We haven’t yet found alien intelligence. Whether we do or not has profound implications for our future on Earth.

In various carefully selected spots strewn about the planet, there sit radio telescopes: large but unobtrusive, silently listening. They look like a giant version of the dish antenna you have at home for the Internet or TV. But instead of trying to catch a movie or the latest news, they’re looking for signals from way beyond this planet.

This is the Search for Extraterrestrial Intelligence.

SETI, as it is called for short, is a non-profit project that has been going on since 1984. The large antennas are only the project’s most prominent component: behind them are billions of units of computing power, to process all that the radio telescopes pick up. They include specialised software and dedicated systems, but also — if you’ve installed the SETI@Home app to volunteer — the extra processing power of your own idle computer.

Together, these machines sift through all the stellar pulses, cloud interference, black-hole ejection streams, solar flares, errant satellites, and the ubiquitous Cosmic Background Radiation, looking for one particular kind of signal: one that could have originated from an intelligent life form.

To date, they have found…none at all.


You will probably agree that SETI’s lack of results is disappointing. The chance that aliens don’t exist does take some of the excitement out of life. However, I would say this is bad news for a more troubling reason: it reflects on what might happen to us, as an intelligent civilisation, as well.

To better understand SETI, it may be helpful to first understand our own planet in this context. For the first four billion years or so, the Earth was a pretty ordinary planet—at least in terms of radio signals. Life was changing the face of the planet, replenishing oxygen in the air, and influencing the composition of the atmosphere. But if you were looking from afar with a radio-telescope, you wouldn’t be able to make out that anything special was going on.

That's because life, for all its prowess, was yet to mess around with radio signals.


The history of the radio can trace its way back to 1888, when a life-form by the name of Heinrich Rudolf Hertz showed that electromagnetic waves could propagate through empty space. His waves were essentially invisible light—invisible to us, that is, but not to the special radio receiver that Hertz had set up.

Over the next century, electromagnetic waves started being used to send long-range signals, but it was in the 1940s, during the Second World War, that signals actually reached a frequency high enough to rip through the ionosphere and make their way out into space.

These escaped signals spread outwards in all directions, forming a bubble of signal that grows larger and larger as it rippled out — and is growing still. Incidentally, the first powerful World War II signals were not for communication but for radar. As technology progressed, it was followed by stronger signals, and today, any self-respecting FM station would be broadcasting its news and entertainment, albeit in a very distorted fashion, to space. This whole deluge of signals have travelled upto about 80 light years away by now...

...which means any alien intelligence within our “closer than 80 light years” bubble would have been able to hear it. And, if this intelligence had at least similar technological and scientific capabilities to our own, it would have been able to make out that these signals were created by intelligent life on Earth.


Flip ourselves with the alien, and this is exactly what SETI is trying to do as well: detect such bubbles from those other civilisations.

A much older civilisation would have been broadcasting for longer and would have a much larger bubble than ours, possibly encompassing the whole Milky Way galaxy. Which means, we’d be definitely within their bubble of visibility.

So, if we haven't found any such civilisation yet, does it mean no such civilisation exists? Perhaps we are the only intelligence that has ever appeared in our galaxy. However, this doesn't seem very likely.


One cannot do statistics based only on a single occurrence, but looking at life’s history on Earth, one must marvel at its tenacity.

Life emerged very early, and then remade the planet to its liking. From the early cyanobacteria that filled the air with oxygen, to plants that dissolved rocks and minerals, evolution has progressed — relatively speaking by leaps and bounds. And don’t forget, all known life-forms today came from that one original ancestor. It means that, once life came into being, it didn’t let go.

A little over 500 million years ago, if you look at the fossil record, you will find the Cambrian explosion. Up until this point, the species are far and few between — a single cell here, or a small colony there, or a simple multi-cellular life form making its simple multi-cellular living. But then — bam!— there suddenly appeared arthropods and sponges, fish and nautiloids, and numerous other species that have since died out. This was the time when the first primitive eyes came into being, as well as the first walking animal, and a representative from almost every class of creature that exists today.

Ever since then, life seems to have been steadily progressing toward complexity, which eventually leads towards intelligence.


Keeping in mind, again, that ours is only a single occurrence, it still seems quite unlikely that life would have started up on some other planet without ever attaining intelligence. Once life comes up, it grabs hold.

So what are the alternate explanations? Well, it could be that life never arose on those planets at all, and we’re incredibly unique in the Universe — but that seems even more unlikely, if anything.

