Falling, as little as possible.

Free-fall time to a centre of mass

A listener asked the question “How long would it take an object to fall into the Sun from one light year away”. The answer to this question turns out to be a Fantastic Physics Formula, which has been attributed to Arthur C Clarke (who also had geostationary orbits attributed to him). In reality, it could just as well be attributed to Johannes Kepler, since it’s really about the mathematics of an orbital system and the relationship between the distance of an object from the centre of mass of an orbital system and the orbital period of that object.

The Principle of Least Action

The principle of least action defines the path that an object will follow in time and space. It can also be used for other things, like defining the shape that something flexible will adopt in a gravity field under particular conditions, but defining the path of a projectile is its most common usage.

 

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