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SO ENDS this second and last weekend on a rational approach to searching for extraterrestrial life signals. It is notable that we have been willfully uncurious. We will see if the recently released UFO report in the US is valuable, or, more likely, milk-toast redacted material suitable for children. View in LinkedIn

SUBSET TARGETS. “Also, our haystack definition included vast swaths of interstellar space where we have no particular reason to expect to find transmitters; humanity's completeness to subsets of this haystack—for instance, for continuous, permanent transmissions from nearby stars—is many orders of magnitude higher.” https://lnkd.in/dKzsrBv View in LinkedIn

THE CHALLENGE. “We should be careful, however, not to let this result swing the pendulum of public perceptions of SETI too far the other way by suggesting that the SETI haystack is so large that we can never hope to find a needle. The whole haystack need only be searched if one needs to prove that there are zero needles—because technological life might spread through the Galaxy and/or technological species might arise independently in many places, we might expect there to be a great number of needles to be found.” https://lnkd.in/dKzsrBv View in LinkedIn

BACK OF ENVELOPE. “However, perhaps more importantly for now, even order-of-magnitude estimates of the SETI space searched to date are valuable because they rebut the pervasive misconception that SETI work to date has significantly "sharpened" the Fermi Paradox or proven so dispositive that SETI can be said to have "failed" to find what it seeks.” https://lnkd.in/dKzsrBv View in LinkedIn

WOEFUL COMPLETENESS. “We show that these assumptions allow us to do our calculation analytically, and we get a result very similar to that of another haystack, as calculated by Tarter et al. (2010): our current search completeness is extremely low, akin to having searched something like a large hot tub or small swimming pool's worth of water out of all of Earth's oceans.” https://lnkd.in/dKzsrBv View in LinkedIn

THE SAD REALITY. “The total volume of Earth's oceans is approximately 1.335 × 10(21) liters, meaning that the total searching done to date is equivalent of ~8000 l of seawater, which is somewhere between the volumes of a large hot tub and a small swimming pool.” https://lnkd.in/dKzsrBv View in LinkedIn

THE CALCULATION. “To illustrate a haystack calculation, we have chosen a particular set of haystack dimensions that might exemplify any particular narrowband radio search with an eye toward determining whether we can yet rule out large numbers of narrowband transmitters in the solar neighborhood (that is, determining a rigorous—if weak—upper limit for SETI).” https://lnkd.in/dKzsrBv View in LinkedIn

LIMITATIONS. “Calculating search completeness requires defining the boundaries of the search; in many cases, one can always look harder for ever rarer or more subtle or more extreme events. The huge range of potential technosignatures also means that one survey cannot hope to be sensitive to all of them, requiring searchers to hypothesize a particular form of signature that they can put interesting limits on with their survey.” https://lnkd.in/dKzsrBv View in LinkedIn

PRIORITIZATION. “As we have seen, the choice of the number of dimensions for a haystack depends on the method used, and for many surveys, multiple dimensions can be "collapsed" into a single dimension, simplifying the problem. For our present purposes, we choose the following (not necessarily orthogonal) dimensions of a radio communication SETI haystack. (See criteria).” https://lnkd.in/dKzsrBv View in LinkedIn

TARGET SENSITIVITY. “This will also be true with haystacks in general: the size, shape, and dimensionality of the haystack—and one's completeness in searching it—will necessarily depend on the sorts of needles one is searching for.” https://lnkd.in/dKzsrBv View in LinkedIn