What happens if we detect alien life?

Scientists have been listening for signals from extraterrestrial civilizations for decades, but what would they do if they actually heard one?
By | Published: May 7, 2024
The Sun-like star Epsilon (ε) Eridani was one of Frank Drake’s first targets in his search for extraterrestrial intelligence. Astronomers have since learned that the star anchors the closest known planetary system, depicted in this artist’s conception, but no detectable life.

[Editor’s note: This article was originally published in the May 2012 issue of Astronomy.]

We’ve never heard a peep from aliens. But improved technology is speeding up the search for extra- terrestrial intelligence (SETI), so what happens if today’s silence suddenly gives way to tomorrow’s discovery of alien life? Would the world rejoice in the news that someone’s out there? Would euphoria engulf humanity, as Nobel Prizes are doled out like after-dinner mints?

That’s one view. But many people think the discovery would be hushed up as quickly as a Mafia informant, assuming that the public couldn’t handle the news. Or scarier still, kept secret for fear that an unauthorized response would tell a hostile race exactly where to send their interstellar battlewagons.

That’s melodramatic enough. But has any serious consideration gone into what happens when our efforts to detect cosmic intelligence pay off and we find a blip of a signal in the sea of radio noise that pours into the SETI antennas?

Some think that addressing that question — even in a speculative way — is hubristic at best and wildly pre- sumptuous at worst. After all, SETI scientists have been torquing their telescopes toward celestial targets for more than half a century without ever detecting such a signal. If we haven’t won the E.T. lottery in all that time, why worry about what would happen if we got the winning ticket?

Simple: SETI researchers are buying more tickets all the time, and the chances of scoring the big one keep going up. As computer power improves and new detection technology comes out of the labs, the search is accelerating. Unless the aliens are excessively secretive or simply nonexistent, we could find evidence for their presence within decades.

So, again, then what?


The Allen Telescope Array and the Jansky Very Large Array (pictured) are powerful enough to detect and pinpoint a possible extraterrestrial transmission with a high degree of accuracy. The latter hosts 27 antennas, while the former boasts 42 and plans to have 350 upon completion.

Dave Finley/AUI/NRAO/NSF

Immediate reactions

In the spring of 1960, astronomer Frank Drake performed the first modern SETI experiment, whimsically dubbed Project Ozma after L. Frank Baum’s fictional queen of Oz. What few people realize is that he actually detected something. While pointing his antenna at the nearby Sun-like star Epsilon (ε) Eridani, Drake heard a strong hammering signal. Surprised by how quickly his search succeeded, he wondered, “What do we do now?”

Drake answered his own question by rigging up additional equipment, and he soon proved that the throbbing bleats from his loudspeaker were terrestrial interference, not Eridanians trying to phone our home.

Project Ozma could tune to only one frequency at a time, but today’s SETI receiv- ers simultaneously monitor hundreds of millions of channels. Consequently, picking up a signal is neither remarkable nor rare: A few dozen typically come up with each scan. Naturally, no one gets very excited about this. Instead, researchers rely on sophisticated software to perform the tedious task of deciding whether these signals are likely to be alien intelligence or (as in Drake’s case) just more human-caused radio static.

Only rarely does any signal survive this automatic scrutiny. But if and when that happens, a series of additional tests occurs. Eventually, the astronomers running the experiment ask someone at another observatory to verify the detection — to rule out equipment bugs, coding errors, or pranks.

The scenario for handling a signal is briefly described in a document developed under the auspices of the International Academy of Astronautics, and referred to as “SETI detection protocols.” These “best practices” boil down to this: (1) carefully verify that the signal is truly extraterrestrial, (2) inform other scientists and the public, and (3) seek international approval before transmitting any reply.

Abridged SETI detection protocols

Confirmed detections:

If the verification process confirms that a signal is due to extraterrestrial intelligence, the discoverer shall report this conclusion in a full and complete open manner to the public, the scientific community, and the Secretary General of the United Nations. All data necessary for the confirmation of the detection should be made available to the international scientific community through publications, meetings, conferences, and other appropriate means.

The discovery should be monitored. Any data bear- ing on the evidence of extraterrestrial intelligence should be recorded and stored permanently to the greatest extent feasible and practicable.

If the evidence of detection is in the form of electromagnetic signals, observers should seek international agreement to protect the appropriate frequencies by exercising the extraordinary procedures established within the World Administrative Radio Council of the International Telecommunication Union.

Post detections:

A Post Detection Task Group under the auspices of the SETI Permanent Committee has been established to assist in matters that may arise in the event of a confirmed signal, and to support the scientific and public analysis by offering guidance, interpretation, and discussion of the wider implications of the detection.

