View Poll Results: After viewing the video which do you see...

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  • Clockwise rotation

    2 20.00%
  • Counterclockwise rotation

    7 70.00%
  • Other

    1 10.00%
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Thread: Direction of rotation.???

  1. #1
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    Direction of rotation.???

    The link below shows a slow motion video of a rotating hammer (beginning at 2:01)... in which direction do you see the hammer rotating.???

    http://www.youtube.com/watch?v=Jpbgg2TRCuw


    EDIT:::
    I want to know which direction you see the hammer rotate in the slow motion part of the video I indicated... not which direction you think it should be rotating... and please vote in the Poll.!!!
    Last edited by P Timmy; 2012-Apr-01 at 02:58 AM.

  2. #2
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    As seen from the side it is difficult to see which way it was turning. I would expect it to be counterclockwise as seen from above, which is the same direction she was turning when throwing it.

  3. #3
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    Quote Originally Posted by Hornblower View Post
    As seen from the side it is difficult to see which way it was turning.
    I can clearly see it rotating CW.!!!

  4. #4
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    I suspect it is moving counter clock wise from hand positions. The athlete is spinning counter clockwise, her hands must move in a counter clockwise fashion while passing in front of her body/face and "snap" in the opposite (CW) direction before starting the next revolution. The clockwise motion is required to keep the hammer stable. If it did not it would have to rotate in her hands.
    Solfe

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    "You're only given one little spark of madness. You mustn't lose it." Robin Williams.

  5. #5
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    Quote Originally Posted by P Timmy View Post
    The link below shows a slow motion video of a rotating hammer (beginning at 2:01)... in which direction do you see the hammer rotating.???

    http://www.youtube.com/watch?v=Jpbgg2TRCuw
    Quote Originally Posted by Hornblower View Post
    As seen from the side it is difficult to see which way it was turning.
    Quote Originally Posted by Solfe View Post
    I suspect it is moving counter clock wise from hand positions.
    Hi Solfe... I'd like to know which direction you see the hammer rotating in the slow motion part of the video... not which direction you think the hammer should be rotating... and Hornblower... does the hammer appear to be rotating to you.???

    To all who view the video... please answer the poll.!!!

  6. #6
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    There are way too many artifacts in the video to be 100%, but I get the impression the head of the hammer is turning counter clockwise while the chain and handle are moving in the opposite direction.

    My prior post is based on personal experience with screwing up with weapons, things like nunchucks (Wii or otherwise) will do the exact opposite thing you expect if you upset them. My personal favorite is when the chain or stick strikes your thumb knuckle (which doesn't hurt at all) and causes the other end to turn and strike you some place between the knees and forehead.
    Solfe

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    "You're only given one little spark of madness. You mustn't lose it." Robin Williams.

  7. #7
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    Quote Originally Posted by Solfe View Post
    My prior post is based on personal experience with screwing up with weapons, things like nunchucks...

    My personal favorite is when the chain or stick strikes your thumb knuckle (which doesn't hurt at all) and causes the other end to turn and strike you some place between the knees and forehead.
    Yes it surly isn't as painful as one might expect or people wouldn't do it... but still... I think beginners should start out nice and easy like the guy in the link below.!!!

    http://www.youtube.com/watch?v=A3NSb434e-4

  8. #8
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    Quote Originally Posted by P Timmy View Post
    Hi Solfe... I'd like to know which direction you see the hammer rotating in the slow motion part of the video... not which direction you think the hammer should be rotating... and Hornblower... does the hammer appear to be rotating to you.???

    To all who view the video... please answer the poll.!!!
    It is obvious that the chain is revolving around the ball. I cannot tell which way by looking at this video, because there is not enough detail visible to indicate which half of the cycle has the chain between us and the ball. Nothing ever transits the ball visibly, and there are no visible mark on the ball.

  9. #9
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    Quote Originally Posted by Hornblower View Post
    It is obvious that the chain is revolving around the ball. I cannot tell which way by looking at this video, because there is not enough detail visible to indicate which half of the cycle has the chain between us and the ball. Nothing ever transits the ball visibly, and there are no visible mark on the ball.
    Nicely explained :-)

    And much like the Spinning Dancer Illusion... some people will see the hammer appear to rotate CW and some will see it appear to rotate CCW because of the reasons you explained above... and also... the hammer can be seen to oscillate back and fourth without making a complete rotation.!!!

    This issue came up years ago when a guy (kdine) questioned why the hammer was rotating CW during its flight down the field when the hammer thrower was clearly rotating CCW when they released the hammer.!!!

  10. #10
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    At 2:06 the handle is clearly moving left and passing behind the hammer. Anticlockwise it is.

    Note: I jumped straight to 2:01 to watch the hammer, before going back to see what direction the thrower was rotating. I was correct!

  11. #11
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    Quote Originally Posted by speedfreek View Post
    At 2:06 the handle is clearly moving left and passing behind the hammer. Anticlockwise it is.

