Wednesday, July 8, 2015

Perils of the Galaxy

If we want to detect aliens unaware, we might look for emigration trains leaving from a doomed planet. Here, doomed means it has a while to remain habitable, but not too long. All planets are doomed, of course, but alien civilizations can live on them for long periods compared to the time needed to emigrate. They can delay emigration until they have to, or they can gradually transfer their civilization to another better planet.

Habitable here means it is possible to have a civilization on it, not that it can just barely support life. A planet which enters a volcanic phase doesn’t exterminate all life on it, but if the volcanoes are frequent and massive, spewing out dust and magma on a daily basis, not just in one location but in many, living within an advanced civilization there becomes untenable. Lower animals could survive and maintain some populations, and certainly lower life forms such as single-celled organisms would go on, and if this particular planet were blessed with cockroaches, they would pull through because they always do. An advanced civilization, living in large cities and recycling everything, requiring large energy sources, and having designed its infrastructure for better times, would need to leave. If the volcanism started slowly, so over the lifetime of a single alien, not too much changed, but over the lifetime of twenty generations, things were markedly worse, there would be time to gracefully make for the exit. Exactly how fast does a change from peaceful tectonic conditions to large lava fields take? Something much shorter than geologic times, perhaps, but still long enough to construct star ships and move away.

This has implications for us here on Earth. No, there are no known predictions that volcanism is on the rise here, but if our ability to examine exo-planets, and get some spectral information on them, continues to follow its present trajectory, we might be able to see the onset of volcanism on one, if we maintained a course of monitoring nearby planets for some centuries. If we could also see a signature of a star ship, perhaps the propulsion system or the exhaust’s infrared signature, or the heating of deflected interstellar gas, or some such thing someone else will think of, then we could correlate it, and understand what was happening. Seeing a planet become different might be a clue to turn our star ship detecting instruments in that direction and perhaps see some of the ships. We would know that we are not alone, even though nobody ever contacts us. Could we, with a couple more centuries of experience in building astronomic imaging devices, see something traveling at a good fraction of the speed of light? If might be very observable.

Some of the Great Filters, those things which block just about every planet from emitting star-traveling aliens, might be overturned. The Happy Life Great Filter, meaning that an alien civilization is content to simply enjoy itself rather than dispersing all over the galaxy, comes to an end if the planet becomes doomed. It would do us good if we could detect these events, and use them as clues that someone might be about to leave.

A peril is used here to mean something that renders the alien civilization’s life on the planet impossible. A long catalog of them can easily be created. There are things which disturb the temperature of the planet, such as something happening to the star it orbits, because of normal stellar evolution or some galactic event. There might be something which disturbs the orbit of the planet, like a rogue Jupiter drifting into the solar system on its way across the galaxy. Rogue planets are things that have only recently been recognized by us as existing in the galaxy, but there may be very many of them. Solar systems are tiny compared to galactic distances, but sometimes the dart hits the bullseye even at ten paces.

The peril everyone knows about are supernovas, and we should probably also include other star types which exhibit abrupt significant changes in output. Supernovas blow up suddenly, but perhaps there are visible signs or ways to predict the blowup and to know when it was going to occur, so that preparations for dealing with it can be made. If both alien astronomers and our astronomers knew just what to measure and look for on stars with supernova potential, they could plan to leave and we could plan to watch them leave, just like Poirot on a stakeout.

There might even be self-induced problems on the planet. If the alien civilization had been somewhat slow in approaching asymptotic technology, and one of the gaps in their knowledge was a terrible one, something could go wrong and they could spoil the planet. We don’t understand what types of power sources they would use, but perhaps there were toxics connected with it and they escaped, and were gradually seeping all around the planet. Time to pull up stakes and leave, from the opposite side of the planet. Could we see the power station blow? Maybe.

Could there be orbital problems? The star is in orbit around the galactic center of mass, and the flow of other stars around that center of mass is statistical, not like the smooth flow of a liquid, but like the flow of a gas, with chaotic motions. Perhaps the relative motion of two stars is such that they come close. Perhaps something related to the magnetic fields that permeate the galactic arms could change over a period where it would make a difference. They shield against charged particle flows, and if they changed, or if the star migrated into a region where the protection was diminished, something might happen. This is now beyond our Earth knowledge, but it is not something beyond what we might have as astronomical knowledge in the not-too-distant future. Any of these things as affecting a planet close enough for us to observe might give us the clue we need to prove we are not the only intelligent creatures in the Sagittarius Arm of the Milky Way. Even if we are not worth contacting in our own right, we can be spectators and watch things happen.

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