But it is also possible, perhaps likely, that some coincidences are in fact higher-level resonances between groups of planets. These would be multi-body proble

But it is also possible, perhaps likely, that some coincidences are in fact higher-level resonances between groups of planets. These would be multi-body problems that may take thousand or millions of years to react to perturbations. The calculations for these may well be beyond our current capabilities to detect (3+ body problems).