    Note: I jumped straight to 2:01 to watch the hammer, before going back to see what direction the thrower was rotating. I was correct!
    Yes the hammer is actually rotating CCW... but with the Spinning Dancer illusion... most people can see it rotate CW or CCW... can you also see the hammer rotate CW.???

  12. #12
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    I watched the slow-motion part about 20 - 25 times.

    While the hammer is in front of the audience, it is
    rotating clockwise relative to the camera.

    The chain *seems* to go on the far side of the ball just
    before the hammer passes in front of the running track
    and grass, becoming hard to see. So up to that point,
    it is rotating clockwise relative to the camera, and
    counter-clockwise as viewed from above. As a result,
    I did not vote in the poll. No choice for "Both".

    -- Jeff, in Minneapolis
    http://www.FreeMars.org/jeff/

    "I find astronomy very interesting, but I wouldn't if I thought we
    were just going to sit here and look." -- "Van Rijn"

    "The other planets? Well, they just happen to be there, but the
    point of rockets is to explore them!" -- Kai Yeves

  13. #13
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    Quote Originally Posted by Jeff Root View Post
    I watched the slow-motion part about 20 - 25 times.

    While the hammer is in front of the audience, it is
    rotating clockwise relative to the camera.

    The chain *seems* to go on the far side of the ball just
    before the hammer passes in front of the running track
    and grass, becoming hard to see. So up to that point,
    it is rotating clockwise relative to the camera, and
    counter-clockwise as viewed from above. As a result,
    I did not vote in the poll. No choice for "Both".
    The poll didn't draw as much interest as I had hoped... I figured the people who saw both directions of rotation would answer "other".!!!

  14. #14
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    I assume you mean if viewed from above. Clockwise.
    I didn't watch the rest of the video to be swayed by the video of her winding up.
    Visually, with no prior conceptions or ideals on one single watch, it looked clockwise.

  15. #15
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    To me, in all of them, it looks, from the rear, like the throwers' right arms are moving forward when they are facing away from the camera. That means they're turning counterclockwise (observer looking down), so the hammer will also be turning counterclockwise when seen from above.

    I wonder if these throwers were all right-handed, and, if so, whether left-handed throwers would spin clockwise.
    Last edited by swampyankee; 2012-Apr-30 at 03:39 PM. Reason: grammar.
    Information about American English usage here and here. Floating point issues? Please read this before posting.

  16. #16
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    they're and they're
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  17. #17
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    Quote Originally Posted by wiggy View Post
    I assume you mean if viewed from above. Clockwise.
    I didn't watch the rest of the video to be swayed by the video of her winding up.
    Visually, with no prior conceptions or ideals on one single watch, it looked clockwise.
    The view I'm going by is the exact view shown in the video... and at first... the direction of rotation in the slow motion part of the video looked CW to me... but since it was pointed out that the direction of rotation can appear either way... I can now see it rotate CW or CCW... even though I know it's actually rotating CCW.

    Quote Originally Posted by swampyankee View Post
    To me, in all of them, it looks, from the rear, like the throwers' right arms are moving forward when their facing away from the camera. That means their turning counterclockwise (observer looking down), so the hammer will also be turning counterclockwise when seen from above.

    I wonder if these throwers were all right-handed, and, if so, whether left-handed throwers would spin clockwise.
    Yes it's actually rotating CCW even in the slow motion part of the video--it was just a fun puzzler as to why some saw CW rotation and some saw CCW rotation.

    Some hammer throwers spin CW.

  18. #18
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    Judging from just the close-up slow-motion, whether we see it
    from "above" or "below" is unclear-- perhaps impossible to judge,
    thus we can't tell for sure whether it is rotating clockwise or
    counterclockwise as seen from above (or below!). However,
    it is unambiguously rotating clockwise as seen from the camera's
    viewpoint. So anyone who doesn't know the full story-- and doesn't
    claim to be able to judge from the visual cues alone whether we
    are seeing it from "above" or "below"-- should say that it appears
    to be rotating clockwise. But they should also specify that that
    is relative to the camera's position.

    -- Jeff, in Minneapolis
    http://www.FreeMars.org/jeff/

    "I find astronomy very interesting, but I wouldn't if I thought we
    were just going to sit here and look." -- "Van Rijn"

    "The other planets? Well, they just happen to be there, but the
    point of rockets is to explore them!" -- Kai Yeves

  19. #19
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    Quote Originally Posted by P Timmy View Post
    Yes the hammer is actually rotating CCW... but with the Spinning Dancer illusion... most people can see it rotate CW or CCW... can you also see the hammer rotate CW.???
    Quote Originally Posted by Jeff Root View Post
    ...it is unambiguously rotating clockwise as seen from the camera's
    viewpoint. So anyone who doesn't know the full story-- and doesn't
    claim to be able to judge from the visual cues alone whether we
    are seeing it from "above" or "below"-- should say that it appears
    to be rotating clockwise. But they should also specify that that
    is relative to the camera's position.
    In the spinning dancer illusion (above)... can you unambiguously see the lady rotate CW or CCW?

