The Fermi Paradox, named after physicist Enrico Fermi, highlights a contradiction in our understanding of alien life: despite billions of stars with potentially habitable planets and the vast age of our Galaxy providing ample time for civilizations to develop and spread, we’ve detected no evidence of their existence.
This absence of contact is particularly puzzling considering that a technologically advanced civilisation could theoretically colonise the entire Milky Way within a few million years—a brief moment in cosmic timescales.
One factor for consideration of course is the number of potential civilisations out there.
The Drake equation is a mathematical formula developed by astronomer Frank Drake to try and estimate the number of active, communicative extraterrestrial civilizations in the Milky Way.
It multiplies several factors, including the rate of star formation, the fraction of stars with planets, the number of habitable planets per star, the fraction of those planets where life arises, the fraction where intelligent life develops, the number of civilizations that develop detectable communication technologies, and the average lifespan of such civilizations.
The Drake equation suggests there should be many civilisations out there yet searches like SETI have not detected any signals.
This raises questions about whether SETI is a valuable scientific effort.
A paper authored by Matthew Civiletti from the University of new York doesn’t directly answer this question but instead offers a way to assess how likely it is that we would have detected a signal by now if a certain number of civilizations were broadcasting.
If the chance is low, the lack of detection may not be surprising; if it’s high, the silence could be meaningful. The paper also shows how these probabilities can help narrow down the possible values in the Drake equation.
The paper begins by exploring the geometric aspects of the problem, then calculates the probability of detecting a single signal and extends this to the probability of at least one detection.
Building on previous studies, it offers an exact solution in two dimensions and a practical approximation for single observations, showing that Earth’s position doesn’t affect the detection chances in simple cases.
This makes it easier to apply the model to more complex scenarios. The key contribution is linking these results to the Drake equation, showing how a lack of SETI detections can help narrow down its parameters.
The paper presents a model to explore the Fermi Paradox and assess the value of SETI in the search for intelligent life. Despite its limitations, the model suggests that the absence of detected electromagnetic signals from alien civilizations can place limits on how many such civilizations exist.
Under certain assumptions, the model predicts a 99% chance of detecting at least one signal if the estimated number of civilizations (based on the Drake equation) is around 1.
Although this is a basic model, it shows that even a lack of results from SETI can help rule out certain combinations of the number and lifespan of civilizations, potentially aiding in solving the Fermi paradox.
Studies like Civiletti’s offer valuable tools for understanding the Fermi Paradox more rigorously. By combining modeling with the Drake equation, the paper highlights how even the absence of evidence can be scientifically meaningful.
As SETI efforts continue and models improve, we may increasingly be able to use non-detections not as dead ends, but as data points that refine our understanding of the cosmos and our place within it.
Ultimately, the search for extraterrestrial intelligence is not just about finding others—it’s also a way to better understand ourselves and the conditions that make intelligent life possible.
Written by Mark Thompson/Universe Today.
