I saw a special documentary on TV that said that the Apollo missions were faked. They gave several mistakes that were pretty convincing, like shadows pointing different directions from artificial lights and the lack of stars. Any comments?

Sigh. Every now and then a TV producer gets snookered by conspiracy nuts into making a show with no merit at all.

1) The shadows pointing two ways is an effect called "perspective" discovered by Renaissance artists. It is also visible in railroad tracks seeming to converge when they're really parallel.

2) The lack of stars is caused by the fact that the sun was up, and a sunlit scene is a factor of about a billion brighter than all the stars rolled up together. The camera is doing well if it can show things separated in brightness by a factor of 100.

However, the people who think the Moon landings were faked will just think up new arguments. Perhaps the best way to answer them is to say that the hardest part of the missions to fake were the launchings! Put it this way. They made something the size of a 36-floor building accelerate upward, out of sight, on a pillar of flame. It was easily visible from 50 miles. It shook the ground with its barely-contained power. It was seen and heard by millions of witnesses, some of whom are indifferent or actively hostile. Then what these conspiracy people would have us believe is that NASA found the relatively small additional effort to throw the tiny modules toward the Moon too difficult? Hardly likely.

I've heard lots of times that the ancient artifacts like the Pyramids are proof that aliens exist because these gigantic projects were too difficult for these primitive peoples. Is this true?

These "alien artifact" theories were started a long time ago by someone whose research was largely secondhand and suspect. When an attractive story gets started, however, it seems to go on forever. There is plenty of archeological evidence that the pyramids were made by Egyptians. There is Egyptian graffiti inside of them. There are thousand of ration bowls buried near the site, huge ropes abandoned inside of them, and nearby quarries with rocks half-removed using simple methods. But the real point of all of this is that this whole movement is another way of wrapping up racism: "Egyptians couldn't have built their Pyramids because the job is too big for African river folk." or "The Maya couldn't have built their gigantic cities in the Yucatan and Guatemala because everyone knows that they are a bunch of lazy jungle dwellers" is what these people are really saying.

Ancient peoples were fully as intelligent as we are and equally capable of acts of piety (which is what the pyramids are). Someone could say, with equal justification, that it is impossible for the poor wattle-and-daub hut dwellers in medieval Paris to have build the Cathedral of Notre Dame.

Are UFOs real?

There are Unidentified Flying Objects (UFOs). The problem is that it is a long stretch to infer that these are alien spacecraft. Before the popularity swing of UFOs, the Astronomical League did a revealing survey of members (the AL is a grouping of local amateur astronomy societies) to find out whether they had more or fewer sightings. You see, the logic was that amateurs spend a lot of time in out-of-the-way places at night. If UFOs were real alien artifacts, amateurs should see them a lot more than the average population. If they were figments of the viewers' imagination, amateurs should see them at far lower than the average rate. Amateur astronomers tend to have a lot more experience looking up at the sky and can interpret what they see with more skill. At the time, about 2 percent of the population thought that they had a sighting. Amateur astronomers saw them at the same 2 percent rate. [With all the publicity, belief and sightings among the general population has increased drastically. In amateur astronomers, the survey has not to my knowledge been repeated.]

So what does this mean?

It probably means that there are a small percentage of real visual sightings of normal aircraft or other phenomena where amateur astronomers and the public alike are fooled by optical illusions, peculiar atmospheric optics, or just plain insufficient cues. People who see UFOs, by and large, are not making this stuff up, but we lack sufficient information to make correct decisions about what they are. I'll give you a few examples that happened to me or people I know personally:

1) During college, I was awakened at 4 AM by some people pulling an all-night study session in my dormitory. They were hopping up and down about knee-high. They had seen a UFO from the roof, and asked me to confirm it. (I didn't ask what they were doing on the roof instead of studying!) I pulled on some slippers and followed them up there. When we got to the roof they pointed out over the skyline at a bright star. They said it was diamond-shaped and was moving back and forth over the city. I looked at it and looked at the sky. It was the planet Jupiter, occupying its correct position above the constellation Scorpius that year. I asked one of them to stand where he could sight past a tower on that roof and asked him if it was still moving. No, he said, he guessed it wasn't. I asked the one who claimed it looked like a diamond to get his glasses and look at it again. There are certain astigmatic eyes that see bright points of light as diamond-shaped. He got them and looked again. No diamond. (Unfortunately, a similar problem with camera optics incorrectly imaging a star as a convoluted shape contributed to the Heaven's Gate mass suicide.)

