The professor offered a scientific explanation for the “invisibility” of aliens: they were stuck on their planets

“Where is everyone?” is the famous question about aliens posed to our quiet galactic neighbors after Manhattan Project physicist Enrico Fermi asked it in 1950, writes the Daily Mail.

But it’s possible that even a highly advanced extraterrestrial civilization could find itself without the resources or key information it needs to escape its home world, at least according to new research from Spain’s Universidad Atlántico Medio.

Some so-called “Super-Earths” may be within the habitable zone of their star, but they are so massive that their gravity makes launching interplanetary rockets virtually impossible.

These and other “Aquarium Worlds” are just one of several ideas presented in a new paper that hopes to help explain Enrico Fermi’s infamous 1950 Fermi Paradox.

The Fermi Paradox has puzzled astronomers for more than six decades, succinctly asking the question: in a Universe teeming with as many as 200 billion trillion stars and even more planets, many of which are capable of supporting life, why haven’t Earth scientists discovered any aliens?

“The image of a planet whose gravity makes it difficult or impossible to leave made me think of the fishbowl metaphor,” the new study’s author, Professor Elio Quiroga, told DailyMail.com.

“I found this to be a powerful analogy,” says Professor Elio Quiroga. Said Quiroga, who lectures at Spain’s Universidad Atlántico Medio.

For one category of his aquarium worlds, prof. Quiroga calculated a value he called the “exoplanet exit factor” (Fex): a value that compares a given exoplanet’s exit speed to Earth’s exit speed of 7 miles per second (11.19 kilometers per second).

Cosmic velocity – the speed required for a spacecraft to free itself from the gravity of any celestial body – be it the Moon, a planet or an asteroid – depends on the mass of this body.

Escape from the potentially habitable exoplanet Proxima Centauri b, located, for example, four light-years from Earth, is relatively easy: a speed of 5.9 miles per second, or “Fex”, just 0.85 times the speed of Earth.

But massive but hypothetically habitable planets like Kepler-131 b, 746 light-years from Earth, require staggering speeds to break free: 21.8 miles per second to escape Kepler-131 b, for example. or Fex is 3.13 times that of Earth.

“Many worlds, especially super-Earths,” Professor Quiroga told DailyMail.com, “could be rejected due to prohibitively high escape velocities.”

But there were also interesting extreme cases, such as the habitable world GJ-1214b, located 48 light years from Earth, which had an escape velocity of about 1.5 times Earth’s.

Planets like these, which also include Kepler-103b, may prove more difficult for an advanced race to take off, but may not trap the species on their home world.

Professor Quiroga’s research, published last October in the Journal of the British Interplanetary Society, suggests that any escape velocity 2.2 times Earth’s could permanently tie a civilization to its home planet.

But Professor Quiroga also pointed to the unique cultural factors that may keep a species on its home planet, in one case discussing a more literal “Aquarium World.”

He suggested that an advanced civilization on an oceanic planet may have mastered long-range communications as a result of its own evolution, given that communications travel much further naturally in a variable environment (think sonar) than in the open air.

In these worlds, Professor Quiroga wrote, “communication between individuals could be accomplished without the need for communication devices,” suppressing the desire for advanced communication technologies.

“Telecommunications technology may never appear in such a world, even if it could become home to a fully developed civilization,” Quiroga argues in his paper.

“Such a civilization would not be ‘communicative’ and would not be considered in the Drake equation,” Quiroga said, citing a famous calculation formulated to predict the likelihood of finding intelligent life in the universe.

In other words, an evolutionary trait such as an innate, biological, underwater sonar would make them silent and unable to listen to humanity’s SETI radio transmissions.

But as Professor Quiroga told DailyMail.com, his research is not yet a reason for astronomers and planetary scientists to radically change policies or research plans.

“The first step is to search for elementary life, simple life forms,” he said. “We are making progress in this direction, but we need more advanced instruments (such as the future Vera Rubin telescope) and better methods for analyzing the faint signals coming from these exoplanets. If we were to discover a world in another star system exhibiting clear and undeniable signs of intelligence, then we might be able to speculate whether these beings have achieved space travel, whether it is within their capabilities or not.”

What these first, successful signs, which researchers call man-made signatures, will turn out to be remains to be seen, he noted, in part because of the truly alien possibilities of life beyond our world.

“We can only claim to know of one civilization in space, and that is our own,” said Professor Quiroga. “We therefore tend to humanize or anthropomorphize everything; it is inevitable. However, there is something intriguing to note. We emerged as a species more or less halfway through the lifespan of our star, the Sun, which suggests something profound: intelligence takes a significant amount of time to develop.”

Perhaps Professor Quiroga suggested that the answer to Enrico Fermi’s famous paradox is that most alien species take as long to evolve as life here on Earth.