In 1950, a learned lunchtime conversation set the stage for decades of astronomical exploration. Physicist Enrico Fermi submitted to his colleagues around the table a couple contentions, summarized as 1) The galaxy is very old and very large, with hundreds of billions of stars and likely even more habitable planets. 2) That means there should be more than enough time for advanced civilizations to develop and flourish across the galaxy.
So where the heck are they?
乐动体育开户This simple, yet powerful argument became known as the , and it still boggles many sage minds today. Aliens should be common, yet there is no convincing evidence that they exist.
乐动体育开户Here are 12 possible reasons why this is so., we could be alone.
2. There is no intelligent life besides us.乐动体育开户 (This assumes, of course, that humans count as intelligent.) Life may exist, but it could simply take the form of miniscule microbes or other cosmically "quiet" animals.
3. Intelligent species lack advanced technology.乐动体育开户 Currently, astronomers utilize radio telescopes to listen intently to the night sky. So if alien species aren't broadcasting any signals, we'd never know they existed.
4. Intelligent life self-destructs. Whether via weapons of mass destruction, planetary pollution, or manufactured virulent disease, it may be the nature of intelligent species to commit suicide, existing for only a short time before winking out of existence., it's like trying to speak with your friend on a 250,000,000,000-channel CB radio, without any knowledge of the frequency on which they are transmitting. You'll probably be channel flipping for a long time.. We can't decipher those just yet.
10. Nobody is transmitting.乐动体育开户 Instead, everybody may be listening. That's basically how it is here on Earth. Apart from a to broadcast strong signals over a narrow frequency band towards the stars above, we've barely made our presence known in the universe. In fact, if aliens have radio telescopes similar to what we have on Earth, our television and radio broadcasts would only be detectable up to 0.3 light-years away. That distance doesn't even transcend the farthest reaches of our solar system.
11. Earth is deliberately not being contacted.乐动体育开户 On Earth, we have policies about contacting indigenous peoples; it's possible that the same thing could be happening with us. , advanced alien societies may enforce rules that limit contact only to species that attain a lofty degree of technological or cultural evolution.
12. Aliens are already here and we just don't realize it. Conspiracy theorists love this unlikely explanation. While the chances are remote, it's not impossible乐动体育开户 that government agencies are concealing the presence of aliens. Although it's more likely that aliens are already amongst us, ..