In the ever-optimistic 1960s, Star Trek envisioned space as the final frontier, a great unexplored wonderland populated by pointy-eared Vulcan geniuses and sexy green alien ladies. 56 years later, with the premiere of the second season of Star Trek: Picard, our own search for extraterrestrial life still continues, with the prospect of first contact seeming more and more like science fiction than anything rooted in science fact.
But how true is that, exactly? Just how alone are we in the Universe?
“There are two answers to that question,” says Martin Dominik, a Reader at the School of Physics & Astronomy at the University of St Andrews. “The first is scientific, which is we don’t know. We have no evidence for us being alone or not being alone.
“Philosophically, however, the Universe is very big. If we assume that there’s a certain probability to find a planet suitable for life and life has a certain probability to evolve, one is a very unlikely number. Even if there was only one planet that hosts life in one galaxy, the Milky Way is one of hundreds of billions of galaxies within the Universe. That would mean life would be quite commonplace.”
This gulf between zero evidence of extraterrestrial life and the high probability of it existing is commonly referred to as the Fermi paradox, named after Nobel Prize-winning physicist Enrico Fermi, who apparently remarked on the puzzling absence of alien contact during a conversation with friends in 1950.
One obvious reasoning for it, suggests Dominik, is that the Universe is simply too big. “We have quite limited means to explore our surroundings,” he says. “Serious searches for any signatures of life stretch around a few thousand nearest stars. That’s an extremely small search space.”
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But if the Universe is so large, and the probability of it featuring alien life so likely, then it stands to reason that an advanced alien civilisation should have reached out by now, right?
One theory for why they haven’t is that any civilisation advanced enough to achieve interstellar travel will destroy itself before they do so. Dominik wryly suggests that we could use this to our advantage. “Something people have seriously suggested is what I call ‘the search for stupid life,’” he says. “It’s where you look for [alien races] engaged in nuclear war with each other and who blow everything up, because that might be a detectable signature.”
There have been significant developments in space exploration in recent years. Before its decommission in 2018, for example, the Kepler Space Telescope was responsible for the discovery of thousands of exoplanets in the Milky Way, many of which could feasibly support life.
In the future, there is hope pinned on NASA’s super-powerful $9.7 billion James Webb Space Telescope, which will further probe Earth-sized exoplanets in the hope that it can find atmospheres similar to our own. Dominik, however, is sceptical.
“Planetary atmospheres can reveal extremely exciting things about a planet’s geology,” he says. “A planet’s geology is related to life on a planet. But to what extent does the geology give us information about whether there’s life or not? It’s hard because we know neither the necessary nor sufficient condition for life to emerge and to evolve. So one thing that we should really think about is how can we better understand the process of the emergence of life. I think that is a big gap in our understanding.”
There is also the question, of course, of whether finding intelligent alien life – or indeed intelligent alien life finding us – would be the greatest of outcomes. “Some people think ‘oh, [making alien contact] is a great thing to do,’” says Dominik, “and some think that it might be the last thing that we ever do.”
The discovery of alien life could also make us rethink our own place in the Universe, much like the first photo of Earth from space led to stronger emphasis on environmentalism.
Dominik cites a 2011 study from theologian Ted Peters, who asked people of various religions whether the detection of extraterrestrial life would cause problems for their personal belief, their specific religion or for other religions. “Almost nobody said it would cause a problem for their beliefs,” he says. “Very few said, ‘oh, it might be a problem for followers of my religion’. But a large majority said it would be a problem for the followers of other religions.”
Then again, as Dominik points out, there is a likely chance that it is an issue we will never be confronted with.
“There was a cartoon I saw once where someone was wondering about whether we are alone in Universe,” he says. “And someone else replies, ‘oh yes, we are alone’. The other said, ‘oh, that must mean we’re the only ones in the Universe?” They said, ‘no, the others are alone as well’. It is extremely conceivable that the Universe is teeming with life, but we will actually never know.”
About our expert, Martin Dominik
Martin Dominik is a Reader at the School of Physics & Astronomy at the University of St Andrews. His research focuses on applications of the gravitational microlensing effect, and in particular on its potential for studying planets orbiting stars other than the Sun.
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