I am a big fan of optical illusions; I love ‘em (see here and here and here and here). A lot of Bad Astronomy is due to one illusion or another, like the Glass Worm, but that’s incidental. I just think they’re cool.
One of my favorites is the in-out illusion, where your brain can’t tell if something is convex or concave. It’s maddening, and fun. The Mighty Optical Illusions site has one of the best examples I have ever seen of it, a spinning silhouette that’ll melt your brain. Go have a look!
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The original BA site (with the Moon Hoax debunking, movie reviews, and all that) can be found here.
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 | Bad Astronomy was chosen as one of Time.com's Best Blogs of 2009. |
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June 29th, 2007 at 11:09 am
Very cool. I was able to see the counter rotation once, and now I can’t seem to get it again. If you like that kind of stuff, you might like this site:
http://www.sandlotscience.com/
June 29th, 2007 at 11:25 am
Or this one from the U. of Texas physics class:
https://webspace.utexas.edu/cokerwr/www/index.html/illusion1.html
- Jack
June 29th, 2007 at 11:37 am
Sorry, I can’t get the rotation to change. I can see the legs flip at one point where the toes point into the page, but it is brief and then changes back. The particular frame you capture has that odd appearance, as if the torso and head are facing out but both legs are facing in, like she’s twisted weird at the waist.
June 29th, 2007 at 11:52 am
No need to feel like a boob here – this one took me a while to figure out, but I think its one of the breast. After a while the animation changes and it spins the other way, but the change is so subtle. If you chest stare at it a while, you’ll see you don’t have to have a knocker for optical illusions to figure out.
At least I think. I’ll stare at it a bit longer…
June 29th, 2007 at 12:37 pm
Well that’s a short leg…
Oh wait! I get it now!
June 29th, 2007 at 12:57 pm
Stare only at the lower foot. Block out the rest of the image if necessary. After the foot changes rotation, you can slowly move your eyes up.
What’s the easiest way to look at that GIF image frame by frame?
June 29th, 2007 at 12:58 pm
Looking at the shadow of the foot helps, but it can take a while to get it to switch.
June 29th, 2007 at 1:03 pm
I too was distracted by the rotating breast for awhile. Then I controlled myself and looked at the foot and saw the change.
June 29th, 2007 at 1:05 pm
IrfanView has a thing where you can extract the frames of an animated GIF. So do a bunch of other graphics programs.
By the way, I posted this GIF on my blog a few days ago, along with a poll. Turns out most people see the girl as spinning clockwise.
It’d be interesting to see some studies on phenomena like these.
June 29th, 2007 at 1:05 pm
I had the Mighty Optical Illusions on my Google homepage(s), but there was some problem with the RSS feed… have to see if it’s working properly.
J/P=?
June 29th, 2007 at 1:12 pm
Looks like there’s 34 frames.
June 29th, 2007 at 2:41 pm
When, Lord, when? When will I see the sailboat?
I’ve given it a few dozen whirls, and I’m still not seeing it. But I do see it all the time in rotating coin images on TV – that’s always weird, when the coin’s edge starts to appear from an unexpected direction.
Conjunction of Venus and Saturn tonight! I think. Better to make a fool of myself yelling this out than to keep it to myself and have someone miss it.
June 29th, 2007 at 4:12 pm
OK, now I see it! I scrolled so the only part of the image on my screen was the foot.
June 29th, 2007 at 5:00 pm
“One of my favorites is the in-out illusion, where your brain can’t tell if something is convex or concave. It’s maddening, and fun.”
Not fun, just maddening, when it happens when looking at crater pictures and you just can’t get your brain to make it look ‘right’ (assuming this is the same illusion you refer to)
June 29th, 2007 at 5:41 pm
Sat looking at the screen for a couple of minutes but couldn’t make it change. My wife came & stood behind me, I asked which direction the image was spinning, she said ‘anti-clockwise.’ I stood up & immediately saw it spinning anti-clockwise but couldn’t make it go clockwise again until I sat down. So for me, changing my distance from the screen seems to help.
June 29th, 2007 at 6:16 pm
What the heck does “J/P=?” mean? does the fact that it has a =? mean that it’s something other than just playing? The context doesn’t really help either… I keep seeing it in completely random places.
Oh, and I can’t see the bloody illusion
June 29th, 2007 at 6:40 pm
Yeah, I saw this last night on Digg. It is definitely the best optical illusion I have ever seen. At first I thought, ‘What’s the big deal?’ it was obviously clockwise, it couldn’t be anything else. Then I looked at the shadow! Whoa!!
