Uncovering Signs of Extraterrestrial Civilizations

[Boeing 757]

Hello, everyone:

I am wondering what are a few possible ways of detecting the cosmic footprints of extraterrestrial civilizations. Specifically, let us suppose for a moment there are four civilizations out there.

A. One of them is a civilization at almost type I, close to our level of technological prowess. This civilization is located, for example's sake, 10000 lighyears away from us.

B. The second is a type II civilization and has technological parity with a fictional universe such as the United Federation of Planets. Let's say that this civilization is situated on the other side of our Milky Way 25000 lighyears beyond Sagittarius A.

C. The third is a type III civilization which has a technological base equivalent to the Galactic Empire from Star Wars. Let us say that this civilization governs almost the whole of our Milky Way Galaxy, or governs a nearby galaxy such as Andromeda or one of the Magellenic Clouds.

D. The fourth is a civilization which spans multiple galaxies like the Xeelee from Stephan Baxter's novels, and whose technology is advanced enough to the point where unbelievable feats of astro-engineering with whole galaxies are conceivable.

So, what I am actually curious about are the following questions. Is our technology and knowledge of science at a sufficient level right now to detect any of these civilizations at the aforementioned specified distances? Which kind of astronomical techniques could we employ so that we could detect the presence of these civilizations? What standards should we set for ourselves in order to refine our search parameters to make our search easier?

[Borgholio]

The only way we can detect those kinds of civilizations is if they want us to. Even the "A" example will be undetectable unless they use a telescope the size of Aricebo to deliberately beam a radio transmission our way. The other civs don't use radio at all anymore, and we can't detect subspace or holonet transmissions. So again, it would only be possible if these civilizations deliberately broadcast radio in our direction.

[Napoleon the Clown]

Even if the civilization that's around our tech level was transmitting directly at us, we wouldn't know until 10000 years after the fact. For us to be getting the message now they'd have to have a 10000 year head start on us.

[Iroscato]

I don't know what the limits to sensitivity are, but couldn't we use modern telescopes like the Kepler (before it was damaged) or similiar, to detect impurities in the atmosphere? If so, we could probably detect the presence of a type l civilisation, if we assume they burn fossil fuels as we do. However, at a distance of 10,000 light years I very much doubt anything we currently have is advanced enough. As for the other two types, there's simply no way in hell we could detect them, unless the type ll has had radio technology for at least 25,000 years, and the type lll, at least several million years. And even THEN, I highly doubt artificial radio signals would be powerful enough to travel halfway across the galaxy, let alone from another galaxy.

[Guardsman Bass]

Could a Kepler-style telescope do spectrography on alien planets if it was sensitive enough? I always though you had to more or less direct-image the planet in question, and get a really good exposure on it if you wanted to figure out what its atmosphere was made of. Kepler just measured transits of planets in front of their stars.

We've got an astronomer or two on the board, so I'd be curious as to what they think about it.

The only way we can detect those kinds of civilizations is if they want us to. Even the "A" example will be undetectable unless they use a telescope the size of Aricebo to deliberately beam a radio transmission our way. The other civs don't use radio at all anymore, and we can't detect subspace or holonet transmissions. So again, it would only be possible if these civilizations deliberately broadcast radio in our direction.

SETI used to have an FAQ page that had the detection ranges for various Earth-borne radio signals if someone was looking for them with a 2000-meter diameter radio telescope. It was rather depressing - most of them weren't even detectable for any significant distance outside of the solar system, never mind from another star. The only exceptions were Arecibo (as you said) and some military radar signals.

[Borgholio]

Kepler can't to spectography, it just detects the planet transiting in front of the star. You need a huge fucking telescope to actually image the light reflected off the planet's atmosphere to get a reading and even then, the amount of gas in the air needs to be high enough to register. So you could probably tell by looking at Earth that we have Nitrogen, Oxygen, CO2, and maybe methane and such. That could very well indicate life but not civilization. I'm not aware of any purely artificial or synthetic gases we're pumping into the air that can be detected thousands of lightyears away...

[Guardsman Bass]

It would come down to how much you detect minute amounts of gases in exoplanet atmospheres, since industrial pollutants would be in the millions and billions PPM level. Trace amounts of sulfur dioxide in an otherwise Earth-like atmosphere might be a sign, although there are natural sources for it as well. Radioactive pollutants if they had a nuclear war.

Agreed on the telescope size. The only planets we've been able to direct-image and do spectroscopy on so far have been bigger than Jupiter.

[Simon_Jester]

One thing that might show up rather sharply would be the engine flares from spacecraft of a Star Wars-type civilization. The stars in the night sky would periodically show sudden increases in luminosity from these very bright, high acceleration engines. They couldn't really be picked out as visually distinct point sources, but we'd be wondering why all the stars in the night sky seem to sprout these mysterious 'extra' black-body radiation sources which bear no correlation to the physical characteristics of the star itself.

