Flagging Down Aliens with World’s Biggest Laser Pointer
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As you’re no doubt aware, humans are a rather noisy species. Not just audibly, like in the case of somebody talking loudly when you’re in a movie theater, but also electromagnetically. All of our wireless transmissions since Marconi made his first spark gap broadcast in 1895 have radiated out into space, and anyone who’s got a sensitive enough ear pointed into our little corner of the Milky Way should have no trouble hearing us. Even if these extraterrestrial eavesdroppers wouldn’t be able to understand the content of our transmissions, the sheer volume of them would be enough to indicate that whatever is making all that noise on the third rock orbiting Sol can’t be a natural phenomena. In other words, one of the best ways to find intelligent life in the galaxy may just be to sit around and wait for them to hear us.
Of course, there’s some pesky physics involved that makes it a bit more complicated. Signals radiate from the Earth at the speed of light, which is like a brisk walk in interstellar terms. Depending on where these hypothetical listeners are located, the delay between when we broadcast something and when they receive it can be immense. For example, any intelligent beings that might be listening in on us from the closest known star, Proxima Centauri, are only just now being utterly disappointed by the finale for “How I Met Your Mother“. Comparatively, “Dallas” fans from Zeta Reticuli are still on the edge of their seats waiting to find out who shot J.R.
But rather than relying on our normal broadcasts to do the talking for us, a recent paper in The Astrophysical Journal makes the case that we should go one better. Written by James R. Clark and Kerri Cahoy, “Optical Detection of Lasers with Near-term Technology at Interstellar Distances” makes the case that we could use current or near-term laser technology to broadcast a highly directional beacon to potentially life-harboring star systems. What’s more, it even theorizes it would be possible to establish direct communications with an alien intelligence simply by modulating the beam.
A Laser to Rival the Sun
At interstellar distances, it’s very difficult to discern a planet from the star it’s orbiting. This is why we’ve only been able to directly image a small number of exoplanets; the only reason we know they are there is by watching for dips in the light output of their host star. The same is of course true in reverse. An alien intelligence that has a telescope pointed towards our solar system is really just going to be looking at our sun. That means any laser we fire out into space with the intention of getting somebody’s attention would need to appear brighter than the sun, otherwise it would be like somebody on the Moon trying to get our attention with a flashlight.
This would require a laser in the megawatt range that could be fired continuously or at least in bursts of several seconds. Admittedly it’s a pretty tall order, but not beyond our current level of technology. The US Air Force explored using an aircraft mounted megawatt laser as an anti-missile weapon in the mid-1990’s, which culminated with the development of the Boeing YAL-1. In 2010 the YAL-1 demonstrated it was possible to track and destroy ballistic missiles during their boost phase using its chemical oxygen iodine laser (COIL), though ultimately the project was canceled due to the tremendous costs involved in building and maintaining an operational fleet of the aircraft.
Regardless of its failings as a practical weapon, Clark and Cahoy cite the YAL-1 as proof that a similar laser could be constructed for interstellar communication. If the military can develop a megawatt laser that can fire for long enough to destroy a missile while still being small and light enough to mount in a modified 747, there’s no technical reason it couldn’t be done in an observatory on the ground.
As an added bonus, the COIL technology pioneered by the Air Force produces an infrared beam with a frequency of 1315 nm. This is particularly advantages for signaling purposes as our sun doesn’t produce much light at this wavelength, so the laser’s beam intermixed with light from the sun would be seen from a distant observer’s perspective as a star with a wildly fluctuating spectral output; an anomaly no alien astronomer could ignore.
Bringing it into Focus
As Clark and Cahoy explain, the megawatt class laser is only half the puzzle; it would still need similarly supersized optics to deliver the beam with the optimal divergence. But even here the hardware they have in mind, namely a 30 m to 45 m telescope, isn’t beyond our reach. The paper specifically mentions that the Thirty Meter Telescope Observatory (TMT) currently in the planning phases and scheduled to be operational by 2030 could provide adequate beam characteristics if it were paired with a 2 MW laser.
Somewhat counterintuitively, the paper argues that a tightly focused beam is not the ideal choice for flagging down our celestial neighbors. For one, such a beam would need to be aimed and tracked with exceptionally high accuracy to hit a target tens or even hundreds of light-years away. More importantly, our ability to detect distant planets is still too rough to produce models of their orbits with sufficient accuracy; we simply don’t know where to aim the laser.
