10 ms·
Physicists Still Don’t Know What Puts the Curl in Curling
- noelwelsh 9y agoInvestigating a complex physical phenomena that isn't tied to either fundamental research or immediate application = little chance of funding. The article is all "oh gosh, curling is so complex" but the real thing here is the limitations of our knowledge, and the ability to apply knowledge across abstraction boundaries.
- CaliforniaKarl 9y agoCurling Canada has a video online (https://www.youtube.com/watch?v=50cSDUIDMuM https://www.youtube.com/watch?v=50cSDUIDMuM) detailing the steps that a rink needs to go through in order to prepare their ice for a championship game. It's kindof amazing how many steps are involved, and I wonder if that has anything to do with it.
- kazinator 9y agoI suspect why the stone curls in the direction of rotation is that the edge on that side is moving more slowly relatively to the ice. It melts the ice less, generating less of a film of water and so experiences more friction. If an axle with wheels rolls such that the left wheel is on pavement and the right hits grass, it will turn right. A glass on a bar table top doesn't melt the surface to create a film; more motion means more friction not less. So, opposite. It probably doesn't matter which edge (front versus back) has more weight on it, but rather which side of that edge (left or right) experiences more friction. I suspect even if you slide the glass up an inclined bar table top so that the weight is on the rear, it will still curl opposite.
- Scarblac 9y agoThis doesn't explain why you get the same amount of curl if the stone rotates twice during its run or twenty times.
- psheets 9y agoThe delta of the ice on stone speed between the sides is not dependent on the rotational speed but liner speed in relation to the rotational speed.
- hexane360 9y agoYou're wrong, and even if you were right that wouldn't argue against GP's observation. V_cm: velocity of center of mass V_l: velocity at left edge V_r: velocity at right edge R: radius of stone w: angular speed of stone (CCW is +) V_l = V_cm + R*w V_r = V_cm - R*w delta = 2*R*w Even if it was dependent on linear speed / rotational speed, the only way to change # of turns / run is to change linear speed / rotational speed.
- leot 9y agoThis seems similar to the Magnus effect: https://en.m.wikipedia.org/wiki/Magnus_effect https://en.m.wikipedia.org/wiki/Magnus_effect (Spinning a pen fast enough can turn it into a wing, causing it to behave strangely when tossed upward)
- vhodges 9y agoThe faster the rock spins, the less it will curl. Ideal # of rotations is about 2.5 or so.
- Nomentatus 9y agoWater is complex; surface tension like effects can happen in thin films of it other than at the surface. At greater speeds, these are reduced so the Magnus effect is reduced.
- sandworm101 9y ago>>Archery, too, is fringe and unexciting Lost me there. Archery is infinitely more exciting than many Olympic "sports", curling included.
- 52-6F-62 9y agoClearly you're not from Saskatchewan
- greaseball 9y agosigh it's not a Saskatchewan Ricky, it's a Samsquanch!
- sandworm101 9y agoWell, I am currently standing in Manitoba. Portage le prairie.
- tonyarkles 9y agoThe beauty of archery in Saskatchewan is that you get to go hunting way earlier in the season than you do with a shotgun or rifle. That means that hunting season doesn't interfere with curling season :)
- megaman22 9y agoMost Olympic sports are fringe and unexciting. Really, who cares how fast somebody runs/bikes/rows X meters?
- jdewald 9y agoWho cares what some author or poet decided to write? Who cares what some scientist found? Who cares what food tastes like? Who cares what article someone posted on Hacker News? Who cares about the bug you fixed? Who cares what software exists? We can all live without any of this, but why?
- simias 9y ago
- jonbarker 9y agoTo investigate the pivot/slide model further why not spin a flat bottomed rock down the ice to see whether it curves?
- da_chicken 9y agoSmarter Every Day did a YouTube video on this (https://www.youtube.com/watch?v=7CUojMQgDpM https://www.youtube.com/watch?v=7CUojMQgDpM) where he talks about the phenomenon and also talks to the exact same guys featured in this New Yorker article. I think he does a much better job than the New Yorker article, too. Destin also notes that, countries that study curling tend to win olympic medals. He said that in 2014, and it's interesting to note that both Sweden and Canada won medals in curling in both 2014 and 2018. [Edit: Though I believe he did say it after the 2014 games.]