It’s also possible that civilisations more advanced than ours emit signals that to us look like having a natural source. We see them, but we don’t realise we’ve seen them — just as a hunting bird fails to notice a stick-insect. But this too is not likely: we are advancing, and we’re actively looking for subtle hidden signals. Even if their signals weren’t as obvious as the ones we’re emitting right now, we’d probably still recognise them at some point. Even stick-insects, eventually, get eaten.

Or, it could mean that the other intelligences did exist…but they did not live long enough for us to detect their existence.


The Doomsday Clock was originally invented by scientists working on the nuclear bomb, as a metaphor to indicate how close we were to man-made catastrophe.

When it started in 1947, it was pointed at 7 minutes to midnight — midnight being the destruction of humanity by an all-out nuclear war. Since then, it has moved back and forth depending on the situation. The simultaneous thermonuclear tests by the Soviet Union and the United States in 1953 pushed the clock right up to 2 minutes — the closest it had ever been for a long time. Later, when the Soviet Union collapsed in 1991 and countries signed a treaty to reduce their nuclear stockpiles, the Doomsday Clock was moved all the way back to 17 minutes.

And then, in 2020, it moved to the closest it has ever been: 100 seconds to midnight.

The Doomsday Clock doesn’t fluctuate and respond to every situation. Instead, a panel of scientists and Nobel laureates meet once a year to deliberate over the situation of the world, and decide how close to move the clock. While it started of as a warning against nuclear holocaust, the Clock now takes into account many other factors that could spell the end of humanity: bioterrorism, runaway artificial intelligence, and the now accelerating threat of climate change.

The Intergovernmental Panel on Climate Change recently released a very urgent alert: unless humans drastically reduce their emissions now, we’re on our way to creating — as some scientists put it — a kind of “hell on Earth”. Will we manage to push back the Doomsday Clock this time? Some people are still complacent, because after all we’ve managed it before, haven’t we?

But before we start drawing conclusions, perhaps we should look at what happened to other intelligent civilisations and whether they managed to survive.


The Universe is vast not only in expanse, but also in time. Consequently, the longevity of alien civilisations may be a factor, and a worrisome at that, in the deafening silence that we are exposed to.

Since we’ve been listening for only a few decades — essentially zero on a cosmic timescale — we’d detect another civilisation only if they existed at the correct time. The period of their existence should have overlapped with the moment of our listening (shifted, of course, by the time it takes for electromagnetic signals to travel).

If the civilisation is too young, then signals from them wouldn’t have reached us yet. On the other hand, if it’s old and long dead, then its signals would have long passed us by. (In ‘bubble’ terms, it isn’t a solid bubble after all, but a thick, hollow ball whose surface begins when the first signals came out and ends where they died down forever).


Now that we get the general idea, let’s work out some probabilities. Assume, for example, that in the last 100 million years, there were 50 technologically advanced civilisation within the distance of our observing capabilities. Furthermore, each of those civilisations managed to exist for one million years. This means that we’d have close to a 50% probability to overlap in time, and detect at least one  of them — a decent chance, I would say.

But, if the lifetime of these civilisations were typically only 1000 years, then the chance of hearing anything would be 1 in 2,000, which is essentially zero.

Flip that logic around, and work on the fact that we haven’t found any signs of life yet. Is it more likely that we’re in Scenario One, on the wrong side of that 50% chance? Or are we in one of the 1,999 wrong sides of the 2000 cases in Scenario Two?

Statistics tells us that it is, of course, the latter. If we haven’t found any signs of extraterrestrial intelligence, it’s probably because we’re in a world where most intelligent civilisations die young — rather than in a world where they live long but we’ve just happened to miss every single them through sheer bad luck.


Hence, SETI is not an academic exercise but something having implications for us all.

The longer SETI yields zero, the darker its meaning is. Combining such silence “out there” with what we observe here on our planet gives more credence to the likelihood that our Doomsday Clock would one day time out; that our civilisation would disappear in a blink of an eye.

On the other hand, there could be no better news for humanity than a positive SETI detection. It would mean somebody “out there” made it for a significant time period! This would imply that we, too, have a fighting chance to cross our scientific adolescence without extinguishing ourselves.

Which side of the coin will our civilisation land on? To find out we’ll have to wait and watch. Of course, the more proactive among can work toward improving the outcome in the meantime, though it isn’t at all clear what actions ought to be taken.

Credits: An earlier version of this piece was published at http://www.infinitetime.org.