Alien beings have long been the stuff of Hollywood films and the public imagination, but do they actually exist?
Astronomers have long sought evidence of extraterrestrial life. To do so, they’re searching the galaxy for exoplanets with habitable environments within their “Goldilocks zone”, not too hot nor too cold.
But is the likelihood of intelligent life emerging in an ecosystem high enough for life to exist high enough?
The Drake Equation
The Drake equation is an increasingly popular model that attempts to estimate the number of civilizations present in our Milky Way galaxy. Unfortunately, its estimates can be highly uncertain and its results vary considerably depending on whether optimistic or pessimistic interpretations of its terms are taken.
Assuming civilizations only last several centuries will produce much lower results than assuming they can last billions of years, and its hard to determine exactly how long a technological civilization can thrive before self-destructing, and this uncertainty has given rise to numerous estimates for L, the average length of detectable civilization. Skeptic magazine publisher Michael Shermer calculated an estimate of 420 years by taking into account 60 historical civilizations in his calculations.
Shermer and other skeptics point out that the Drake equation fails to take into account several other variables that could impact our chances of finding extraterrestrial life, such as whether abiogenesis (the process by which living organisms form out of inanimate matter) occurs more commonly on other planets than it does here on Earth.
Another factor reducing our chances of finding ET could be communication across interstellar distances. Thankfully, scientists are exploring methods to increase the chance of alien civilizations recognizing our signals.
The Drake Paradox
Frank Drake observed two sun-like stars near Earth in the 1960s with his telescope, hoping to detect radio signals produced by alien civilizations but coming up empty-handed. Since then, many other astronomers have diligently and systematically been listening for any signs or inkling of alien life that we might detect, yet nothing has come our way – not even the faintest hint!
Scientists have long debated how best to estimate the number of extraterrestrial civilizations out there. One popular approach involves counting how many rocky planets lie within the Goldilocks zone around each star – not too hot, not too cold, just right for life formation.
Critics contend that the Drake equation overlooks important variables that could increase or decrease our odds of contact with extraterrestrial intelligence, including Earth-like planets’ existence which doesn’t guarantee ET life.
Over time, skeptical astronomers have attempted to provide empirical support for their claims using Bayesian analysis, a statistical technique which attempts to ascertain how much of an outcome stems from actual data and how much comes from biases among scientists’ prior assumptions.
Princeton professor and former graduate student working in astrobiology are employing Bayesian statistics to test an age-old theory about why we should expect alien lifeforms to exist, in their paper published today in Proceedings of the National Academy of Sciences. These scientists estimate the probability that rocky planets might contain life, as well as how frequently such life forms could emerge from them.
The Search for Extraterrestrial Intelligence
Searches for extraterrestrial intelligence (SETI) haven’t produced any concrete results in half a century of search, yet. That could soon change though; at a meeting of London’s Royal Society today (20 July), Russian billionaire Yuri Milner announced an ambitious $100-million project he intends on using to conduct one of the most extensive hunts yet.
No one has ever witnessed alien life, yet most still believe there exists another form of life somewhere beyond Earth’s solar system. A 2015 survey showed that three-quarters of Americans believe intelligent life exists on other planets – this figure increases further among younger adults. Men tend to believe more strongly in alien existence than women do and college-educated adults often subscribe to this view.
Astronomers have recently sought to lend such pronouncements more empirical basis by employing Bayesian analysis. This involves calculating the odds that an environment will provide conditions suitable for life to emerge on it and eventually turn it into intelligence.
Results from this work have cast serious doubt on some prominent arguments for expecting alien life elsewhere, such as Earth. One study published in 2016 in Proceedings of the National Academy of Sciences suggests that Earth may not be an accurate reflection of life elsewhere;
The Search for Extraterrestrial Life
Astronomers have spent decades searching for signs that intelligent life exists within our universe, hoping that one might show them proof. Listening for radio waves or scanning for organic molecules around stars and planets are just two methods used by astronomers in search of proof that life may exist somewhere out there.
SETI scientists remain optimistic, believing the odds of life on other planets are much higher than once thought, and that an intensive search will soon pay off.
A large segment of society believes alien life exists elsewhere, which has fuelled their faith. A recent government report shows that about two-thirds of Americans say it’s likely intelligent life exists on other planets – however most UFO researchers tend to be inclined to believe in aliens themselves.
Recently, Princeton Astrophysical Sciences professor Edwin Turner and co-author David Spiegel published an article in Science using Bayesian analysis to disentangle facts regarding extraterrestrial life from assumptions in calculations. They used data from studies of abiogenesis — how life formed on Earth — to rerun probabilities and estimate what they really mean.
They discovered that numerous variables can influence the outcome of probabilities and that many are unknown with any certainty, making the Drake equation an imprecise tool that may be difficult to use accurately.