- peeters 9y agoCanada has won medals in men's and women's curling every year since they reintroduced it in 1998. 2018 was actually the first year we didn't, winning only in the new mixed doubles event. The Swedish women have medalled in all but one. So I wouldn't read too much into this. Countries where curling is popular tend to win Olympic curling medals, and countries where curling is popular also tend to study it.
- sigzero 9y agoThis was the first year I watched the event. I knew "generally" what curling was but not I am hooked. I loved watching it. Going to see if there is a team close by.
- tempestn 9y agoIt really is fun to at least try. I've only gone once, but had a blast.
- flukus 9y agoFor anyone that lives in a warmer climate, can't ice skate or wants more to watch I'd suggest you checkout lawn bowls (https://en.wikipedia.org/wiki/Bowls https://en.wikipedia.org/wiki/Bowls). The games are very similar and typically people that like one like the other.
- 9y ago
- bluetwo 9y agoDo stones curl in the opposite direction in the southern hemisphere? Would that be called the curliolis effect?
- jjeaff 9y agoI believe the coriolous effect doesn't actually affect things on a small scale. The water around a drain changing depending on hemisphere is a myth.
- bluetwo 9y agoFear not. I was just kidding. It was too good of a pun to pass up.
- deleted 9y ago[deleted]
- garrettdc 9y ago...i see what you did there ( ͡° ͜ʖ ͡°)
- macintux 9y agoReminds me a bit of Feynman's spinning plates.
- tambourine_man 9y agoPhysics Confession https://xkcd.com/1867/ https://xkcd.com/1867/
- joenot443 9y agoIs that true? Do we really not know how ice skates work?
- jbosh 9y agoThis paper came out and changed the game a few years ago. It's called scratch theory and the front edge of the stone scratches tracks for the back edge to run along. There was a sweeping summit this summer to discuss brooms and how to make them scratch the ice less because it caused players to have extremely high stats for tournaments. Brad Gushue video showing the effect: https://www.youtube.com/watch?v=haEuz42YCdM https://www.youtube.com/watch?v=haEuz42YCdM These brooms have been made illegal in tournament play. Some Scotties players describing the effect: https://www.youtube.com/watch?v=147vRw0kmAY https://www.youtube.com/watch?v=147vRw0kmAY The scratch theory paper: https://www.thesalmons.org/lynn/curling/A5.pdf https://www.thesalmons.org/lynn/curling/A5.pdf
- alansmitheebk 9y agoI think the real mystery here is that it's considered a sport. Can someone explain that to me? I mop the floors in my apartment with a Swiffer all the time. No one ever shows up to give me a medal...
- leeoniya 9y agoFeynman on "why is ice slippery?" https://www.youtube.com/watch?v=MO0r930Sn_8 https://www.youtube.com/watch?v=MO0r930Sn_8
- The_suffocated 9y agoHis explanation, actually first given by Michael Faraday in 1859, was later found to be wrong. According to a 2005 article "Why Is Ice Slippery" published on Physics Today, even when a layman is wearing a pair of skating blades, his/her weight can only lower the melting point of water by about three to four degrees. Yet skating is still possible when the temperature of the ice surface is as low as -30 degrees Celcius. Pressure melting cannot explain why skating blades can make ice surface slippery enough in this scenario.
- echlebek 9y agoOne of the professors at the university I went to recently released some research on curling. https://www.unbc.ca/newsroom/unbc-stories/researchers-discover-why-curling-rocks-curl https://www.unbc.ca/newsroom/unbc-stories/researchers-discov...
- Wile_E_Quixote 9y agoTHE SOLUTION IS SIMPLE I suspect that the reason curling stones curl the way that they do is primarily due to one side of the stone being subjected to “static” friction while the other side experiences “kinetic” friction. This would also explain why the curling doesn’t start to happen until the stone’s linear velocity has sufficiently decreased. If a stone is moving down the ice, away from the observer, and spinning to the left (that is, counter-clockwise when looking down on it), the right-side edge of the stone is moving in the same direction that the stone travels while the left-side edge of the stone is moving in the OPPOSITE direction that the stone travels. This means that the right edge of the stone is moving faster across the ice than the stone’s linear velocity. And the left edge of the stone is moving slower across the ice than the stone’s linear velocity. As the stone’s linear velocity decreases, there will come a point when the left edge of the stone is no longer moving relative to the ice, while the right edge of the stone is still moving at 2 times the stone’s linear velocity relative to the ice. This means the left side of the stone is now being subjected to static friction while the right side is only being subjected to kinetic friction. The force opposing the left side of the stone is greater than the force opposing the right side of the stone, causing the stone to pivot around the left edge of the stone, “curling” to the left, until the stone's linear velocity reaches zero.
