Chapter 1: Drake's Equation & Fermi Paradox 

 Dhanush Ekollu

Ethan Wong

November 18, 2022 (Last Modified November 23, 2022)

Alone In the Universe?: Co-Author Series


After decades of observing the universe with even the best of what modern technology can offer, there have never been any major signs or evidence supporting the current existence of extraterrestrial life, and most of the information gathered show nothing–no signs of intelligent life, no matter how far into the dark reaches of space we look. During a lunch break in 1950, a brilliant physicist named Enrico Fermi proposed a question to his colleagues, essentially asking why no intelligent life form has been observed or conquered the galaxy yet–given its size and age of existence. Within our solar system lies a star that harbors 8 planets, along with hundreds of other small moons and dwarf planets. The Milky Way Galaxy encompasses over 100 billion other stars like our own Sun, many hosting solar systems. Outside of our galaxy–which spans around 100 million light years across–many galaxies surround to form a cluster, many of which form the Virgo supercluster, and so on, multiplying over and over until we get the observable universe–teeming full with its incomprehensible number of galaxies and planets. Therefore, the Nobel prize winner does have merit to his question. Earth lies millions of light years from any galaxy that has the possibility of harboring intelligent life, so, for us in the present, communicating or traveling to those areas in the universe is out of reach. However, Fermi pondered why any other super-intelligent extraterrestrial form hasn’t contacted our solar system yet, given that by this time, some incredibly advanced civilization must have the ability to travel light years through galaxies. This is now known as the Fermi Paradox.

In the year 1975, after Fermi’s death, Micheal Hart wrote a document titled “Explanation for the Absence of Extraterrestrials on Earth”. Sara Seager, an astrophysicist from MIT, shares her information in a detailed report too about finding exoplanets using color spectrums for elements used in carbon-based life forms. This series will dive into the above theories and also dive deeper into variations of the Fermi Paradox, including a variety of research papers that will be broken down throughout the articles. This article in particular will cover the famous equation that sparked various strands of research from different scientists about this very topic: The Drake Equation.

In 1961, Dr. Frank Drake formulated a unique equation that could provide astronomers with an approach to understanding the amount of extraterrestrial life there was in the Milky Way Galaxy. He shared this equation at the Search for Extraterrestrial Intelligence (SETI) conference with several other astronomers, including Carl Sagan. Many equations in astronomy and the sciences can be quite difficult and perplexing, yet Drake’s formula is based on rough calculations that allow for a relatively simple guesstimate of the number of alien civilizations. His equation is shown below:


N represents the number of alien civilizations that humans are capable of communicating with

R* represents the rate of stars developing that allows intelligent life to grow

fp represents the fraction of those developing stars that contain planets (like our Solar System)

ne represents the number of planets in each of those solar systems that can harbor life (for example, has the presence of Carbon, Oxygen, Nitrogen, Hydrogen, Sulfur–and the rarest being Phosphorus. These are the key root ingredients to create/sustain life)

fl represents the number of planets where life is evident/life exists there

fi represents the INTELLIGENT life that evolves from the basic/bare minimum of what defines “life” (advanced alien species that has similar developments in comparison to humans)

fc represents the number of intelligent civilizations that grow to build technology and advance themselves enough to be detectable/known to/from Earth (satellites, space probes, signals)

L represents the amount of time that these alien societies can produce signals of their existence (an example would be the lifespan of the dinosaurs: from birth to extinction)

Yet, a considerable number of people find his equation impractical for such a question, as it comes with many tricky values that must be inserted. For example, from the equation above, one would need to find the fraction of stars suitable for the development of life with planetary systems and then the fraction of planets that would be suitable to harbor life. Some of these answers are only possible to plug into the equation with a terrible guess. For example, humans do not have the capabilities to capture and provide evidence of life existing outside of our solar system, which would mean that plugging a number for fl would be a complete guess. Due to this, some astronomers have decided that his formula provides an inaccurate set of calculations to refer toward. However, it has proven to be quite useful and other scientists have also created their formulas based on the Drake equation. 

Although this equation feeds off of rough guesses, and technological advances in space are still not enough, and travel between stars is extremely advanced for our society today, recent astronomical discoveries and the survival of Mars rovers and Voyager probes provide humans with some hope in our search. Within even our own solar system remains a vast amount to discover. Various moons like Europa and Enceladus have been speculated to possess liquid water beneath a thin crust of ice or rock–a home where life, even if unintelligent, could still live. Exoplanets have also been found with elements like carbon dioxide providing humans with hope for the existence of undiscovered interstellar life, which will be covered more in the next chapter. Only time will tell if we, a tiny blue dot surrounded by billions of stars and galaxies, are truly alone in the universe.