Are aliens watching old TV shows?

Are aliens watching old TV shows?
Electromagnetic Spectrum

You've probably heard the trope about how aliens have been watching old episodes of "I Love Lucy" and might think these are our "historical documents". How far have our signals reached?

Television transmissions expand outward from the Earth at the , and there's a trope in that have learned everything about humans by watching our . If you're 4 light-years away, you're see the light from the Earth as it looked 4 years ago, and some of that light includes television transmissions, as radio waves are just another form of electromagnetism – it's all just light.

Humans began serious in the 1930s, and by the modern era, there were thousands of powerful transmitters pumping out electromagnetic radiation for all to see. So are aliens watching "I Love Lucy" or footage from World War II and believing it all to be part of our "Historical Documents"?

The first radio broadcasts started in the early 1900s. At the time I'm recording this video, it's late 2014, so those transmissions have escaped into space 114 years ago. This means our transmissions have reached a sphere of stars with a radius of 114 light-years.

Are there other stars in that volume of space? Absolutely. It's estimated that there are more than 14,000 stars within 100 light years of Earth. Most of those are tiny , but there would be hundreds of sunlike stars.

As we're discovering, almost all of those stars will have planets, many of which will be Earthlike. It's almost certain some of those stars will have planets in the , and could have evolved life forms, technology and television sets and were able to learn of the Stealth Haze and the Mak'Tar chant of strength.

Will the signals be powerful enough to stretch across the vast distances of space and reach another world so that many generations of aliens can hang their hopes that James Tiberius Kirk never visits their planet with his loose morals, questionably applied prime directive, irresistible charms and pants aflame with who knows what kinds of interstellar STIs?

Here's the problem. Broadcast towers transmit their signals outward in a sphere, which falls under the inverse square law. The strength of the signal decreases massively over distance. By the time you've gone a few light years, the signal is almost non-existent.

Are aliens watching old TV shows?
The Square Kilometer Array

Aliens could build a huge receiver, like the being built right now, but the signals they could receive from Earth would be a billion billion billion times weaker. Very hard to pick out from the background radiation. And by Grabthar's hammer, I assure you it's only by focusing our transmissions and beaming them straight at another star do we stand a chance of alerting aliens of our presence. Which, like it or not, is something we've done. So there's that.

We've really been broadcasting our existence for hundreds of millions of years. The very presence of oxygen in the atmosphere of the Earth would tell any alien with a good enough telescope that there's life here. Aliens could tell when we invented fire, when we developed steam technology, and what kinds of cars we like to drive, just by looking at our atmosphere. So don't worry about our transmissions, the jig is up.


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'Mirage Earth' exoplanets may have burned away chances for life

Source: Universe Today
Citation: Are aliens watching old TV shows? (2015, January 20) retrieved 26 May 2019 from https://phys.org/news/2015-01-aliens-tv.html
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Jan 20, 2015
Loved the Galaxy Quest reference ;-)

Jan 20, 2015
I can't remember now but didn't someone make a (B or C class) movie about aliens watching soccer matches and decided they didn't like the way we booted that little 'animal' around? The aliens decided to put a stop to it.
That is to say, even if Aliens did 'listen in' they might not interpret things the way we do.

Jan 20, 2015
The big factor that busts the "Star Trek Bubble" is deep time. Mankind, on a planet perfect for life and indeed for advanced life, has existed for about 200 thousand years, of which we have radiated technology for less than 150 years. In the four and a half billion year age of the earth, that is a mere blink of the eye. It is even more brief in relation to the 14 and a half billion year lifespan of the universe. Most of us want so desperately to believe that we are not alone, and by inference, that a superior alien race may rescue us from ourselves, but the numbers don't even remotely support that. Statistically, we will find pond scum on any planet with liquid water, but the odds of actually encountering intelligent life during mankind's life span is near zero. Better start saving ourselves.

Jan 21, 2015
There's another reason they're not watching our shows: Most TV stations share a limited number of channels, and are broadcasting multiple programs at the same time. Even if they could detect the signal, it would be such a mess that they'd never pick one program out of it.

