# Timepieces and Moving Parts

The sundial keeps time with the fewest number of moving parts.

Which timepiece has the most moving parts?

• Upvoting, because I don't think this deserves the downvote. an hourglass is a reasonable answer to this riddle, without getting too tricky and exotic. – ThePopMachine Oct 13 '14 at 20:27
• Does anyone have an estimate for the number of moving electrons in my smartphone? – Peter Taylor Oct 14 '14 at 15:19
• Should we narrow it down to timepieces made by humans? Otherwise, one could argue the entire universe as a means of keeping time for beings powerful enough. – Engineer Toast Jun 24 '15 at 12:24
• You could argue that. If we were in scifi.SE. – generalcrispy Jun 25 '15 at 17:53

Well, one with a lot of moving parts would be an hourglass. Each grain of salt is a 'moving part'. Just scale it up as big as is needed to trump other options.

• Many kinds of timepiece can be "scaled up as big as needed to trump other options" – Joe Oct 8 '14 at 13:20
• Mainly just added that to avoid the obvious question of 'I have this really small one minute hourglass, there's not that much sand in it.' – Tim Couwelier Oct 8 '14 at 13:22
• If we're counting each discrete particle of a fluid as separate moving parts, then a water clock beats an hourglass by about 20 orders of magnitude. But if you argue "each drop of water counts as a moving part, not each molecule", then the hourglass goes back to winning. – Kevin Oct 8 '14 at 13:39
• Yeah, it's a deep rabbit hole of "Molecules weakly attracted to each other by polar forces do count as separate moving parts, but molecules bound by strong covalent bonds don't count" and then the question becomes highly subjective based on where you draw the line. – Kevin Oct 8 '14 at 13:49
• If you take each molecule as one moving part, the sundial has by far the most moving parts! Given the giant size of the sun, I guess that this also holds for each other granularity that could possibly work with a fluid. – Alexander Oct 13 '14 at 12:58

A water clock.

A typical water clock might contain about $10^{25}$ water molecules. Compare to a paltry $10^{9}$ for an hourglass. (Give or take a couple of orders of magnitude)

The system of stars (including the sun) which we have used since antiquity.

Or maybe the body clock: http://en.wikipedia.org/wiki/Circadian_rhythm

The myriad year clock perhaps. It can be wound once every year and over 1000 parts: http://en.wikipedia.org/wiki/Myriad_year_clock

• The universe/cosmos/stars is a decent answer, but I'm looking for something specifically designed to keep time. – generalcrispy Oct 8 '14 at 13:03
• @generalcrispy are you sure this is a "puzzle"? at the moment it's seeming like a trivia quiz :p – d'alar'cop Oct 8 '14 at 13:13
• I'm beginning to think it's a trivia quiz. I'm learning more about timepieces than I expected to! – generalcrispy Oct 8 '14 at 13:20

The universe?

It keeps time as it contains all other known timepieces and it kind of defines what time is.

A floral clock.‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍

It might have hundreds of flowers on its hands, all moving together.

An atomic clock: if you count each atom as a time-keeping part, it has a gigantic number of these, all moving.

• The atoms themselves don't keep time... the mechanical parts observing the atoms do. Good guess, but there is actually a timepiece that has way more parts than an atomic clock. – generalcrispy Oct 8 '14 at 13:08