Aliens Watching Us

[mishalak]

Rather than detecting our radio waves first wouldn't an alien civilization, if at all curious about the possibility of life elsewhere, detect our planet first? Think about it. Unless we run into some unexpected problem we are likely to have built instruments capable of directly imaging planets nearby to our own before the end of the 21st century. Perhaps even before 2040.

So as I see it there are four possibilities.

One, there is a civilization of technologically advanced aliens that has been observing us using very powerful telescopes. If within 100 or 200 light years of earth they probably suspect the fact that we have a technological civilization based upon measuring the changes in our atmosphere brought on by industrialization. They might be deciding or have already sent a message on this basis and SETI could detect it at any time.

Two, there is a species of intelligent aliens within 100 light years of us, but they have yet to advance to technological civilization. We will detect their planet using our telescopes sometime in the next century and then keep the planet under observation. If they advance to technological civilization anytime after this and we're still watching we'll detect it, suspect what is going on, and then send a message of our own hoping they'll detect it.

Three, there are intelligent aliens, but they aren't interested in discovering life elsewhere. They've either turned inward after achieving technological civilization, or are not that interested or capable of technology. We'll discover their planet if close to ours in the next century, but we won't be able to guess they are there or even if we do we won't be able to contact them.

Four, the most likely possibility, is that there are no intelligent aliens anywhere close enough to earth to ever be detected.

Comments

[pompe]

Maybe the aliens have discovered Earth and noted the atmospheric composition, roughly, and so they know the planet is life-bearing but they can't be sure it has a civilization. CO2 and aerosol effects could be interpreted as "natural" - rising levels of volcanism, climate change, and so on. So the mainstream alien planetologists have pegged Earth 210 light years away as a life-bearing planet but only the fringe alien planetologists actually believe what they see is civilization.

[mishalak]

Yes, rising CO2 alone could just be natural processes. But I think it very likely that taken in combination with rising nitrous oxide levels that someone would say, "Hey, something is up here!" Which would lead to launching more sensitive instruments that could detect the persistent particulate pollution, peroxyacetyl nitrate, and volatile organics. And long before that you can be that without permission some enthusiast will beam a message on the off chance. I think it highly unlikely that a technological civilization will be able to control its enthusiasts anymore than ours could even with a world government.

[pompe]

Assuming the alien civilization knows what to look for. We're sort of doing the easy thing to assume another civilization will develop like we did and that we'll mirror them. What if the aliens went technologically advanced themselves without a large rise in fossil fuel use? What if their signatures of civilization would be, I don't know, say, evidence of wide-absorbtion photosynthesis in oceanoculture?

Or even worse... ...maybe the aliens can't scan thousands of planets continously. So the readings of rising CO2 levels might be decades, even centuries apart, and instead of doing more surveys they'd simply blame the old records on old unreliable instrumentation and put it in a Maybe pile.

[mishalak]

I'm going to turn that observation around the other way. What would get humans 'irresponsibly' speculating about intelligent life on a planet we know to be harboring life? Possibly any relatively sudden change in characteristics we can observe. A change in albedo that does not fit with previous seasonal variation. Novel chemical composition that does not fit with our model of that planet's volcanic and rock weathering cycle.

And how much observation time will there be? I would guess large amounts, much of it automated so that humans can go sifting through huge amounts of data with computers. I bet that it will be rather like finding the first planet. A group of scientists had three planet in their data, but did not know it until they re-sifted it looking for planets larger and closer to stars than they had previously suspected in response to the first discovery. One of the things that it seems like we are getting closer to as a civilization is better access to information in the long term. Look at the way google is getting things more organized and the ongoing decrease in the price of a kilobyte.

If I was going to write an SF story about first contact given what we know now I would have it happen by a graduate student using a new technique to look at old data sometime in the 24th century. And he finds a 'weird' result. He publishes a boring little paper and some SETI enthusiast reads it and gets all excited and builds his own little project to beam a message at this system for 20 years or so until he runs out of money or enthusiasm. And the aliens notice it 80 years later using a radio telescope looking for something else. It wouldn't necessarily have to be evidence of burning mass amounts of stuff, either. Industrialization by whatever path will result in massive changes, because there are always side effects. If we'd industrialized using massive numbers of reservoirs and dynamos there would be something that would stand out by 'suddenly' putting all that land under water.

If they are out there I think it more or less inevitable that we'll notice each other given the increasing capability of our instruments.