[Boeing 757]

One thing that might show up rather sharply would be the engine flares from spacecraft of a Star Wars-type civilization. The stars in the night sky would periodically show sudden increases in luminosity from these very bright, high acceleration engines. They couldn't really be picked out as visually distinct point sources, but we'd be wondering why all the stars in the night sky seem to sprout these mysterious 'extra' black-body radiation sources which bear no correlation to the physical characteristics of the star itself.

Interesting. Do you think that with our current technology we would be able to detect an event like the Death Star's destruction of Alderaan or the Battle of Endor?

How about the Mutara Nebula collapsing to form a planet instantaneously? Seeing an event like that would most likely have astronomers scratching their head.

As far as the spectrometry issue goes, how would a planet like Coruscant or even a Dyson Sphere appear to telescopes?

[Boeing 757]

The only way we can detect those kinds of civilizations is if they want us to. Even the "A" example will be undetectable unless they use a telescope the size of Aricebo to deliberately beam a radio transmission our way. The other civs don't use radio at all anymore, and we can't detect subspace or holonet transmissions. So again, it would only be possible if these civilizations deliberately broadcast radio in our direction.

So essentially there is no way of detecting a radio broadcast unless they are either A)within range or B)intentionally reaching out to others.

[LaCroix]

One thing that might show up rather sharply would be the engine flares from spacecraft of a Star Wars-type civilization. The stars in the night sky would periodically show sudden increases in luminosity from these very bright, high acceleration engines. They couldn't really be picked out as visually distinct point sources, but we'd be wondering why all the stars in the night sky seem to sprout these mysterious 'extra' black-body radiation sources which bear no correlation to the physical characteristics of the star itself.

In case of that civilisation, the sheer number of flights would probably resut in a saturation effect. We would probably simply think that the star in question must be huge and luminous, when in fact, it is barely the size of our sun.

Betelgeuze, I'm looking at you...

[Borgholio]

Interesting. Do you think that with our current technology we would be able to detect an event like the Death Star's destruction of Alderaan or the Battle of Endor?

Alderaan didn't seem to explode in a massive flash of light, it was somewhat subdued compared to, say, a supernova. I doubt we'd be able to see it unless we were looking right at it physically...and then we'd just see a small moon approaching and the planet breaking up.

How about the Mutara Nebula collapsing to form a planet instantaneously? Seeing an event like that would most likely have astronomers scratching their head.

Again, we'd have to be looking at it directly. I can't find any numbers on how big the thing is though. If the nebula is several lightyears across, we'd be able to see it easily. If it's not that big, we might have a hard time seeing it.

As far as the spectrometry issue goes, how would a planet like Coruscant or even a Dyson Sphere appear to telescopes?

Coruscant would show high levels of industrial pollutants, I'd expect. If we could image the surface we'd see large amounts of processed metals reflecting light. Dyson Sphere would be pitch black, we'd need to look at it via infrared.

Of course, all this is based on the assumption that we'd have a telescope sensitive enough to image an earth-like planet directly. We could build one, but we just don't have one yet.

[Borgholio]

So essentially there is no way of detecting a radio broadcast unless they are either A)within range or B)intentionally reaching out to others.

Correct.

[Borgholio]

Betelgeuze, I'm looking at you...

Eh? It's the size of the orbit of Jupiter...a tad bigger than our own sun.

[krakonfour]

We have to wait until a noticeable proportion of the sun is obscured by solar energy devices, or if an extraterrestrial emission of extreme wavelengths (x-ray, gamma) nowhere near a place where they could be naturally produced. Anti-matter/matter annihilations for example produce a distinctive wavelength which we could trace.

[LaCroix]

Betelgeuze, I'm looking at you...

Eh? It's the size of the orbit of Jupiter...a tad bigger than our own sun.

Not quite...

[Borgholio]

Depends on who you ask, really.

http://en.wikipedia.org/wiki/Betelgeuse#Diameter

The star is at the end of it's life and is shedding a shitload of mass. It could be as small as that picture, or it could be as large as the orbit of Saturn. It's hard to tell due to the amount of the star's envelope that is blowing away. The general consensus is that it is definitely larger than the orbit of Mars.

[Simon_Jester]

In case of that civilisation, the sheer number of flights would probably resut in a saturation effect. We would probably simply think that the star in question must be huge and luminous, when in fact, it is barely the size of our sun.

Betelgeuze, I'm looking at you...

No, because the light sources would come and go in highly variable ways, and would not form a remotely typical luminosity curve. Since most stars even in Star Wars don't have large fleets of spaceships moving around them at all times, I don't think it'd be a problem.

