Saving to read later. Sounds interesting.
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.
Without having read it yet I'd say that it makes intuitive sense that we can't place any meaningful limits on the number of alien intelligences in general. But we can confidentially say that there are no Galactic Empires, and I for one still find that worrying. It ought to be easy to colonise the Galaxy on astronomical timescales but it hasn't happened. I don't find any of the proposed solutions to this convincing, not even combinations of solutions.
https://arxiv.org/abs/1809.07252
The solution I find the most convincing is that we are those Ancient Precursor Proteans that plague nearly every space opera show. After all, the Universe is still very young, the age of stars barely begun and a few billion years may be a rather short time to evolve sapience.
ReplyDeleteIf we go for a probabilist argument, that is we're no special observers, I suspect this means the first Galactic Empire will take all resources and change conditions, making emergence of new sapience improbable. And that the number of individuals will decrease while lifespan will increase, so whole star sectors may contain only one or a handful of sapient minds.
Or we're simply the random first ones, because someone has to be.