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It is a mathematical thing based on how orbits work. Orbits that are very close to a resonance but not quite there will tend towards being even closer, so it's
by FreeFull 7y ago
It is a mathematical thing based on how orbits work. Orbits that are very close to a resonance but not quite there will tend towards being even closer, so it's a stable system. If this wasn't the case, you wouldn't ever expect to observe anything like this, due to disturbances to the orbits (from other bodies tugging gravitationally on the objects) building up.
- mirekrusin 7y agoResonance is natural selection.
- lmilcin 7y agoNo, it is not. It would be if we saw many colliding orbits and only those that had resonance surviving in long run. But resonances are perfect ratios and no random orbits will ever have perfect ratios of orbit times. Instead what happens is that collisions seem to be extremely rare occurrence. Once two moons find themselves on close orbits they will tend to exchange energy until they find some kind of resonance that will keep true for a very long time until disturbed.
- mirekrusin 7y agoAnd what is your (absolute offset and) observation timeframe compered to the lifetime of the system?
- lmilcin 7y agoThere are simulations that show great deal of how and what is the likelihood of different systems forming.
- mirekrusin 7y agoYou simply cannot have long lived, same radius orbiting objects, they must stabilize on resonance to exist.
- patcon 7y agoIt might be more apt a metaphor than it seems...? Resonant orbits might not be natural selection, but they might participate in a form of thermodynamic selection: two simple forms and structures selecting for and reinforcing one another. They are both subsets of the same thermodynamic processes of structures/arrangements sticking arouns when they mutually support one another creating persistence in a chaotic system My understanding is that some folks believe there are similar mechanisms underlying the emergence of both -- a generalized form of selection between mutually reinforcing structures that encode elements of prediction of the chaotic environment they reside in, be that the periodicity of orbits (that "know* a stable path that will reasonably persist) or life itself (that have similar baked in prediction abilities we perceive subjectively as consciousness). Disclaimer: biochemist, technologist and armchair follower of complexity science
- gus_massa 7y agoThe idea is that the gravity of a moon affect the trajectory of the other moon and vice versa, until they are in resonance. It's a bad analogy, but it's closer to Lamarckism than Darwinism, but it's still a bad analogy. There are nothing similar to random mutations.
- mirekrusin 7y agoBy natural selection I meant that if you have two (or more) bodies on the same orbit they'll crash or they'll find stable orbit (resonance). Of course you see resonating ones because ones that wouldn't would collide millions of years ago.
- Aperocky 7y agoI agree that in principal most things are natural selection. The things that are not on a current time (a certain proportion of which bound to exist) frame are behaviors that will eventually be eliminated.
- kkylin 7y agoPresumably any moons that did not end up in a nice stable resonant orbit would have had a higher chance of being ejected or colliding with something.
- hcrisp 7y agoSo could two earth-sized planets be in resonant orbits around a sun that would otherwise intersect? If so, what does this mean for the definition of a planet as something which "clears the neighborhood"?