1. Standard memberjoneschr
    Some guy
    Joined
    22 Jan '07
    Moves
    12299
    20 Apr '10 21:361 edit
    A fun optical brain teaser.

    http://www.neatorama.com/wp-content/uploads/2010/04/not-a-spiral1.jpg

    Why does it appear to be a spiral?
  2. Standard memberjoneschr
    Some guy
    Joined
    22 Jan '07
    Moves
    12299
    20 Apr '10 21:42
    I thought perhaps it had something to do with depth perception - but closing 1 eye doesn't trick it in anyway.
  3. Standard memberadam warlock
    Baby Gauss
    Ceres
    Joined
    14 Oct '06
    Moves
    18375
    20 Apr '10 21:53
    I think it has to do with the losangles in every concentric circle.
  4. Joined
    07 Sep '05
    Moves
    35068
    20 Apr '10 22:03
    Looks to me it's because the "radial" lines aren't actually radial. So locally, it looks like the "spiral" arms are moving closer to the centre.
  5. Subscribersonhouse
    Fast and Curious
    slatington, pa, usa
    Joined
    28 Dec '04
    Moves
    52619
    22 Apr '10 18:39
    Originally posted by joneschr
    A fun optical brain teaser.

    http://www.neatorama.com/wp-content/uploads/2010/04/not-a-spiral1.jpg

    Why does it appear to be a spiral?
    It appears to be a spiral because it IS a spiral. I think you are saying it should be a TURNING spiral or something.
  6. Joined
    07 Sep '05
    Moves
    35068
    22 Apr '10 21:23
    Originally posted by sonhouse
    It appears to be a spiral because it IS a spiral. I think you are saying it should be a TURNING spiral or something.
    It's not a spiral by any definition I've heard before. What do you mean by "spiral"? And "turning spiral" for that matter?
  7. Standard memberjoneschr
    Some guy
    Joined
    22 Jan '07
    Moves
    12299
    23 Apr '10 03:40
    I'm not sure if sonhouse didn't catch the figure, or he's a step ahead of all of us ๐Ÿ™‚
  8. Joined
    23 Mar '06
    Moves
    20827
    23 Apr '10 03:47
    Originally posted by sonhouse
    It appears to be a spiral because it IS a spiral. I think you are saying it should be a TURNING spiral or something.
    I think a spiral has to revolve around a point and get larger at the same time.

    This is not a spiral, it is a set of circles inside other circles.
  9. Cape Town
    Joined
    14 Apr '05
    Moves
    52945
    23 Apr '10 07:28
    There are two basic effects at work.
    1. There are essentially sections of spiral arranged in a circle.
    2. The design confuses our eyes so that we cannot see a complete circle at once.
    The combination of the two effects is that we believe it to be a spiral based on the hints (sections of spiral).
  10. Subscriberjoe shmo
    Strange Egg
    podunk, PA
    Joined
    10 Dec '06
    Moves
    7733
    23 Apr '10 12:32
    Originally posted by sonhouse
    It appears to be a spiral because it IS a spiral. I think you are saying it should be a TURNING spiral or something.
    If you dont believe it is not a spiral, take your finger and place it on the "spiral" Then follow it down to the center...You will realize it is just concentric circles.
  11. Subscribersonhouse
    Fast and Curious
    slatington, pa, usa
    Joined
    28 Dec '04
    Moves
    52619
    23 Apr '10 15:37
    Originally posted by joneschr
    I'm not sure if sonhouse didn't catch the figure, or he's a step ahead of all of us ๐Ÿ™‚
    Well my bad for sure! I followed the curve around and saw circles second time round. Great illusion.
  12. Standard memberforkedknight
    Defend the Universe
    127.0.0.1
    Joined
    18 Dec '03
    Moves
    15975
    23 Apr '10 19:191 edit
    The effects that I see that make it look like a spiral.

    1) Alternating black/white and light/dark blue squares from one concentric circle to the next are alternating, so the squares themselves (e.g. just the black squares) DO form a spiral toward the center.

    2) the diamond pattern at the corners of the black/white squares make it appear that each square is "slanted" in the direction of the apparent spiral. Therefore, the entire circle appears to be nearing the center as you follow it around.
  13. 42.4ยบ N / -71.2ยบ W
    Joined
    11 Jun '01
    Moves
    78257
    30 Apr '10 19:53
    Originally posted by joneschr
    I thought perhaps it had something to do with depth perception - but closing 1 eye doesn't trick it in anyway.
    It may still have something to do with depth perception. Many of the clues for depth are not binocular (.e.g, occlusion); they can still operate with just one eye open. That's why the world does not go flat when you close one eye.
Back to Top