Response to signals:

In the case of the confirmed detection of a signal, signatories to this declaration will not respond without first seeking guidance and consent of a broadly representative international body, such as the United Nations.

(From the International Academy of Astronautics Commission 1 “Space Physical Sciences” Meeting on October 2, 2011)

Not so fast

These are all patently good ideas that seem to suggest that everyone would handle a discovery soberly. However, such interesting signals are bound to provoke a response that’s both messy and confused because verification will take many days, at the least.

During all that time, word of the possible detection will surely spread via blogs and tweets from the researchers themselves (there’s no policy of secrecy in SETI). So you can bet that long before any official press conference announcing that we’ve found the aliens, you’ll have heard about it many times over. Indeed, you should brace yourself for plenty of future false alarms caused by signals that — at first blush — look promising. This has occurred in the past and shows the error of those who think that a discovery could be covered up.

Any real detection would be a headliner, everyone agrees. SETI practitioner Paul Horowitz of Harvard University in Cam- bridge, Massachusetts, says it would “easily be the most interesting discovery in human history. Journalists would go wild, at least for a month or two.”

Astronomer Jill Tarter, who heads the SETI Institute’s listening efforts in Mountain View, California, concurs: “The general public will be in an excited state for a while, fueled by the media. But UFO enthusiasts will yawn because they knew it all along.”

A public reaction of initial enthusiasm, and not mayhem, has precedent. Consider the 1996 announcement that NASA scientists had found fossilized martian microbes in a meteorite. That story ran in The New York Times with billboard-sized headlines for three days. The public’s reaction to the possible detection of life beyond Earth? “That’s interesting. Tell us more.”

The meteorite story was a stunted reprisal of astronomer Percival Lowell’s reports of martian canals a century earlier. Again, people were tantalized, but few seemed to panic.

When astronomers announced that a martian rock contained fossilized microbes (the tube-like structures, less than one-hundredth the width of a human hair) in 1996, the public proved itself capable of “handling” an extraterrestrial discovery.

Early results

Of course, in 1996 no one felt threatened by dead protozoans, even if they were from Mars. But SETI searches for intelligent life, and given that human beings are still the new kids on the technological block (consider that we’ve only had radio technology for a hundred years), you can be pretty sure that anyone we hear will be more advanced than us — possibly much more advanced.

That might sound unsettling, but most people don’t see it that way. A 2005 survey by the National Geographic Channel, the SETI Institute, and the University of Con- necticut found that 72 percent of Ameri- cans said they would feel “excited and hopeful” to learn about a signal from E.T. Only 20 percent confessed they would be “anxious and nervous.”

Again, perhaps that’s not too surprising, given that any transmission we discover likely will be from beings many hundreds of light-years distant, a seemingly safe remove. And, at first, we won’t know much more than the signal’s existence.

But you can bet your paycheck that every telescope on Earth will aim straight for the transmission. Is a star waiting there? Does it have planets? In the rush to learn more, even a stalled project like NASA’s Terrestrial Planet Finder might see new life as scientists shake it out of its comatose state, infuse it with new vigor, and hurl it into orbit.

There are some things we could learn quickly about the signal’s source. Within a thousand light-years lie tens of millions of stars. Consequently, a few arcminutes separate them in the sky, on average. A high-resolution radio telescope, such as the Jansky Very Large Array in New Mexico, has a beam size of about 5 arc seconds at the commonly used SETI frequency of 1420 megahertz. It would have little difficulty pinpointing which star hosts the detected aliens. We’ll know exactly where they live.

And that’s not all. Two decades ago, radio astronomers Jim Cordes and Woodruff Sullivan considered what we might learn by looking at the subtle variations of any alien signal. This includes small frequency shifts due to the Doppler effect (which alters a signal’s frequency according to its motion), as well as intensity changes due to the atmosphere of E.T.’s planet or simply its daily rotation.

Careful measurement could theoretically pin down the length of the aliens’ day and year, the size of their world, the presence of moons, and possibly even information about their atmosphere and magnetic field.

Initial questions

All of that would be tasty fodder for the technically inclined, but everyone else is going to ask an obvious question: What are the aliens saying? That, of course, assumes that they’re saying anything — that they’ve included a message in the signal. After all, the extraterrestrials might withhold commentary if they want us to reply first, per- haps so they can gauge what level of conversation is appropriate.

But let’s suppose that E.T. is trying to tell us something. Just getting the message “bits” could be hard. SETI observations add up incoming static for seconds or minutes to increase the sensitivity to weak signals.

