Humanity cannot hide from radio transmitting civilizations

[farmerben]

If aliens send us a radio message, we have no choice but to reply.

All the other humans on Earth will eventually find out about the alien signal.  With a moderate amount of wealth any human could send a directional radio signal back toward the alien star without the other humans even knowing about it.  

No matter what government policies are adopted.  There is almost zero probability that transmission capability will not fall into the hands of 14 year old boys, and cult leaders, etc.  

Therefore to try to hide is to accept the reality that other humans will act against your interests.  

Therefore our safest bet is show them what credible humans are like, because we must warn them against pranks, hoaxes, and viruses we cannot prevent other humans from sending.  

[DDE]

@farmerben, that assumes the recipients would be able to decipher the improvised message - or they would even care what the message is besides evidence of sentient life and hence a potential threat.

[Bill Phil]

One can argue that we can’t hide period, given that civilization emits waste heat.

[Guest]

Interesting take. What prompted this?

[Canopus]

For the same reason i think the Zoo Hypothesis is invalid, because there could always be a rogue element not adhering to a "prime directive".

Edited July 21, 2019 by Canopus

[magnemoe]

2 hours ago, Bill Phil said:

One can argue that we can’t hide period, given that civilization emits waste heat.

Our waste heat is very minor to the overall heat. Hiding that earth has life is way harder, yes you can theoretically mask it it only work over an narrow angle and don't work backward in time, solving this on an billion year scale will be hard
And yes an planet with lots of life would be something to watch. 

More so any signal we get is most likely to be an one off wow signal, High power radio waves like "no Jeb you can not aerobrake an asteroid" or an high power radar pointing in our direction by random.
High power laser for pushing ships starshot to moth in the gods eye would be detectable far longer away. 

But yes making an transmitter to send an return signal will require some very rich (at least if secrecy is required) having you private large radio telescope is far cheaper you don't need to be an billionaire. 
For most countries it would be trivial, but it would hardly matter. 
Time for signal to return, the chance of anybody listen is low. Anybody who would hang around and listen know earth has life. 
Either they are to far away to mater or they had send probes. 

[magnemoe]

3 minutes ago, Canopus said:

For the same reason i think the Zoo Hypothesis is invalid, because there could always be a rogue element not adhering to a "prime directive".

Yes, in short its very unlikely some is willing to expend the force and cost to enforce the blockade over geological time. 
You can imagine an hive mind or monolithic civilization but they would probably run into some issues like agree that electricity is too dangerous if they ever have the creativity to invent it. 
And blocking of an planet with primitives sounds more like something we would do. 

 

[Guest]

@magnemoe

>_<, I think there's a few issues with your ideas.

43 minutes ago, magnemoe said:

Hiding that earth has life is way harder, yes you can theoretically mask it it only work over an narrow angle

what does this mean? 

43 minutes ago, magnemoe said:

High power laser for pushing ships starshot to moth in the gods eye would be detectable far longer away

If the laser isnt dispersed by the sail material and is pretty much just reflected the beam should be extremely hard to detect due to it being confined to a narrow beam. you wouldnt see it unless you were in it's path, while even the best laser beam will probably expand over great distances we are still talking an insanely low probability of anything being in its path. 

Or are you saying aliens would attempt to contact us via high powered laser? Maybe. highly focused electromagnetic radiation of any kind is a possibility, I believe Breakthrough Listen has either started or about to start observing our atmosphere for the reactions of highly energetic forms of radiation hitting it, to see if there are any messages from ET therein. 

43 minutes ago, magnemoe said:

But yes making an transmitter to send an return signal will require some very rich (at least if secrecy is required) having you private large radio telescope is far cheaper you don't need to be an billionaire. 

I dont think you need to be rich to send transmissions into space, pretty sure any plane with radar would be doing it for free, not to mention the soup of emissions we are probably leaking into space indiscriminately (But im not an expert on stuff like that so maybe im way off >_<) 

Do most radio telescopes transmit as well? I thought they were just receivers. 

