thinking about the Drake Equation...

[aramis]

Makes me think of the Drake equation...

Ruling out zeroes, the more conservative runs of the Drake come out with around 1000 extra-terrestrial technological species capable of communication with us... but our currently most sensitive dishes can only pick up our loudest single transimissions to abut few parsecs based upon the ability of them to pickup V2's 22.4 W transmitter at 130 AU and a 70m dish. Rerunning the numbers...

Pc in AU (Earth & Sky mag via google):	206,265 AU​	1
Voyager 1 distance Apr 2022	149 AU​	2
Voayer 2	123.6 AU​	2
Voyager Antenna wattage	22.4​	3
Most powerful broadcaster	~2 MW​	4
So.... using as a fudge...	2.5 MW 2500000 W​
Max BCP /Voy	111607.1429​
Square root to find relative distance multiplier	334×​
AU (rounded to 1 decimal)	49,777.4​
divide by AU/Pc	0.2413​
multiply by 3.26 to get LY	0.787​	rounded to 3 places
Assume ×10 distance for near future improvements and extra-atmospheric dishes	7.8 LY​ 2.4 Pc

1: https://www.google.com/search?q=par...sABAdoBBggBEAEYCdoBBggCEAEYCA&sclient=gws-wiz
2 https://voyager.jpl.nasa.gov/freque... of April 2020, Voyager,about 3.3 AU per year.
3 https://www.wired.com/2013/09/vinta...r 1 has a 22.4,antennas, just to hear Voyager.
4 https://en.wikipedia.org/wiki/Transmitter_Solt

And... the detection range is further for Earth as a whole as multiple overlapping signals in space capable bands can be "visible" at once, but the combined signal becomes just loud static. So...
not doing the math, but I'd estimate a handful - say 4, at that level would push detection out to nearly 20 Pc... but seti rejects automatically noise channels...
At present signal rates and earth matched signal, assuming near future improvements, we'd need civs in the Alpha/Beta Centauri, (Rigel Kentarus & Toliman), Proxima Centauri, Barnard's Star, Luhman 16 (WISE 1049−5319), WISE 0855−0714§, or Wolf 359.
If Aliens are at our current TL7.9... the most likely nearest is simply too faint to make out.

And I've ignored that the 22.4 W is a dedicated near monodirectional, while the broadcasts are omni, so getting a lot less as well....

So, unless they do tight beam multi-megawatt transmissions, we'll be lucky to get a few parsecs radio detection, and that is 6 known systems, likely 1-2 other Class T or class Y dwarfs as yet undetected.

We're not even likely to hit a "Wow!" level when our METI signals get there....

 

[kilemall]

Wouldn’t a deep space array out in say Jupiter distance get us better sensitivity?

 

[aramis]

Wouldn’t a deep space array out in say Jupiter distance get us better sensitivity?

That's part of that ×10 range I factored in. I'm also assuming some maximizations of the receiver - basically a prediction bonus.
Putting out near jupiter would help with the Voyagers, but not really much for the interstellar... the voyagers are still very low fractions of a light year out... and one would be losing only 10 AU off the distance, but also increasing the positional variation from ±1 AU to ±10... prettu trivial at the LY or AU ranges.

If we wanted to, we could build a 100m orbital (about double the surface area and thus antenna gain)... or maybe even bigger... but the collimation matters more. a nicely tight beam can get a lot more power out; I've used non-colimated source because broadcast (vs narrowcast) is more likely to be the signal found. The current 70m have a sub degree field of view and +70 dB gain at each end would be ×1e7 power and 1e3.5× range (about 3000× the range)... but that requires intentional linking...

More realistically, if a world within 50 LY somehow guesses we're technologically capable, they could, in theory,, builda 2 MW 100m directional antenna to send a radio signal we might be able to read...

but I'm talking about the eavesdrop side... which is current installs just about 3/4 of a LY... just past the oort cloud.

Essentially, we don't hear anyone because they aren't shouting at us...

IMTU, I explained the "Wow!" signal as a Vilani misjump into the Oort cloud and their search radar...

 

[Rigel Stardin]

I don't think so. The is allot of interference out there by natural objects.

 

[Dragoner]

I was recently watching something on some of the current signals, and one of the researchers mentioned that sending a signal is around 200 billion in cost, and that while not impossible, it is unlikely to be done at that price.

 

[BackworldTraveller]

"Hey guys. I've just thought - we could let the neighbours know we were here by artificially inducing our sun to go nova!"

 

[Rigel Stardin]

That just might work? However, the time delay on those long distance calls is a killer...

 

[Rigel Stardin]

Flash of insight here...

For all the bad reviews the movie 'Battleship' got, it did bring up an important question: Do we really want to blindly contact another race?

The other side of that coin is: If there has been a race listening to us for the past one hundred years, they might not think it's a good idea to let us know they are there."

Fear is a fickle thing. It can be a deterrent as well as a call to arms. I mean, look at all the media we've created about hostile aliens because we need an allegory for the Soviet Union or another country we didn't like or were hostile too? We didn't want to say they were bad out right because we didn't want to ramp up the fear and mistrust of each other. Such nuances, could lead to misunderstandings. It might also give them the wrong idea about us?

I know of at least one radio play, several Twilight Zone / Outer limits epsiodes, and countless books that discuss this issue.

