Back in 1961 he came up with a formula which has become known as Drake Equation, which allows one to calculate the number of extraterrestrial civilizations in the Milky Way galaxy by looking at the probability of specific factors arising which are thought to play a role in the development of such civilizations.
Since then, the Search for Extraterrestrial Intelligence (SETI) has owed a great deal of its observational and theoretical framework to the Drake Equation.
There have been a number of solutions to Fermi’s Paradox.
Current SETI searches rely on detecting intentional or unintentional signals at a variety of wavelengths. These searches generally set upper limits on the population and broadcast strength of communicating civilizations, but with only one civilization in our sample (humanity), predicting which proposed solution to Fermi’s Paradox holds true is extremely difficult.
What if the extraterrestrial civilizations annihilated themselves long before we actually started attempting to find them?
Adam Stevens, Duncan Forgan and Jack O’Malley James used the Earth as a test case in order to categorize the potential scenarios for complete civilizational destruction, quantify the observable signatures that these scenarios might leave behind, and determine whether these would be observable with the current technology or technology which might be available in the near future.
The results of their research have been published by the Cornell University Library.
The astronomers therefore analyzed various ways that humanity could destroy its own civilization, and the observational signatures these events may produce.
Those ways include: i) complete nuclear, mutually-assured destruction ii) a biological or chemical agent designed to kill either the human species, all animals, all eukaryotes, or all living things iii) a technological disaster such as the “grey goo” scenario, or iv) excessive pollution of the star, planet or interplanetary environment.
The researchers also discussed the timescales on which these signatures might persist, and prospects for their detection by present and future observations.