  20. #20
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    I spent quite a long time looking at that. I finally got her to
    go clockwise as imagined from above, and eventually could
    keep her going clockwise for maybe half a minute, or make
    her switch directions almost at will. Even after doing it many
    times it looks impossible that it could change directions. But
    then it happens!

    -- Jeff, in Minneapolis

    .
    Last edited by Jeff Root; 2012-Apr-30 at 07:16 PM. Reason: removed excess word
    http://www.FreeMars.org/jeff/

    "I find astronomy very interesting, but I wouldn't if I thought we
    were just going to sit here and look." -- "Van Rijn"

    "The other planets? Well, they just happen to be there, but the
    point of rockets is to explore them!" -- Kai Yeves

  21. #21
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    Quote Originally Posted by HenrikOlsen View Post
    they're and they're
    Fixed, and thank you. Need to reboot my grammar processor.
    Information about American English usage here and here. Floating point issues? Please read this before posting.

  22. #22
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    Quote Originally Posted by P Timmy View Post
    In the spinning dancer illusion (above)... can you unambiguously see the lady rotate CW or CCW?
    I can select which way I want her to rotate, and get her to change direction. I started a thread on this some time ago.

  23. #23
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    agreed; this is an old illusion and with a little practice you can make the apparent rotation switch just like the transparent table with four legs illusion can switch to seeing it from above or below. Once you have mastered it, the switch gets easier so I guess it is a brain function that can be trained rather like getting used to wearing bi-focals. A similar effect happens with those pictures that are pixelated and if you deliberately defocus you see an object in apparent 3D, it can take a long time to see it at first and then it is obvious. The brain is a remarkable vision processor!

  24. #24
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    Originally Posted by P Timmy
    Yes the hammer is actually rotating CCW... but with the Spinning Dancer illusion... most people can see it rotate CW or CCW... can you also see the hammer rotate CW.???
    Originally Posted by Jeff Root
    ...it is unambiguously rotating clockwise as seen from the camera's
    viewpoint.
    In the spinning dancer illusion (above)... can you unambiguously see the lady rotate CW or CCW?
    Quote Originally Posted by Jeff Root View Post
    Even after doing it many times it looks impossible that it could change directions. But then it happens!
    Do you agree that from the camera angle in the slow motion part of the hammer throw video I specified... that the hammer can be seen to rotate CW or CCW... just like the dancing lady illusion?

    Quote Originally Posted by Perikles View Post
    I can select which way I want her to rotate, and get her to change direction.
    Quote Originally Posted by profloater View Post
    agreed; this is an old illusion and with a little practice you can make the apparent rotation switch
    Can you two also make the hammer switch its direction of rotation (in the slow motion part of the video I specified)?

  25. #25
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    Quote Originally Posted by P Timmy View Post
    Do you agree that from the camera angle in the slow motion
    part of the hammer throw video I specified... that the hammer
    can be seen to rotate CW or CCW... just like the dancing lady
    illusion?
    Of course. I think everyone understood that from the start.
    At least I did. If I hadn't understood it, I would have thought
    your question was crazy. There is obviously not enough detail
    in the slow-motion shot to make the direction of rotation relative
    to the vertical (which is the tacit standard) obvious.

    On the other hand, not much detail is needed to make the
    direction of rotation relative to the camera obvious, and that
    detail is present.

    In the slow-motion of the hammer, we have information which
    tells us fairly exactly where the vertical is, but almost none
    which tells us when the chain is closer to the camera than the
    ball. In the dancer animation, we have only spurious cues as
    to when parts of the dancer's body are closer to the camera.
    Those cues are false -- only imagined by the viewer. There is
    no perspective or any other other real cues that might possibly
    be found in the video. The direction of vertical in the animation
    is ambiguous in the radial direction from the camera.

    -- Jeff, in Minneapolis
    Last edited by Jeff Root; 2012-May-01 at 11:41 AM. Reason: removed a quote I didn't notice
    http://www.FreeMars.org/jeff/

    "I find astronomy very interesting, but I wouldn't if I thought we
    were just going to sit here and look." -- "Van Rijn"

    "The other planets? Well, they just happen to be there, but the
    point of rockets is to explore them!" -- Kai Yeves

  26. #26
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    Quote Originally Posted by P Timmy View Post
    Do you agree that from the camera angle in the slow motion part of the hammer throw video I specified... that the hammer can be seen to rotate CW or CCW... just like the dancing lady illusion?
    Quote Originally Posted by Jeff Root View Post
    Of course.
    That wasn't clear since you only mentioned "clockwise" in your post below.

    Originally Posted by Jeff Root
    ...it is unambiguously rotating clockwise as seen from the camera's
    viewpoint. So anyone who doesn't know the full story-- and doesn't
    claim to be able to judge from the visual cues alone whether we
    are seeing it from "above" or "below"-- should say that it appears
    to be rotating clockwise. But they should also specify that that
    is relative to the camera's position.

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