The Search for Extraterrestrial Intelligence in Radio

The Search for Extraterrestrial Intelligence in Radio

While there are a number of ways currently
on the table to search for evidence of extraterrestrial civilizations, known as technosignatures,
one stands out as the focus of a majority of SETI experiments both past and present. It’s the radio part of the electromagnetic
spectrum. But why? What makes that method of communication so
attractive over interstellar distances? Firstly, electromagnetic radiation is easy
to produce, we do it all the time with our own signals in everything from our cell phones
to satellite communications to radio stations. They also travel as fast as you can in the
universe, in a vacuum traveling at the speed of light, because it is light. Some have said that radio communication isn’t
likely to be used by aliens as it’s an old technology, one we’ve had for about a century. It’s been pointed out that alien civilizations
might not use radio as a method of communication, rather they may do something far more advanced,
such as the use of gravitational waves or neutrinos for communication. Or even some method we have no knowledge of
yet. It’s very difficult to look for something
for which you have no knowledge of, since you have no idea what you’re looking fo,r
so that’s out, at least for now. As to gravitational waves and neutrinos, with
gravitational waves they would have obvious advantages as everyone with sensitive enough
detectors would see such messages if announcing your existence is the goal. But, you need a whole lot of mass and energy
for this, you are manipulating gravity after all. A lot of it. Short of moving planets or neutron stars around,
this method probably just isn’t worth it when you simply want to communicate something. And then there is the problem of receiving
such communications, it’s far harder to pick up gravitational waves than it is picking
up a radio signal. Likewise, neutrinos are also difficult to
detect. Not impossible, but clarity of communication
is important and radio wins out here as well. So as to the unknown or conceptual forms of
communication we know about, it becomes a situation similar to that of fire. Humans have been using fire since the beginning,
it’s a very, very old idea. Yet we still use it today because, for its
applications, it’s still quite useful in comparison to its alternatives. Another advantage to radio is that one section
of the radio spectrum is naturally very quiet, whether you’re here or on an alien planet. It’s an area where you don’t get much
interference from the galaxy that you do with lower frequencies, but you also don’t get
the noise from your own equipment that comes with higher frequencies. Yet another advantage that aliens would know
about is that the dust of the galaxy is fairly transparent at these wavelengths, unlike in
the optical area of the spectrum where it blocks light quite well. This all will be the case for advanced aliens
anywhere in the galaxy and why they might indefinitely use radio. Just because an idea is old, doesn’t automatically
make it bad so it still seems like aliens would understand and use the radio spectrum
indefinitely. This is one of the reasons why the focus has
been on radio in SETI. It simply works. If some anomaly is ever detected in the world
of gravitational waves or neutrinos, then we’ll see that as well, but it doesn’t
seem likely. The idea of searching for alien signals in
the radio spectrum goes back to a paper published in 1959 by Guiseppe Cocconi and Philip Morrison
where they envisioned that alien civilizations might build beacons to announce their presence
to the galaxy. They proposed that scientists search the nearest
sunlike stars for signals, just in case someone might be out there. Most importantly, they proposed a very special
frequency in which to look. 1420 Megahertz, or the 21 centimeter line. This frequency is that which hydrogen emits
radio waves in nature. Alien scientists will know this frequency
as well as they study radio emissions from hydrogen clouds in the galaxy. Hydrogen is the most common element in the
universe, it’s everywhere and any species with science is going to know what it is and
how it behaves. This makes the 1420 mhz frequency an attractive
place to locate a signal, since if you just sent out a signal at any random frequency
anyone that you would wish to contact would need to just happen to tune into that frequency
to hear you. That’s not likely to happen, so a galactic
benchmark is needed. 1420 mhz seems like an obvious choice, though
modern SETI experiments look at far more frequencies than just that one. And there are other choices. Another example would be the frequency at
which hydroxyl emits radio at around 1660 mhz, hydroxyl and hydrogen together make water,
the most likely solvent for life in the universe. And there are many other possible places to
locate a signal like that. But the hydrogen line seems the most likely
place. Now, if we look at the hydrogen line, won’t
we see a bunch of interference from hydrogen? Yes and no. While hydrogen emits narrowband at the hydrogen
line, it only stays there if it’s absolutely stationary in a lab. Hydrogen clouds in the galaxy constantly move
around causing blue and red shift, as does earth and the sun, so the end result is a
broadband interference around the hydrogen line. When you break that down into millions of
narrow channels, then comparatively little interference gets in the way. One issue with radio however is the earth’s
atmosphere. The various gases in the atmosphere absorb
some wavelengths of radio. This could help or hurt our chances of detecting
alien signals. If the aliens have a completely different
atmosphere, or no atmosphere at all as may be the case for a machine civilization, they
may not think to transmit at frequencies that will pass through an oxygen, nitrogen, water
vapor atmosphere like our own. And, there is some terrestrial radio interference
to contend with as well. Only eventual SETI experiments in space, such
as a radio telescope on the far side of the moon where the moon will block earth interference,
