Despite bleak predictions, humanity's search for interstellar life persists

Where are all the aliens? No, I don't mean microbes on Mars or creatures swimming beneath the ice crusts of Europa or Enceladus, but honest-to-God intelligent aliens, capable of space travel?

The Fermi Paradox asks that question. Given the very high probability of intelligent aliens, given the immense size of the universe, why have we not detected them yet?

According to the Guardian, a NASA astrophysicist named Robin Corbet has an intriguing, albeit depressing, suggestion as to why.

Corbet’s idea is that alien civilizations never create technology, such as interstellar travel, megastructures or interstellar communications that make them detectable. After a certain amount of development, they plateau and keep to themselves.

Corbet’s theory is a version of the Great Filter, which supposes that civilizations destroy themselves after reaching certain technological and civilizational milestones, perhaps through nuclear war, environmental catastrophe or AI run amok.

The idea makes one recoil, since it suggests that a technology plateau is also humanity's future and not some Star Trek-style future of exploring strange new worlds, seeking out new life and new civilizations and boldly going where no one has gone before.

Other answers for the Fermi Paradox include:

• The aliens exist but we haven’t found them yet. Perhaps they communicate with technologies that we haven’t developed yet “like neutrino beams or quantum entanglement.” Or, perhaps, we just aren’t looking in the right place and the right time.
• The aliens are hiding from us. Either they are afraid of being attacked by some imperialist species such as the Klingons from Star Trek or we are under a “prime directive” restriction, to be contacted only when we are advanced enough.
• The Great Silence, which supposes that in all the observable universe, we Earth humans are alone insofar as intelligent species which have developed technology are concerned.

How, then, do we search for intelligent life elsewhere in the universe?

Scientists have been searching for radio signals from hypothetical alien civilizations for decades using radio telescopes. Currently, the nonprofit SETI Institute has been taking the lead in searching the skies for signals of alien civilizations.

Besides attempting to detect alien radio and video signals, some scientists have started to look for flashes of laser light — the theory being that an alien civilization might use lasers as a communications technology. The downside is that we are unlikely to detect such signals unless they are directed at Earth.

Another way to hunt for alien civilizations is to look for evidence of huge structures like Dyson spheres. A Dyson sphere is an outer shell built around a sun that can absorb its light and heat and where people can live on the inside of said sphere.

In 2016, scientists thought they may have discovered something like a Dyson sphere around an object called KIC 8462852. The object is better known as Tabby’s Star, after Tabby Boyajian, the astronomer who led the investigation of what was going on around the F type star located 1470 light years away.

Many stars will dim periodically as their planets pass between them and Earth. However, Tabby’s Star was dimming at random occasions, as much as 22 percent at times.

Theories about what was causing this phenomenon included dust clouds and swarms of comets. One interesting idea was the possible presence of a swarm of objects that formed, what was in effect, a Dyson sphere, albeit more loosely arrayed than a solid shell.

Sadly, scientists are currently leaning toward a more natural cause for Tabby’s Star dimming.

In the meantime, NASA is proposing a new space telescope that will be a successor to the Hubble, the James Webb and the upcoming Nancy Grace Roman telescopes. Its current name is the Habitable Worlds Observatory, designed to image known extrasolar planets in the optical, infrared and ultraviolet ranges.

The Habitable Worlds Observatory will attempt to detect signs of life on worlds that are thought to be habitable. Such signs include water, oxygen and methane.

Once habitable worlds are detected, a paper published by Penn State University suggests looking for signals from such worlds to other worlds in their same solar system. The idea is that an alien civilization would send probes to such worlds much as Earth has sent probes to planets such as Mars and the outer planets and will need to communicate with them

If and when alien intelligence is discovered, we will know for sure that we are not alone in the universe. It will be a world historical event that will, hopefully, inspire humanity to avoid the future suggested by Corbet and seek a future among the stars.

Mark R. Whittington, who writes frequently about space policy, has published a political study of space exploration entitled “Why is It So Hard to Go Back to the Moon?” as well as “The Moon, Mars and Beyond” and, most recently, “Why is America Going Back to the Moon?” He blogs at Curmudgeons Corner.