Saturday, December 30, 2017

Asteroid Defense


We live in a fairly benign solar system. Earth has not had a major asteroid impact for 60 million years, however, that one was an extinction event. Large asteroids hitting an inhabited planet can create large shock waves that sweep through the atmosphere, megatsunamis that can cover almost all of the land surface, dust to fill the atmosphere and block photosynthesis long enough for most plant life to die, vulcanism at the impact site or at the antipodal point, or simply pumping so much heat energy into the atmosphere that non-aquatic life mostly dies out, as well as near-surface dwelling sea life.

In a solar system with more frequent extinction events, with the events happening more frequently than the recovery time needed by life on the planet, asteroid impacts might simply result in almost uninhabited planets, with only single-celled organisms or perhaps small creatures remaining. Is it possible that these are the norm? If so, it could prevent any alien species from ever arising and taking on the job of traveling to other solar systems beyond their own. Earth, as an exception to this norm, would be alone in the galaxy.

Asteroid impacts consume asteroids. Each time an asteroid hits a planet or a satellite, it is destroyed and there is then one less asteroid to impact a planet later. Asteroids do not typically form after the formation time of the planets, so any period of heavy consumption will free up later periods to have periods long enough for intelligent life to form. Astronomers like to talk about the Early Heavy Bombardment, when there were many more asteroids than now, and very many of them were hitting planets and satellites. One might assume it was a sort of random process, and try to figure out the decay time of the rate. If it was short enough, an alien planet might become free of asteroid impacts early on, and easily proceed to evolve all manner of life. If it was long, meaning the cleaning process to remove asteroids did not work very quickly, asteroid collisions would be spaced out so that impacts, not being common initially, did their work for a long time.

Where the asteroids are, and what type of orbits they occupy, makes a great deal of difference in this cleaning process. If there were only a few large asteroids, and they occupied stable orbits in reference to a couple of shepherding gas giants, there would be no collisions, just like we do not expect Mars to hit Earth any time soon. The only problem is that this doesn’t work as well with tiny bodies like asteroids, as there is likely to have to be some dissipative forces to move planets into stable orbits, relative to the gas giants. Asteroids are too small to have enough of these, as they would go as a second power or higher of the mass of the asteroid. Thus asteroids just keep the orbits they were born with, unless they do a gravitational slingshot with a giant planet. They may be in the vicinity of a stable orbit relative to the shepherding gas giants, but not as close as a rocky planet or something larger.

The sweeping clean of orbital areas should be proportional to the cross section of impact, and a gas giant has hundreds of times the cross section for collision that a small planet would. Thus, those orbits which intersect the gas giant’s orbits are likely to get swept clean early on, but not the orbits which intersect the small planet’s orbit. The orbits from which a gravitational slingshot can happen are those which will be swept clean early, so the later periods of a solar system would be when asteroids were concentrated in the areas where there were minor planets, which are the ones where life can form.

Let’s do some numbers on asteroid collisions. First, suppose there was an asteroid in an orbit similar to Earth’s, fairly circular, in the same stable notch caused by the gas giants. That notch might be of the order of a quarter of the distance from the mean orbital radius of Earth to that of Mars. The cross section of Earth compared to the cross-section of the notch, assuming it is circular is of the order of ten to the seventh. If the difference in periods is about ten percent, this implies the cleaning of Earth’s co-orbital vicinity is short compared to the age of the solar system. But for asteroids not in co-orbit with the Earth, another factor, comparable to the radius of the Earth and the radius of its orbit, about a million, comes into play. This makes the cleaning time much longer than the age of the solar system, and implies that for some solar system like our own, with an Earth-sized alien planet at something like the radius of Earth from its star, asteroids will be coming for the whole lifetime of the solar system.

As soon as an alien civilization became expert at astronomy, it would realize this peril existed. Probably there would be geological evidence of the same thing. Thus, asteroid defense would be considered. Is it feasible that an alien civilization could prevent an asteroid from hitting their planet?

Destroying a larger asteroid is probably impossible, but fracturing one into two pieces might work for some of them. However, the destruction operation is likely to involve large amounts of explosive, which means that the resulting course of the pieces is uncertain. This would therefore have to be done far away from the planet to allow the pieces to go far wide of the alien planet. Other asteroids, larger ones, might be impossible to fracture. Diverting them would be possible, if their orbits were sufficiently precisely determined.

Before any destruction or diversion can happen, the asteroids would all have to be located and tracked. Those with the possibility of crossing the orbital radius of the alien planet would have to be tracked more precisely. Could the alien planet find the resources to do this? If the number of asteroids was in the millions and their orbits ranged over the whole solar system, they might not.

The other defense, a backstop to anything else, is to make self-sufficient outposts on other planets or satellites so that if there was a large collision with an asteroid, it would not spell complete extinction of the alien species. This raises the question of whether in a typical solar system, if a very competent and dedicated alien species could figure a way to sustain life on at least one other planet or moon in the absence of support from the home planet. Would doing that leave any signatures that could be detected from Earth with a sufficiently large telescope or other observing devices?

