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DIMENSIONALITY. “Tarter (2006, 2010) described the search space as a "nine-dimensional haystack" in terms of three spatial dimensions, one temporal dimension (when the signal is "on"), two polarization dimensions, central frequency, sensitivity, and modulation.” https://lnkd.in/dKzsrBv View in LinkedIn

RATIONALIZED PARAMETERS. “Similarly, Papagiannis (1985) described the "SETI search space" of two NASA SETI search programs for narrowband transmission in terms of the frequencies searched, fraction of sky surveyed, and instrument sensitivity. He distinguished between the Targeted search that parameterized the haystack in terms of the number of targets surveyed (discrete sources at good sensitivity) and a Sky Survey program parameterized in terms of sky coverage (i.e., a shallower search for any transmitters in the beam).” https://lnkd.in/dKzsrBv View in LinkedIn

COSMIC HAYSTACK. “They then "compressed" the three dimensions of polarization, frequency of transmission, and signal modulation by considering only obvious, continuous signals searched for with receivers sensitive to orthogonal polarizations. Next, they compressed the three spatial dimensions into a single axis in terms of the number of targets or beams surveyed. They then graphically illustrated a three-dimensional "Cosmic Haystack" through which various SETI programs had hunted, looking for "needles." https://lnkd.in/dKzsrBv View in LinkedIn

MANY TYPES OF SIGNALS. “Unlike solar neutrinos, however, the potential number of technosignatures is quite large and difficult to parameterize. In one early visualization of the search space for radio communication SETI, Wolfe et al. (1981) identified several relevant parameters: polarization, repetition rate of transmission, signal modulation, three spatial dimensions, central transmission frequency, and receiver sensitivity. “ https://lnkd.in/dKzsrBv View in LinkedIn

PARAMETER SPACE. “Contra Ćirković, it certainly does not "tremendously limit the parameter space describing very advanced civilizations." Nonetheless, it represents a necessary first step toward more stringent and meaningful upper limits on Type iii Kardashev species.” https://lnkd.in/dKzsrBv View in LinkedIn

WEAK UPPER LIMIT. “For instance, Griffith et al. (2015) put weak upper limits on the total waste heat across entire galaxies, concluding that out of 100,000 galaxies, none had a galaxy-spanning species harnessing more than 85% of the galaxy's starlight. This result might hardly be surprising given that this upper limit is near the extreme limit of what galaxy-spanning technology could accomplish.” https://lnkd.in/dKzsrBv View in LinkedIn

FALSE UPPER LIMIT. “Similarly, in SETI, the first upper limits will necessarily rule out only extremely obvious manifestations of alien technology, and may seem at first to "have no bearing on the question of the existence of" alien life.” https://lnkd.in/dKzsrBv View in LinkedIn

FALSE PREMISE. “But the reviewer is incorrect. It is not at all hard to imagine that prehistoric humans around the world performed just such an experiment, told others about it, and in so doing significantly advanced their understanding of the cosmos.” https://lnkd.in/dKzsrBv View in LinkedIn

TIME FUNCTIONAL. “A given telescope and instrumentation performing a survey of a given type will take some amount of time to complete a survey for a given sort of technosignature down to a given sensitivity. Intuitively, one would like to define a survey speed—i.e., haystack volume surveyed per unit of time—that was more or less constant throughout the survey and described the haystack volume searched to date as a linearly increasing function of integration time or telescope time.” https://lnkd.in/dKzsrBv View in LinkedIn

ACUITY. “Artifact SETI seeks astrophysical anomalies and exotica that are consistent with predictions for alien technology, but may not be dispositive of such technology. Here, the metaphor breaks down somewhat, but we might interpret the needles and straw in these haystacks to be hard to distinguish. Finding such maybe-needles nonetheless helps communication SETI efforts to narrow down which parts of their haystack to focus on to find more unambiguous needles.” https://lnkd.in/dKzsrBv View in LinkedIn