The solution is a beam that has a large enough divergence to compensate for our poor aim. In fact, Clark and Cahoy suggest a beam wide enough to illuminate large swath’s of a star system could be ideal in some scenarios. Multiple planets within a star’s habitable zone would be able to see our laser at the same time, greatly reducing the amount of repositioning we’d have to do on our end.
Against the Odds
Of course, there’s still plenty of variables in play that make such an attempt a very literal shot in the dark. For instance we can fire our laser towards Gliese 667, where Kepler previously detected a planet within its habitable zone, but its possible that the organisms who reside on that planet are insectoids with no appreciable technology. So whether it’s a rerun of “I Love Lucy” or a blast of infrared light from across the cosmos, they aren’t likely to pay it much mind and we come away with no more knowledge of our place in the universe than we had before.
But paling in comparison to technological or logistical hurdles is the most obvious problem: the economics of such a system. If even the United States Air Force didn’t think it was cost effective to continue operating a megawatt laser that proved it could destroy incoming ballistic missiles, who would possibly pick up the tab for an even more powerful and elaborate long-shot that arguably has no practical function other than to placate our yearning for exploration? Missions to the Moon or Mars can be argued to have practical benefits to mankind that offset their multi-billion dollar price tags, but shining a monstrous laser into the eyes of alien creatures that may or may not even exist for nearly the same price is a much tougher sell.
In the end, James R. Clark and Kerri Cahoy make a compelling and well-reasoned argument for interstellar laser communications. That the idea could work, and that it’s within humanity’s capabilities to bring such a system online within the next few decades is difficult to refute. But like so many great ideas, it seems unlikely it will ever see the light of day without the sort of concerted global effort that to date we’ve been largely unable to muster.
34 thoughts on “Flagging Down Aliens with World’s Biggest Laser Pointer”
Wouldn’t the beam become very weak again if it is intentionally left out of focus?
I hope they figured out if their signal was going to be detectable above the noise. Lot of R squared to deal with. I doubt that I Love Lucy is reaching the LGM out there.
(Little green men)
Could we try to detect reflections to our pulses from the distant planets and try to estimate their orbits beter due to runtime differences / doppler shifts? At least we’d learn something about the targeted system even if there are now lifeforms to answer
Jeez, we’re talking about making a light that’s noticeably brighter than our star… but imagine how bright a star is… now imagine how bright we’d have to be in order to reflect a detectable amount of light back at us! If there were a civilisation living in the targeted system that might justifiably be an act of war >.<
“How quaint, they are still using inferred lasers.
Respond with a focused gamma ray burst to the following coordinates…”I would still be like a whisper among starlight.
The likelihood that we can ever communicate meaningfully above the din of interstellar radiation using our tiny machines is pretty far-fetched. The megawatt laser mentioned in the article would be the barest minimum, hardly detectable with even the most ideal of circumstances. And that of course depends on both perfect timing and perfect aim on the part of the receiver, which would be pure luck. Luck against odds that make the lottery look like a game of rock-paper-scissors against a man with no fingers.
The vastness of space can only be known intellectually; it’s impossible to properly contextualize. Travel to another star would be outrageously difficult, more comparable to a religious miracle than mere engineering. But even simple communication is more ambitious a goal than anything humanity has yet attempted. These are seriously ballsy dreams, and even though I don’t have any hope for success I have to respect the people working on them for their sheer audacity.
Slightly less dangerous than an implied laser, not as bright as a known one.
A reflection scatters in all directions, unlike the laser transmitted which is pretty narrow. The returned pulse would be completely undetectable.
« There are forms of intelligent life out there. We need to be wary of answering back until we have developed a bit further » said Stephen Hawking in his book « Brief Answers to the Big Questions »
Especially because the ability to respond in and of itself would amount to a civilization-destroying level of energy. Any interstellar capability whatsoever would be tantamount to a cosmic weapon of mass destruction; one that makes our defenses look like brief motes above a campfire.
The Kzinti lesson: An engine’s effectiveness as a means of propulsion is directly proportional to its effectiveness as a weapon.
“the ability to respond in and of itself would amount to a civilization-destroying level of energy” – that’s only true if “respond” means “come here”. A response could be anything from the amount of power we use upwards. A megawatt laser is pretty powerful, but it’s not going to end a civilisation.
I doubt Hawkins said that by thinking in terms of energy and/or power. The simple cohabitation of two civilizations at unequal stages of evolution is likely to result in the disappearance of the least evolved. Even if no aggressive attitude has been shown on both sides
This sounds so much like the system used in the movie “Battleship” – https://en.wikipedia.org/wiki/Battleship_(film) – to send the signal to the extraterrestrial planet.
