Are we alone in the universe? It is perhaps one of the most significant unanswered questions in the history of humankind. For millennia have humans gazed upon the stars wondering if there is something, or someone else out there, beyond the darkness and glaring stars? Perhaps, as soon as ancient people developed the ability to think, they may have wondered if there was something more up there, in the sky.
Thousands of years later, and despite our fancy technologies and life-changing gadgets, we are unable to understand the cosmos we live in full, and explain and answer, are we alone in the universe? But if we were to make an educated guess, and base it on facts such as the number of stars in our galaxy, the number of confirmed exoplanets, and the idea that each star is home to at least one planet, I think we could then say that it very unlikely that we are the only planet where life developed, in the entire universe.
Now, a new study has estimated the odds of not life but intelligent life emerging beyond our planet, and the results are unsurprising. A researcher from the University of Columbia has used Bayesian statistics to better understand the odds of alien life emerging in the universe. Bayesian statistics is a system for describing epistemological uncertainty using the mathematical language of probability.
To understand alien life, we must look first at our own planet and its evolution. Scientists say that life on Earth sprung into existence the moment our planet’s environment was stable enough to support its formation. We know for a fact that the first multicellular organisms—which eventually gave rise to our modern civilization—took longer to evolve, around 4 billion years.
But even with this knowledge, we are still unable to explain if life emerged on another planet in the universe.
Although we may not be able to answer whether aliens exist, David Kipping, an assistant professor in Columbia’s Department of Astronomy has opened don’t new paper published in the Proceeding of the National Academy of Sciences which takes a look at the emergence of alien life from a statistical point of view.
“The rapid emergence of life and the late evolution of humanity, in the context of the timeline of evolution, are certainly suggestive,” Kipping explained. “But in this study, it’s possible to actually quantify what the facts tell us.”
Using data such as the chronology of the earliest appearance of life on Earth, and the evolution of humankind, the researcher questions how often could we expect life and intelligence to re-emerge on our planet if Earth’s history were to reset and repeat. Essentially, the researchers asked what the chances were for life and intelligent life to come into existence if Earth was a young planet that just met the necessary conditions for life as we know it to exist. Would something have gone differently, or would everything be repeated?
“The analysis can only provide statistical probabilities, but the case for a universe teeming with life emerges as the favored bet.” Kipping explained.
Kipping proposed four possible answers;
- Life is common and intelligence emerged more often than not.
- Life is rare but can develop intelligence.
- Life is common, although the emergence of intelligent life is rare.
- Life is rare and rarely develops into intelligent life.
“The technique is akin to betting odds,” Kipping said. “It encourages the repeated testing of new evidence against your position, in essence, a positive feedback loop of refining your estimates of the likelihood of an event.”
The four above-mentioned theories were incorporated into Bayesian mathematical formulas, which allowed the researcher to weigh the models one against the other.
“In Bayesian inference, prior probability distributions always need to be selected,” Kipping said. “But a 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.”
Kipping argues that if exoplanets in the universe have similar conditions and evolutionary timelines to Earth, life should be able to spontaneously emerge across the universe.
As to what are the odds for the emergence of intelligent life? Kipping found just 3:2 odds that intelligence is rare. In other words, “if we played Earth’s history again, the emergence of intelligence is actually somewhat unlikely,” Kipping explained.