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Optical Illusions

Which square appears to be darker, square A or square B? This is an optical illusion you can do at home for yourself!

Want to do this yourself? Download the graphic and give it a try!

Announcer: Frostbite Theater presents... Cold Cuts! No baloney!

Joanna and Steve: Just science!

Joanna: Hi! I'm Joanna!

Steve: And I'm Steve!

Joanna: During Jefferson Lab's Science Series lecture, Dr. Eric Mazur of Harvard University showed the audience an optical illusion that we thought we'd share with you!

Steve: Here's the basic set-up. There is what appears to be a green cylinder casting a shadow on a checker board. One square is labeled 'A' and another square is labeled 'B.' The question is 'Which square is darker, square A or square B?'

Joanna: You know how the game is played. This wouldn't be an illusion if squares A and B were actually different. While square A looks darker than square B, they're really both the same color. It's easier to see this if we remove the rest of the diagram.

Steve: Okay, but this could be a trick. How do you know we didn't change the color of the squares when we edited the graphic? Well, here's another way to do this. We made a transparency of the image and cut it in half. When we line everything up, square A still looks darker than square B. When we split the image apart, the pieces of square A still match each other and the pieces of square B still match each other. Now, we can slide the piece of square B up to square A and... they match! We can do it the other way, too. We can take the piece of square A and bring it down to square B to see that they match as well. Square A and square B are really the same color!

Joanna: Still don't believe us? You can download the graphic from our website, print it out, cut it, and try it for yourself! Dr. Mazur has also made the slides from his presentation available on-line. So if you'd like to learn more about illusions and the way the brain processes visual information, you might want to check it out!

Thanks for watching! I hope you'll join us again soon for another experiment!

Steve: Yeah, something about this still doesn't look right...

Joanna: I know what you mean. There's definitely something...

Seven things were intentionally changed between the opening and closing scenes. Can you find them all?

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