and there is no atmosphere to contend with, will be able to get past these issues and
open up other potential areas of the spectrum for searching. One interesting thing however is that by international
agreement, the 1420 mhz hydrogen line is not intentionally broadcast on by humans, or at
least it isn’t supposed to be, leaving it free for radio astronomy. That’s not to say that it’s completely
clean, spy satellites often do things they aren’t supposed to, and you can also get
interference due to harmonics of other frequencies invading the line as well. But, there is an interesting aspect here,
the idea of narrowband signals as signs of technology. In general, and only in very specific cases,
does nature generate truly narrowband signals. But technology almost always does. There are several reasons for this, number
one it saves energy. Broadcasting broadband takes more energy than
broadcasting narrowband. It’s assumed the aliens would know this
and be sensible and economical with their signals. The second is that narrowband signals don’t
bleed all over the radio spectrum, useful if you want things like radio and television. Third, in respect to SETI, if you want everyone
to know that you’re there, narrowband is an indicator of a technologically produced
signal in and of itself. It seems logical for an alien civilization
to employ this type of signal if they want to be seen and verified. The problem though is that narrowband is narrowband,
and the more narrowband you get, the more channels you need to pick it up to the point
of millions or more, though signals travelling through interstellar space and being affected
by it do place a limit on what’s practical here. The plus to looking at such narrow slices
of the spectrum is that any signal found that narrow would make for an excellent candidate
for an extraterrestrial signal. It’s worth nothing here, though not overstating,
that such signals have been found. The most famous example is the Wow! Signal of 1977. The receiver that detected it had only 50
channels, but wow was seen in only one of them. It was very narrowband. Secondly it was very close to the hydrogen
line, just slightly above it. And, no the wow signal was not due to comets,
that hypothesis was shot down by the scientific community fairly quickly after the paper came
out. If comets emitted that strongly at 1420 mhz,
radio astronomers would have seen that by now. It’s often forgotten how powerful the Wow! Signal actually was, it was 30 times greater
than the background, and was the strongest candidate signal the telescope that detected
it ever found over decades of searching. The Wow signal stands as the best candidate
signal ever detected thus far for a signal from an alien civilization. While the design of the telescope essentially
eliminated the possibility of it having been interference from here, there is one thing
about the Wow signal that renders it useless. It never repeated, and unless it ever does,
it will forever be a huge question mark. And, even if it does repeat, it takes us into
rather mysterious territory. There was no modulation in the signal that
could be detected, just a raw radio signal similar to radar. There was no message in the main signal itself. But there was an interesting pattern in the
other numbers that are circled on the printout. What those are is unknown, nor is it known
if they are related to the main signal, or are just random other signals. But unless it repeats, we won’t ever know
what those were either. Wow! Does illustrate that even narrowband signals
in SETI can be ambiguous. And you’d think aliens trying to announce
themselves would try to do it unambiguously. But it’s not the only candidate signal. A similar experiment called META in the 1990s
found 37 events that were strong signals that looked good with no immediately obvious natural
explanation, but not a single one has ever repeated. Modern receivers would have told us much more
about these signals. But in the end, the receiver is only one part
of the equation. To receive anything, someone must be transmitting,
and that transmission must cross the vastness of interstellar space. The further from the transmitter, the weaker
a signal gets, but you don’t need that much power to transmit if you do it directionally,
the power of a radio station for example put into a directional beam could be seen over
a hundred light years away with a modest dish. But the signal would have to be aimed right
at us. So, how would an alien civilization seeking
contact know to do that? This is where things get interesting. While human civilization has only been detectable
for a short time, about a century, Earth’s biosphere has been detectable from
a distance for millions upon millions of years. These types of signatures are biosignatures,
and in the case of earth include our atmosphere which is profoundly affected by life. The alien civilization would see a world that
has very odd levels of methane and oxygen. They might take a closer look in infrared
and detect our vegetation, known as the vegetative red edge where plants become highly reflective
in that area of the spectrum. Essentially, anyone with a big enough telescope
in the galaxy may know about this planet, and know that it has life. They may send a signal just in case there
is someone intelligent here. But a civilization within 100 light years
would be able to detect our civilization directly, providing they were looking right at us. If they were watching long term, they would
notice changes to the atmosphere that can’t be natural, such as the addition of CFCs. They might also pick up our radar, or possibly
even our television or radio signals. Contrary to popular belief however, they would
not pick up the 1938 Berlin Olympics broadcast. That was far too weak. Some have suggested in the past that civilizations
might be so interested in communications that they might broadcast their signals omnidirectionally. That would be a daunting task. Firstly it requires enormous amounts of energy
to run a beacon transmitting in all directions. Sure, it would make it obvious to anyone in
the galaxy looking, the broadcast does not need to be aimed directly at you here rather
