Physical limitations may stop them from leaving their planets.

Planet Bound

The Drake equation, formulated by astrophysicist Frank Drake in 1961, explores the question of why we still have yet to encounter an extraterrestrial civilization.

The equation takes a number of different factors into consideration, including the number of stars that have planets orbiting them, the rate of star formation, and the fraction of planets that could actually develop and sustain life.

In a new article published in the Journal of the British Interplanetary Society, first spotted by Universe Today, Elio Quiroga Rodríguez, a professor at the Universidad del Atlántico Medio in Spain, argues that Drake's equation didn't go far enough.

He suggests there's a chance that water or other liquid-dwelling aliens, as well as civilizations on super-Earths, may actually be trapped on their planets due to "physical limitations," even if they wanted to leave — a fascinating new wrinkle to one of the core questions at the center of our search for intelligent extraterrestrial life.

Fishbowl Dilemma

In his article, Quiroga argued the Drake equation should consider two additional possibilities.

The first would be civilizations on planets much larger than Earth would need much higher escape velocities to surmount their planet's mighty gravity.

If it were too high, extraterrestrials "would not be able to leave the planet using any conceivable amount of fuel, nor would a viable rocket structure withstand the pressures involved in the process, at least with the materials we know," Quiroga wrote.

Second, the researcher considers "fishbowl worlds" where the impetus to develop long-distance communication technologies is much lower since messages already can travel over vast stretches without having to be amplified with complex tech in a fluid environment.

For such an underwater species, "communication between individuals could be feasible without the need for communication devices," Quiroga argued. "Such a civilization would not be 'communicative' and would not be contemplated in the Drake equation."

In short, it's an extension to an already considerable conundrum facing us today. Could there really be woefully unaware aliens living inside massive oceans, or frustrated civilizations struggling to break past the immense gravitational well of their planet?

It's a brain teaser certainly worth mulling over.

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