Talk:3087: Pascal's Law
I remember learning about this and thinking it was intuitive, but I didn't really think of these consequences. Maybe everybody is making powerful lifting machines for lifting cars and houses with your bare hands, rather than explaining the article, that there isn't one yet. Pascal's law basically says that if you make one end of a container of fluid X times larger, then any force exerted on the small end is multiplied by X on the large end, so you can make it near-infinite by making the small end very small. But you'll need a little more machinery added (like a gear system) if you want the distance actually moved to be higher. Actually I think that might undo the gains in force entirely. That might be how it happens, it might swap distance for force so the same work is performed.
Hey, remember that comic where Randal challenged people to fold a paper too small? This hand-makeable device could get farther on that! 172.70.111.110 21:46, 9 May 2025 (UTC)
- yes, that's how it works; the total work is constant and the hydraulic system is converting a small force over a long distance to a large force over a small distance. if you additionally want the force to be over a larger distance, you need to put more energy into the system or else you could push this machine with its own output and get free energy from nothing. really though hydraulics are just smoother, backlashless, equivalents to a gear train in the first place so you generally wouldnt need to use both. - Vaedez (talk) 23:37, 9 May 2025 (UTC)
- Small tube needs to be X times as long to get same displacement. Good for linear force rather than torque. Fluid's own pressure can be the force if tube is long enough. 172.68.55.33 11:41, 10 May 2025 (UTC)
As someone old enough to remember the slashdot effect, I wonder if XKCD comics generate a similar effect on search engines. Though I doubt they would buckle under the weight these days. 172.69.60.148 22:00, 9 May 2025 (UTC)
To whoever wrote the initial transcript, remember that we don't include the title text. Barmar (talk) 22:06, 9 May 2025 (UTC)
I have to wonder whether he has the same disbelief of, say, levers... which allow one to move the Earth. Jordan Brown (talk) 23:34, 9 May 2025 (UTC)
Although some laws of physics are absolute and lead to extreme consequences, others are taught in a simplified form that can lead to wrong conclusions. For example, "Light and heavy objects fall at the same rate" can be used to prove that objects fall at the same rate on the Earth and the Moon - which is far from correct. If the Moon were somehow dropped onto the Earth, it would fall at a certain rate. The Earth dropped on the Moon would necessarily fall at the same rate. So if the Moon falling on the Earth fell at the same rate as a bowling ball, then the bowling ball would have to fall at the same rate on the Moon. When I read Heinlein's _The Rolling Stones_ as a pre-teen, where he describes things falling slower on the Moon, I applied this reasoning and concluded that Heinlein must have made a mistake. The solution to this paradox is that something as big as the Moon will not only accelerate toward the Earth, it will significantly accelerate the Earth toward it, so the Moon does not actually fall at the same rate as a bowling ball. Cphoenix (talk) 01:01, 10 May 2025 (UTC)
- I think if you stand at the shared center of mass of the Earth and Moon, that then you see the Moon falling toward the Earth according to its constant field of gravitational acceleration, as well as the Earth falling toward the Moon according to its constant field of acceleration. It was indeed confusing for me to realize this, involving visit to pages such as https://en.wikipedia.org/wiki/Gravitational_acceleration . F=Gm1m2/r^2 so if m1 is taken out you get a constant F=m1 a2 and vice versa. But I think the page says this only holds if the masses are far enough from each other to be treatable as points. 172.68.55.47 11:57, 10 May 2025 (UTC)
Besides, isn't it better to just believe in Pascal's Law if it offers a reward of near-infinite force? StapleFreeBatteries (talk) 04:58, 10 May 2025 (UTC)
- I'll wager that you're pleased with that reference... ;) (Whether or not you actually were!) 172.71.26.43 15:58, 10 May 2025 (UTC)
Could this be referencing or inspired by this recent paper talking about the use of hydraulics to build pyramids? https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0306690 172.68.234.169 08:52, 10 May 2025 (UTC)
It could be noted that simple machines can multiply forces more or less arbitrarily, but only up to what the machine itself can withstand. Many "why didn't the ancients do that?" can be answered with "bronze kind of sucks". 172.69.246.149 14:19, 10 May 2025 (UTC)
- Right. Archimedes's "Give me a lever long enough..." assumes that the lever is made of a material that won't buckle or snap under the weight of the Earth. If there were a material like that it would make building long bridges much simpler. Barmar (talk) 16:58, 10 May 2025 (UTC)
Is there a name for the teacher character (a cueball with tufts of hair on the sides of his head)? Barmar (talk) 16:58, 10 May 2025 (UTC)
Here's a reference that claims that water hammer, rather than just depth pressure, was the major effect used in ruina montium: https://blog.ferrovial.com/en/2022/08/ruina-montium-use-water-for-digging-romans/ -- Dtgriscom (talk) 00:04, 11 May 2025 (UTC)
A few years back I posted a question on Stack Exchange (https://history.stackexchange.com/questions/60189/which-mountain-collapsed-in-france-in-1820-21) about a report, in a 19th-century biblical commentary, of a mountain collapsing due to just this kind of thing - fluid pressure building up. First thought when I saw the reference to ruina montium in the comic was that maybe that's it - but no. So, just curious: anyone have any thoughts on what event is being referred to in that commentary? (The one suggestion that someone made there, about a glacier advancing, doesn't seem to fit.) Thanks! 172.71.23.87 03:38, 11 May 2025 (UTC)
