Saturday, January 10, 2015

Is Your World Upside-down?

So, how do we really see the world? You might remember this from science class, out eye basically focuses light through a lens and small opening to the retina at the back of the eye.

Similar to how light enters the eye is the age-old Camera Obscura. Ancient philosophers knew about what happens on a bright day when light is allowed to enter a dark room through a very small pinhole. A detailed image of what’s outside will appear on the opposite wall, flipped upside down.

This phenomenon has been termed “Camera Obscura,” a Latin phrase translated literally as “dark chamber.” Arab philosopher Abu Ali al-Hasan, a.k.a. Alhazen (965 – 1040 AD) recorded his experiments with light, including playing around with the camera obscura. Alhazan not only wrote extensively about optics, working with prisms and refracted light 700 years before Newton, but was the first to make some good guesses about how the human eye really worked.

Try making your own camera obscura with this tutorial!

Or try this - grab a magnifying glass and a white piece of paper. Stand near a strong light source, light a light bulb or a brightly lit window. Hold the paper in one hand, and place the magnifying glass between the light source and the paper. Move the magnifying glass back and forth until an image appears - and notice how the image goes out of focus just by moving the lens slightly. Check out that just as in the camera obscura, the image appears upside down.

And most amazingly, scientists have proven (again and again) that although our eyes to "see" the image of the world around us inverted, our brain straightens it all out so that we can successfully navigate the world.

We have discovered this fact through the use of inversion goggles, which you can learn more about in the links below.

George Stratton first documented his experiment with inverting sight in the 1890's.

This experiment was repeated in 1950 and documented in film by Ivo Kohler and Theodor Erismann at the University of Innsbruck in Austria.

I've also seen this educational film circa 1970 titled Perception: Inverted Vision in which an artist wears a pair of inversion glasses and learns to navigate in the world.

And even more recently, the guys from Good Mythical Morning had an inversion glasses challenge!

What's the obsession with the insanity glasses, right? I'm not sure, but you can find a pair online if you'd like to torture yourself with this experiment.

Or, DIY a pair with this YouTube tutorial!


Eileensews said...

Thanks for writing this. Afterimages was fun to do. I'll be having my students try them out.

smazoochie said...

Did Miss Fidget love doing this? It looks so fun!

Cindy said...

Great job teaching about how eyes work! I'm posting about viewing this week's meteor shower "through the corner of your eye" and this is a fantastic reference. Thank you!