Summary: The question is far less academic than it may appear. It has been argued that because of energy requirements, interstellar travel is "Impossible." Also for other intelligences. But most space propulsion specialists disagree.
The question is far less academic than it may appear. It has been argued that because of energy requirements, interstellar travel is "Impossible." Also for other intelligences. But most space propulsion specialists disagree. According to a preliminary CIESPAL survey, 80 percent of those interviewed feel confident that we will reach low c velocities in less than two centuries. NASA director Dan Goldin spoke of plans to send a craft to Alpha Centauri in 20 to 25 years. Therefore, to think that civilizations thousands or millions of years more advanced technologically and scientifically than we would not have a spacefaring capability seems extremely farfetched, to put it mildly. Both Carl Sagan and Arthur C. Clarke have emphatically advocated a much more optimistic view. If we have reason to believe that much older intelligences abound in the universe, than we must admit that the probability that such aliens might send spaceships or automatic probes to explore the Galaxy and stray upon our expanding electromagnetic wavefront is neither greater nor smaller than the chance to find "the needle in the haystack" via radioastronomy. Contact could occur either way. While no solid evidence backs the UFO myth, the possibility should not be ruled out that an alien craft or probe may enter our solar system and attempt an encounter with us.
The principles of Protocol Two, elaborated by the IAA SETI Committee, apply only to the scenario of the reception of a verified alien intelligent radio signal. But what if an alien spacecraft really approaches us, as I posit in my forthcoming book "Contact with ETI: Are We Ready For It?", or if we detect a scouting alien probe, as Alan Tough proposes? Since the impact and consequences of this contact scenario would be incomparably greater than in the former case, it seems to be not only legitimate but urgent to formulate a similar Protocol. We need to be prepared for this eventuality with an adequate legal framework binding nations. A first proposal was submitted by me to the Conference on Bioastronomy in Capri in 1996 [Legal Frameworks for Two Contact Scenarios, P. Schenkel, JBIS, July 1997]. It is always better to have a plan for facing a critical emergency situation, than to be caught by it unprepared without any plan.
Quite erroneously it has been argued that a Third Protocol would "tarnish" Protocol Two because of its "association with UFOlogy." This allegation has even less merit than the one stated in the beginning. At its root is the fear that discussing the hypothetical case of an alien visit or probe may offend and scare off benevolent funding of SETI. But Carl Sagan postulated that the dangerous avalanche of pseudoscience makes it imperative for science to help the public "distinguish between what SETI stands for and the fraudulent claims of UFOlogy." Neither should we capitulate to the UFO gurus nor subordinate a genuine scientific inquiry to expediency. Hopefully SETI via radioastronomy will hit paydirt. But mankind should be prepared politically, legally, communicationally and psychologically for all Contact scenarios, not just for one.