WE FOUND ALIENS?
An Analysis of the Problem
The active Search for Extraterrestrial Intelligence (SET!) has been ongoing for half a century. To date, no ET signals from stellar systems have ever been detected.
Here are popular theories on why our search has come up empty.
THE RARE EARTH
Basically, 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. Hence, we are one of akind.
THE GREAT FILTER
THE GAIAN BOTTLENECK
'They didn't survive, The Gaian Bottleneck hypothesis, by astrobiologist Dr. Aditya
Chopra, suggests that alien beings are all dead: they simply didn't make it.
Life forms on "habitable" planets failed to emerge quickly enough to stabilize the
planet and pave the way for more life.
THE GREAT SILENCE
Earth was subjected to the Great
Filter-five mass extinction events-but nevertheless evolved complex creatures.
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?
Earth had a headstart. In a study, Dr.
Peter Behroozi said that 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.
A LONG ROAD AHEAD OF US
Basically, we've got long way to go, and a lot more searching to do. SETI has barely surface of the radio universe-there are many more wavelengths to scan, so we shouldn't give up hope yet.
Alas, we're not worth it. The Great
Silence hypothesis posits that advanced beings who belong to a Type 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 0 bipeds?
NOT LIFE AS WE KNOW IT
We've had it wrong all the time, ETs may not be biological beings like us at all.
Noted astronomer Lord Martin Rees said they might be machines-not organic creatures. So we should be looking for solar-harvesting, non carbon-based structures instead of listening for radio
IN A GALAXY FAR,
46.5 billion light-years is the distance to the edge of the observable universe
(that's really far!). We've scanned for ET signals to just around 40,000 light-years from Earth; we haven't even outpassed the bounds of our galaxy, which is
100,000 light-years wide. Alien intelligences could simply be too far away for our current technology to reach.