it’s going out to everyone, the amount of energy and challenges inherent to broadcasting
such a signal make it seem somewhat unlikely. So what happens when a signal is discovered? Verification. One of the first things to do is to determine
if it’s earth interference. This is relatively easy, if you move the telescope
slightly away from the source of the signal you should still see the signal if it was
interference from earth. With something distant, you won’t. Then you track the motion of the signal itself,
if it moves with the earth’s rotation, as the Wow! Signal seemed to do, then that eliminates
any real likelihood of satellites and other sources here on earth or nearby it. And there are other indicators that the signal
is far away that can be used. Once that’s all accomplished and a signal
seems to pass muster, the scientists would simply call other scientists and have them
point their radio telescopes at the source and see if they pick it up as well. If they do, then such a signal becomes very
interesting indeed. But what happens if and when they do detect
a signal? One comment I often see on this channel is
that the government would never let that information out. There are many problems with that thinking. Firstly, which government? There are nearly two hundred countries on
earth, all of which have governments. And SETI experiments are not limited to any
one country. They are done in Russia, the US, China, and
others. You’d need at least several, if not tens
of governments that don’t really get along that well to all agree to keep the secret. And then you have to keep the scientists quiet. Internationally. SETI in the US is privately funded, contrary
to popular belief NASA stopped doing SETI decades ago when a particular congress person
went on a rampage throughout the government and did everything he possibly could to get
funding for it canceled. It hasn’t been government funded in any
meaningful way since. And you don’t really even need scientists
to do SETI searches, there are many private amateur radio astronomers also building dishes
and taking a look. Point is, this would not be a very keepable
secret. And, in the end, an alien civilization light
years away very likely does not pose an immediate threat to national security. If they’re close enough to know to send
a radio signal, they already know about earth at least, and probably would have been here
with the invasion fleet by now if they wanted this planet. And, it’s worth noting that such a hostile
civilization wouldn’t seem likely to give up the element of surprise and send out a
signal saying they’re on their way. And, to be honest, there really isn’t anything
here for an alien civilization to expend all the energy to get here to take. The earth is made of the same materials as
the rest of the universe, things like gold are everywhere. It would make more sense to mine a local asteroid
for that sort of thing rather than spend years crossing space at great energy expense just
to take earth’s gold. Same with the water, the universe is so loaded
with ice that you don’t need to leave home to find it. It’s also worth remembering that Earth does
not even have the largest liquid water ocean in the solar system, that distinction belongs
to Ganymede. And even Europa has about twice the amount
of liquid water that earth has. So any water seeking aliens would probably
go there rather than here, earth does have a rather large gravity well that you need
to defeat to take the water. Less so with the Jovian moons. That said, scientists within SETI have thought
out a system of protocols for what should ideally happen after a detection. They are common sense, and very extensive. Essentially once it’s known that the signal
is of likely alien origin, and not a false alarm, but a verified unambiguous signal where
alien origin is the best explanation then the public gets told. Openly, from the Secretary General of the
UN to you and I. This would be one of the greatest, most profound
discoveries in human history, it should and would be out there. What else is in the protocols is that no response
should be given to such a signal until it’s internationally agreed on just what to say,
if we even think it’s prudent to respond. And that’s where we get into what may be
a huge problem with this whole thing. We may never be able to decipher the message,
if there is one at all. It may be something creative, like a description
of hydrogen similar to our own pioneer plaque which depicted just that since all civilizations
with the science to send interstellar signals or find wandering probes would know of hydrogen. Or it may be much more disappointing. Imagine waking up one day to an announcement
of the unambiguous discovery of an alien civilization in the radio spectrum. Imagine the scientists proudly stating that
we are not alone. And then would come the questions from the
press. What are the aliens like? We don’t know. “What did the message say?” … “There wasn’t one, it’s just a very
powerful raw signal.” … “Well, what’s that tell us? The reporters would ask. The answer might simply be “The aliens have
radar.” And that may be all we ever know about that
particular alien civilization. And that would be poetic, since some of the
strongest signals we have ever emitted came from the Arecibo radio telescope. There were two types. One was a radar signal to map some asteroids
that never repeated, and the second was an intentional message to alien civilizations,
and it never repeated. If anyone ever picks either of those up, we
will be their Wow! Signal. What does that tell us? Thanks for listening! I am futurist and science fiction author John
Michael Godier currently addressing the commenters regarding the existential
crisis crab rangoon concept from last week. I defeated the takeout food, and consumed
it. Decisively. It no longer exists. But the next day there may have been regrets
and be sure to check out my books at your favorite online book retailer and subscribe
to my channels for regular, in depth explorations into the interesting, weird and unknown aspects
of this amazing universe in which we live.


