Pendulums swing at a rate determined mostly by their length rather than by their weight.

The longer version

Gravity pulls each bob with a force proportional to its mass, while the mass also resists acceleration in the same proportion, so the two effects cancel. What remains is the geometry: a longer swing arm takes more time to complete one arc. Amplitude matters slightly, which is why small swings are preferred.

Doubling the weight changes nothing measurable; lengthening the arm by four times doubles the period. This independence surprised early experimenters and made the device practical, since a clock could be regulated by adjusting one screw rather than rebuilding its whole mechanism. Temperature therefore matters more than load, as heat lengthens the rod.

Where this entry sits

These facts wander through clocks, calendars, time zones, and the long human effort to measure passing hours. You will find leap years, odd month lengths, ancient sundials, and the reasons modern timekeeping works the way it does. The full list sits on the Time and Calendars page, where every entry is listed in order.