A Maximum Likelihood Approach to the ETI Hypothesis
York Dobyns, PhD
Maximum likelihood methods are usually developed as part of a rigorous mathematical formulation for a problem domain involving exact quantitative measurements and models. The same concept, however, can be applied to less well-quantified situations. The only essential requirement for such a semi-quantitative approach is that it must be possible to identify distinct hypotheses as being either more or less likely than others. If, at every possible decision point in a hypothesis evaluation, one chooses the formulation that is more likely than every competing alternative, one will emerge with the most likely hypothesis, even if the degree of relative likelihood is impossible to evaluate.
A popular hypothesis, frequently examined by numerous SSE members, is that Earth has been (and perhaps is being) visited by spacecraft containing extra-terrestrial intelligences (ETI). The primary evidence presented in favor of this hypothesis consists of eyewitness reports, and occasional corroboration such as photographs or instrument records, of objects that appear to be artificial vehicles and cannot be identified with any known human vehicles or technology. A subset of this witness testimony and other documentation indicates that at least some of these vehicles seem to have occupants, usually approximately humanoid, who are able to operate (possibly with protection) in a human-compatible environment as regards temperature, atmospheric chemistry, gravitation, and so forth.
The current presentation does not attempt to evaluate the quality of this body of evidence but simply stipulates its existence and attempts to construct a maximum likelihood version of an ETI model consistent with observation. Evaluation of likelihood is based on the premise that what is known to be possible is more likely that what has merely not yet been proven impossible. Thus, for example, technologies already implemented by human beings are more likely than technologies based on known physics but not yet successfully implemented by humans, and these in turn are more likely than technologies based on speculative physics not yet confirmed to be real. Similar, though looser, constraints apply in other sciences such as biology. Background knowledge, such as the fact that we are not presently engaged in widely known, public communication with any ETI species, will sometimes be invoked as well.
The conclusions can be summarized briefly by saying that the ETI model of highest likelihood, given the data, is that a substantial ETI civilization is present in the Solar System exploiting deep-space resources (such as minerals in the asteroid belt and volatiles in the Kuiper belt) in ways we have not yet managed to observe. Inferences from this basic model include the conclusions that the main civilization is deliberately pursuing a policy of concealment (perhaps not primarily from us) and those individuals who have allowed their vehicles or even themselves to be observed by humans have been violating the behavioral norms of their culture of origin.
Recorded at the 33rd annual SSE Conference in 2014 at the Hyatt Regency San Francisco Airport,
Burlingame, California, USA.
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Published on November 18, 2018