Edited July 21, 2019 by Guest

[magnemoe]

6 minutes ago, Dale Christopher said:

@magnemoe

>_<, I think there's a few issues with your ideas.

what does this mean? 

If the laser isnt dispersed by the sail material and is pretty much just reflected the beam should be extremely hard to detect due to it being confined to a narrow beam. you wouldnt see it unless you were in it's path, while even the best laser beam will probably expand over great distances distances we are still talking an insanely low probability of anything being in its path. 

Or are you saying aliens would attempt to contact us via high powered laser? Maybe. highly focused electromagnetic radiation of any kind is a possibility, I believe Breakthrough Listen has either started or about to start observing our atmosphere for the reactions of highly energetic forms of radiation hitting it, to see if there are any messages from ET therein. 

I dont think you need to be rich to send transmissions into space, pretty sure any plane with radar would be doing it for free, not to mention the soup of emissions we are probably leaking into space indiscriminately (But im not an expert on stuff like that so maybe im way off >_<) 

Do most radio telescopes transmit as well? I thought they were just receivers. 

Its some theoretical ways you could mask the signature of earth. have an laser fill out the gap of oxygen absorption and so on, very theoretical and not something we can do for an long time. 

Laser is very nice for deep space communication if you know the target location if your sender is in space. 
An light sail will leak around the edges as you beam is not perfect and you want to minimize the size of the sail. 

Radars on civilian planes no, high end military ones perhaps, high end sam systems like patriot obviosly but its not stuff you can buy. 
Radio telescopes can not transmit but that is an upgrade, many have it for one you can use radar against close asteroids to get details. 

Again either aliens is to far away for us to care about or so close they know about us if they bothered 

[Guest]

@magnemoe  interesting.

41 minutes ago, magnemoe said:

Again either aliens is to far away for us to care about or so close they know about us if they bothered 

Yer, we dont really have to worry about aliens knowing we're here. Either they saw life was on this planet sometime in the last billion years or so and theres nothing we can do about that or, the electromagnetic emissions of our civilization are detected, but they'd need to be so extremely close to us astronomically speaking since we havent been transmitting technological indicators into space for very long, that the chances of that are really small.

It's worth mentioning that with our current planet finding expertise we still probably wouldnt be able to detect Earth even if it was orbiting our closest neighboring star, except in the case of some extremely lucky circumstance. Ie being lined up to see it transit (Our orbital period is too slow, we'd need a new generation of telescope.) Though whether or not we would notice our own radio emissions I duno.

Edited July 21, 2019 by Guest

[kerbiloid]

Due to all reasons listed above, the first radio transmission received by any civilization,  every time is their neighbors'

Spoiler

pirate radio in a cheap DJ station orbiting a gas giant and using its magnetosphere as an omnidirectional amplifier.

TODO: Find the typical resonant frequencies and tune the receiver in the car.

Edited July 22, 2019 by kerbiloid

[farmerben]

Knowing where to aim the signal changes everything.  

Sending a directional signal involves one of 3 things.  A phased array, a reflector, or a lens.  A laser is combination of all three.  

I believe that phased arrays and reflecting dishes both give divergence on the order of 5 degrees.  Commercial lasers have divergence of about 0.05 degrees.  Intensity still falls as a function of 1/r² , based on the cross section of the beam at some distance.  

Reflecting dishes are within the grasp of millions of 14 year old boys.  That is all it takes to multiply the signal by more than a factor of 100, and thereby drown out everybody with a similar power transmitter not so aimed.  

A high power phased array is expensive but simple.  It would look something like the HAARP project.  Tricky but not impossible to hide from other humans.  The components used for 50kW radio stations are available, the only modification required is the antenna.  The power lines of village can serve as an antenna.  The only way other humans will detect it is by flying through the beam.  This is within the reach of millionaires, cult leaders, or even the city councils of small towns.  Again we are talking about boosting the signal about 100 times, but this time it is enough to drown out nearly all the other radio noise from Earth, as seen for a distant star.  

