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Fun-fact pot-shot time! The first paragraph states the thesis that there's something about wind patterns in the northern hemisphere that make windmill directio
by floatrock 6y ago
Fun-fact pot-shot time!
The first paragraph states the thesis that there's something about wind patterns in the northern hemisphere that make windmill directionality important.
The first paragraph also says:
> It is convenient to have all clock hands turn in the same direction, but it is an accident of history which direction that is.
Clockwise is not a random coin-flip of history. Ironically, clockwise is clockwise also because something about the northern hemisphere: the shadows on a sundial move clockwise in the northern hemisphere, so when europeans first started making clocks, they continued the sundial convention!
- Demiurge 6y agoThat's a really good point, and comes up in first result to a google query: https://www.google.com/search?q=why+is+clockwise+to+the+right https://www.google.com/search?q=why+is+clockwise+to+the+righ... ...
- thoraway1010 6y agoBeat me to this. Water also drains clockwise and foucault pendulums process clockwise in northern hemisphere. These are somewhat less likely to have a bearing on the matter than a sundial.
- Angostura 6y agoThe coriolis effect is too weak to have any appreciable effect on the way that water drains in any sink or bath.
- jcims 6y agoDefinitely has an effect - https://www.youtube.com/watch?v=mXaad0rsV38 https://www.youtube.com/watch?v=mXaad0rsV38 Whether or not it meets the standard of 'appreciable' is subjective i suppose.
- Jedd 6y agoThis is poor science, and very weak support for 'definitely'. I didn't watch this all the way through this time, but I do recall watching it back in 2017 when it was posted -- IIRC he did this experiment <sic>, asserting all variables were controlled for, but in a garage with leaky walls, on a poorly insulated floor, with no control test and only once, in one location. Consider that hurricanes don't form within 5 degrees (~ 550km) of the equator - which gives a good indicator of just how strong (or not) the Coriolis effect is.
- emmelaich 6y agoThere has been experiments, published in Nature in the 60s that did confirm an effect. I personally know one of the authors. The tub they used was something like 60cm deep and 3 or 4m in diameter. I can pull up the reference if you like. It wasn't perfectly reproducible though; in classic fashion when they demonstrated for a local newspaper (Sydney Morning Herald) the water went the "wrong" way. I have given the url / details here in HN a few years back.
- Jedd 6y agoThat it's not perfectly reproducible should be setting off alarm bells, even for people who would really like this effect to work at the scale of a few metres.
- emmelaich 6y agoI'm not sure that any experiment is perfectly reproducible. Though I would be very surprised to see a hurricane going the wrong way at mid-latitudes! Anyway, we're in agreement that it is a thing, and we just need a big enough tub to demonstrate it, correct? The force is perfectly calculable, and we can compare that to the effect of, say, a breeze across the top. ps. the reference https://www.nature.com/articles/2071084a0 https://www.nature.com/articles/2071084a0 "Published: 01 September 1965 The Bath-Tub Vortex in the Southern Hemisphere LLOYD M. TREFETHEN, R. W. BILGER, P. T. FINK, R. E. LUXTON & R. I. TANNER pps. my earlier mention https://news.ycombinator.com/item?id=15122988 https://news.ycombinator.com/item?id=15122988 Nature volume 207, pages1084–1085(1965)"
- viggity 6y agoI've been to the equator in Ecuador. It was clever how the "museum" made everyone think that simply by walking 20 yards north or south equator that the water would drain differently. They had a rectangular basin with a drain in the center. When we were in the northern hemisphere, they poured the bucket so it would induce a clockwise swirl, and counterclockwise in the southern hemisphere. When were were on the equator, they just poured it right in the center so no swirl was induced.
- jjtheblunt 6y agotypo: process -> precess
- bvandewalle 6y agoThis must be one of the most misunderstood pieces of popular science. The Coriolis effect is WAY too weak to affect the direction the water is flowing. Typically the way the water moves initially and the shape of the container will have an outsized impact in the final direction.
- kbenson 6y agoI think the issue is between people who interpret the statement as "water is predisposed to drain in a particular direction depending on hemisphere" or as "water will drain in a particular direction depending on hemisphere". Does it have an effect and can it sometimes be seen? Yes. Is it often swamped by other factors and rendered irrelevant? Also yes. That doesn't mean it's false, but it does mean that some statements that rely on it as a factual basis are at best mistaken.
- marcosdumay 6y agoWhen you have a large reservoir with a drain, keep it still, and the water reaches the level where it starts to rotate, the Coriolis effect is the dominant influence. It is something large enough to be plainly visible, but not something that appear on every drain.
- nostromo 6y agoYou just made me spend 5 minutes wondering if sundials would work on the equator, and if so, do they go counter-clockwise or clockwise during which parts of the year. Also, a fun fact: even if you have a wall-mounted sun dial (which was common in the ancient era) it still moves clockwise in the northern hemisphere, even though noon would be near the bottom of the clock.
- jaggederest 6y agoOf course they do. On the equinox it would follow a straight line through the middle of the pointer with times marked on it. At other times of the year, they behave Northerly in the northern summer and Southerly in the southern summer. Always west-to-east, though, obviously.
- minikites 6y agoAnd around noon near the equinox, there's no shadows at all: https://en.wikipedia.org/wiki/Lahaina_Noon https://en.wikipedia.org/wiki/Lahaina_Noon https://boingboing.net/2017/04/13/lahaina-noon-when-the-sun-is.html https://boingboing.net/2017/04/13/lahaina-noon-when-the-sun-...
- yencabulator 6y agoEven an approximation of that is quite convincing. In the right time of year, palm trees in Los Angeles have their shadows pretty darn perfectly centered, and if the top of the tree is narrow the shadow is nearly invisible.
- colanderman 6y agoA sundial on the equator has a horizontal gnomon (oriented north-south), and the shadows move underneath it from west to east. (There is of course a slight curve in one direction or the other based on the seasons.) See e.g. https://en.wikipedia.org/wiki/Sundial#/media/File:Sundial,_Singapore_Botanic_Gardens.jpg https://en.wikipedia.org/wiki/Sundial#/media/File:Sundial,_S...
- 6y ago
- teraflop 6y agoYou could argue that the fact that we use clock face designs derived from sundials built in the northern hemisphere, rather than the southern, is itself an accident of history.
- abraae 6y agoYou could argue that the bulk of the world's landmass and hence people being in the northern hemisphere is itself an accident of history.
- CydeWeys 6y agoBut that we call it the "north" hemisphere is itself an accident of history. We could've easily called it the south hemisphere instead. /s
- ajuc 6y agoThat's just English. In my language directions are named from where the sun is at given time, so it wouldn't change. East is "sunrise", south is "midday", west is "sunset" and north is "midnight". Context and grammatical case differentiate between midnight as time vs midnight as direction.
- ashtonkem 6y agoThat’s both true and not. Yes, it’s true that once clock makers started adding dials they used clockwise because they mostly lived in the northern hemisphere, and decided to mimic the design of sundials. What’s less obvious is the inclusion of dials at all. While in popular imagination the road from sundial to clock is clear, in reality some of the first modern clocks had no faces at all. The initial responsibility of medieval clocks was actually chiming, first in “liturgical hours” and then eventually regular hours. Their weight, cost, and inaccuracy meant that they were more commonly used to call monks to pray (hence liturgical hours) than for economic activity. Jumping from chiming to circular clocks was actually a pretty significant leap for clock makers, and one that only seems obvious in retrospect. Especially since sundials typically trace semi-circular paths and not the full circle that a clock uses, and the installation of clocks into tall, prominent locations took a few centuries.