How Much SETI Has Been Done? Finding Needles in the n-Dimensional Cosmic Haystack (1809.07252v3)

Abstract: Many articulations of the Fermi Paradox have as a premise, implicitly or explicitly, that humanity has searched for signs of extraterrestrial radio transmissions and concluded that there are few or no obvious ones to be found. Tarter et al. (2010) and others have argued strongly to the contrary: bright and obvious radio beacons might be quite common in the sky, but we would not know it yet because our search completeness to date is so low, akin to having searched a drinking glass's worth of seawater for evidence of fish in all of Earth's oceans. Here, we develop the metaphor of the multidimensional "Cosmic Haystack" through which SETI hunts for alien "needles" into a quantitative, eight-dimensional model and perform an analytic integral to compute the fraction of this haystack that several large radio SETI programs have collectively examined. Although this model haystack has many qualitative differences from the Tarter et al. (2010) haystack, we conclude that the fraction of it searched to date is also very small: similar to the ratio of the volume of a large hot tub or small swimming pool to that of the Earth's oceans. With this article we provide a Python script to calculate haystack volumes for future searches and for similar haystacks with different boundaries. We hope this formalism will aid in the development of a common parameter space for the computation of upper limits and completeness fractions of search programs for radio and other technosignatures.

• The paper quantifies the effectiveness of SETI searches by analyzing an eight-dimensional parameter space that models the cosmic haystack.
• It demonstrates that current SETI programs explore only an extremely small fraction—comparable to a hot tub in an ocean—of the total search area.
• The study standardizes SETI methodologies and sets new benchmarks for evaluating and expanding future search strategies.

Overview of "How Much SETI Has Been Done? Finding Needles in the $n$-Dimensional Cosmic Haystack"

The paper, "How Much SETI Has Been Done? Finding Needles in the $n$-Dimensional Cosmic Haystack," authored by Jason T. Wright, Shubham Kanodia, and Emily Lubar, presents a rigorous quantitative analysis of the efforts made in the Search for Extraterrestrial Intelligence (SETI). The authors introduce a comprehensive eight-dimensional model of the "Cosmic Haystack" that researchers traverse in search of extraterrestrial technosignatures—principally radio transmissions.

Key Concepts and Findings

• Fermi Paradox Context: The paper scrutinizes the assumptions of the Fermi Paradox, particularly the proposition that if intelligent extraterrestrial beings were communicating, we would have observed their transmissions by now. The authors emphasize that the fraction of the cosmic parameter space evaluated by existing SETI endeavors remains minute.
• Eight-Dimensional Haystack Model: The paper develops a multidimensional model describing the parameter space through dimensions such as transmission frequency, sensitivity, distance, and polarization. By employing an analytic approach, the authors evaluate how extensively different large-scale radio SETI programs have scoured this parameter space.
• Analytic Approach: The analysis reveals that, despite technological advancements, our search coverage is still comparable to a volume as trivial as a large hot tub when compared to Earth's oceans. This analogy is indicative of the vastness and complexity of the SETI parameter spaces yet to be explored.
• SETI Completeness and Limitations: Quantifying the completeness of SETI coverage, the authors assert that current programs only explore an exceedingly tiny volume of the parameter space. This counters the misconception that the Fermi Paradox disproves the presence of detectable extraterrestrial technologies.
• Contribution to SETI Methodology: With this paper, the authors propose a formalism aiding in the defining of a consensual parameter space, thus standardizing the calculation of upper limits and completeness fractions in SETI searches. These methodological contributions could potentially recalibrate expectations and direct future search strategies.

Implications and Future Directions

• Practical Implications: For SETI to approach any degree of comprehensiveness, searches must be amplified both in their duration and their parameter space dimensions. This underscores the need for broad-spectrum, persistent, and strategically targeted searches that capitalize on innovations in radio astronomy technologies.
• Theoretical Implications: The research challenges the notion of a fully silent universe by illustrating the negligible fraction of the cosmic haystack that has been probed. Thus, it both renews and refines the inquiry into potential technosignatures left by extraterrestrial civilizations.
• Future Developments: The authors advocate for more consistent and expansive surveys across the haystack. This points to the potential for leveraging next-generation telescopes and computational advancements to enhance SETI detection capabilities progressively.

In conclusion, while the paper modestly refrains from deeming its findings as revolutionary, it provides substantial clarity on the limitations of current SETI efforts and underlines the extensive realms remaining unexplored. For the SETI community, it sets a groundwork for recalibrating strategies that address both technical and theoretical aspects of the search, aspiring towards the lofty yet enticing hope of answering humanity's profound questions about cosmic companionship.