Why Haven’t We Found Aliens yet: 8 theories

Gathering various hypotheses on the possible causes behind why we haven’t found Alien life yet, I could highlight the following main 8 theories, and simplified them.

1- The Rare Earth: we’re unique. The rare Earth hypothesis argues that planets with complex life, like Earth, are extremely rare and that intelligent extraterrestrial life is highly improbable.

2- The Gaian Bottleneck: they didn’t survive. Alien beings are all dead. Life forms on “habitable” planets failed to emerge quickly enough to stabilize the planet and pave the way for more life.

3- The Great Filter: Earth was subjected to five mass extinction events but survived. What if all “habitable” planets were hit with killer asteroids, scorched by solar flares, torn apart by geological upheavals, seared by supernova blasts or gamma ray burst radiation, and that of all worlds only Earth successfully hurdled the stumbling blocks.

4- The Great Silence: we are not worthy. Advanced beings who belong to a Type III civilization on the Kardashev Scale, able to harness the energy output of a whole galaxy, simply do not reach out to insignificant carbon — based humans. Why bother with Type O bipeds.

5- Early Birds: Earth had a head start. Compared to all the planets that will ever form in the Universe, the Earth is actually quite early. The last star will burn out 100 trillion years from now and 92% of planets are yet to be born. We are the first, but not necessarily the last.

6- Different “Lifestyle”: Extraterrestrials may not be biological beings like us. They may be machines, for example, not organic creatures. So we should be looking for solar-harvesting, non carbon-based structures, instead of listening to radio signals.

7- We have only done little: SETI has barely scratched the surface of the radio universe and there are many more wavelengths to scan, so we shouldn’t give up hope yet.

8- They may be far away: 46.5 billion light years is the distance to the edge of the observable universe. We’ve scanned for extraterrestrial signals to just around 40,000 light years from Earth. We haven’t outpaced the bounds of our galaxy yet, which is 100,000 light years wide. Alien intelligence could simply be too far away for our current technology to reach.