2) I was returning one night from an observing expedition where we were clouded out. As I approached town a really big aircraft that had just taken off was coming toward me with its headlights on. It was moving up into an exceptionally flat-bottomed cloud. Now, I should explain that I lived at the time in an airport approach corridor. I saw airplanes with their headlights on all the time and I recognized it at once, but everyone has not been so prepared. I could not hear it at that distance because it was in an acoustic shadow or its noise was mostly directed at the rear. I remember thinking offhand that an excitable person might misinterpret that view as a UFO. Then I got a bonus. As it passed into the flat clouds, the two spotlight shapes of the headlight beams moved quickly toward it, merged with it instantly, then - slap! - the whole thing disappeared as it buried itself into the clouds. I had just "seen" a mother ship redock two scout ships and then vanish. No doubt it had gone into hyperdrive!

3) A friend of mine once saw a flock of Canada geese pass overhead at night. The part he saw was the white underbellies lit by distant streetlights; there wasn't enough light to see the wings. Lacking scale information, he thought they were miles overhead and they seemed huge. Then one of them honked and he realized that they were only a few hundred feet away.

4) Once, I was returning to my car at night in a parking lot. I looked into the sky and saw a perfect self-luminous white circle with radiating red spokes. It was enormous. My jaw dropped and I scrambled for a little telescopic monocular that I always carry. Using the optical aid, I saw the tiny gondola and realized that I was seeing a white blimp, with red trim illuminated from the interior, pointed right at me. As I continued watching, the blimp suddenly turn sideways and puttered off toward its resting berth at the airport (I guess it was the end of the day). Along its side was the advertisement BUDWEISER. That blimp, when I had first seen it, had shown a very un-blimplike aspect. What if I had not had the telescope or what if I had run inside for another witness when it decided to scoot for the airport? Might I not now be a True Believer?

But couldn't there be a small percentage that are real?

Sure, there could be. But remember the scientific principle of Occam's Razor: don't overcomplicate. We have two hypotheses. One: that all of the sightings are mistakes. Two: that all but a tiny fraction of the sightings are mistakes, and that a fabulous technology, for which there is no other evidence, is apparently hiding among us. The simplest solution is to assume that the only reason we have a few unexplained sightings is because we lack some key component of the explanation or are dealing with a corrupted record. In other words, assuming that the unexplained sightings are just noise in the measurement is the likeliest solution.

What would be regarded as strong evidence?

There was a astronomer back in the fifties and sixties, J. Allen Hynek, who tried to grapple with the evidence and types of evidence. He went off the deep end and became a True Believer (for which he attracted a great deal of criticism) but he made some very good points, too. Maybe his aim was to deliberately make himself heard by the UFO watchers to improve the quality of the reporting.

His point was that there are at least four kinds of evidence: a) objects in the sky, b) close-up viewing of spacecraft within a distance where detail could be easily seen (my blimp almost was one of these), c) tangible evidence such as radar contacts or detritus, and d) actual human-aliens contact.

He expressed the opinion that type a), seeing lights or distant artifacts, was next to worthless (and this is what most sightings are), type b) very suspect because of misinterpretation and wishful thinking, and type c) inconclusive. Sightings of type d), actual human-alien contact, were the only sightings that would settle the matter.

In other words, seeing lights or what you believed to be spacecraft in the sky, detecting radar bogies, or finding rings of burnt or flattened grass were interesting, sure, but they didn't prove anything. The trouble is that the kind of sober, credible, people that you would trust in a court of law have made mostly reports of type a) through c). The type d) reports seem to come from people with a looser grip on reality. [By the way, type d) was coined by Hynek a "close encounter of the third kind." He didn't even rate distant lights in the sky as decent encounters!]

Are you saying that people who claim contact are crazy?

Not crazy; human. I'll give you an example that was related to me at a meeting (I wish I remember who told me, but I don't). There is a beach near Pensacola that has a very high density of UFO reports. This person went there one night and he found a group of people who made it their hobby to observe UFOs. The person relating the story said that every object that passed in the air turned out to be a "real UFO" to these people, including private aircraft and Navy planes with clearly visible markings! When he gently pointed this out to the regular watchers, they immediately became hostile. Of course, they said, the aliens disguised their craft! One guy seemed to want to fight him. He backed away and left. Clearly belief had taken over. In earlier ages ghosts, demons, and other inhabitants of the ethereal realms had occupied much the same locations in peoples' hearts. A poll shows that up to 2 percent of the American public believes that they, personally, have been the subject of alien abductions. That is 5 million people. The aliens, if they are there, aren't doing very well at hiding.