Why are stupid people in charge. Just a few centuries ago we didn’t have cars, computers, and so on. We can barley handle the tech we have new. Nukes and so on. These people with the quest for more knowledge from possible other intelligent beings is simply stupid until we have learned how to control ourselves. We are no more than children playing with big toys, and no where near ready for any kind of real power.
Who is this “we” and how would “we” become “ready” or grow beyond this childhood?
I agree. Poking at the hornets’ nest is not a wise thing to do.
Don’t worry, the limits of physics have all but made sure we won’t say hello to anyone else out there, let alone meet them or share technology with them. We’ve essentially hit a wall–it hardly matters how far we advance in the face of such distance and time. It’s an extremely non-trivial problem. Even with lasers.
Unless we make some really, really good Von Neumann machines. Even that is doubtful. After all, carbon-based life on Earth essentially represents bajillions of highly advanced and durable Von Neumann machines that have been replicating for billions of years, yet we haven’t taken over the galaxy yet. Not even the solar system. Hell, not even the Earth. There are still vast portions of our own planet that would appear lifeless to a cursory observation. I think the simplistic estimates of exponential growth spanning the galaxy in a few million years are pretty absurdly optimistic. Which is, once again, a good thing. If building machines like that was possible, all matter would have already been converted to those machines. Perhaps billions of years before we even had a chance to evolve. Obviously that didn’t happen. Permanent exponential growth is impossible for a good reason.
And FTL is about as likely as a genie appearing and granting us a wish. There are advances which may come in the future, while on the other hand there is baseless fantasy and logical nonsense. FTL certainly falls within the latter category.
Stupid people are in charge because stupid people vote for them. They win the vote, because there are loads and loads of stupid people. It will ever be thus, at least on a relative scale. And even across time, is the average, or dim, or smart person now, all that smarter than their counterpart 300 years ago, or 2,000?
We’ve learned more, we have better technology, thanks to an absolutely tiny proportion of the human race. I suppose some of the others did work in producing food and clothing for the smart ones. But they hold us back by falling for stupid manipulations and propaganda, and once you give the silly bastards a way to easily form groups, they start believing in a flat Earth. For the first time in history! Even the Greeks knew the world is spherical! Prior to that, maybe some dim Stone-Agers thought the world was flat, and the sky was flat above it, but they didn’t have the benefit of knowing about other planets, or the laws of gravity, or the vast, huge panoply of other knowledge.
Many people now are stupid on purpose. It goes alongside people being arseholes on purpose. And voting for that right.
“BE QUIET OR THEY WILL HEAR YOU”
“Once there were three tribes. The Optimists, whose patron saints were Drake and Sagan, believed in a universe crawling with gentle intelligence — spiritual brethren vaster and more enlightened than we, a great galactic siblinghood into whose ranks we would someday ascend. Surely, said the Optimists, space travel implies enlightenment, for it requires the control of great destructive energies. Any race which can’t rise above its own brutal instincts will wipe itself out long before it learns to bridge the interstellar gulf.
Across from the Optimists sat the Pessimists, who genuflected before graven images of Saint Fermi and a host of lesser lightweights. The Pessimists envisioned a lonely universe full of dead rocks and prokaryotic slime. The odds are just too low, they insisted. Too many rogues, too much radiation, too much eccentricity in too many orbits. It is a surpassing miracle that even one Earth exists; to hope for many is to abandon reason and embrace religious mania. After all, the universe is fourteen billion years old: if the galaxy were alive with intelligence, wouldn’t it be here by now?
Equidistant to the other two tribes sat the Historians. They didn’t have too many thoughts on the probable prevalence of intelligent, spacefaring extraterrestrials — but if there are any, they said, they’re not just going to be smart.
They’re going to be mean.
It might seem almost too obvious a conclusion. What is Human history, if not an on going succession of greater technologies grinding lesser ones beneath their boots? But the subject wasn’t merely Human history, or the unfair advantage that tools gave to any given side; the oppressed snatch up advanced weaponry as readily as the oppressor, given half a chance. No, the real issue was how those tools got there in the first place. The real issue was what tools are for.
To the Historians, tools existed for only one reason: to force the universe into unnatural shapes. They treated nature as an enemy, they were by definition a rebellion against the way things were. Technology is a stunted thing in benign environments, it never thrived in any culture gripped by belief in natural harmony. Why invent fusion reactors if your climate is comfortable, if your food is abundant? Why build fortresses if you have no enemies? Why force change upon a world which poses no threat?”
