# Does an hourglass weigh less while sand is falling? **URL:** \ **Category:** Factual Questions\ **Created:** [July 28, 2024, 2:08pm UTC](https://boards.straightdope.com/t/does-an-hourglass-weigh-less-while-sand-is-falling/1004895 "2024-07-28T14:08:21Z")\ **Posts on this page:** 18\ **Page:** 2
**Author:** ![jjakucyk](https://avatars.discourse-cdn.com/v4/letter/j/3d9bf3/32.png) [@jjakucyk](https://boards.straightdope.com/u/jjakucyk)\ **Post date:** [July 29, 2024, 7:25pm UTC](https://boards.straightdope.com/t/does-an-hourglass-weigh-less-while-sand-is-falling/1004895/21 "2024-07-29T19:25:21Z")
I doubt that statement is entirely accurate either, sir. ---
**Author:** ![markn\_1](https://avatars.discourse-cdn.com/v4/letter/m/f9ae1b/32.png) [@markn\_1](https://boards.straightdope.com/u/markn_1)\ **Post date:** [July 29, 2024, 7:47pm UTC](https://boards.straightdope.com/t/does-an-hourglass-weigh-less-while-sand-is-falling/1004895/22 "2024-07-29T19:47:26Z")
It only works if the bottom of the ship is porous, but then you’ve got another problem. ---
**Author:** ![jjakucyk](https://avatars.discourse-cdn.com/v4/letter/j/3d9bf3/32.png) [@jjakucyk](https://boards.straightdope.com/u/jjakucyk)\ **Post date:** [July 29, 2024, 8:02pm UTC](https://boards.straightdope.com/t/does-an-hourglass-weigh-less-while-sand-is-falling/1004895/23 "2024-07-29T20:02:29Z")
It’s not that kind of ship 😉 ---
**Author:** ![running\_coach](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/running_coach/32/15836_2.png) [@running\_coach](https://boards.straightdope.com/u/running_coach)\ **Post date:** [July 29, 2024, 9:21pm UTC](https://boards.straightdope.com/t/does-an-hourglass-weigh-less-while-sand-is-falling/1004895/24 "2024-07-29T21:21:16Z")
> [@markn\_1](#): > > It only works if the bottom of the ship is porous, but then you’ve got another problem. - > [@jjakucyk](#): > > It’s not that kind of ship 😉 - It’s an entirely different kind of sinking, altogether. ---
**Author:** ![Crafter\_Man](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/crafter_man/32/458_2.png) [@Crafter\_Man](https://boards.straightdope.com/u/Crafter_Man)\ **Post date:** [July 29, 2024, 9:34pm UTC](https://boards.straightdope.com/t/does-an-hourglass-weigh-less-while-sand-is-falling/1004895/25 "2024-07-29T21:34:16Z")
> [@jnglmassiv](#): > > Yes, they measure a bunch of forces, not just weight. If you mount the balance horizontally and press on the pan, it will respond though nothing is meaningfully weighed. Correct. But if you were to mount it horizontally, and gently push on the pan, the balance will push the pan back to it original position. It will then measure the amount of force it is producing to maintain the original position. ---
**Author:** ![Lucas\_Jackson](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lucas_jackson/32/303_2.png) [@Lucas\_Jackson](https://boards.straightdope.com/u/Lucas_Jackson)\ **Post date:** [July 29, 2024, 10:49pm UTC](https://boards.straightdope.com/t/does-an-hourglass-weigh-less-while-sand-is-falling/1004895/26 "2024-07-29T22:49:32Z")
> [@Chronos](#): > > It’s more of a frogs-in-a-truck problem. Only tangentially related to the frogs-on-a-treadmill problem. ---
**Author:** ![Stratocaster](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/stratocaster/32/16393_2.png) [@Stratocaster](https://boards.straightdope.com/u/Stratocaster)\ **Post date:** [July 29, 2024, 11:58pm UTC](https://boards.straightdope.com/t/does-an-hourglass-weigh-less-while-sand-is-falling/1004895/27 "2024-07-29T23:58:21Z")
Just keep ‘em out of a pot of water if you plan on turning the burner on. ---
**Author:** ![Crafter\_Man](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/crafter_man/32/458_2.png) [@Crafter\_Man](https://boards.straightdope.com/u/Crafter_Man)\ **Post date:** [July 30, 2024, 12:04am UTC](https://boards.straightdope.com/t/does-an-hourglass-weigh-less-while-sand-is-falling/1004895/28 "2024-07-30T00:04:32Z")
Speaking of which… what would happen if the hourglass were attached to a vertical treadmill? ---
**Author:** ![ekedolphin](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ekedolphin/32/10003_2.png) [@ekedolphin](https://boards.straightdope.com/u/ekedolphin)\ **Post date:** [July 30, 2024, 12:30am UTC](https://boards.straightdope.com/t/does-an-hourglass-weigh-less-while-sand-is-falling/1004895/29 "2024-07-30T00:30:53Z")
You understood the reference! ---
