all by itself.

So the first question we have to ask about any claim that a particular technological advance required the existence of outside help is this: Is there a continuous technological tradition of which this particular event or structure is a part? If the answer to this question is yes, then the need to assume the existence of outside help becomes less stringent.

There is another question we can ask that is similar to the first one but that depends a little more on our knowledge of ancient technologies. Going back to our example of the Sears Tower, one of the reasons it would have been out of place in the 1890s is that engineers at that time lacked the technological ability to put the building together. Thus, even if the question of the technological tradition were unclear, our imaginary anthropologist would be justified in looking for outside assistance if he knew that the people living around the building simply lacked the ability to do the job. So the second question we have to asks is: Did the local population possess the means to carry out the feat, regardless of whether there was a tradition leading up to it or not?

I would suggest that if we look at some ancient engineering achievement and find that the answer to both of these questions is yes—that is, that the building is the culmination of a long tradition and was within the technological capabilities of the builders—we would be justified in saying that no ancient astronauts were needed to construct the building. I would further suggest that common sense (or the principle of sufficient reason, if you have a more formal turn of mind) then demands that we reject that particular building as evidence for ancient astronauts.

The most striking example of an ancient building that has been put forward as evidence for the existence of ancient astronauts is the Great Pyramid of Giza, near Cairo, Egypt. The reasons for this are not hard to grasp, since the statistics on the pyramid are truly mind boggling (see the box above). It remains the largest stone structure ever erected, consisting of more than 2 million blocks of stone, weighing more than a ton each. If the stone in the pyramid were cut into blocks one foot on a side and these blocks were laid end to end, they would make a line reaching from San Francisco to Moscow and back again!

How in the world could something like this have been built by people who didn’t even use the wheel? Surely, the Egyptians could not have carried out a project of this magnitude without outside help, and, since there were no other civilizations on earth more advanced than the Egyptians at that time, this outside help must have come from extraterrestrials. This, in essence, is the argument of Von Däniken and others.

There is certainly a strong temptation to agree with this assessment when we look at the pyramids, but suppose we stop for a few minutes and ask the two questions we talked about earlier.

The pyramids are apparently burial places for pharaohs, so the way to approach the question about whether or not the Great Pyramid is a break with previous practice is to look at Egyptian burial buildings that were constructed before and after it was built. When I started looking into this question, I discovered some surprising facts. Although there are only three pyramids at Giza, there are literally hundreds of pyramid-shaped tombs scattered up and down the Nile Valley. The group at Giza contains the largest such structure, but that one is neither the first nor the last that was erected.

The first tombs were low brick structures (presumably modeled after houses) built over tomb excavations. These buildings were rectangular in shape and go by the name mastaba. Sometime about 2700 b.c., the shift from building with brick to building with stone was made. This improvement in building techniques, small as it may seem to us, allowed Egyptian engineers to do two things: they could now put up bigger buildings (because of the greater strength of stone) and they could put up buildings which would last longer. As far as burial customs were concerned, the simple rectangular mastaba was elaborated into a structure called a step pyramid, in which successively smaller rectangles are laid on top of each other. The most famous of these is the tomb of Zoser (the man who is supposed to have developed the technique of stone building) at Saqquara, which is a few miles from the site at Giza.

Fortunately for archeologists, the transition from the step pyramid to the more usual pyramid form can be seen in the pyramid at Meidun, where the interior core of a step pyramid was enclosed in a smooth outer coating. Weather and human assaults on the pyramid have removed enough of the outer covering so that the interior structure can be seen. We thus have convincing visual proof that the true pyramid developed when the regular outer walls of the step pyramid were smoothed out. In fact, by the time Cheops began the work on the Great Pyramid at Giza, there were no fewer than three true pyramids already in existence to serve as models. So there is a clear line of evolution from the mastaba to the true pyramid in Egyptian architecture, and the Great Pyramid itself does not mark any radical new ideas.

This fact goes a long way toward refuting another ancient-astronaut argument about the Great Pyramid—that it served some purpose other than that of a burial place for the pharaoh. If a particular structure is clearly part of a long series of buildings, and all of the other buildings are tombs, then there is little reason to suspect that the building in question isn’t a tomb as well. The only thing that differentiates the Great Pyramid from the pyramids that came before and after it is its size.

