Humans have long been fascinated by extraterrestrial life and particularly intrigued by how aliens might communicate.
It's the central plot of blockbuster science fiction films like Arrival, Contact and Close Encounters of the Third Kind.
Yet this question is not just for sci-fi movie fans. Xenolinguistics is the study of languages that may be spoken by intelligent life forms, and a team of experts is giving this some serious thought.
In 2022, the Cambridge Institute of Exo-Language at Cambridge University (CIEL) dedicated to understanding potential extraterrestrial languages, was established in preparation for making contact with intelligent life that may exist beyond our galaxy.
Indeed, the criteria for extraterrestrial life to be considered "intelligent" is the ability to develop a technological civilisation.
Ian Roberts, professor of linguistics at the University of Cambridge, helped to establish CIEL.
He told ABC RN's Future Tense he's confident intelligent extraterrestrial civilisations exist and that these civilisations also have a common language.
"Any species which, like us, develops some kind of technological civilisation will have language," Professor Roberts says.
Why now?
CIEL is adding to the work of METI International, a US-based not-for-profit organisation founded in 2015, which attempts to communicate with extraterrestrial beings.
METI International's founder and president Douglas Vakoch says it's imperative that serious research is undertaken into the principles of language and communication in preparation for this type of potential contact.
"We might be faced with decrypting a message from an unknown civilisation, and linguists could provide the key to cracking the code," Mr Vakoch says.
Like Professor Roberts, Mr Vakoch believes in the existence of intelligent life beyond earth.
"We know the basic chemical building blocks are strewn throughout space, so there is a lot of real estate where life could exist, as well as the chemical ingredients for life.
"It would be a miracle if there were no intelligent life anywhere, and I don't believe in miracles," he says.
The aim of CIEL could be considered slightly premature, given that we aren't yet aware of the existence of intelligent extraterrestrials.
But Professor Roberts says the logistics of contacting a solar system or exoplanet (a planet outside of our solar system) will be no easy feat.
The initial hurdle would be establishing the form of message to be sent. Then, given the closest exoplanets are about four light years away, it could mean a minimum eight-year wait to send and then potentially receive a response. So scientists are really in this for the long haul.
How exactly would we communicate with aliens?
Critics have often compared any efforts to communicate with extraterrestrial beings with humans' inability to communicate with animals on earth.
And clearly, while hand gestures and instructions are understood by dogs and some primates, for example, humans are yet to have deep conversations with another animal species.
Professor Roberts counters this common theory.
He says that, with the possible exception of dolphins, most other animal species on Earth are generally considered to be less intelligent than humans.
So, he argues, it's not a fair comparison.
However, Dr Arik Kershenbaum, zoologist and lecturer at the University of Cambridge, says we can look to animals to see how different types of communication have evolved in different environments.
"If an extraterrestrial civilisation evolved in an alien ocean, then we can look at dolphins and whales to see what kind of signals travel well underwater, and what constraints ocean-living puts on how much information can be conveyed," he says.
Laws of evolution
When it comes to alien technological civilisations, Professor Roberts says there is a greater likelihood that their language would have similarities to ours because the laws of evolution are likely to be similar.
"One thing that is very widely believed among people who think about the nature of extraterrestrial life is that the laws of evolution must be the same everywhere," he explains.
Mr Vakoch agrees. He says there's likely to be a limit to the number of configurations of life and environments.
"We shouldn't be surprised to find alien life that bears strong similarities to familiar life forms here on Earth," he says.
And so it's likely that the structure of an alien civilisation's language would also have similarities to human communication.
The difficulty lies in establishing how exactly the language of extraterrestrials could be channelled.
Dr Kershenbaum has explored what those channels could possibly be.
"One can't help wondering whether aliens might have evolved a language based on a completely different communication from ours [perhaps] whistles instead of words, images instead of sounds, [or] electrical pulses," he says.
While humans primarily use speech, written language and other forms such as sign language, Professor Roberts says this is one of the most uncertain factors to determine.
"I think it is really quite unpredictable, we will only know when we find them."
What if they're smarter than us?
If aliens do exist, Professor Roberts suggests there is a good chance that they're more advanced than humans.
"Any technological civilisation we make contact with will be much more advanced than us because we are, in technological terms, a very young civilisation," he says.
Professor Roberts explains that humans are considered a relatively young civilisation because we've only been emitting radio waves into the universe for just over 100 years.
"The overwhelming likelihood is that any civilisation we encounter will be older and therefore significantly more advanced than us," he says.
"And the implications of that [will be] very interesting."
Consequently, if they are more advanced than us, then Professor Roberts also believes they're likely one step ahead of us and aware of our existence — and our language.
So, how prepared are we?
The recent Pentagon UFO report released by the US Department of Defense debunked calls that Unidentified Anomalous Phenomena (UAPs) were extraterrestrial life forms.
Mr Vakoch says we'll undoubtedly be surprised by first contact with other civilisations if and when it happens.
He says we can never anticipate all the relevant issues that may crop up, but considering communication could help us prepare.
"The beauty of designing interstellar messages and sending them to other stars is that it forces us to make clear our assumptions about what intelligence is and how language works," he says.
Professor Roberts says it's currently possible for us to potentially establish rudimentary contact with another civilisation, but any genuine communication will rely on language.
"Language has to be the means of communication," he says.
"We have to find a way to decipher their language, and they have to find a way to decipher ours."
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