[LeoPanthera]

I would imagine that analogue randomness is easier than doing it in a deterministic digital system. Surely there are all sorts of creative methods. Dice or coins in a box? A ball falling through a galton board? Sampling a double-pendulum? Floating particles in a heated liquid?

[bombcar]

All of those things I know how to use - if I have some sort of digital measuring device watching/monitoring them.

How do I make a mechanical thing happen at a random time with a lava lamp?

The ball on the board with a hole might be something I could figure out …

[addaon]

> How do I make a mechanical thing happen at a random time with a lava lamp?

Use a heat lamp interrupted by the lava globules to activate a wax motor. If you get the angles right you can probably do this with the same light that runs the lamp itself, or you can put another lamp at a 90° angle (but will have to adjust the main lamp to keep the total heat at the level you want).

Or do similar with muscle wire; more temperature needed to trigger the actuator, but you can get them much smaller so the total heat can be smaller, if you run e.g. a collimated infrared laser as your heater across the lamp.