The "bubble" Fraser Cain refers to isn't an accurate characterization of individual stations. As the Earth rotates, for a remote target, at some instant the stations optimally reaching that target using some particular frequency band will be small. I'd expect at times a single station would outshine all others sufficiently that there would be a signal to pick apart.

Jan 21, 2015
Did anyone here see the original 1951 version of 'The Day the Earth Stood Still'. Klaatu says that 'they' listen to our broadcasts and learn our languages that way. However, in the movie 'they' live much closer to Earth but the principle is similar. So this idea is at least 64 years old.

Jan 22, 2015
Can't resist. Inverse square law. Stars billions of light years away and we can see them. Such a silly idea. The stars are much closer than is believed.

We can with considerable difficulty receive low rate signals from the Voyager space craft and that's barely outside our solar system. Chances of a terrestrial TV signal getting through our atmosphere/ionosphere and beyond our solar system is zero. Crikey, we still don't even get good quality video from the space station!


Jan 22, 2015
SETI folks usually search for coherent, narrowband signals that would almost certainly be artificial. A good example is the "carrier" component of an analog TV signal, which would be *far* easier to detect at interstellar distances than the actual video or audio. North American digital TV has a carrier-like "pilot tone" but it's much weaker. Its design is also much more complicated. The rest of the world (naturally) uses a different standard.

Jan 22, 2015
Bluehigh: Radio physics is *very* well understood (I'm a radio ham and a radio communications R&D engineer). We do know how far away the stars are. We know how our signals are affected by the ionosphere: VHF/UHF is barely affected at all. And we know exactly how strong our signals would be from an antenna of a given size on a planet orbiting a given star. None of this is a mystery. We simply don't know if there are any technological civilizations out there listening.

Jan 22, 2015
Ok, there's a couple of things wrong with this "aliens watch Earth TV". The signal strength issue is an obvious one.
But if we postulate aliens building receivers that can sort THAT kind of signal out of the noise then they have a techological capability which easily enables them to just come here, rent an appartment, kick bakc on the couch, crab some chips, and watch the TV shows live.

Jan 22, 2015
@antialias_physorg or maybe they have their own TV shows here...Now we're into to David Icke's ideas

Jan 22, 2015
We do know how far away the stars are.
- KA9Q

In the fullness of time you will learn that you are mistaken.

Your puny radio transmissions are almost just part of background noise before they even leave your solar system. With all you seem to know then go do a calculation using the inverse square on the signal power from a TV station at 10 light years. It's just noise.

These mighty alien civilisations will need to be fairly nearby, say within 100 light years. Not much on your TV 100 years ago.

Jan 24, 2015
Several years ago, there were reports out of Texas of 40 to 50 year old shows coming being received. The family tracked down the date of transmission from the station records.

Previous reports had been ascribed to TV transmissions being written to magnetospheric VanAlphen waves.

Jan 24, 2015
Military RADAR beams in the mult i megawatt range are considered a good identifier of our or other's technological civilization. They are beams, and given the rotation of the Earth, the beams won't stay on target for long. Note similarity to Ohio State University Ah Ha signal.

Jan 24, 2015
Bluehigh: with all due respect, you should learn that you are mistaken right now. Without knowing the size and gain of the receiving antenna you simply can't put any limits on range other than the obvious one that TV transmissions started less than a century ago.

As I said, this stuff is very well understood, although apparently not by you. Path loss in decibels between a pair of isotropic antennas is 20*log10(4*pi*d/lambda), where d/lambda is the distance in wavelengths. This is the inverse square law folded in with the effective size of an isotropic radiator.

The gain of a parabolic antenna is 20*log10(pi*d/lambda) - 10*log10(nu), where d/lambda is the antenna diameter in wavelengths and nu is the illumination efficiency (usually about 50%).

That gives you the received signal strength. The other side of the equation is the noise level. Noise power in watts is kTB, where k is Boltzmann's constant, T is the system temperature in kelvins, and B is the bandwidth in hertz.

Jan 24, 2015
Expressed as dB, the noise power is -228.6 dBW + 10*log10(TB).

