The Fermi Paradox: Are We Alone In The Universe?

Meet Enrico Fermi.


Fermi was an Italian physicist who basically developed and explained a huge chunk of quantum mechanics that we still rely on and reference today. He built the world’s first nuclear reactor and is referred to as the “father of the atomic bomb”. He has so many things named after him that Wikipedia had to make an entire list just to keep track of them. He also had magical powers that basically let him estimate anything under the sun with little or no data whatsoever. No… seriously. It was weird.

Fermi correctly estimated the strength of an atomic bomb by throwing pieces of paper in the air and seeing how far they were blown by the blast. He also used his ridiculous skills to answer a mind-boggling question that has confused and confounded us all.

Just how many piano tuners are there in Chicago?


“Gee, man, I dunno.”

To answer this, Fermi made some basic assumptions. He decided that the population of the city is 9 million people. Each household has about 2 people in it. Around 1 in every 20 households have pianos that are regularly tuned. Pianos that are regularly tuned are tuned once every year, on average. This means that there are about (9,000,000/2 * 1/20 * 1) or 225,000 piano tunings in Chicago each year.

Now, from the other side, every piano tuner takes around 2 hours (including transit time) to tune a piano. All piano tuners work an average of 8 hours a day, 5 days a week, 50 weeks a year. Thus, every piano tuner performs about (50 * 5 * 8/2) or 1,000 piano tunings every year.

From this, Fermi estimated that there are (225,000/1,000) or 225 piano tuners in Chicago. The actual number of piano tuners is 290.


Told you he was magic.

His number was a great estimate, considering the simple back-of-the-envelope calculations involved. In fact, Fermi was so good at making such estimates that this method of guessing an unknown number using very limited data is called the Fermi method.

So, what does this have to do with extraterrestrial life, you ask? Well, when Fermi was not making new science or dropping jaws with his arithmetic skills, he was pondering the prospect of life on other planets, or more specifically, about one question in particular.

Where are all the aliens?

Fermi approached the problem with his usual method. The arguments he proposed are :

  • The Sun is an ordinary star in the Milky Way, and there are billions of stars that are billions of years older.
  • It is highly probable that at least a significant portion of these will have planets that are Earth-like.
  • If Earth is a typical planet (and there seems to be no reason to believe it is not), at least some of these planets should have developed intelligent life.
  • If civilizations did arise on these planets, some of them should be developing interstellar travel, just as the Earth is investigating at present.
  • Even if interstellar travel is at speeds much much less than the speed of light, the galaxy can be entirely traversed in about a million years.

Given all these arguments, it is highly improbable that humans have not yet made contact with extraterrestrial life. Thus, there seems to be a mistake in logic somewhere that can explain why we have not yet received any indication of intelligent life outside our planet. Scientists call this anomaly the Fermi paradox (because, really, who else would they name it after?)

Heisenberg? Yeah, right.

But Where is the Mistake?

No one really knows. It is believed that one of the terms of the Fermi method must have been wrongly assumed. There have been many hypotheses. Some say that our Earth is a very rare instance where all the factors conducive to life appeared at once, so it is highly improbable that it has happened on any other planet.

Others contest that most civilizations are doomed to kill themselves off long before they achieve interstellar flight. They would either engage in all-out nuclear warfare (which threatened to occur on Earth not so long ago) or destroy their planet with pollution from their technological advances (which is currently threatening us now).

Some have taken an even more sinister tone and said that aliens will be apex predators (like humans are in our own environment), and they wipe out any intelligent life that they meet. That is why we are not meeting any other civilizations; the ones out there are getting wiped out because the first one they meet destroys them.

So… Is There Intelligent Life Out There?

Who can say? The Fermi paradox is unresolved, and will remain probably remain so until we can find a civilization on another planet. Or can’t. To quote Arthur C. Clarke, “Two possibilities exist: either we are alone in the Universe or we are not. Both are equally terrifying.”

Carl Sagan's pale blue dot. Look it up. Source: NASA/ Rebecca J. Rosen

Carl Sagan’s pale blue dot. Look it up. Source: NASA/ Rebecca J. Rosen


  1. Fermi Paradox – Wikipedia
  2. Fermi’s Paradox – James Schombert v7.0 (University of Oregon)
  3. Wait But Why
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