The Test(ing) of Time: The Surprisingly Good Hourglass
[The results are] better than I expect for cheap plastic timers that sell for less than $1 each– the uncertainty in the time is about 0.3% of the time, which is pretty darn good. But it’s actually much more interesting than that, if you dig into the data a little.
(Which reminds me I have a half-written timing post that somebody needs to finish)
From the citation, “..even cheap plastic made-in-China crap holds some surprises…” Yeah, like their over-achieving graduate students versus the US diversity standard of indolence and ignorance.
Jamming hinders particle flow, as does countercurrent gas flow. Decoupling force and direction breaks symmetry and allows exits. Upscale hourglasses use steel microbeads to prevent static charging. Type IIb boron-doped electrically conductive diamond dust would be interesting. Forming the containing diamond hourglass is left as an exercise for the alert reader.
Dry sand deeper than the length of a test can; three otherwise identical test cans: Sealed on both sides, one base removed, both bases removed. Perpendicularly shove into the sand The middle one shoots right in. It is all about airflow expanding the close-packed dilatant fluid.
Far out and solid!