59 Replies to “In Turn”

  3. When one imparts an “out turn” rotation to a curling stone it curves to the left. When one applies the same rotation to a bowling ball, it also curves to the left. There is no meltwater under the bowling ball to cause this effect. True, the shape of the contact area is somewhat different, but the result is the same. Having been an icemaker for 25 years I know that the amount of curl can be changed by varying pebble water temperature, pebble size, ice temperature, air temperature etc. A way to eliminate a curving path is to impart a rapid spin to the stone. Does this cause meltwater to form at the rear of the stone so it doesn’t curl? I have done very little bowling, but it appears to me that the amount of curve can be altered by spin speed , and very little else.
    I would like to know if people more knowlegeable in the science of physics than I, can see a similarity in these actions.
    Len

  4. Interesting question. I thought it had something to do with the Coriolis effect. If that thesis is correct, it means that the rock would curl in the opposite direction in the southern hemisphere.
    So, find a curling rink in Terra del Fuego, Chili, or the southmost point of New Zealand, or Antarctica and check it out.

  5. Physics is riddled with such questions. There’s even been recent debate to question our understanding of what creates lift in planes. Interestingly enough I spoke to people who work in aerospace and they agreed that it wasn’t perfectly understood but that perfect understanding wasn’t really necessary to build an airplane.
    We’re approaching the point where we can design technology through artificial intelligence using a n evolutionary design process. Nasa has designed some wacky antannae arrays strictly using computers crunching through various designs in a darwinian process. The results are downright wacky, super effecient and things that human beings would probably have never thought of themselves.
    So regardless as to whether or not the curling thing gets solved you may see high performance, HAL 9000 designed curling whatchamacallits in the very near future.

  6. Re: curling � While I have not done the math, the cause is likely akin to a similar effect demonstrated by a soccer ball as it �curls� in the air to pass a wall of defenders. The cause is a change in stick-slip movements on/through the ice/air due to the changing speed of rotation of the stone/ball. It is a process driven by change in the quality of friction between the object and the medium in which it travel. The coriolis force is way to weak to noticeably affect a stone motion. (BTW: it does not determine how water flow down the drain either).

  7. Funny you should mention this kate. I was experimenting with rye and pepsi last nite, trouble is the weight of the glass kept changing, and as you can imagine i had a good deal of trouble controlling my shots.
    Sorry to say, i never arrived at any conclusive evidence, but i had a ball.

  8. Jose � the fun stuff! To be pedantic (my job): We do understand �what creates lift in planes� � it�s the pressure differential. I do, however, get your point. The local dynamics are not entirely understood. We can describe them exactly with a mathematical equation, it is just that we cannot solve the equation except for relatively simple cases � even computational efforts have their limitations.
    Regarding your comment on �evolutionary design theory��Sorry � hate to disabuse an enthusiast, but �it ain�t so easy.� This �design approach� (shudder) is a brute force �search all possible solutions consistent with the given constraints and rules�modify the later this way if x happen, that way if y happens�. There is nothing here of the Darwinian �let�s make the next model better� bootstrap process, despite the comments made by some who ought to know better.
    As for the �engineered systems� that have been �designed� by such algorithms, they tend to be fragile. In Darwinian terms, they are not �fit�. In engineering terms, they are generally not robust or scalable. If the geometry or the material properties are changed slightly, the system functions poorly. Yes, one can write the algorithms to deal with these issues to a greater or lesser extent. Whole new can of worms�
    We do not have proper predictive understanding of complex systems � indeed, our understanding is poor in general. HAL 9000 will not be out-curling humans in the near future.
    Apologies for the length, and for going off-topic�this kicked me into work mode.

