In 1950, a conversation over lunch paved the way for decades of astronomical exploration. Physicist Enrico Fermi gathered his colleagues around the table and released some statements, summarized as:
1) The galaxy is very old and very large, with hundreds of billions of stars and probably more habitable planets;
2) This means that there must be more than enough time for advanced civilizations to develop and evolve across the galaxy.
So where are they?
This simple yet powerful argument became known as the Fermi Paradox, and it is still a disturbance to people who are dedicated to studying the topic. Aliens must be common, but there is no convincing evidence that they actually exist.
Here are twelve possible reasons for this:
1. There are no aliens to find: As unlikely as it may seem in a galaxy with hundreds of billions of stars and up to 40 billion Earth-sized planets in habitable zones, we may be alone.
2. There is no intelligent life besides us: Life may exist, but it may simply take the form of tiny microbes or other cosmically “silent” animals.
3. Intelligent species lack advanced technology: Astronomers currently use radio telescopes to listen closely to the night sky. So if alien species aren’t transmitting signals, we’d never know they existed.
4. Intelligent life self-destructs: Whether through weapons of mass destruction, planetary pollution, or manufactured virulent disease, it may be the nature of intelligent species to commit suicide, existing for a short time before they leave life.
5. The universe is a deadly place: In cosmic time – think that the galaxy has existed for billions of years – life can be fleeting. All it takes is a single asteroid, supernova, or lightning burst to turn a vivid planet into a lifeless environment.
6. Space is big: The Milky Way alone is 100,000 light-years across, so it’s conceivable that the signals emitted by intelligent aliens, which are limited to the speed of light, simply haven’t reached us yet.
7. We have not observed long enough: Eighty years. That’s the approximate time range in which radio telescopes allow us to detect alien signals. And we’ve been actively looking for extraterrestrial signals for maybe sixty years. That’s not a long time.
8. We’re Not Looking in the Right Place: As mentioned earlier, space is big, so there are millions of regions where we can hear alien signals. If we are not hearing precisely in the direction from which a signal originates, we will never hear it. As Andrew Fain explained on Universe Today, it’s like trying to talk to your friend on a 250,000,000,000-channel CB radio, without any knowledge of the frequency they’re broadcasting on. You’ll probably be looking for the right channel for a long period of time.
9. Alien technology may be very advanced: Radio technology may be common here on Earth, but on distant worlds, extraterrestrial societies may develop more advanced communication technologies, such as neutrino signals. We may not be able to decipher their technologies yet.
10. No one is streaming: Instead, everyone can be listening. This works basically the same way as it does here on Earth. Aside from a few paltry efforts to transmit strong signals across a narrow frequency band toward the stars, we can barely know our own presence in the Universe. In fact, if extraterrestrials have radio telescopes similar to those we have on Earth, our television and radio emissions would only be detectable up to 0.3 light years away. This distance does not exceed even the most distant limits of our solar system.
11. The Earth is not being deliberately contacted: On Earth, we have policies of contact with indigenous peoples, for example, and it is possible that the same will happen to us. As in Star Trek, advanced alien societies can impose rules that limit contact only to species that achieve a high degree of technological or cultural evolution.
12. Aliens are already here and we just don’t realize it: While the chances are remote, it’s not impossible that government agencies will hide the presence of aliens, or perhaps it’s more likely that aliens are already among us, watching humanity and planet Earth like a laboratory or a big zoo.
