Do you believe there's other life out there?
“I’m hoping there’s at least a sign of something on another planet: that we’re not the only life in the most expansive thing physically imaginable, even if it’s just the smallest, atomic-sized bacteria. Otherwise it’s just us, existing alone in a vast cosmos.”
For thousands of years, humanity has looked to the stars and wondered: are we alone?
The odds are that we’re probably not, given that the universe has existed for roughly 13.8 billion years and is 93 billion light years across (and still growing, mind you). That’s a lot of space and a lot of time for life to have found a way.
But the tricky part has been finding our potential cosmic companions: have we missed them? Are we too early? Are they too far away?
And – if we ever did meet them – what would we say?
How are we looking for life in the universe?
We haven’t found any convincing signs of life yet, but that doesn’t mean we’ve given up – after all, we've only recently developed the technology to start looking.
NASA has recently announced a dedicated team investigating 'unidentified aerial phenomena', and the most powerful telescope ever launched into space – the James Webb Space Telescope – is expected to share its first images in July.
There are a few ways we’re searching for alien life, including biosignatures and technosignatures, according to UQ astrophysicist Dr Benjamin Pope.
"A biosignature is anything that indicates the presence of life," Dr Pope said.
"One of the most important biosignatures is disequilibrium chemistry, which is when you find molecules that ordinarily cannot coexist together without life.
"Methane and oxygen are a good example of this: together, they react, and methane eventually burns until it is gone. For the two to exist together – like they do on Earth – something would need to be constantly replenishing the methane.
"On Earth, that something is bacteria."
The idea with disequilibrium chemistry is to look for two molecules co-existing when – by the laws of chemistry – they can’t, which might indicate the presence of life. It’s what happened in 2020, when researchers discovered phosphine on Venus (although whether this indicates life is still highly contested).
Technosignatures, on the other hand, are about looking for technological (and hence intelligent) life. They can include radio transmissions from alien civilisations, technological artefacts from intelligent civilisations (known as Bracewell probes), or waste heat produced by alien civilisation.
"The idea of waste heat was popularised by physicist Freeman Dyson in the 1960s," Dr Pope said.
"It assumes that an advanced civilisation would outgrow the energy resources of its own planet and need to harvest energy from a star or galaxy.
"They would subsequently encircle the star or galaxy with a physical structure that collects the energy, known as ‘Dyson Spheres’.
"We could find these structures by looking for stars producing heat at the wrong temperature: the intense heat from the star would be re-radiated by the alien industry at a much lower temperature," he said.
To date, we haven’t found any Dyson Spheres. We also haven’t received any alien radio messages, or replies from our own interstellar broadcasts, including the famous Arecibo interstellar radio message in 1974 (which carried encoded information about the technological achievements of humanity).
But before you give up, remember: the universe is a really big place.
When we broadcasted the Arecibo message, we were aiming it at a cluster of stars 25,000 light years away. Given that radio travels at the speed of light, that means our message will take 25,000 years to reach the cluster, and if there’s a reply, another 25,000 years back. 25,000 years ago, we didn’t even know what radio was.
Image: Sergey Nivens/Adobe Stock
How likely is it that intelligent life exists?
A scientist in the 1960s actually came up with a way to measure this through what became the ‘Drake equation’.
In 1961, US astronomer and astrophysicist Frank Drake was gearing up for the first scientific meeting of SETI – the Search for Extra-Terrestrial Intelligence – when he came up with a way to estimate the number of radio-communicative civilisations in the Milky Way by multiplying a series of estimated values, like rate of start formation and the fraction of intelligent civilisations that develop communication.
N = R* x fP x ne x fl x fi x fc x L
Dr Pope said while the Drake Equation is an interesting idea, it produces a lot of uncertainty because we have no definite numbers for the values in the equation.
“The Drake equation isn’t a deep law of physics like Newton’s laws. It’s really a back-of-the-envelope estimate,” Dr Pope said.
“If you sub in reasonable numbers, for the most part, it indicates there could be quite a lot of life.
“On the other hand, if the estimates are on the lower end, then actually there’s a very good probability that there’s no – or almost no – life in the universe.”
If we’re optimistic with our estimates for the Drake equation, there should be a lot of life out there for us to find. So why haven’t we found it yet?
This is called the Fermi Paradox, named for physicist Enrico Fermi, and it asks just that: if the universe is so big, where are all the aliens?
There’s been a few attempts to answer Fermi’s question in the years since, including economist Robin Hanson’s idea of a great filter, which is an event or situation that would either prevent the evolution of intelligent life or ensure its destruction.
Dr Benjamin Pope
Dr Benjamin Pope
“It might be that the great filter is behind us, and that almost no civilisation makes it to technology, and those that do live for billions of years,” Dr Pope said.
“Or, it might be that there’s something ahead of us – lots of alien civilisations make it to technology, then they get wiped out.”
“I think that’s more plausible.”
Others have put forward ideas to explain the absence of intelligent life. There’s the ‘cosmic zoo’ theory, which proposes that aliens know we exist but choose not to interfere. Then there’s Michael Hart and Frank Tipler’s ideas on colonisation, which posit that it isn’t likely intelligent alien life exists, because if it did, it would have conquered us by now.
However, before you get too worried about galaxy-conquering alien lifeforms, Dr Pope asks us to reconsider our assumptions about intelligent alien life.