Crud, my brother brought this up in one of his stories and how it could be used against us. I guess, the point is do we really need/want to take that risk in broadcasting our location and our thoughts to the races that might be out there?

 

[bookwyrm]

our broadcasted media might be considered a reflection of who, or what, humanity is like by other beings who might be our neighbors. they could be hoping we never get off of our planet, or are actively working on making sure we don't get farther than the moon. or maybe we've already been 'Red Zoned'. or maybe we're in the process of being 'Manipulated' away from that which terrifies them to becoming a more productive and safe member of an interstellar society.

in the movie Battleship, it seems the scientists weren't thinking of the consequences the communication technology being used to reach out to those others who might be out there. at least, not until the others came to let us know that they weren't happy about being contacted by us...

 

[mike wightman]

This week's PBS Spacetime has an interesting take on things:

 

[JohnCalyn]

"Hey guys. I've just thought - we could let the neighbours know we were here by artificially inducing our sun to go nova!"

Just think of the Science! How much we'd learn!

 

[bookwyrm]

we could all learn something new from a once in a lifetime eve..........(nt)

 

[Enoki]

On contact: You are some interstellar capable species. What possible reason do you need specifically the Earth for anything? You can go to other systems. You have your choice of thousands of planets, almost all of which don't have life that's going to fight back.

As far as finding them, or them finding us... How long will electromagnetic transmissions remain our means of communication? 300 years? How about 500, or a 1000? If EM signals are a short-term thing, that is centuries in use then something else replaces them, we have a very short window to receive those transmissions from another intelligent civilization. So, for example, let's say such a civilization transmits such signals for 500 years then moves on to something else. On Earth the first of these signals arrives in the year 1200. Well, we missed our chance to find that civilization now, didn't we?

 

[Rigel Stardin]

You could also reason, their signals could be weaker than ours or the way they are broadcast sounds like static. I bring this up because, we really don't know how an alien use the same technology? On top of that, we are looking for a pattern in a signal and the strength signal. If we don't know how they are using the tech or what their language sounds like we could have missed it.

 

[mike wightman]

If the laws of physics are as universal as experiment to date show then there are certain 'signals' that you could look for.

Mind you it is also possible that the laws of physics as we understand them are not the same in other parts of the galaxy or wider universe, but the experimental data suggests that our key theories of thermodynamics, general relativity and quantum field theory are universal. Not that there are not issues with each of them...

 

[giant.robot]

1. Our omnidirectional broadcasts would barely be detectable by an Arecibo equivalent (giant collector area, super cooled i.e. sensitive receiver front end) a light year away and not really detectable beyond that distance. No alien species is watching I Love Lucy broadcasts.

2. Our most detectable transmissions are high powered radars. But these have extremely narrow beams. Not only do they sweep the sky themselves but Earth is rotating, orbiting the Sun, which itself is flying through the galaxy. The odds high power radars sweep across an alien system while they're pointing at Earth are infinitesimal. Even worse if they're waiting for a second signal.

3. There's no stealth in space. An alien civilization with telescopes able to get spectra on Earth are well aware there's life here. The reflectance spectra of Earth is filled with biomarkers like free oxygen, methane, and chlorophyll. A civilization with appropriate telescopes within about 150ly could tell there's likely an industrialized civilization here from spectra of air pollution.

So the idea that any civilization will detect another from spurious radio transmissions is unlikely. At the same time life on Earth has been announcing its presence for hundreds of millions of years. We're just getting to the point where we can detect biomarkers in the atmospheres of exoplanets. It's a matter of political will more than technology to build the telescopes that will find Earth sized planets around Sun sized stars.

If a civilization wants to explicitly broadcast a beacon, it'll need to do so continually and with a high powered transmitter at specific targets. An omnidirectional high powered transmission will vaporize the transmitter. So they'll need to pick targets and transmit continuously because there's no guarantee the target will/can receive the transmission once it reaches the system. That's an idea that's not really captured by the Drake equation, the likelihood the technological phases of civilizations overlap and they point radios/telescopes at each other. We're not going to detect an alien civilization's intentional transmissions with any omnidirectional antenna.

 

[robject]

On contact: You are some interstellar capable species. What possible reason do you need specifically the Earth for anything?

1. Slaves
2. Cattle
3. Breeding stock ("Our previous Human colony failed for some reason.")
4. Science experiment subjects ("My daughter. She insists that she can win the science fair this time... with a Human exhibit.")
5. Organs and other body parts
6. Feel important by crushing someone else's civilization


Unfortunately, I think the above scenarios are too silly for most Traveller games.

 

[Condottiere]

Mace mice.

 

[kilemall]

1. Slaves
2. Cattle
3. Breeding stock ("Our previous Human colony failed for some reason.")
4. Science experiment subjects ("My daughter. She insists that she can win the science fair this time... with a Human exhibit.")
5. Organs and other body parts
6. Feel important by crushing someone else's civilization


Unfortunately, I think the above scenarios are too silly for most Traveller games.

Specific atmosphere, temperature and other factors may make our planet very desirable for similar species.

Our planet might produce optimal genetic products.

The magnetic field generating core creating a radiation protective envelope may be rare and highly desirable even if biome replacement is preferable.

 

[mike wightman]

Any culture that could get here could build living space out of the material found in a system without having to bother with planets.

The most likely reason for an alien race to contact us would be to destroy us to get rid of the competition.

Or harvest us for their anagathics...