So I was thinking about the longitude problem, which was the problem of determining the longitude at sea. It caused great problems in sea navigation. See: https://en.wikipedia.org/wiki/Longitude#Determination
Ultimately it was solved by proper clocks I believe. And I wondered if it could also be solved by a continuously running gyroscope that was started (and resetted) at ports where the longitude was known. Would this have solved the problem? Could it even practically be done? Maybe you could've used mirrors to measure small angles like in the cavendish experiment. It would need to be regularly sped up but maybe you could've used something like a weight-falling device.