Tuesday, July 7, 2015

Stellar Death and Interstellar Escape

Imagine you are a member of an alien civilization. Further imagine it is one that has never done an interstellar voyage, although the technology is there to do it. You and everybody else in the civilization just never decided to do it. Your civilization has been around a long, long time, and your civilization is millennia or maybe thousands of millennia past the achievement of Asymptotic Technology, where you know everything there is to know. To be more specific, you personally don’t know it all, but the knowledge is around somewhere, in the master computer where all knowledge and history and anything else important is stored, and in the heads of various people. If you have a head, that is. Perhaps your brain is in your abdomen. That’s not important to this discussion. What is important is that you are trapped behind the Happy Life Great Filter.

Recall that a Great Filter is a reason why a planet never develops space travel. More exactly, it is a common reason why planets in general do not develop space travel, and is why people on Earth have not had alien visitors. A Great Filter is why nobody is going anywhere. It may be because there is nobody, and the Great Filter has prevented intelligent life from forming, with one known exception. But other possibilities exist to explain why nobody wants to visit Earth, and many of them occur when an alien civilization is well established, prosperous, smart, and able to take off for other stars, but just doesn’t. This blog is trying to figure out what we can about these Great Filters and other factors influencing interstellar travel or the lack of it.

Back to your life on your home planet. You have everything you want to eat, and the menu is varied every day. You do have some restrictions on your life, such as the need to recycle everything, but they are not onerous and machines exist to make it easy. You don’t have to work, but there are plenty of interesting occupations you can do for a while when you want to. Art is there, and you can become an artist if you want, or you can enjoy fabulous art of every variety possible, which includes lots of things an Earther might have a hard time imagining because they haven’t been invented here yet. Population has been stabilized for ever as has the production of energy and all the things you use in your life. You breath clean filtered air, as the recycling systems take out anything except what it is that your organism likes to breathe, maybe oxygen, maybe nitrogen, maybe methane, maybe carbon monoxide, but whatever it is your lungs or gills or some other organ require, you have it in a perfect balance. Maybe every day you look at the media and learn what the parade is today so you can decide if you want to go, and when the shows begin, and what parties are open still, and take in a little comedy while you are still absorbing the media, and a little news, although not much really happens.

The news announcements give some stories about who was elected to be the principal speaker at the upcoming festival, the latest menu creations of three members of your civilization who decided to become chefs, although a chef in your civilization isn’t anything like a chef was back on Earth before you began imagining. A news bit comes on about a graduation ceremony, and another about the passing away of someone who was known for his splendid artistic achievements, in several media successively, and then a bit about some information from one of the orbiting observatories that the sun is dying, and the planet will be destroyed soon, and then it goes on to describe the overhead displays at tomorrow’s party in the central auditorium.

A little bell rings inside your brain. Stellar death? Planetary destruction? That’s interesting. You tell the media controller to get the master computer to tell you about that. Within an instant, a beautifully formatted, well laid out presentation starts. Hmmm. Maybe somebody else already asked for this so it was ready for you. It goes on about the varieties of stars in the galaxy, ranging from the very hot giant O stars down to the cool red dwarfs, and how they all have lifetimes, and evolve through time as the nuclear fuel is burned. You may never have been outside to look at the sun, but you know what type it is by what kind of eyes you have – if you see UV very well, it’s probably an early sequence giant and your planet is far away from it. If you see IR very well, it’s probably a red dwarf, and your planet is close by its star in order to be habitable. They all evolve, maybe burning up their planets, and you have absolutely no problem in understanding the nuclear physics that the presentation contains, because, after all, you are the product of asymptotic genetics and have the best intelligence genes science can devise.

So, you tell the master computer you want to work on the problem of stellar death and planetary destruction, and help design and build your civilization’s first ever starship. The master computer takes your ID down, but informs you that the entire planet has volunteered. Well, that’s nice. It means that there is an important meme existing that was taught to you right after you broke out of your cocoon, or metamorphosed, or whatever you did to become sentient. The meme said: “You do whatever is necessary for the civilization to survive.”

Time to stop imagining and come back to Earth. It is fairly clear that some Great Filters which have kept the alien civilizations of the Sagittarius arm of the Milky Way from coming here are not immune to galactic perils, like the death of the star, or to be more specific, to changes in the character of the star which will render a planet inhabited by an advanced alien civilization uninhabitable. Of course they would see it coming long in advance, as asymptotic astrophysics would be able to predict the course of evolution of stars of every type in the galaxy. We on Earth are not there yet, but we are advancing in that direction quite clearly.

There may be other filters which are impervious to impending planetary destruction, such as Idiocracy, where the population does not have the mental abilities to construct a starship successfully. We have not yet figured out what all the Great Filter candidates might be, nor how many of which ones might actually be the obstacles blocking alien civilizations from star-faring. But some, like the Happy Life Great Filter, are prime candidates to cease their existence when the survival of the civilization is put at risk.

Possibly there is another planet in the same solar system they can just jump out to, and over the course of a million years, which is short in stellar evolution times, except for the very biggest stars or the very earliest stars, they can move their civilization to it. This depends on where the planet is, what resources it has, and how much terraforming (planet-forming might be a better word as their planet could be nothing like Earth) is needed. But if there is no planet there which is suitable, they are forced into interstellar travel, and in a unique way.

What they would do, as they do not have the meme for colonization of other planets or even exploring the galaxy in person, is travel once to a suitable planet. Then they stay there forever, meaning until the new star has problems.

Stellar evolution timescales are so long that the civilization would not all have to rush to get off the planet. Members could live out their lives, while a seed population could travel to another home. Perhaps, in order to carry everything necessary, there would have to have a large number of ships, but not anything like the number needed to carry all the population’s members to the new planet. Sooner or later, there would be a final ship with the last members of the civilization, and they would turn the lights out on their former home, leaving it to burn up when the star gets around to it.

In this situation, space travel would not be non-existent, but it would be rare. Stars do not die frequently. If the population of the stars in the Milky Way is a hundred billion, with one intelligent civilization per ten solar systems, and the lifetime is five billion years, something of the order of two civilizations a year go under. If a stellar emigration to the nearest planet suitable for some civilization’s new home is a couple of hundred light years in distance, and they travel at 5% of light speed, meaning a trip lasts two thousand years, at any time in the galaxy at the most there should be only about four thousand emigrations going on. With a galaxy as large as ours, that’s hardly any. But it’s not zero, and depending on how the ships work, they might someday be visible, assuming we figured out how to build a ship and then what its signatures might be, as well as how to build a giant observatory to see one, and so on. If there is a long string of starships heading along the same path, for possibly centuries of shipping, it would be much easier to see them, but we don’t understand yet how many ships they might need.

Searching for emigrant starship trains might be a more productive way to find alien civilizations than SETI, but since we don’t understand much yet about alien civilizations, there might be a truly excellent and ingenious way to do SETI so it works. Wait for it.

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