Shortly after discovering the law of gravity, Isaac Newton wondered whether it would allow our Solar System to remain stable. At face value, the problem seems trivial. The gravitational perturbations the planets exert on one another are at least 1000 times smaller than the dominant central force from the Sun. The catch is that the relevant timescales are astronomical. Planetary systems like our own live for roughly 10 billion years (10 Gyr) before their central star runs out of nuclear fuel. Do these tiny gravitational tugs then simply average out, or can their effects build up and lead to instabilities and planetary collisions over such long timescales?
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