Hard Science

# Astronomer calculates the odds of intelligent alien life emerging

A new study discovers the likelihood of extraterrestrial life in the universe.
Key Takeaways
• A Columbia University astronomer calculates the odds of extraterrestrial life emerging.
• The probability comes out in favor of aliens existing.
• The search for life in space should be encouraged, concludes the scientist.

The sheer amount of space boggles the mind and makes one wonder, where are all the aliens? Surely, we aren’t the only ones who made it out onto a cosmic rock alive. Of course, there might be numerous reasons we have not encountered aliens yet, from having poor technology to the aliens not desiring to be seen. A new study tries to take a statistical approach to the question, finding out the likelihood of complex extraterrestrial life emerging on other planets.

For his new paper, David Kipping of Columbia University’s Department of Astronomy, used the statistical technique called Bayesian inference to arrive at the conclusion that there’s a greater chance than not that aliens should exist. The odds he calculated come out 3 to 2 for the aliens.

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Kipping based his analysis on the chronology of life’s development within 300 million years of the Earth’s oceans forming and the human evolution on the planet. He wondered how often life would emerge if we were to repeat Earth’s history over and over.

To figure this out, he used the method of Bayesian statistical inference, which works by updating the probability of a hypothesis when new evidence or information appears.

“The technique is akin to betting odds,” Kipping explained. “It encourages the repeated testing of new evidence against your position, in essence a positive feedback loop of refining your estimates of likelihood of an event.”

He came up with four possible answers, as reported in the press release:

• life is common and often develops intelligence
• life is rare but often develops intelligence
• life is common and rarely develops intelligence
• life is rare and rarely develops intelligence

Using Bayesian math, Kipping pitted the models against each other. According to him, the “key result here is that when one compares the rare-life versus common-life scenarios, the common-life scenario is always at least nine times more likely than the rare one.”

This means that life is 9 times more likely to emerge than not. But would this life be intelligent? The answer here is more muddled and less optimistic. Still, Kipling concluded that under similar circumstances and conditions to Earth, the odds are 3:2 that some planet out there would sport complex, intelligent life like ours.

Why are these odds lower? Kipping thinks that as humans appeared rather late in Earth’s habitable history, it’s clear their existence was not a foregone conclusion. “If we played Earth’s history again, the emergence of intelligence is actually somewhat unlikely,” he pointed out.

He also maintains that while the likelihood of alien life may not be overwhelming, it’s still quite strong, and “the case for a universe teeming with life emerges as the favored bet.”

Check out his paper published in PNAS, Proceeding of the National Academy of Sciences.

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