The Fermi Paradox won’t go away. It’s one of our most compelling thought experiments, and generations of scientists keep wrestling with it. The paradox pits high estimates for the number of civilizations in the galaxy against the fact that we don’t see any of those civs. It says that if rapidly expanding civilizations exist in the Milky Way, one should have arrived here in our Solar System. The fact that none have implies that none exist.
Many thinkers and scientists have addressed the Fermi Paradox and tried to come up with a reason why we don’t see any evidence of an expanding technological civilization. Life may be extraordinarily rare, and the obstacles to interstellar travel may be too challenging. It could be that simple.
But a new paper has a new answer: maybe our Solar System doesn’t offer what long-lived, rapidly expanding civilizations desire: the correct type of star.
To understand the Fermi Paradox, you need to understand the Drake Equation. The Drake Equation is a probabilistic estimate of the number of civilizations in the Milky Way. It doesn’t tell us how many civs there are; it summarizes the concepts we have to wrestle with if we want to think about how many civilizations there could be.
A critical component of the Drake Equation concerns stars. The Equation considers the rate of star formation in the galaxy, how many of those stars host planets, and how many of those planets could host life. The Equation gets more detailed by asking how many of those planets develop life, how much of that life becomes technological civilizations, and how many of those civilizations reveal their presence by releasing signals into space. Finally, it estimates the life spans of those civilizations.
By using different variables to answer each of those questions, we get different estimates of how many technological civilizations there might be. It’s a thought experiment, but one informed by evidence, though the evidence is rudimentary.
A new paper addresses the Fermi Paradox by focusing on star types. It says that not all types of stars are desirable to an expanding technological civilization. Low-mass stars, particularly K-dwarf stars, are the best migration targets for long-lived civilizations.
The paper is “Galactic settlement of low-mass stars as a resolution to the Fermi paradox,” and the Astrophysical Journal has accepted it for publication. The authors are Jacob Haqq-Misra and Thomas J. Fauchez. Haqq-Misra is a Senior Research Investigator at the Blue Marble Space Institute of Science in Seattle, Washington. Fauchez is a Research Assistant Professor in Physics from the American University in Washington, DC.
The paper begins with a summary of the Fermi Paradox: “An expanding civilization could rapidly spread through the galaxy, so the absence of extraterrestrial settlement in the solar system implies that such expansionist civilizations do not exist,” the authors plainly state.
The authors point to one of the most famous analyses of the Fermi Paradox. It came from American astrophysicist Michael Hart in 1975. Hart’s paper was “An Explanation for the Absence of Extraterrestrials on Earth,” and it was published in the Quarterly Journal of the Royal Astronomical Society. It’s considered to be the first rigorous analysis of the paradox. In his paper, Hart showed how a civilization could expand through the galaxy in a period of time shorter than the galaxy’s age. Hart explained what would happen if a civilization sent out colony ships to the nearest 100 stars. They could colonize those star systems, then each of those colonies could do the same, and the process could keep repeating.
“If there were no pause between trips, the frontier of space exploration would then lie roughly on the surface of a sphere whose radius was increasing at a speed of 0.10c,” Hart wrote. “At that rate, most of our Galaxy would be traversed within 650,000 years.” Hart pointed out that a technological civilization would’ve had ample time to reach us unless they had started less than two million years ago. For Hart, the only explanation for the lack of evidence of alien civilizations is that there are none.
In his paper, Hart arrived at a couple of conclusions: SETI and similar efforts are a waste of time and money, and if anyone colonizes our Solar System, it’ll probably be our descendants who do it.See the rest of the article at Universe Today.