It should now be apparent why carriers are far easier to detect than entire TV signals, and why SETI@Home uses very long integration times.

The system noise temperature can be very low; depending on the frequency, the antennas of the NASA deep space network achieve total system noise temperatures between 10K and 25K. It's higher in the TV bands, but the upper UHF band is still pretty quiet.

Jan 24, 2015
MRBlizzard: Indeed. One of the most important is the Navy's SPASUR space surveillance system. Three high-powered CW (carrier only) transmitters located across the US transmit "fan" beams up into space to detect objects in orbit. They operate just above VHF channel 13.

You'd have to be in the right place to detect these fans as they sweep across you, but they would be *very* bright. The Lake Kickapoo transmitter has an EIRP (Effective Isotropic Radiated Power) of over 6 gigawatts!

Jan 24, 2015
@KA9Q obviously you are experienced in radio. When do think transmissions from here would have been powerful enough to have been detected?. What I'm hinting at is that it depends on how far away possible alien detectors are, that is, if we have been 'on air' for only a short time then our signals will not yet be detected. My 'alien detectors' is deliberate because it is possible, and I would think likely, that any advanced alien culture would have their own probes etc in orbit around a body closer to us than their home.
As a layman I'm asking a question on another point. Although our present understanding is that some phase v is ftl but cannot carry info. Is it possible that alien, and perhaps us in the future, have found a way to organise such non-well defined packets into well defined systems that could carry info? Like to hear your ideas on this...or am I just thinking fiction here ha!

Jan 24, 2015
Mimath-Breaking News...The white spot on Ceres...Aliens don't use radio signals but large mirrors.....'
NASA "Yes, we can confirm that it is something on Ceres that reflects more sunlight, but what that is remains a mystery,"
Sorry chaps, just couldn't resist a joke.

Jan 25, 2015
Mimath224: not sure I understand your question, since it depends both on how powerful our TV transmitters were at a given date and how big the aliens' purported receiving antennas are. If you believe Carl Sagan's "Contact", it would be the coverage of the 1936 Olympics in Berlin with a receiver at Vega.

Another assumption is that the aliens would be pointing their directional antenna directly at us. But this is not unreasonable if they're conducting a "targeted search" of the nearest stars; that's something we do too.

Jan 25, 2015
Mimath224: I seriously doubt that we'll ever get faster-than-light communication. The speed of light seems to be a fundamental constant of the universe. SF writers like to talk about wormholes, but they seem awfully unlikely as a practical means of communication even if they exist.

Jan 25, 2015
we fool ourselves if we judge the capabilities of others through the cracked lens of our own recent inventions. So we have a square kilometer array. How about looking outside the box and imagining a huge array covering a million or more kilometers; and that is only thinking about it for a few seconds.

Jan 25, 2015
Lasers are fundamentally no different from radio transmitters; both are equally subject to the inverse square law. It's just that it's easier to get lots of transmit antenna gain at optical frequencies, but even a tight laser beam still spreads with distance. The inverse square law is geometric: the surface area of a sphere increases with the square of the sphere's radius.

That said, radio signals are still more effective for interstellar communications because the background noise level at optical wavelengths (think of all those stars) is much higher than in the microwave radio spectrum.

Jan 25, 2015
Light from Stars billions of light years distant and your telescopes can resolve images - lol. Such a silly notion. Regardless of your understanding, sometimes you need to consider what's incorrect in your data or calculation methods when the results are clearly absurd.

Ren82 .. A valid question. Depends if you have a million kilometre square array receiver or not! The answer would so impractical as to be unrealistic. However, some people want to believe anything is possible. It's not.

Jan 26, 2015
@Ren82 I can't say I understand your first part. It doesn't matter what frequency (or wavelength) we're talking about, or how you generate it, light and radio are both forms of electromagnetic radiation, and they're equally subject to the inverse square law.

You are making claims that are intrinsically quantitative. That is, you are making claims that involve numbers, yet you aren't presenting any. I've given you the basics of how to compute what we radio engineers call a "link budget", so before you can say that interstellar communication is impossible you really ought to understand them and actually do them.