High powered lasers are mostly classified military projects.  But, it seems there are already many lasers out there that can pulse >10kW.  Which means the captain of an Israeli destroyer, can on a whim, send a signal to another star millions of times stronger than other radio noise.  

[kerbiloid]

angle of divergence ~= 1.22 * wavelength / diameter of the beam source: lens or mirror

So, an UV laser looks the best.

So, an UV spot diameter, km ~= 1.22 * 10*10^-9 * 9.5*10¹⁵ * distance,ly / (1000 * emitter diameter,km ) / 1000  ~= 100 * distance,ly / emitter diameter,km

To have the emitter and receiver of more or less equal size and to waste as less emitted energy as possible, the ships should be equipped with ~10 * sqrt(distance,ly) wide antennas.
It's unlikely possible.
So, either they agree to waste almost all emitted energy and to allow the ray follow to infitity, or they should communicate using a base with extra-wide antennas.

Or they should invent a way to use gamma rays.

An electron/positron pair emits photons with >= 0.511 MeV, so < 2.4*10^-3 nm wavelength.

So, the gamma spot diameter, km ~= 1.22 * 0.0024*10^-9 * 9.5*10¹⁵ * distance,ly / (1000 * emitter diameter,km ) / 1000  ~= 0.24 * distance,ly / emitter diameter,km

If the ship and its receiver are ~1 km wide, and distance ~= 100 ly, the emitter should be ~10¹ km wide.

So, if they generate a volumetric source of electron-positron annihilation ~100 km in diameter and modulate its emission, they can communicate with their ships in hundreds ly and stay invisible.
The problem is the lightspeed delay.

Edited July 22, 2019 by kerbiloid

[farmerben]

We could use the solar corona as a lasing medium.  The Corona is 3 million degree plasma that emits X-rays, but at such low density it is mostly transparent.  

All we need is 2 large mirrors to build up a coherent wave of X-rays where they already exist, and send the beam through an aperture. 

We might be able to use mirrors located at Mercury's Lagrange points, so that the Sun is cornered by a triangle of mirrors.  Our beam might be constrained to spin like a lighthouse, but talk about a lot of bang for the buck.  

 

 

[Wjolcz]

On 7/22/2019 at 12:37 AM, magnemoe said:

Its some theoretical ways you could mask the signature of earth. have an laser fill out the gap of oxygen absorption and so on, very theoretical and not something we can do for an long time. 

I don't really think there's much point hiding it anyway. Our planet has been screaming "LIFE!" for the past 500 million years or so.

Probably the best thing we could is to focus on being the ones who discover life somewhere else by building really big (like Earth-Moon distance big) interferometers.

[kerbiloid]

Right now there is a contact sci _{sci? well, let it be sci} -fi series Another Life about our radiotransmissions and their consequences (in episode 10).

Edited July 28, 2019 by kerbiloid

[Guest]

14 minutes ago, kerbiloid said:

Right now there is a contact sci _{sci? well, let it be sci} -fi series Another Ground about our radiotransmissions and their consequences (in episode 10).

That all I could find

[kerbiloid]

3 minutes ago, Dale Christopher said:

That all I could find

Another Life, sorry

[Guest]

6 hours ago, Wjolcz said:

Our planet has been screaming "LIFE!" for the past 500 million years or so.

Don’t worry, we will silence them forever soon :|

9 minutes ago, kerbiloid said:

Another Life, sorry

Hmmmm, this is the first article I found >_<...

Quote

Another Life is a bloated, blasé heap that follows two tepid tales: one on the ground and one out in space. Both are about teams trying to make contact with mysterious aliens that have plopped a mesmerizing monolith down on Earth.

-IGN

XD

but I will put it on my To Watch list.

( the article is not great publicity but at the same time I question the author’s taste to illiterate so much in one sentence  >_<)

 

Edited July 28, 2019 by Guest

[kerbiloid]

7 minutes ago, Dale Christopher said:

but I will put it on my To Watch list.