25 thoughts on “The Search for Extraterrestrial Intelligence in Radio”

  • Sire DragonChester says:

    They can’t be bother with us, other odd few odd or rogue aliens who simple fly by and interested for few then continued on. We are simple ANTS/cattle to them atm. As human being we mostly ignore ants unless you study them.

    Though still hope one day meet alien species.
    I suspect it very well could be something like Star Trek. Until a civilization reaches at certain point of Evolution, ( war drive/light speed etc) were ignored till that criteria is met and or they see earth as threat or interest. Hopefully it’s not just mine four our resources, or we/earth is food lol

  • Opps. You made an error. You said the 1938 Olympics was too faint for other civilizations to receive. But we know that, at a minimum, Gilligan's Island and the Galaxy Quest "historical documents" were received.

  • I honestly believe that governments already have agreed to keep any detection/evidence of alien life entirely undisclosed. It is in their own best interest to do so, since all governments want the same thing: a calm and compliant populace. A legitimate disclosure of alien life or alien contact would create a level of upheaval we've never witnessed. Christians and Muslims would likely react with varying measures of violence and panic. Piles of non-religious people would likely react with horror and outright panic as well. It would be a hugely affecting event, globally, so for this reason, I disagree that just because governments can't seem to unify or lay down their hostilities is some justified proof that there's no cover up.

  • There is one extremely rare resource on earth that can't be found just about anywhere in the universe… Complex life. If aliens come to earth it will only be for one of two reasons. Reason number 1) because they seek knowledge and scientific discovery or reason number 2) We are a food source for a starving overpopulated extra terrestrial planet. I think reason number one is most likely though as the likelihood that we wouldn't be poisonous to alien life is very small and thats if they even eat like us at all. Then there is crossing the vastness of space to pick up oxygen breathing, resource eating, water drinking beings. If you have that kind of technology just to collect humans you would probably have the necessary tech to terraform a near by planet and grow crops suited to your biology.

  • Suthin Scientist says:

    Extraterrestrial radio might be more advanced than our own radio. Maybe that's why we can't find radio signals from extraterrestrials.

  • KillahSMOKEofYAHUSHUA says:

    if space is what they tell us then I think that its either humans like us are out there or hybrids from fallen angels and demon gods but I think they are going to hoax a fake alien invasion one day

  • JMG, out of curiosity, what WOULD be valuable to an advanced alien civilization? You spoke of gold and water. Are there other materials that might be of interest, would it be worth a hypothetical alien civ coming to us, or would they be more likely or more easily find it amongst the stars or locally?

  • We should be firing relay satellites from orbit out of the solar system. Long chained launches. May not exactly be all that useful now, but will be crucial in time.

  • Great video John! I wonder if one of our signals is some alien race's Wow signal? Perhaps their version of you just made a video about it. 😁

  • And so now even if we’re to Contact an Highly Intelligently Advanced Alien Civilization one day wouldn’t both us and whatever that Alien Race is not be able to even understand either one’s Particular Languages Given the very fact Aliens wouldn’t haven’t a Clue either on how to Communicate with us Nor would we understand their language either ????

  • Everybody keeps bringing up the "wow signal" even after it was proven to have been a comet. You could read about it in Journal of the Washington Academy of Sciences.

    Also noteworthy is all the crazies trying to shout down the work. Within a week after the work was published dozens of websites went crazy and tried to discredit the work. Sorry, but it was a comet.

  • Considering that everything in the universe is moving and the source of any signal would probably be very distant, it's likely that if we responded to a contact signal they would never receive it anyway.

  • I really want to thank you for including the english subtitles in your videos. I have no trouble listening, reading and wrinting basic english, but I'm brazilian and not everyone here knows the language. Contrary to what people believe the auto-translate function of Youtube for other languages is very good and accurate, but the author needs to include the subtitle/CC file with the video, otherwise YT uses the much less accurate auto-generated english (which is still not bad for those asking, but lacks precision and sometimes translate some things wrong). Since I like astronomy and astrophysics A LOT and also like to disseminate knowledge about the subject, I usually share some of your videos in forums, messages, twitter and such. So thank you very much.

Leave a Reply

Your email address will not be published. Required fields are marked *