But size is precisely what enters the picture when we ask the second question: Could the Egyptians have built such a colossal structure without assistance? Because so many claims are made about the building of the pyramids and about the accuracy of the construction involved, it would be a good idea to review some of the salient features of the structure. Its base is approximately square, the sides each being about 756 feet long. The difference between the longest and the shortest side is about eight inches (see the box below). Similarly, the angles of the base differ from a right angle by as little as three degrees of arc.

This means that the base of the pyramid was surveyed to an accuracy of one part in 1000—a truly magnificent feat of engineering for Egyptians equipped with primitive instruments. But if we want to bring in ancient astronauts, there is a serious problem, because modern commercial surveying (the type that might be done in laying out a new housing subdivision) is routinely done to one part in 10,000, ten times better than that of the pyramids, and accuracies considerably higher than this are achieved in places like downtown Manhattan, where every fraction of an inch matters. Thus, the accuracy with which the pyramid is laid out turns out to be an argument against ancient astronauts, since they would surely have been able to do the job at least as well as a modern surveying team.

A similar argument can be made about the claim that the pyramid could not have been built by the Egyptians because if you divide the height by half of the perimeter of the base, you get pi (3.14 . . .). If you check this claim against the actual numbers, you again find that this is true to an accuracy of one part in 1000. So while the Egyptians obviously picked the pyramids’ proportions so that the height was the radius of a circle whose circumference was equal to the circumference of the base of the pyramid, the accuracy was much poorer than we could achieve today. Can you really believe that the members of an advanced race would flunk freshman surveying?

The quality of the stone work can be used to come to the same conclusion. The furnished surfaces of the stone, where needed, were level to within about one fiftieth of an inch. For reference, this is about half the thickness of a dime. A skilled mason using the type of stone-cutting tools found in old Egyptian quarries could, with care, achieve this sort of accuracy. But a spaceman using a laser cutting tool (as has been imagined by some pyramid buffs) would do a couple of orders of magnitude better.

So the workmanship of the pyramid is of a quality that would be just within the reach of what we know the Egyptians of the period could do but is very poor for anyone who had access to modern technology. And if this is true, the only refuge left for the ancient-astronaut notion lies in the claim that the Egyptians simply couldn’t have moved all that stone and put it into place in the pyramid.

This argument has a certain surface credibility. After all, we know that the Egyptians did not use wheeled vehicles at the time of the construction of the Great Pyramid, and there are simply no surviving records which discuss how any of the pyramid construction was actually done. Egyptologists believe, however, that these stones were moved from the quarries in southern Egypt in boats. It turns out that during the annual flood, the Nile used to come to within about a quarter mile of the pyramid site, so that the stones had to be moved only a relatively short distance before being pulled up a sand ramp and set in place.

The conventional thinking on how the stones were transported is that they were mounted on runners (something like a sled) and then pulled with ropes while water was poured along the path to ease friction. While this may sound difficult, we do have carvings dating from 1,000 years after the building of the pyramids which show a sixty-ton statue being moved in just this way by a team of 172 men. And this was after the Egyptians had the wheel.

Unfortunately, we don’t have much in the way of surviving records to tell us how the pyramids were actually built. The Greek historian Herodotus passes along what he heard from Egyptian priests in his day, and there are some surviving bits of a manuscript by a priest named Manetho, but both of these were written well after the actual building. Estimates of the number of men employed as laborers on the pyramid vary from 400,000 per year to 100,000, working during the three-month inundation season, when they were not needed on farms. Herodotus says that the tradition during his time was that it had taken twenty years to erect the structure. If we take the most conservative estimate of the work force, the question then comes down to this: could 100,000 men have moved 115,000 blocks per years for a twenty-year period? This is the minimum that would have to be done to get all 23,000,000 blocks into place in the allotted time.

