Ending Hynek's Embarrassment

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The idea that Unidentified Flying Objects are alien spacecraft visiting the Earth is sometimes referred to by UFO enthusiasts as the Extra-Terrestrial Hypothesis, or ETH for short. Allen Hynek, an astronomer who investigated many UFO sightings, suggested that the sheer number of reports was in itself an objection to the ETH. He described it as an "embarrassment of riches", because to account for all the incidents that could not be explained by known phenomena the aliens would have to be visiting Earth on a regular basis. To understand why this seemed so problematic, it is necessary to know that Einstein's theory of Special Relativity predicts that nothing can travel faster than the speed of light. It also predicts that the mass of an object will increase as its speed increases, and although this effect only becomes significant at very high speeds it ensures that no object with mass - such as a spaceship - can even reach the speed of light. The faster you go, the harder it gets to go any faster. Unfortunately, space is so vast that even light takes years to pass between the stars. Indeed, we measure the distance to them in terms of light years, where one light year is the distance that light travels in a single year. That's about 9.46 million million kilometres. The nearest star to our own Sun is the triple-star system Alpha Centauri, the two main stars of which are about 4.3 light years away. In a spaceship that could reach 90% of the speed of light it would take about 4.8 years to get there. Add some extra time for accelerating and braking and a few months studying the Alpha Centauri system, and a round trip takes between 10 and 11 years. But to reach such speeds would require a technology far beyond our own. Engineering studies such as Project Longshot and Project Daedelus suggest that we could build an unmanned interstellar probe capable of about 10% of the speed of light using plausible near-future technology. That would increase the travel time to Alpha Centauri to at least 43 years, with a manned round-trip taking perhaps 90 years. That's just for the nearest star. Yet our galaxy is about 100,000 light years in diameter and is just one of many, so by cosmic standards Alpha Centauri is right on our doorstep. If there is no way round the speed of light limit - no warp drive or navigable wormholes - then an alien expedition to Earth would take decades, if not centuries. Hence the "embarrassment" of flying saucers supposedly flitting between the stars at will. One solution is to assume that there is some way to exceed the speed of light. But to throw out Relativity to protect the ETH is to reject a rigorous and well-tested theory for the sake of an unproven and highly speculative hypothesis. Fortunately, the two can be reconciled by considering the practicalities of such a lengthy interstellar mission. We cannot guess how hypothetical aliens might think, but we can consider what practical difficulties they would face because they would be the same for us. The spacecraft would have to carry enormous supplies of food, breathable air, fuel and spare parts. It would need extensive laboratories, living space for the crew, and storage space for samples from Earth. Perhaps the crew could be kept in some form of suspended animation during the voyage and then grow their own food and recycle their waste once they arrived. Perhaps the aliens would send robots rather than coming in person. But even with these efficiencies, the spacecraft would still have to be huge. There would be no way of getting help from the home planet so the crew, whether biological or robotic, would have to bring everything they might possibly need with them. Instead of a little silver saucer it would be more like the Battlestar Galactica. It's very unlikely that the ship would be designed to land on Earth. Even if it was technically feasible, it would make construction of the vessel much more difficult and they would risk losing the whole mission if there was any problem during the descent. They would also have the problem of concealing it from the indigenous life forms to avoid disturbing their normal behaviour patterns and to avoid being attacked by them. With such a long voyage the aliens could not be certain what level of military technology the locals might have by the time they arrived, or how aggressive they might be. It's much more likely that they would keep the main ship a safe distance from Earth and visit the surface in small short-range craft designed specifically for that role. UFOs would therefore be the ET equivalent of the Apollo lunar module. They would need to be re-usable spaceships with a range of perhaps a few million miles and the ability to manoeuvre freely within the Earth's atmosphere. They would probably be able to deploy small rovers or UAVs (Unmanned Aerial Vehicles) to explore the area around their landing site, and would probably be capable of operating with or without a pilot on board. If we can build remotely-piloted aircraft then the aliens could too, and the extraordinary manoeuvres reported in some UFO sightings are more plausible if we don't also have to assume that there is a living creature on board that can withstand extreme g-forces. Modern air-to-air missiles can turn and accelerate at 30-g or more, and it is reasonable to assume that unmanned fighter aircraft will be capable of UFO-like manoeuvres by the end of this century. By that time we should also have reliable re-usable spacecraft, and combining the capabilities of the two would be challenging but not impossible. A multiplicity of sightings is not a problem if we assume that the UFOs are only making short-range flights to and from a mother ship. Once the aliens arrived, they would naturally want to take as many samples from different sites on Earth as possible. However, the fact that there were so many sightings in the decades immediately following World War II doesn't mean that the aliens must have arrived at that time. Cold War fears and the recent experience of aerial bombardment made people much more aware of what was going on in the sky, and more inclined to interpret an anomalous object as an unknown aircraft rather than as a natural or supernatural phenomenon. Also, radar and high-flying jet planes made it possible to observe things in the upper atmosphere that would previously have passed unnoticed. Having said all that, I do remain sceptical of the ETH. To prove it would require hard physical evidence, in the form of an actual alien or an artefact that could not possibly be of Earthly origin. No such evidence has ever been produced. To even conclude that the ETH was the most plausible explanation for UFO sightings would require far better evidence than we currently have about the physical properties of UFOs, to rule out other potential causes. However, we can conclude that Hynek's "embarrassment of riches" is not a valid objection to the ETH. It is in fact perfectly consistent with an interstellar mission mounted in accordance with the known laws of physics and using technology no more than a few centuries ahead of our own.

		Last Updated: 1 Oct 07