Then most astronomers don't believe in aliens at all?

Scientists DO believe alien technological civilizations are possible, but they are unconvinced that they are here right now. Nevertheless, if civilization has happened in one place, it is likely to occur in others as well. But there is something called the Drake equation to give upper limits to the number of carbon-based, water-drinking, air-breathing civilizations in the galaxy (sightings involving space-suited aliens are few so we have to assume that their environment is similar to ours). Basically, it's a string of fractions like fraction of favorable stars, the fraction with planets, the fraction having a planet where water is likely to remain liquid, number where life develops intelligence, number that don't blow themselves up, and so forth.

How many does the Drake equation estimate?

There are many versions, but a well-thought out recent one, assuming that there are no unforeseen impediments, is somewhere between 150 and 1. Biologists calculate the pessimistic end. Physicists calculate the optimistic end.

A calculation of 150 would be plenty to account for UFOs!

It would, except for the distances involved. Using conservative estimates for the size of the galaxy, the closest such civilization is at least 2000 light-years away, and probably much more than that because the stars are denser toward the center of the galaxy. Surely no more than one or two types would have made such a journey. Yet we see the descriptions of UFO aliens change through time. Suspiciously, for any given UFO flap, we find most of the descriptions model fairly closely whatever was reported first or was depicted in the media earlier. Aliens have changed from a kind of hairy, short creature to the modern ovoid-head, big-eyed, skinny creature. The Ovoid-Heads started appearing after a science-fiction television program somewhere in the late 50 and early 60s had an episode entitled "To Serve Man" in which such aliens were depicted. Now, after the movie Close Encounters, they are nearly all that are reported. The time-progression of alien shapes is extremely suspicious. Which aliens we allegedly see should not be subject to fashion.

But what if the aliens have made some sort of breakthrough that makes such long-distance travel really easy? Then the population of aliens could change.

True. If space travel is really easy there could be a lot of aliens, but then we have to suppose that the reason they don't walk up and shake our hands is because they have some sort of law that prevents unauthorized contact, a "Prime Directive" in Star Trek parlance. If that is the case, why are they doing such a bad job of it, a worse job even than Captain Kirk at The Planet of the Sex Goddesses? UFO abductees are found to be equally distributed among the US population? Wouldn't it be easier to grab someone who lives at the edge of the Nevada desert if they need biological samples? Wouldn't it be easier to find people alone in the country? If aliens have indeed snapped up 2 percent of the US population, we should expect them to grab nearly 100 percent of the farmers while leaving the city dweller alone. It's much easier to get in and out unseen.

Is the difficulty of space travel the worst evidence against space aliens?

No. The worst evidence is that the statistics of the sightings aren't right. During any given period a given number of UFO reports are made. Investigators (most of them friendly to the concept of UFOs but wanting to weed out the incorrect cases) declare most of them IFOs, or Identified Flying Objects after some questions are asked. The number of UFOs compared to IFOs is approximately a constant over the short haul. It varies some over the long haul with the varying individual zeal of investigators, of course. Then a UFO flap hits; suddenly it becomes popular to report UFOs. What direction do you expect the ratio of UFOs to IFOs to change? Even the most avid UFO believer expect most of the additional reports during a flap to be just copycat, me-too, garbage. You would expect the true UFOs to be a constant low level beneath the current fad, so the ratio should drop considerably. In fact, you might expect the aliens to lay low for awhile, avoiding attention; this drops it even farther. But in fact it remains fairly constant. This is precisely what you would expect if all UFOs were just insufficient information.

Then there is the flat distribution of abductions. I can't believe that the aliens would be so stupid as to choose subjects in the reported geographic distribution. If they were really grabbing people, then they would do so in a distribution that minimizes the cross section for interaction, namely in countries with less access to communications and rural areas at that.

And finally there is the statistics for the described alien shape and technologies. They have progressed along a time curve. They should not have changed much over the last 50 years and advanced technologies should not have gotten "prettier" with the increased sophistication of the observer. Yet their appearance has changed and their technologies have changed, sad to say, to match the latest TV shows or movies.

I'm going to ask only one more question. What about the famous "alien autopsy" film?

It was a fabrication. Brand-name appliances on the wall of the room have been identified that could not possibly have been in existence on the alleged date of the autopsy.