**Author:** ![jjakucyk](https://avatars.discourse-cdn.com/v4/letter/j/3d9bf3/32.png) [@jjakucyk](https://boards.straightdope.com/u/jjakucyk)\ **Post date:** [July 30, 2024, 1:11am UTC](https://boards.straightdope.com/t/does-an-hourglass-weigh-less-while-sand-is-falling/1004895/30 "2024-07-30T01:11:04Z")
Of course I do. It is a witticism, a gag, a bon mot, a fluctuation of words concluding with a trick ending. 🙂 ---
**Author:** ![markn\_1](https://avatars.discourse-cdn.com/v4/letter/m/f9ae1b/32.png) [@markn\_1](https://boards.straightdope.com/u/markn_1)\ **Post date:** [July 30, 2024, 7:35pm UTC](https://boards.straightdope.com/t/does-an-hourglass-weigh-less-while-sand-is-falling/1004895/31 "2024-07-30T19:35:32Z")
But that’s not important now. ---
**Author:** ![dougrb](https://avatars.discourse-cdn.com/v4/letter/d/76d3ee/32.png) [@dougrb](https://boards.straightdope.com/u/dougrb)\ **Post date:** [July 31, 2024, 12:51am UTC](https://boards.straightdope.com/t/does-an-hourglass-weigh-less-while-sand-is-falling/1004895/32 "2024-07-31T00:51:05Z")
Let’s get this thread back on track. I’m reading a Sean Carroll book now and it talks about hamiltonian mechanics (you google it if you want your brain to melt). He boils it down to NOT thinking about momentum (P) as M x V but as a fundamental property on its own and rewriting Newtons F=Ma as dP/dt = -dV/dx. Notice the negative sign. The balance between moving and not moving. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [July 31, 2024, 12:10pm UTC](https://boards.straightdope.com/t/does-an-hourglass-weigh-less-while-sand-is-falling/1004895/33 "2024-07-31T12:10:21Z")
Note: V there is potential energy, not velocity. ---
**Author:** ![Lucas\_Jackson](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lucas_jackson/32/303_2.png) [@Lucas\_Jackson](https://boards.straightdope.com/u/Lucas_Jackson)\ **Post date:** [July 31, 2024, 11:21pm UTC](https://boards.straightdope.com/t/does-an-hourglass-weigh-less-while-sand-is-falling/1004895/34 "2024-07-31T23:21:50Z")
> [@dougrb](#): > > I’m reading a Sean Carroll book now and it talks about hamiltonian mechanics (you google it if you want your brain to melt). I watch a lot of his videos. Some are understandable, some get deep fast. Smart cookie. ---
**Author:** ![dougrb](https://avatars.discourse-cdn.com/v4/letter/d/76d3ee/32.png) [@dougrb](https://boards.straightdope.com/u/dougrb)\ **Post date:** [August 1, 2024, 12:18am UTC](https://boards.straightdope.com/t/does-an-hourglass-weigh-less-while-sand-is-falling/1004895/35 "2024-08-01T00:18:58Z")
One thing I have learned from reading his books is an understanding of the Heisenberg Uncertainty Principle in terms I can understand. Take digital samples of an analog waveform and only look at one sample and you can’t know the frequency. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [August 1, 2024, 12:54am UTC](https://boards.straightdope.com/t/does-an-hourglass-weigh-less-while-sand-is-falling/1004895/36 "2024-08-01T00:54:07Z")
Yup. One thing that most layfolk don’t realize about the Uncertainty Principle is that it isn’t really a principle of quantum mechanics. It’s a principle of waves. All waves, from guitar strings to ocean surf to organ pipes. It’s just relevant to quantum mechanics because waves are a part of quantum mechanics. ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [August 1, 2024, 1:20am UTC](https://boards.straightdope.com/t/does-an-hourglass-weigh-less-while-sand-is-falling/1004895/37 "2024-08-01T01:20:11Z")
> [@jnglmassiv](#): > > Weighing live animals is itself an art. Like the sands of that hourglass only with more skittering about and urine Not that hard. Just start with a suitably large tank of water. Weigh that as your tare. Hold the animal submerged until it ceases moving. Weigh the result and subtract the tare. Done. Oh you wanted to re-use the animal? Oops. Unless it a fish or similar.,) ---
**Author:** ![jnglmassiv](https://avatars.discourse-cdn.com/v4/letter/j/f07891/32.png) [@jnglmassiv](https://boards.straightdope.com/u/jnglmassiv)\ **Post date:** [August 1, 2024, 2:33pm UTC](https://boards.straightdope.com/t/does-an-hourglass-weigh-less-while-sand-is-falling/1004895/38 "2024-08-01T14:33:47Z")
> [@LSLGuy](#): > > Oh you wanted to re-use the animal? Oops. I thought of that. Then, you gotta deal with loss of weight to the tank due to evaporation and struggle splashes. Actually, the urine weight is often not trivial. I don’t weigh animals myself but, as I understand it, a lot of ‘natural weight loss’ can happen during the scary transfer to the weigh station. [Previous page](https://boards.straightdope.com/t/does-an-hourglass-weigh-less-while-sand-is-falling/1004895.md?page=1)