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- Aliens Don’t Exist—AT Invisible Evidence
- Aliens Don’t Exist—AT Zoo Hypothesis
- Zoo hypothesis is ridiculous
Aliens Don’t ExistET doesn’t exist – if aliens were anywhere in the UNIVERSE they would be hereNew Scientist, ’96 (Marcus Chown, “Is there anybody out there?”, November 23, L/N) But if the zoo hypothesis and other suggestions to explain why the Solar System has stayed resolutely off the interstellar tourist map are all undermined by the logic of diversity and exponential expansion, what about other, more fundamental reasons for the absence of extraterrestrials? One possibility, according to Shostak, is that it simply takes too much energy to propel an interstellar probe between the stars at an appreciable fraction of the speed of light. Tipler dismisses this as a weak argument. "I would remind everyone of the prominent American astronomer Simon Newcomb, who in 1904 'proved' that heavier-than-air vehicles would require too much energy to be practical," he says. Tipler believes that an advanced civilisation would find interstellar travel easy. "In fact, we've already launched interstellar probes - Pioneer 10 and 11," he says. "They've already passed Pluto and could reach the nearest star in about 80 000 years. This has controversial implications for SETI, which involves looking for intelligent radio or optical broadcasts from nearby stars. "If extraterrestrials sent a radio signal, they would have to trust that there would be someone at the other end with the necessary equipment and patience to listen," says Tipler. "A far more efficient strategy would be to send a spaceship." Tipler says the same logic would apply if, instead of radio waves, extraterrestrials signalled with gravity waves or neutrinos, a suggestion made by Walter Simmons and his colleagues at the University of Hawaii in 1994 ( Quarterly Journal of the Royal Astronomical Society, vol 35, p 321). "Whatever way you look at it, SETI is a waste of time," he says. Nothing, it appears, can deflect Tipler from his almost messianic conviction that we are alone in the Galaxy. And he goes further. For the irresistible logic of exponential expansion implies that if an intelligent race had arisen anywhere in creation, it would have arrived in the Solar System by now. "Not only are we the first intelligence to evolve in our Galaxy, we are the first intelligence to evolve in the whole Universe," says Tipler. "We are totally alone." Aliens Don’t Exist—AT Invisible EvidenceEvidence would be noticeable – the Oort cloud and asteroid belt wouldn’t exist if ET didNew Scientist, ’96 (Marcus Chown, “Is there anybody out there?”, November 23, L/N) Understandably, other scientists are reluctant to accept that we are alone in the Universe. Some say Tipler is premature in claiming there are no extraterrestrials in our backyard. "It's impossible to tell," says Edward Harrison of the University of Massachusetts at Amherst. "The evidence of life may be written across the sky and we may simply not recognise it." Many others share Harrison's view that the absence of evidence is not necessarily evidence of absence. "The whole point is we don't know whether they're out there or not," says Freeman Dyson of the Institute for Advanced Studies in Princeton. Some scientists point out that extraterrestrials could be here without ever letting on. "Say there were nanoprobes abroad in the Solar System," says Seth Shostak of the SETI Institute in Mountain View, California. "How would we ever know?" However, Tipler claims that if the Solar System had been visited the signs would be unmistakable. "There would be no Oort Cloud of comets and no asteroid belt," he says. "All the available resources would have been turned into structures." Tipler's idea is that, on arriving at a new star system, a von Neumann probe would not just make copies of itself to send to other stars, but it would also exploit all the available mineral and energy resources of the star system. In our Solar System, for instance, the comets in the Oort Cloud and the asteroids in the asteroid belt would be obvious sources of minerals, which is why Tipler believes they would be long gone if extraterrestrials had ever visited. He has no idea what kind of technological artefacts such resources would be used to create, but that's not unreasonable. After all, the Romans would have had no idea that future civilisations would turn sand into computers, or bauxite into aeroplanes. The disappearance of resources is a logical consequence of Tipler's "biological" model for interstellar colonisation, in which life's success in filling all available niches and exploiting all available resources on Earth is repeated by intelligent life in the greater arena of the Universe. Aliens Don’t Exist—AT Zoo HypothesisWe’re not a zooGonzalez , ‘98 (Guillermo, Astronomer at University of Washington , Society, “Extraterrestrials: A modern view”, July/August, Volume 35, Issue 5, Proquest) Another proposed solution to Fermi's paradox is the idea that the Earth is being isolated as a kind of "zoo." Michael Hart, and more recently, Ian Crawford, have pointed out a number of very serious problems with this line of reasoning. For example, for most of its history the Earth has been inhabited by simple lifeforms, and thus there should have been little incentive to isolate it until relatively recently. Even if a civilization wanted to keep the Earth isolated, it would have to do so for billions of years, keeping other civilizations away. This does not seem at all likely. Very recent visitation is also unlikely on temporal grounds: why after billions of years would two advanced civilizations (ours and one other) arise nearly simultaneously in the Milky Way? Zoo hypothesis is ridiculousNew Scientist ’96 (Marcus Chown, “Is there anybody out there?”, November 23, L/N) Yet another possible explanation for the absence of extraterrestrials is the "zoo hypothesis". According to this hypothesis, emerging civilisations such as ours are cordoned off by star-faring civilisations of the Galaxy as part of a Star Trek-like non-interference policy. But, according to Tipler, this idea also has its Achilles heel. "It's a universal truth in human society that if you have three members of a society, you will have four opinions," he says. "There will inevitably be a diversity of opinion among Galactic societies about whether we should be contacted or not." Tipler also believes it would be impossible to enforce such a non-interference policy. "It would be necessary to patrol the perimeter of the Solar System," he says. "Even light beams would have to be stopped from entering." It is hard to imagine the existence of a coherent Galaxy-wide society when it takes 100 000 years for a communications signal to cross from one side to the other. But if the extraterrestrials could communicate faster than the speed of light, then perhaps the society could enforce a non-interference policy, as pointed out last year by Ian Crawford of University College London. ( Quarterly Journal of the Royal Astronomical Society, vol 36, p 205). However, there remains the serious problem of maintaining an unwavering policy over millions or maybe hundreds of millions of years, when the lesson from Earth is that no society stays unchanged forever. 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