Of all the groundbreaking inventions of the early 20th century, the radio must be one of the most overlooked. Most of us listen to it daily, or use radio waves to talk on the phone or watch TV. Gugliemo Marconi may not be a household name like Alexander Graham Bell, but his invention is quite literally everywhere.
Gugliemo Marconi, however, may have doomed us all.
To understand how, we need to start by contemplating an extraterrestrial paradox known as the 'Great Silence'.
Mathematically speaking, we’re unlikely to be the only intelligent species in the history of our galaxy to have invented the radio. There are plenty of planets out there with conditions that could support life. We’ve already discovered 3,200 in the small areas we’ve looked at. According to the Drake Equation, which uses a number of variables to estimate the density of cosmic life, we should be one of 20 neighbouring civilisations.
We also know intelligent life doesn't take long to evolve: homo sapiens took just 350,000 years to invent the radio. If the history of Earth was shortened to a single day, our ascent from ape to radio broadcasters has taken place in the final minute and 17 seconds.
So if there’s billions of liveable planets out there, and it doesn’t take long for intelligent species to evolve and invent the radio - why is the galaxy so silent?
This question is known as Fermi’s Paradox, and it has puzzled academics for decades. There are a number of explanations. Perhaps we haven’t met any other forms of intelligent life because they don’t exist in our galaxy. Space is prohibitively enormous, so maybe intelligent life exists in nearby star systems but, like us, hasn’t yet figured out how to travel through interstellar space. Maybe they have and we just don’t know it, or that they could figure it out if they wanted to but just can’t be bothered.
However, studies argue that the distribution of life through the galaxy is not dependent on propulsion technology. Researchers have run simulations of interstellar settlement, including variables such as spacecraft velocity, and found that the natural movement of stars over a long enough time period is itself enough to create a galactic civilisation.
So it seems remarkable that we have yet to gain even a hint of another civilisation. Humanity has been inadvertently broadcasting signals into space since the invention of the radio, and stronger TV signals have reached well beyond nearby habitable planets. We’re spending millions looking for similar signs of modulated radiation from other civilisations. Why haven’t we at least heard something?
None of the usual answers explain why no civilisation seems to have ever talked to any other over billions of years. They all rely too much on chance. The odds that we exist in time of transition from a silent galaxy to a populated one is infinitesimally small, because intelligent life doesn't evolve and advance simultaneously across the whole galaxy.
It also seems unlikely that all possible advanced civilisations out there, in the whole history of the galaxy, could have progressed to a communication technology we aren't aware of without leaving a trace of evidence of that progression. We didn't stop using the radio when we invented the Internet.
Whatever the answer, it needs to explain why the galaxy has always been completely, utterly silent. The sheer number of planets out there means cosmic diversity should tend to prevail unless there is some kind of systemic, universal mechanism preventing it. In other words, the answer must explain why no civilisation has ever talked to any other over billions of years.
There is an answer that does. Maybe civilisations that invent the radio don’t live long enough to tell the tale.
Now the question is, if aliens are out there - why are they hiding?
As Chinese author Liu Cixin puts it: the galaxy may be a dark forest, each civilisation a quiet hunter eliminating those it encounters before they can do the same.
This explanation may seem far-fetched. Yet it is grounded in game theory, and according to a paper from the Royal Astronomical Society, is one of only plausible hypotheses explaining the ‘Great Silence’; it provides a mechanism to systematically prevent all contact over vast time periods, is wholly consistent with all the factors in the Drake Equation, and fits our observations of the galaxy’s electromagnetic environment.
This was the view taken by Stephen Hawking, who once compared possible contact with interstellar intelligent life to the arrival of Europeans in North America. Only one civilisation of the many possibly out there would need to follow this path for the theory to work, destroying all other civilisations soon after they invent the radio.
But there may be a bright side. As we've advanced, our species has progressively become less and less violent. Humanity is actually less violent today than we have ever been, increasingly pulled towards peace by what Steven Pinker called the ‘better angels of our nature’ – empathy, reason, self-control. Pinker argues this trend is a product of the same logic used in the ‘Dark Forest’ theory.
If humans have become less violent as our technologies have evolved, despite outbursts of war and what the news leads us to believe, then perhaps the same is true of other space-faring civilisations. As scientist David Brin wrote: “It might turn out that the Great Silence is like that of a child’s nursery, wherein adults speak softly, lest they disturb the infant’s extravagant and colourful time of dreaming.”
A version of this was originally published in ADM.