This is completely analogous to astronomical photography — the longer the exposure time, the fainter the stuff you can image. Unfortunately, just as a long exposure would obliterate the rapid flashes of an optical pulsar, so too would these long SETI observations smooth away any message. If, for example, the alien transmission included a television-type signal, researchers would need an antenna roughly 10,000 times larger than most of today’s radio telescopes to see the picture. Building such an enormous antenna would require impressive amounts of money and time. However, after a signal’s detection, it’s reasonable to assume that research money would be practically unlimited, unlike today’s situation.

In the meantime, the public would be confronted with the fact of cosmic company. We wouldn’t know what they’re like, nor what we might learn from them, only that they exist. Anthropologist Ben Finney of the University of Hawaii at Manoa has predicted that an “interpretation industry” would quickly sprout — facile pundits who, out of conviction or merely greed, will explain to the masses what contact means and how we should feel about it.

And in particular, how should religions react? Research in this area is lacking, but most mainstream theologians have expressed the upbeat view that our belief
systems could adapt. As Vatican Observatory astronomer Brother Guy Consolmagno has said, “If your religion has survived millennia — if it can handle Copernicus, Galileo, and even Darwin — then E.T. should eventually prove palatable.”

Mainstream religion might easily incor- porate the discovery, but fundamentalists will have a harder time. They are less will- ing to accept a cosmic circumstance that’s not found in scripture. And unless you’re inclined to consider seraphim, nephilim, or angels as alien beings, most religions don’t anticipate the presence of intelligent life on other worlds (an exception is Mormonism).

The fundamentalists would likely rail against the discovery, claiming it’s “just Satan, tempting you,” according to sociologist Bill Bainbridge of George Mason University in Fairfax, Virginia.

Perhaps learning that we’re not alone in the universe would help unify our species like never before. Of course, some thought the same would happen after early space exploration showed Earth as a tiny blue ball. We’ll have to wait and see how mankind reacts.

Significance sets in

Without doubt, learning of other beings among the star fields of the Milky Way would be discomfiting to some. But the most profound consequences of a SETI detection would surely be the long-term impacts. And these would affect everyone.

The degree to which a signal would alter the lives of our descendants depends on whether we could decode any attached message. This might sound like a tractable problem — merely a matter of time and effort. After all, humans eventually deciphered hieroglyphics, Linear B, and other “messages” that once seemed as inscrutable as teenage behavior. But the universe is old, and consequently the content of any message might simply be incomprehensible to our 3-pound hominid brains.

Still, let’s take the sunny view and assume that we eventually learn what the aliens are saying. Because, as noted, they’re likely to be well in advance of us, the information might include such practical topics as all of physics and astronomy, the extent and nature of cosmic biology and intelligence, the whether and how of faster-than- light travel, and many other things that are the provenance of science fiction today. To suddenly learn such matters would trigger a sharp discontinuity in our species’ history — a kind of “wormhole” to a future that we might otherwise reach only after thousands or millions of years.

Aside from such a torrent of knowledge, we would confront the fact that the differences among humans are of trivial import compared to the gulf between extra-terrestrials and ourselves. Some people, such as SETI’s Tarter, suggest that this would lead to more human harmony and less worry that we’re on the road to destruc- tion. After all, if they’ve survived their technical adolescence, then we could, too.

Sociologist Don Tarter of the University of Alabama, Huntsville, is less sanguine. He notes that the idea of the world’s peoples coming together in sweetness and light — popular in the early days of space exploration with the first pictures of Earth as a small blue orb against a vast, dark sky — was shattered by subsequent wars and terrorist attacks. We’re back to the usual conflict and competition.

And what about a response? If we know where the aliens live, do we dare reply with our own shout out? Or would that, as some aver, merely expose our planet to possible future destruction because we’ve given away our existence and position?

In fact, while no one can say whether aliens would be peaceable or pugnacious, we’ve been sending radio, television, and (most visibly) radar signals into space inad- vertently for more than 90 years. Any society that has the capability to travel interstellar distances and threaten our world could easily pick up these “leaked” signals. Indeed, by using their own sun as gravitational lens, the nearest could theo- retically see the lights from our cities. Any deliberate reply from us would simply add to information they already have.

The great unknown

Frankly, predicting the truly durable consequences of a SETI success is a fool’s errand. Consider if members of the Spanish court in 1492 had written a treatise on what the discovery of a new continent might eventually mean. An interesting exercise, but not one likely to have much currency a few hundred years down the road.

But this much we can say: If SETI succeeds, we’ll have proof that biology is as much a part of the cosmos as pulsars and pockmarked planets. And, while instant brotherhood is unlikely to erupt suddenly on Earth, we’ll at least know we’re neither the crown of creation nor even particularly exceptional. For as long as our species exists, we’ll be aware that we’re just one more duck in a row.

And you can be sure that news will ruffle a few feathers.