Alderaan didn't seem to explode in a massive flash of light, it was somewhat subdued compared to, say, a supernova. I doubt we'd be able to see it unless we were looking right at it physically...and then we'd just see a small moon approaching and the planet breaking up.

The energetics involved make me very suspicious of that; dumping enough energy onto a planet to blast it into rubble HAS to heat the material enough to make a very, very conspicuous source of hot matter that will glow.

[Borgholio]

The energetics involved make me very suspicious of that; dumping enough energy onto a planet to blast it into rubble HAS to heat the material enough to make a very, very conspicuous source of hot matter that will glow.

It might be one of those cinematic things where what they show on the screen is for dramatic effect, vs what would really happen if you dump 7,000 years worth of solar energy into a planet over a fraction of a second. So yeah I'm sure you're right, it'd be glowing hot for awhile.

[Irbis]

One thing that might show up rather sharply would be the engine flares from spacecraft of a Star Wars-type civilization. The stars in the night sky would periodically show sudden increases in luminosity from these very bright, high acceleration engines. They couldn't really be picked out as visually distinct point sources, but we'd be wondering why all the stars in the night sky seem to sprout these mysterious 'extra' black-body radiation sources which bear no correlation to the physical characteristics of the star itself.

Engine flares? Even something the size of SSD has flare the size... Let's see, it would be like trying to observe changes of Earth's luminosity (from Voyager I position) cased by single camp fire.

Stars are big, really big

[krakonfour]

One thing that might show up rather sharply would be the engine flares from spacecraft of a Star Wars-type civilization. The stars in the night sky would periodically show sudden increases in luminosity from these very bright, high acceleration engines. They couldn't really be picked out as visually distinct point sources, but we'd be wondering why all the stars in the night sky seem to sprout these mysterious 'extra' black-body radiation sources which bear no correlation to the physical characteristics of the star itself.

Engine flares? Even something the size of SSD has flare the size... Let's see, it would be like trying to observe changes of Earth's luminosity (from Voyager I position) cased by single camp fire.

Stars are big, really big

And we can already detect the Shuttle's maneuvering jets from Pluto. The main problem is distinguishing the heat signature from the myriad of other sources we can see, and having something like fusion (x-ray) or anti-matter (gamma rays) greatly helps putting the signature under the 'artificially produced' category.

[Borgholio]

And we can already detect the Shuttle's maneuvering jets from Pluto.

Really? I wasn't aware that we had any space telescopes out there.

http://en.wikipedia.org/wiki/File:Pale_Blue_Dot.png

Oh wait nevermind. Yep, there goes Discovery! I see it right there in the corner.

[Sky Captain]

One thing that might show up rather sharply would be the engine flares from spacecraft of a Star Wars-type civilization. The stars in the night sky would periodically show sudden increases in luminosity from these very bright, high acceleration engines. They couldn't really be picked out as visually distinct point sources, but we'd be wondering why all the stars in the night sky seem to sprout these mysterious 'extra' black-body radiation sources which bear no correlation to the physical characteristics of the star itself.

Engine flares? Even something the size of SSD has flare the size... Let's see, it would be like trying to observe changes of Earth's luminosity (from Voyager I position) cased by single camp fire.

Stars are big, really big

I guess engine burns of heavy vessels would stand out not because of visible light, but because most of the energy would be in the form of relativistic particles. That is assuming their engines operate like normal rockets by throwing stuff very fast out of the back. So in the end they may show up as a brief fluxes of high energy particles from a star that naturally should not emit anything like that.

[Borgholio]

I guess engine burns of heavy vessels would stand out not because of visible light, but because most of the energy would be in the form of relativistic particles. That is assuming their engines operate like normal rockets by throwing stuff very fast out of the back. So in the end they may show up as a brief fluxes of high energy particles from a star that naturally should not emit anything like that.

Stars emit a shit-ton of high energy particles, including neutrinos. What kind of particle could be emitted by engine exhaust that isn't created by a massive fusion reactor the size of...well...a star? Also, what are the odds of a large enough group of particles actually making it to Earth and be detected?

[Irbis]

I guess engine burns of heavy vessels would stand out not because of visible light, but because most of the energy would be in the form of relativistic particles. That is assuming their engines operate like normal rockets by throwing stuff very fast out of the back. So in the end they may show up as a brief fluxes of high energy particles from a star that naturally should not emit anything like that.

We are already observing anomalously powerful particles - sadly, space is kinda big and dispersion between from whatever they came from and here obscured all traces of their origin or starting position. These might even come from ISD engine for all we know, doesn't make us any closer to detecting any alien civilizations, though.