Well, the average block weighed two and one half tons, or 5000 pounds—about the weight of a big station wagon or pickup truck. If the work force were split into crews of eight men each, there would be 12,500 crews, and each would have to haul about ten rocks during the three-month period. This amounts to hauling one rock every nine days. So the size of the transportation problem which looks so formidable when we consider the bulk of the pyramid itself looks much more manageable when we bring it down to a more human level. Could eight men haul a station wagon mounted on a wooden sledge two city blocks (a quarter mile) in nine days? There’s no question that they could. So, then the most difficult job in the construction of the pyramids—the moving of the stone blocks—appears to be well within the capabilities of the Egyptians. In fact, when we look at things this way, the truly outstanding feature of the entire project is the organizational skill shown by the builders in coordinating the work of the labor force.

When all is said and done, then, the pyramids, as impressive as they are, give no evidence at all for the presence of advanced technology at work in ancient Egypt. The buildings are manifestly part of a long line of development that stretches back into early history and continues for a thousand years after the Great Pyramid was finished. The building tradition shows no discontinuous breaks of the kind we would have if ancient astronauts had suddenly appeared on the scene. In the same vein, both the construction details and the bulk-transportation system are well within the limits of what we could expect from the technology that we know the Egyptians possessed.

Some Claims about the Great Pyramid

• The Great Pyramid is built on bedrock and is therefore invulnerable to earthquakes.

  It is indeed built on bedrock, although this doesn’t make it earthquake-proof. Bedrock moves during earthquakes too. And besides, would you really expect a building this size to have a sand foundation?

• The Great Pyramid is shaped to deflect meteors.

  A really big meteor, like the one that fell in Siberia in the early 1900’s, would destroy the structure completely. From an engineering viewpoint, a hemisphere or geodesic dome would be a much more efficient shape for this purpose.

• The Great Pyramid is designed so that the air shafts will be above the water line if the polar ice caps melt.

  I would feel more at ease with this argument if most of the chambers and the entrance to the structure were not below the “high water line.” But if you want to take this seriously, then any structure whose top is 200 feet above sea level will serve the purpose. A partial list includes (a) the Empire State Building, (b) the entire city of Denver, and (c) my neighbor’s chicken coop.

• It would be impossible to duplicate the Great Pyramid today.

  Consider the following facts:

  1. steel girders weighing much more than the pyramid blocks are routinely fitted into place in suspension bridges and atop skyscrapers—a much more difficult task than piling up rocks on a flat plain;
  2. during the flooding following the building of the Aswan Dam, a small group of western construction engineers, using modern earthmoving equipment, disassembled, moved, and reassembled several large temples whose component parts were as large as those of the pyramid.

  The reason that no other stone structure as large as the Great Pyramid has been built is really quite simple. The civilization that, after the Egyptians, first started building on a massive scale was that of the Romans, and they had developed concrete. There was simply no call to build with stone any more.

Susan Clancy, the author of Abducted: How People Come to Believe They Were Kidnapped by Aliens, has probably gotten more personally involved with alien abductees than any other skeptic. Clancy is frank in her belief that extraterrestrial visitation is exceedingly unlikely and that the alien-abduction experience can be explained more plausibly in terms of sleep paralysis with hallucinations, the availability of cultural scripts, and the development of false memories through hypnosis and other guided imagery techniques. Nevertheless, Clancy is not out to debunk the alien abduction myth, nor does she try to disabuse her interviewees of their delusions. Rather, her purpose, as the title of her book indicates, is to probe the psychological and cultural factors that lead some people to believe they have had encounters with extraterrestrials.

One theme that runs through the book is the observation that alien abductees are, in all other respects, very ordinary people. Clancy’s interviewees, as a group, exhibited the same general ranges of education, socio-economic status and religious upbringing as the population at large. Even more importantly, her sample of alien abductees were no more likely to be psychotic than the general population. This observation is an important counterargument to the pat explanation that those who claim to have been abducted by aliens are simply crazy. Nor can abduction claims be explained in terms of publicity seeking, since many abductees are reluctant to share their experiences with the general public.

