The Fermi paradox is a theory about alien life forms and the probability of them ever reaching the earth via interstellar travel. Put simply, the Fermi paradox asks, "If there are billions of planets in the universe, why do we seem to be the only one with intelligent life?"
Enrico Fermi was a physicist, and his paradox and its possible solutions rely on equations about the universe and its origins. But if you’re totally freaked out by the thought of complicated scientific and mathematical formulas, don’t worry. This list will take you through Fermi’s paradox step by step and break down all the complex physics into easily understandable, bite-sized pieces of information.
So who was Enrico Fermi? He was an Italian theoretical and nuclear physicist who won the Nobel Prize in Physics in 1938. After winning the prize, he and his wife fled Mussolini and immigrated to the United States, where he was a major part of the Manhattan Project, producing the first nuclear chain reaction. For that reason, he is often called the “architect of the atomic bomb.”
Fermi's knowledge of physics, as well the darker side of politics and world history, influenced both his paradox and its possible solutions. Some of the implications of Fermi's paradox are chilling, but all of them are fascinating.
Where Is Everybody?
In 1950, Fermi was visiting Los Alamos National Laboratory, where he went to lunch with Emil Konopinski, Edward Teller, and Herbert York. Each person has a slightly different memory of the events surrounding the lunch, but they all remember one thing clearly: seemingly out of the blue, Fermi blurted out, “Where is everybody?”
He was talking about extraterrestrial life forms. Konopinski believes Fermi followed his question up with calculations about the size of the galaxy and the likelihood of another planet having intelligent life forms.
Just How Unique Is the Earth?
The Drake equation is a formula used to determine the number of other civilizations capable of communicating with us in our galaxy. It was published by Dr. Frank Drake in 1961. It uses a number of variables, including the number of sun-like stars and Earth-like planets, to do this.
Our Sun Is One in 40 Billion
So, let’s say that, in order to find a planet similar to Earth, which is similarly capable of hosting life, that planet must orbit a star that is similar to our sun. Makes sense, right? In the Milky Way galaxy, there are an estimated 40 billion stars that are similar to our sun.
There Are Almost 9 Billion Potential Earths
A study published by the National Academy of Sciences estimates that approximately 22% of sun-like stars have Earth-like planets orbiting them. That means that there are approximately 8.8 billion planets similar to Earth in the Milky Way. When you consider just how many planets 8.8 billion is, it's hard to believe that only our planet has life on it.
Our Sun Is Still Young
So now we have some sense of just how many earth-like planets are out there. The second part of the puzzle has to do with space travel - and how long it takes for messages or vessels to cross vast distances.
To begin, remember that our sun is more than 4.5 billion years old, but that’s relatively young for a star. In 2013, astronomers discovered HIP 102152, a sun-like star that is 8.2 billion years old.
An Older Sun Might Support An Older Earth
Let’s use HIP 102152’s age as an example. HIP 102152 was formed 8.2 billion years ago. If, as in our solar system, an Earth-like planet was formed at approximately the same time, then there would be a planet capable of supporting life that is 3.7 billion years older than Earth.
Older Planets Could Host Older, More Advanced Civilizations
If there are Earth-like planets that are billions of years older than Earth, and there are intelligent lifeforms living on some of those planets, then there could be civilizations that are billions of years more advanced than we are.
It Would Take 100,000 Years to Cross the Galaxy
Traveling at the speed of light, it would take us 100,000 years to cross our galaxy. But remember: it’s possible that there are civilizations that are far more advanced than we are. So even if they were traveling at "only" the speed of light, they would still have reached us or sent a signal to us a very long time ago.