-Peter Watts, Blindsight
They probably won’t. Somebody noticed, a few years ago… The theory was that, as technology advances, we’ll produce more and more radio waves that are obviously artificial, eventually lighting our sky up enough that aliens will be able to see us. But that was the old analogue days.
For one thing, we have data compression. And it’s some law or other, that the more efficiently data is compressed, the more it resembles noise. Any redundant information or repetition is coded away, so removed. There’s also things like QAM, where the more distinguishable levels of power you can send in a signal, the more data you can fit in. Practically every form of computer communication uses this now. Mobile phones, and TV, certainly.
So data looks less and less like data. And sure there’s probably more noise than there was, but not much more compared to the background of a planet in space.
So it turns out a civilisation, ours at least, only uses detectable radio waves for perhaps 100 years or so. It starts out from nothing, then sparks and big beams, then back towards noise again as the data rate goes up. This is particularly relevant for things like SETI, it’s likely only ever to pick up signals deliberately coded and aimed at us. Though that was true anyway.
“As you’re no doubt aware, humans are a rather noisy species.”. Compared to who?
The Others… obviously, you haven’t heard of them. Hence the comparison with us…
Compared to all the other species we know about. You’ll hear no morses from horses, see no satellite dishes of fishes, there’s no rhino radio.
In a hundred years we’ve gone from megahertz to gigahertz. Why would any advanced civilization be listening to Channel 2 TV?
They have whatever comes long after SDR and listen to everything from gravity to Higgs bombs.
The idea of flashing light on a dying boat in a sea potentially full of pirates. What could possibly go wrong ?
Even if the target specy is peaceful, why on ea…**ahem** space would it answer?
This would reveal their existence to a species that can be peaceful or not. It’s extremely easy to destroy a planet (we can already do it with only 10% of our nukes), would you bet your only planet just to meet your “neighbors” ?Hmm, if you look at what happened to the native populations of countries that were discovered by our explorers (eg the Americas, Australia, the Arctic), you get a bit wary of being a native population attracting attention from interstellar explorers…
More likely the nukes that have been set off in war and research would attract attention then a regulated transmission of radiation. Then there’s supercolliders.
Just sell it as an anti-satellite weapon to the space marines and wait until it is being decomissioned 🙂
““Dallas” fans from Zeta Reticuli are still on the edge of their seats waiting to find out who shot J.R.”
Don’t forget fans of “Single Female Lawyer” who will be watching in Omicron Persei 8, a thousand light year away, a thousand years from now.
https://en.wikipedia.org/wiki/When_Aliens_AttackThe thing that bothers me about either receiving a message, or sending a message is something I have heard neither camp address: planetary motion, solar system motion, and galactic motion- to whit: the earth is rotating 15 degrees per hour, while orbiting in another axis at a little over a degree per day (360/365.25), and our solar system is moving in another orbit in the Milky Way at some degrees per second, in yet another orbital plane, and then there’s the galactic motion of the Milky Way, through the universe. Just taking our planetary human emissions (radio and TV waves, microwaves that can transit our atmosphere, etc.) into account- there’s the plane of polarization of the launches radio waves- vertical, horizontal, left circular polarized or right circular polarized, and the fact these beams are being swept about into the universe with a given beamwidth. Think about the dwell time any given signal will “illuminate the surface of some remote planet. Seconds? Fractions of seconds? Can a civilization detect the signal? If so, can they determine that brief blip of energy actually contains information? If they could do the foregoing, could they demodulates the signal and determine the signal is voice, or video? What if that part of signal was a recording of tree leaves rustling in the breeze or rain fall, or the babbling of a brook, or the road of a tornado? If they wanted to receive another signal from Earth, could they? Their planet is spinning in some eccentric axis like ours, inclined in its orbit, like ours, in a given arbitrary plane of rotation about its star, in a given orbit about its galaxy, with its own galactic motion. How can anything intelligible be detected? How long to wait until the transmitter and receivers are aligned again? Think of the melange of spectrum being emitted from our little planet- which time segment of signal goes with which other time segment?
A LASER system, regardless of power or columation, is going to sweep through space in the manner of radio waves, but be an even smalller angular subtended angle than a given radio wave, so it’s dwell time on the remit planet probably won’t be as long as the radio wave discussed earlier. Maybe that is a good thing- maybe we don’t want to be found. After all, God is said to protect fools and innocents… Which are we?“God is said to protect fools and innocents… Which are we?”
Whichever, it’s a good thing he made such a vast universe, so we don’t bother our neighbors.
Sorry for the typos- my iFoam is randomly autocorrupting words in my missive, lowering my IQ around 80 points…
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