If you like Mortal Combat in sci-fi interiors and several kg heavy viruses (sic!) with tentacles.

(Though, maybe they meant a parasite)

Edited July 28, 2019 by kerbiloid

[Guest]

8 hours ago, kerbiloid said:

If you like Mortal Combat in sci-fi interiors and several kg heavy viruses (sic!) with tentacles.

(Though, maybe they meant a parasite)

Bah... I can’t stomach the interpersonal drama... it’s just cheap filler writing to pump out episodes imo >,> 

I tuned out when the leader was asking the people at the briefing if they felt awkward and didn’t hear why and then turned it off >_<. 

Thanks for the heads up anyway! I’m always happy to find another sci-fi to watch! Until I actually watch them.  

[kerbiloid]

10 minutes ago, Dale Christopher said:

Bah... I can’t stomach the interpersonal drama... it’s just cheap filler writing to pump out episodes imo >,> 

I tuned out when the leader was asking the people at the briefing if they felt awkward and didn’t hear why and then turned it off >_<. 

Thanks for the heads up anyway! I’m always happy to find another sci-fi to watch! Until I actually watch them.

That's why I mentioned only the last episode, lol.

[DDE]

On 7/27/2019 at 10:31 PM, farmerben said:

We might be able to use mirrors located at Mercury's Lagrange points, so that the Sun is cornered by a triangle of mirrors

Grazing incidence X-ray mirrors are woefully inefficient and a nightmare to work with.

[Riven]

But what if the life that is almost statistically certain to be out there is so advanced that they don't use anything in the electromagnetic spectrum? And who knows what that might be? Something utilizing an aspect of quantum physics we haven't discovered perhaps? Or if they do use a form of EM, perhaps their encoding is so advanced and data rate is so fast that we wouldn't be able to tell there was a message sent. And like DDE said,

On 7/21/2019 at 10:23 AM, DDE said:

@farmerben, that assumes the recipients would be able to decipher the improvised message - or they would even care what the message is besides evidence of sentient life and hence a potential threat.

When SETI beamed their famous message to M13 from Arciebo in 1974 (as a test of their system, not really for the intent of communicating with aliens), they were assuming that it was in a decipherable form.

Just like the point that has been brought up a few times in this thread already, would aliens even care to look? Because of the absurdly low chance of finding something they (and we) can understand at an acceptable signal to noise ratio, is it even worth looking for life this way? Would they even know what to look for in terms of radio frequency? Maybe the best way of looking for sentient life in EM is in the visible regime where you widely distribute an array of telescopes that point in the same direction kind of like ALMA, except larger? (Then you have to consider light delay, stationkeeping, so on and so forth.) It's literally anyone's guess.

I'm not saying we should stop looking for life, my point is that we should search for sentient life in a more feasible manner, which may not involve RF.

[magnemoe]

12 hours ago, Riven said:

Just like the point that has been brought up a few times in this thread already, would aliens even care to look? Because of the absurdly low chance of finding something they (and we) can understand at an acceptable signal to noise ratio, is it even worth looking for life this way? Would they even know what to look for in terms of radio frequency? Maybe the best way of looking for sentient life in EM is in the visible regime where you widely distribute an array of telescopes that point in the same direction kind of like ALMA, except larger? (Then you have to consider light delay, stationkeeping, so on and so forth.) It's literally anyone's guess.

I'm not saying we should stop looking for life, my point is that we should search for sentient life in a more feasible manner, which may not involve RF.

Lasers probably makes more sense for interplanetary communication. However their cone is even narrower so they mostly work if you know target location well. 
You also don't want to send an signal stronger than you want to. Not only does it use more power and require an more expensive transmitting system but you also take up more bandwidth. 
Radio noise from earth is probably going down as we move away from huge transmitting towers over to cell networks. 
Yes it cases you want lots of power like an search radar but this is not used all the time. 

Probably easier to look for bio signatures as they don't require high tech civilizations using specific technology.