[conservatism_IS_compassion]

Actually, the clock was extremely useful when the STARs and Planets were not visible.

Longitude and the Académie Royale

That link is exceedingly interesting. But it doesn’t indicate that anyone can navigate using a clock alone, without reference to celestial observation.

Once the timing of the Moons of Saturn/Jupiter were well know, and printed in an almanac; then any old 'clock' could be reset to a fairly accurate time.

Back then, “any old clock” was pretty worthless for keeping time on board a ship at sea. They were all pendulum clocks, and it turned out that gravity was enough of a variable with location that you just couldn’t “set your watch” by a pendulum clock at sea.

[Elsie]

But it doesn’t indicate that anyone can navigate using a clock alone, without reference to celestial observation.

Of course; one CANNOT navigate ANYWHERE without some 'reference' to SOMETHING.

---

They were all pendulum clocks, and it turned out that gravity was enough of a variable with location that you just couldn’t “set your watch” by a pendulum clock at sea.

Uh; not the 'gravity', but the fact that the clock had nothing stable to sit upon.

[Elsie]

Fun extra point puzzle.

A penguin is sitting on the South Pole.

If he (she?) walks one mile North,
then turns left and walks one mile West,
then turns left again and walks one mile South;
how far away will it be from the South pole?