If there were two exact replicas of Earth in the solar system (both in an equally habitable and stable orbits), with all of the people included, how would they diverge economically and technologically? Would they develop in parallel?
closed as primarily opinion-based by RonJohn, Vincent, L.Dutch♦, dot_Sp0T, Secespitus May 16 '18 at 7:04
Many good questions generate some degree of opinion based on expert experience, but answers to this question will tend to be almost entirely based on opinions, rather than facts, references, or specific expertise. If this question can be reworded to fit the rules in the help center, please edit the question.
Chaos theory kinda forces these two earths to diverge in drastic ways regardless of the closeness of their starting conditions. Maybe the Cuban missile crisis triggered a thermonuclear war, maybe William Shakespeare advocated for a democratic republic in Britain, maybe the Assyrian empire conquered Persia, maybe all the first humans were eaten by wolfs, and maybe its maybelline.
how would they diverge economically and technologically?
They would not diverge.
Because they would not be.
The habitable zone around our Sun is too narrow, allowung only for a single planet. If two planets have very.similar orbits, they crash in a few million years.
It happened before. Theia, about the size of Mars, shared an orbit with the Earth for a few dozens if millions of years. They ultimately collided, and what was left of Theia became the Moon.
If instead of a Mars sized planet the Earth had been hit by two other Earths, we would probably have a planet much bigger and very different from Earth. There is no telling how life would evolve on it, so we can't even speculate about any societies that could arise on it.
If you assume that the worlds can diverge, then they will.
Perfectly coupled worlds, where an event could only take place if it is simultaneously taking place in the other world are by definition, not capable of diverging.
Non-perfectly coupled worlds would diverge quickly, for one simple reason. A radioactive atom is known to decay, but the time at which such an atom is to decay is provably unknowable. In a population we can talk about the rate on average; but, for any single atom, the time is not predictable.
Therefore in worlds that can diverge, two lumps of radioactive elements would decay at the same rate, but the actual atoms within those lumps, compared to their counterparts on the other world, would decay at different times.
One can easily extrapolate that if one of the atoms can decay later than its counterpart, it might trigger an effect that was felt at different times between the two worlds. The accumulation of these difference would eventually lead to different worlds.
The key to the answer is timing: when do you start the identical copy and at what timescales do you look for divergence? If, as you seem to suggest by with all people included, this is rather late, the question is rather interesting.
From one point of view, more social-science-centered, because it introduces the (old) question of free will. If you assume that there is indeed free will and not just the appearance thereof, divergence will be fast and interesting from the storytelling point of view. It will allow you to think about whose individual decisions are the ones that, being almost equally probable, have the most intense diverging effects.
From the other point of view, a little more physics-centered, because it plays with the concepts of minima vs saddle points in trajectories. In some systems that are very stable (also in some parts of societies), circumstances will be convergent so that small deviations have a negligible effect; this is what happens in minima within an energy landscape. More dynamical, this is when we slide down a valley where there is only downward slope in one direction, so the dynamics are robust. In other, more unstable (or also: chaotic) systems, circumstances will be such that a minor deviation will have an effectively infinite effect; this happens in a saddle point, which has two equally downward directions to choose from: there, the dynamics are fragile. As beautifully shown by mechanical saddle trap videos, there are some circumstances where small deviations tend to be cancelled, even in saddle points. Also in societies, this can happen in strongly driven or full or control mechanisms. So this gives you space to think about the regulating mechanisms of your societies and where the societal instabilities/saddle points lie, in terms of different possible&similarly-likely society dynamics.