Jan 26, 2015
@bluehigh Any stars billions of light years away are in distant galaxies, and no telescope we have can resolve individual stars at those distances except perhaps for active supernovae.

But our Milky Way galaxy is "only" about 100,000 light years across, and we can indeed image many individual stars, especially the closer ones. Some naked-eye stars are a few thousand light years away, e.g., Deneb is 2,600 ly away, but it's a super-giant, roughly 200,000 times as bright as the sun. Most stars are red dwarfs, including Proxima Centauri, the closest star to earth beyond the sun at 4.24 ly, and it takes a good telescope to see it at all.

Jan 26, 2015
Just to give you an idea of what can be done, I ran an approximate "link budget" for two copies of the Arecibo radio telescope pointed at each other across a distance of 100 light years. For a transmitter power of 1 megawatt on X-band the receiver would not only easily detect the signal, but they'd be able to communicate digitally at a couple of kilobits/sec. Not exactly a fast Internet connection, but not bad given the distance.

There appear to be about 10,000 stars within 100 light years of us, but most of them are red dwarfs. About 2,000 are sun-like.

Jan 26, 2015
The stars you mention are not so far away. You misunderstand the concept of your result being illogical and the need to reexamine the methods you use to derive your conclusions. You also seen to be confused regarding the transmission of coherent light using lasers and broadcast TV signals using vhf/uhf from dipole antennas. Quite different radiative effects.

You professing to be an expert, I would expect you to plug in the numbers to your models. So far nothing but hot air. Answer the question that Ren82 asked with you providing some numbers. You can't. Fact is terrestrial TV carrier signals don't even get beyond our solar system. If you think they do, then describe the size and geometry of the antenna required for detection. I say a million kilometre diameter dish. You got a number?

The stars are not so far way. That's why we can see them.


Jan 26, 2015
That's new information. Radio telescopes transmitting reruns of 'I love Lucy' with video at a couple of kilobits/sec. Get a patent on your compression technology.

With your amazing abilities, do tell us what is the visible light flux density received at Earths surface of a Sol like star 100 light years distant. I say almost zero. You got a number?


Jan 26, 2015
Any less than an incident power of 3.58 x 10-18 W then the human eye cannot see it. Crunch the numbers. The stars must be closer than you believe else we simply could not see them. I suggest stars induce a field effect similar to that of a concave lens.

In any case, no aliens are watching our old TV shows. Unless they are in a nearby orbit. The TV signals are just noise beyond a light hour or so.


Jan 26, 2015
@bluehigh You're beginning to sound like a crackpot. Real scientists know how to use numbers, and they don't challenge widely accepted theories unless they've got the evidence to back them up.

We know the distance to the stars by a method called "parallax". A nearby star appears to shift back and forth every 6 months against the background of distant stars as the earth orbits the sun. We know exactly how big the earth's orbit is, so we can calculate just how far away the star is. That's where the 'parsec' unit of distance comes from. It stands for "parallax second of arc".

Or am I just wasting my time in explaining all this?

Jan 26, 2015
Commonly understood methods. Maybe new to you!

Still waiting for the numbers from your calculations on the size of an antenna to receive terrestrial TV signals at 100 light years.

You just Googling the techniques and can't do the math?

Radio telescopes, lasers, military radar - lol.
You're no radio engineer, just a Google surfer.

Answer the questions with your calculations, if you can.

Otherwise there's not much more to talk about.


Jan 26, 2015
I wonder if the alien-Skippys are as mad as me about the Leverage not being on anymore? If they did like I did they got it on the DVD so they can still watch it when they want to.

Jan 26, 2015
@bluehigh If you actually read what I said, you'd know I was talking only about detecting the carriers in TV signals, not actually recovering the video and audio. SETI is all about detecting carriers because they're not produced naturally.

I'll thank you to avoid the personal attacks. I have two degrees in electrical engineering, and I'm retired from a career as an R&D engineer at Bell Labs, Bellcore and Qualcomm.