- mysterypie 9y agoThat does in fact sound like a reasonable hypothesis. But you have to account for why a beer bottle or an upturned glass sent spinning down a table curls in the opposite direction; i.e., why is it different for a curling stone? Also, why won't a stone curl if the ice is not pebbled? Your hypothesis should account for that too. By the way, I think you got downvoted earlier because you started off with the words "the solution is simple", sounding extremely sure, rather than saying you have a theory.
- laxd 9y agoThe beer bottle case is explained in the article: "Take a beer bottle or an upturned glass and send it spinning down a table: if it rotates to the right, clockwise, it will curl to the left; if it rotates to the left, it will curl to the right. That’s because the bottle, as it moves forward, also tips forward slightly, adding weight to the leading edge. More weight means more friction." I guess a heavy curling stone with a lower center of gravity and on a slippery surface would'nt tilt forward like a bottle. Came back to this thread to see if someone had written an enlightening rebuttal of GP rather than downvoting him.
- mcguire 9y agoFor those of us who don't curl, "It’s like golf: it’s easy to watch a guy hit a golf ball, and you think, ‘This isn’t very athletic.’ And then you get out there yourself and find that it’s incredibly difficult." Anyone know how much force is applied to the golf ball on a professional's drive?
- hornbaker 9y agoTour pros routinely swing driver at 120-125 mph, and produce ball speeds of 180-190 mph. I’ve seen numbers in the range of 2,000 - 4,000 pounds of force applied to the ball.
- bkanber 9y agoIf you're #50 in the PGA in terms of average ball speed [0] and drive a regulation ball (46g)[1] at 175 mph (78 m/s), that ball has an energy of 140 J. If it accelerated from 0 to 78 m/s in 0.5 ms [2], it accelerated at 156 km/s^2 for that short time, at a power of 280kW (375 horsepower). The force applied to the ball was therefore 7100N, corroborated here [3]. A driver is 45" standard, but assuming that you don't hold the club at the tip we can call it 42" or 1 meter. You don't rotate the club where you hold it, but rather roughly at your shoulders (I will neglect hip rotation), and the average arm length is 25". Arms are not locked straight so let's call it a little shorter, and add 0.6 meters for the arm length. You now have a 1.6m moment arm applying a force of 7100N through the ball, requiring 11.4 kN-m of torque, or 8400 lb-ft. Edit: I have discovered that wrist torque is significant, and that your wrist and your arms individually supply about 150 and 400 N-m of torque respectively. [4] To compare, a high-end sports car might have 500 HP (compared to the golfer's 375 HP), and the Tesla P100D has 920 lb-ft of torque. Of course, the golfer sustains this output for only half a millisecond, and a lower output during the rest of the swing (around 1 second). A car can do it until the tank or battery is empty. Also I have neglected hip rotation, differing driver and arm lengths, and energy loss due to deformation. But this is a decent first approximation, and at very least in the correct order of magnitude. [0] https://www.pgatour.com/stats/stat.02402.html https://www.pgatour.com/stats/stat.02402.html [1] https://en.wikipedia.org/wiki/Golf_ball https://en.wikipedia.org/wiki/Golf_ball [2] https://dspace.lboro.ac.uk/dspace-jspui/bitstream/2134/11470/7/Measurement%20of%20Contact%20Time%20in%20Short%20Duration%20Sports%20Ball%20Impacts.pdf https://dspace.lboro.ac.uk/dspace-jspui/bitstream/2134/11470... [3] https://hypertextbook.com/facts/2001/EmilyAccamando.shtml https://hypertextbook.com/facts/2001/EmilyAccamando.shtml [4] http://rspa.royalsocietypublishing.org/content/465/2102/551 http://rspa.royalsocietypublishing.org/content/465/2102/551
- iteriteratedone 9y agoIs this title not bs ... more speed equals less pressure Sweeping on one side reduces the atmospheric pressure on that side ... causing it to move towards that side How do airplanes work ??? Come on , bachelors physics
- jsizzle 9y agoScience has failed us. If it can't figure out how curling works, there's no way it actually put a man in the moon.
- em3rgent0rdr 9y agoCurling is probably a result in a glitch in the simulator's programming of our universe. Maybe a benign side-effect of some optimization that the great simulator thought we would never encounter...
- deleted 9y ago[deleted]