  12. None of this answers the question: why do liberals speak so much yet say so little? 🙂
    (My guess is intellectual entropy. Any conservative engineers want to weigh in on this one? 🙂

  13. I’d always speculated that the curling of the stone had to do with meltwater and friction, i.e in imparting counter-clockwise spin to the rock, the left side (as seen by the thrower) is travelling slightly slower down the ice vs the right side which is travelling slightly faster. The left side is therefore generating less sliding friction, melting less water and therefore “sticking” more, wereas the right side is travelling faster, melting more ice and gliding more. This would explain why the rock curls more near the end of the throw than at the beginning where the relative effect is amplified, and would explain why sweeping minimizes the effect. (It does not, however, explain why MY rocks always seem to wreck on the front guards). Am I right or totally out to lunch?

  14. The coriolis effect might be valid if one had say a 200 mile long curling rink – and one hell of a throw. I would hate to sweep though. 😉

  18. As a seventy year old who used to stand with rabbit ears held in left hand, lead foil tinsel draped on both ears, and a chunk of steel wool stuffed in a very uncomfortable spot so my father could watch the six o’clock news, I say leave these mystries to the ages,

  19. As a seventy year old who used to stand with rabbit ears held in left hand, lead foil tinsel draped on both ears, and a chunk of steel wool stuffed under my hat. so my father could watch the six o’clock news, I say leave these mystries to the ages,

  21. The article is close, but ever so far away. Wet friction is infact the cause, but hte article states that the meltwater paritally frozen allows the back to turn the rock. Which makes no sense.
    If we assume that the moisture film is a resulty of friction then the back sliding surface should in theroy create the same friction/ melting as the front (more since it is already paritally warmed/melted) Since the same/more effect is on the back, it should create less friction then the front, therfore the same effect as dry friction should occur.
    DrD is correct it is not the left right motion of the rock in spin, but the front back that creates the movement. The side turning faster creates more friction, the slower side less.
    More speed = more heat = more water = less traction. So with more traction on the side turning slower we see the rock pull to that side.
    (can’t remember where I read this study, but they actually did some work on the subject instead of just theroizing b/t ends)
    Speaking of curling, Kate the city clubs miss a few posters now and then, is there any good mens/mixed/open spiels comming up out in Delisle before the end of the curling season?? I am a few games short of having too much fun this year.

  22. Bernoulli’s Principle is the theory that allows planes to fly and sailcraft to move forward. They are actually pulled by the wind rather than pushed.(look down on an Americas Cup sailboat from above and the sail looks very much like the cross section of an airplane wing) The jist is that rapidly moving fluids (including air) exert less lateral pressure than slower moving fluids. As an aircraft moves through the air, the shape of the wing causes the air above the wing to travel farther than the air below. The air above moves more quickly above and lift (lower pressure) is generated.
    This theory ‘could’ be applied to bowling balls and billiard balls acurately based on thier direction and velocity of spin. I doubt the same could be said about a curling rock considering the extra friction due to the large footprint of the rock and the rather slow rotation. I’ll go with the slurry thingy.

  23. Well, I must say, my poor little blog has never received as many hits as it has since Kate linked to it with this post. Thanks, Kate!
    For those interested, Dr. Mark Shegelski’s own article on this topic, which he wrote for Canadian Curling News in 2000, is online at http://icing.org/game/science/shegelsk.htm.
    The article published in the Canadian Journal of Physics which led to a number of news stories and my own column in 2004 is also available online in PDF format at (sorry, long URL) http://article.pubs.nrc-cnrc.gc.ca/ppv/RPViewDoc?_handler_=HandleInitialGet&journal=cjp&volume=82&calyLang=eng&articleFile=p04-020.pdf

  24. Henry-
    My understanding of the subject of computer design more or less matches yours. I was using the term Darwinian rather loosely and you rightly called me on it. Thanks for the expanded details, ever consider running a science and technology blog?

  35. A couple of points…
    The foot print of a rock on the sheet is rather small. It is a ring of contact less than 2 mm wide and about 18 cm in diameter (the center of the rock base being concave.) but it must be remembered that the pebble size and spacing reduces the contact area even further.
    I think the curling of a rock due to the regelation slurry is more akin to the slip angle of a race car’s tire in cornering than to the rotational spin of a baseball or bowling ball.

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