“Scientists are well aware that life isn't exactly like it is on Earth,” he said.
“The idea that because you can explore the galaxy, then you're going to do galactic conquest, is unlikely. Humans have certainly done in the past, but it’s not to say that will always happen.
“Not all civilisations on Earth have driven for colonisation, and there's no reason to think aliens will necessarily want to colonise the galaxy either.”
Image: Sergey Nivens/Adobe Stock
Say we do find alien life. How would we communicate with it?
Films like Arrival have offered some interesting cinematic ideas about how we might interact with aliens, and while they’re on the right track, UQ linguistics expert Professor Ilana Mushin said it would likely be more complicated than what we see on screen.
Alien biology, for example, could complicate things significantly. What if they don’t have mouths? Or eyes?
“Language is obviously connected very much to the human anatomy and physiology,” Professor Mushin said.
“Our eyes see a particular range in the spectrums of light, our ears pick up a specific range of frequencies, and our brain processes all these signals in particular ways.
“We’re also bipedal [walking on two legs] and we have opposable thumbs, and all of that impacts how we interact, and communicate, with the world.
“You can’t assume an alien life is going to have any of that.”
Professor Ilana Mushin
Professor Ilana Mushin
There’s a lot of other things you take for granted when you speak your language, from facial expressions to gesticulations.
“If I encounter a language I’ve never heard before in my own species, there’s things I’m going to assume are universal, like pointing,” Professor Mushin said.
“You wouldn’t have that with the creatures in Arrival.
“In human language, we also use metaphors for things that aren’t easy to explain: like talking about numbers or temperatures going ‘up’.
“When you start thinking about that, it’s very abstract: we feel temperature change, but in what sense is that up or down? Yet it’s a very concrete thing we all understand.”
UQ experts believe there could be other significant hurdles: our points of references could be different (for example, if aliens reproduce asexually, familial words like ‘mother’ and ‘father’ wouldn’t be applicable in their culture), or that it can be very difficult to tell when words begin and end when hearing a foreign language.
But there’s also things we’d probably have in common, according to Professor Mushin, which might be helpful in the process.
“I would assume all possible life in the universe is going to exist within time, meaning what you do and say has a knock-on effect to the next thing you do in time. So you’d assume alien language would have a temporal dimension to it,” Professor Mushin said.
“Another thing is displacement, or the ability in human language to displace ourselves in time conceptually and linguistically.
“Unlike animal communication, we can talk about things that don’t exist in the here and now: we can tell stories, talk about memories, plan for the future.
“If we’re encountering aliens which have developed technology, those aliens would have needed to be able to coordinate, plan and imagine to build that technology.
“That suggests something more like human language capacity.”
Image: SciePro/Adobe Stock
Are we optimistic or pessimistic?
So far, the stars – metaphorically, and perhaps literally – haven’t quite aligned.
According to Dr Pope, life could be all around us in the universe: it just doesn’t get very far.
“My really boring answer to the Fermi Paradox is that space is big, and spaceflight is expensive and dangerous,” he said.
“If you’re struck by a dust particle in interstellar space and you’re moving at 0.2 of the speed of light, it’s like being hit by a nuclear bomb.
“There could be a lot of civilisations at our size or bigger dotted throughout the galaxy that have never conquered it, or maybe it’s just rare to travel outside of your solar system.”
If you ask the executive team of the UQ Stargazing and Astronomy student association (UQSA), there’s a similar hope that life exists somewhere beyond us in the universe.
“I think the biggest issue with life is the need to overlap,” UQSA’s Treasurer Chandler McGovern-Greco said.
“Maybe in a few hundred years, we’ll get a rocket that was sent by an alien race that is long extinct, or maybe they’ll see Voyager in billions of years and realise that we were once here.
“When you look at the existence of exoplanets and what we know about what life could be, I think it’s very likely that life exists out there.
“But I don’t think I’m hopeful that we’ll ever interact with them.”
Outgoing UQSA President Flynn Linton had a similar take.
“We’re in the last, little fraction of the whole calendar of the universe,” he said.
“The probability that we'd encounter another life form existing in the exact same infinitesimal period is not impossible, but it’s extraordinarily small.”
The UQSA team at their first event of 2021, watching Interstellar.
The UQSA team at their first event of 2021, watching Interstellar.
The group’s current President, Tom Channell, points to the sheer size of space.
“The nearest galaxy to us is 2.5 million light years away. No physical being could make a 2.5-million-year journey, and that’s at the fastest velocity possible with our current knowledge of physics,” he said.
“So you’ll probably never even make contact, even if life is out there, because they have to exist for millions of years to even reach us first.”
And yet – despite the odds being so monumentally against us – the idea of alien contact remains healthy and alive in the human imagination. It occupies our films and novels, and many of us continue to hold out hope that, one unexpected afternoon, extra-terrestrial life will descend from the sky and change human history forever.
Why the enduring fascination? Perhaps it’s because we’d like to believe that we aren’t alone in an impossibly big universe.
“I’m hoping there’s at least a sign of something on another planet: that we’re not the only life in the most expansive thing physically imaginable,” Tom said.
“Even if it’s just the smallest, atomic-sized bacteria. Otherwise it’s just us, existing alone in a vast cosmos.”
Words: Zoe McDonald
Editing and design: Michael Jones
Image: Sergey Nivens/Adobe Stock
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