There is one aspect, though, in which abductees are different from the general population. On personality tests, they score higher on a characteristic called schizotypy. Schizotypic personalities are prone to fantasy and magical thinking. They also have more difficulty distinguishing real from imagined events than the general population, and they are more likely to hold paranormal beliefs. In addition, they may be more likely to develop full-blown schizophrenia, and there is evidence for a genetic link between schizotypy and schizophrenia. On the other hand, schizotypic personality is not necessarily maladaptive; in fact, artists, poets and other highly creative people generally score high on the schizotypy dimension. However, there are plenty of people with schizotypic tendencies that do not develop beliefs in alien abductions, so there must be other causal factors involved.

Clancy was struck by the clarity of the memories and the intensity of the feelings that many of her interviewees had about their supposed abduction experience. It was clear that they had had some sort of traumatic experience, and that they were trying to find some “reasonable” explanation that fit their memories and the strong emotions they felt. In most cases, the traumatic experience was consistent with the condition known as sleep paralysis. During REM (rapid eye movement) sleep, when most dreaming occurs, the body is paralyzed, presumably to prevent the acting out of dream content. Usually, the paralysis ends when REM does, but sometimes when a person awakes from REM sleep, the paralysis continues for a minute or so. Waking up paralyzed is terrifying enough, but often this experience will be accompanied by a crushing sensation on the chest and a sensation of suffocation. Furthermore, the dream content during the REM sleep may continue as the sleeper awakens, leading to hallucinations. Feelings of floating or spinning are common as well. The experience is bizarre, but to the person not prone to magical or paranormal thinking, it will likely be interpreted as nothing more than a momentary perceptual aberration. However, to the paranormally inclined, the experience perfectly fits the alien abduction.

Another theme running through the book is the idea of the alien-abduction scenario as a cultural script. Clancy argues that the “the common features of the alien-abduction stories . . . are not evidence for validity” but rather come from “shared cultural knowledge.” She notes that alien-abduction claims are mainly limited to North America, and that alien abduction reports did not begin until after “they were featured on TV and in the movies.” In particular, Clancy maintains that the first North American alien abduction report, the Betty and Barney Hill case, bears a striking resemblance to the plot of an episode of The Outer Limits, down to the physical description of the extraterrestrials, as well as to the plot of the movie Invaders from Mars. Betty Hill, who was a flying saucer aficionado, had seen both shows. In fact, a common element in the development of abduction memories is a prior interest in alien abductions. That is, abductees already know what is supposed to happen to them before their first episode of sleep paralysis or hypnotic regression, and so the emotional events they experience are easily molded into a standard alien-abduction script.

The cultural and historical aspects of the alien-abduction experience could have been better developed in this book. Clancy does spend several pages tracing the history of the belief in extraterrestrials—all the way to the ancient Greeks, in fact. However, the existence of life elsewhere in the universe is not really relevant to the question of alien abductions; given the vastness of the universe, there is at least some probability that intelligent life has evolved elsewhere. But if our understanding of physics is correct, it is extremely improbable that extraterrestrials could ever travel such vast distances to get here, regardless of how advanced their technology is. And even if they had a way to span the distance, as Clancy asks, “Wouldn’t you think these mentally and technologically superior beings would have something more interesting to do . . . than to hang around North America kidnapping its . . . inhabitants, in order to do the same experiments over and over again?” I would also ask: Even if they got here somehow, why would they want to have sex with us? For it is the sexual component of the alien abduction script that links it culturally and historically with phenomena such as the incubus and succubus visitations of sixteenth- and seventeenth-century Europe as well as Satanic ritual abuse and recovered memory syndrome, two other sex-related cultural scripts of late twentieth-century North American paranormal belief.

Abducted provides a good introduction to skeptical research on alien abductions, in particular the work done over the past eight years by Clancy and her colleagues at Harvard University. In this book, Clancy vividly portrays the human side of this line of research, which has necessarily been excluded from her academic publications. The book also provides the layperson with a good portrait of the day-to-day grind of psychological research. Abducted is not the definitive book on the alien-abduction experience (not enough research has been done for that book to be written yet), but it is well worth reading for anyone interested in gaining a deeper understanding of the psychological and cultural factors that can compel people to believe they have been in contact with extraterrestrial beings.