June 29th, 2007 at 9:35 pm
Oran_Taran:
Welcome to the world of computers. I don’t know how my .sig file (which is what it is) is appearing randomly, since it’s ONLY supposed to be on my posts, but perhaps you should check your medication.
Perhaps you should look up : SIG FILE and PARADOX, maybe someone will explain it to you.
Oh, and also look up TROLL.
J/P=?
June 29th, 2007 at 10:11 pm
Hey! Who’s gonna clean up this mess?!? Brain puddles all over the floor…
June 30th, 2007 at 1:08 am
[...] reasons no one quite understands, our brains trick us into thinking it’s bigger. There are many optical illusions out there, many of them attributable to our brains using some nearby reference point from which to [...]
June 30th, 2007 at 8:31 am
Being a woman, I had no problem just looking at her feet, so I got it right away. You can even make her just sway back and forth with practice. I have a lot of trouble with the crater/dome illusion, though.
June 30th, 2007 at 9:57 am
I got it pretty quickly. ANd I think my cat saw it but was freaked by it she just started staring at it and would bat at it .
June 30th, 2007 at 3:28 pm
[...] Bad Astronomer had a link to this cool illusion. Interestingly, I have a very hard time seeing her spin clockwise, [...]
July 1st, 2007 at 2:29 pm
Blink on/Blink off. Just look away from her, look at the refection below her & presto!
July 2nd, 2007 at 2:42 pm
Okay, I finally saw it. It took staring only at her foot with the rest blocked, and then I had to manually force the image reversal. I mean concentrate hard to make it reverse. Then I repeated the process with the full image. Yes, it worked. Her raised leg switches from right to left as she switches directions.
Weird. And no, looking at the shadow didn’t do it. The shadow confidently conformed to whatever the rest of the image was doing.
July 3rd, 2007 at 11:01 pm
This is making me crazy. She is obviously spinning anti-clockwise. I can’t even imagine how it could seem to be anything different. I’ve been staring for like 10 minutes. What in the world are you people talking about?
July 6th, 2007 at 11:35 am
Charles, it was very difficult for me to get her to change directions. It took isolating what I could see to just her pivot foot, using another window to block the rest of the page. Then watching her foot and consciously perceiving the foot rotating the opposite direction. Just like convex/concave images, you have to pick which direction is in and out of the page, so with the foot I picked which direction was in and which was out as the toes swung around. That reversed the foot rotation direction. Then uncover the rest of the image and see the lady rotate the opposite direction. May have to repeat the process a couple of times before it works right on the whole.
July 6th, 2007 at 11:38 am
Oh, yeah, the shadow can be important. The shadow foot shows up when the foot is nearer to you than when it is farther away. This only happens if she is spinning clockwise, right leg raised. When spinning anticlockwise, left leg raised, looking at the shadow is one of the things that breaks the image for me.
July 16th, 2007 at 6:50 am
[...] Spinning Sihouette Optical Illusion This one’s a doozy. (via Phil) [...]
July 17th, 2007 at 7:34 am
[...] called the same color illusion, illustrates that purely human observations in science may be ambiguous or inaccurate. Even such a seemingly direct perception as relative color. Similar illusions exist [...]
November 7th, 2007 at 9:26 am
The first time I saw the dancing girl she spun clockwise about five times and then spontaneously went off in the other direction. I thought she was programmed to do that, so I began counting rotations, but she kept on her anti-clockwise track. I then tried to make her go the other direction–and she did. Now she is completely under my control. I can just think “other way” and she switches. I can get her to swing her leg while facing me, until I release her. One of the tricks is to concentrate on her frontal view, thinking “Face me.” I haven’t been able to make her change directions when her ponytail is facing me. This is all fun, but I wish I could figure out how the image is constructed. I understand that it does not change. The change occurs in my brain–a bit disturbing, as it represents a disconnect between what is out there and what I think I’m seeing.
January 6th, 2008 at 2:40 pm
LA SOMBRA DE LA CHICA NO TOCA EL SUELO,
QUE RARA VISIÓN DE LA INFORMATICA….
June 26th, 2009 at 4:02 pm
Well, for the life of me, I can only see it spinning counter-clockwise. It seems to stop for a fraction of a second every once in a while, but I don’t see any change in rotation.
Now I’m going to stay awake nights wondering what *that* means . . .
March 16th, 2011 at 2:09 pm
[...] to add: if you like this illusion, then you might want to check out this audio illusion, and this one of a spinning woman’s sillhouette which is one of my all-time favorites. [...]
September 13th, 2011 at 4:41 am
whoa , at first it start to vibrate and then the foot is ….like , turn it ….whoa !! hmmm , but it turn it for a moment …maybe i will stare at it longer.