Saturday, December 9, 2017

Alpha Pair Strategies in Alien Civilizations


Many animals here on Earth use alpha pair strategies to control reproduction in times and locations where scarcity prevails. Primates, canines, birds, and others have been observed using it, and there are probably many others as well. In short, the strategy involves the formation of a group of one species, usually incorporating both sexes, which hunt or forage together. There is an accepted strategy for selecting an alpha pair, who are the dominant animals of the group. They get the first food and are the only ones or the preferred ones to breed. Others in the group may serve as assistants, or protectors or nurturers of the alpha pair’s children. There may be a second tier, the betas, who get some of the privileges that the alphas get.

This is not the same as territorial domination, but it may co-exist with it. With territorial domination, a pair, or a single sex of a pair, may take actions to exclude others of the same sex and species from hunting or foraging within an area controlled by the alpha. With the hunting region divided into territories, some animals of the species will get none, which is the equivalent of them not achieving alpha status and having reduced chances for breeding. The alpha pair strategy and territorial domination achieve the same goal over the long term: animals who can achieve dominance feed better and breed more. Successive generations will emphasize the traits involved in the competition, rather than traits necessarily concerned with survival in the environment.

Alien civilizations face the threat of idiocracy, or some other type of dysgenics, once they pass the industrial revolution and affluence takes hold. With a negative correlation between reproduction rate and any positive attribute, the average of that attribute will decline with time. The period between when affluence hits at least part of the population and the time when genetics is taken control of after the genetics grand transformation is when the population is vulnerable to this effect. It may be that no response is given, even that no notice of the problem exists in some particular alien civilization, or it may be that they debate what strategy should be followed to abate it.

The only government reproduction policy that has been effected here on Earth is the one-child policy by China. For the period 1979 until 2015, only one child was allowed for many women, and forcible involuntary contraception implantation or sterilization was used to enforce the rule. There were numbers of exceptions, allowing typically two children, in cases where a child was handicapped, or even if the first child was female. This policy had debatable results, as reproduction rate was already declining before the policy, and it has declined in some other areas which did not have such a policy. Most likely, it exaggerated an already strong trend toward lower reproduction rates. This type of policy is ostensibly neutral toward dysgenics, in that it allows the same dysgenic effects to occur as would occur without them, but perhaps reduces their effects by disallowing large families.

To control this problem, an alien planet might have a similar policy. But can alternatives exist? Is it possible that an alien population might be descended from pre-intelligent animals that employed the alpha pair strategy? Humankind’s exact ancestors are long extinct, but related animals, the higher primates, have strategies of this kind, or something similar, such as the bonobo’s alpha female strategy. When and why might it be lost, and would the same transition necessarily occur in alien populations on similar planets?

Reproduction rates on the gene or chromosome level are determined by two factors, survival of the individual carrying those genes to reproductive maturity, and then reproduction of the individual. The transition to a different reproductive strategy might occur with the transition from an individual hunter-gatherer culture to a clan hunting culture. Hunting large prey which requires the cooperation of a group of hunters means that there must be some tendency toward equality of activity or sharing of the rewards of the hunt. This sociological trend is referred to as the ‘big man’ strategy of food-sharing, in which status, and therefore leadership, is given to the person who arranges for others to eat. This means that survival to a degree is now decoupled from individual capabilities, and these capabilities are sorted out for reproduction in a different way. Individual hunters reproduced because they were good at hunting and therefore found mates. This might be correlated with strength or balance or tool-using ability. Group hunters all share in the spoils of the hunt, and leadership of the group is given to the individual who organizes the hunt the best. These qualities are mostly mental, although obviously good physical characteristics are needed. Thus, intelligence is supported if there is a breeding strategy that rewards the hunt leaders.

If the group is large enough, it cannot reproduce sufficiently if an alpha pair strategy is followed. Population will decline and hunting of large prey will become more difficult with a smaller group. However, if there is a multilevel hierarchy, and reproductive rights only go to the alpha and betas, then reproduction might be adequate to maintain the population of the group and allow it to continue to preserve itself and its strategy. This policy is vulnerable to the departure of the non-selected, either in pairs or in groups, in a schism of the group. Polygyny or polyandry would tend to make the formation of the schism less likely, as would the provision of food from successful hunting. If hunting is difficult, staying for the food might outweigh leaving for reproduction opportunities.

From what limited pre-historical resources we have, it appears that humankind shifted to a monogamy strategy early on, and did not follow any type of alpha pair strategy. This left them vulnerable to dysgenics unless there was not a negative correlation with capability, but positive. The positive correlation solves the problem completely. So the question to ask about is what leads to a negative correlation of productive capability with reproduction? To see if any of these strategies might be profitably used by an alien civilization requires some more thinking about the timing and causes behind the changes in human society.