Jan 26, 2015
@bluehigh You actually asked an interesting question about how bright the sun would be at known interstellar distances.

Apparent magnitude varies as 2.5*log10(b), where b is the brightness ratio, so applying the inverse square law it varies as 5*log10(d), where d is the distance ratio. Sol has apparent magnitude -26.74 at 1 AU, and 100 ly = 6324107.7 AU, so its apparent magnitude @ 100 ly = -26.74 + 5*log10(6324107.7) = +7.26. That's between the brightness of Uranus and Neptune at Earth. Too dim to be seen by the naked eye, but you could see it with good binoculars and very easily with a small telescope.

This is basic, understood physics and math. What do you have against that?

Jan 26, 2015
Bluehigh: Radio physics is *very* well understood (I'm a radio ham and a radio communications R&D engineer). We do know how far away the stars are. We know how our signals are affected by the ionosphere: VHF/UHF is barely affected at all. And we know exactly how strong our signals would be from an antenna of a given size on a planet orbiting a given star. None of this is a mystery. We simply don't know if there are any technological civilizations out there listening.


@ Phil-Skippy

I'm with you on this one so I'm giving you the five karma points this time. And I'm glad to make your acquaintance.

Jan 26, 2015
@Ren82 Yes, a laser focuses light into a very tight beam, and it will be brighter at a given distance (assuming it's pointed there) than emitting the same power uniformly in all directions. But the beam still diverges with distance according to the inverse square law.

Just think of a laser as an optical transmitter with a very high (but not infinite) gain antenna, because that's exactly what it is.

Jan 26, 2015
@Ren82 I don't know what you're trying to say in your other notes, but it reads a lot like the usual creationist arguments against evolution and/or abiogenesis. Life does not arise or evolve by the purely random assembly of molecules, making both the underlying assumptions and the results incorrect. The fact that we're here is proof of that.

Jan 26, 2015
@bluehigh To further verify my calculations for stellar distances and brightness, at 4.366 light-years Sol (our sun) is magnitude -26.74 + 5*log10(276000) = +0.46, roughly the brightness (but not the color) of Betelgeuse.

4.366 light years is the distance to Alpha Centauri, the nearest visible star system. It consists of two stars orbiting each other, one a little bigger and brighter than the sun (apparent magnitude 0) and the other a little smaller and dimmer (magnitude 1.3). Just as expected, Sol is between those two.

Jan 26, 2015
@ Phil how you are again Cher? I'm still good too.

I look you up on the Zed place if you know what I am talking about. I am the Extra like you are too. But you are the old hand and I am the brand new greenhorn me. Like you I go to the engineer school too, but you went the real science engineer school that I didn't. I am the engineer on the tow-boats on the Mississippi river.

Anyhoo, I took the exam to get my ticket back in November. At first I was only trying to the Tech ticket, but when I finish him the VE-Skippys ask me, "Ira-Skippy do you want to try the Gen?" and I said sure I might as well try him too since I don't anything else to do today. I pass him real good too and the VE-Skippy ask now you want to try the Extra? Since they didn't ask for any more money I said yeah, I'll try him too. Passed him too like the others ones but not as good as the Tech and the Gen but passed still him good.

I'm running short of letters so I have to P.S. you. Okayeei?

Jan 26, 2015
P.S. for you Phil-Skippy.

A lot peoples here make me the misere all the time and I made the big mistake when I first bragged here about getting my ticket, I was proud of that I gar-ron-tee you. You got the 2 by 1 call but they ran out of those so I did not get the 2 by 1 or the 1 by 2 like I was hoping to get. I had to settle for the 2 by 2 from the Group B calls like they used to give the Advanced peoples.

I almost forget. What I was going to say, after I wrote a bragging message here with my 2 by 2 in it, I found out what all people can find out about you from just that and since so many peoples give me the misere I wish I had not put him up there. It took me a lot email and message writing but finally the nice peoples at physorg took that message down for me even though a lot more than the 3 or 2 minutes go by, more like 3 or 2 days.

One more another thing. If you see somebody talking about the aether here, that's Zephir-Skippy and it is not the same as our aether.

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