String Crossing

What do you see?

Stretch a string in front of you, look at it and ask what do I see?

Material

A meter of plain white string

To Do and Notice

Hold one end of the string under your nose.

Stretch the string straight in front of you and hold it at arms length.

Look at the string.

What do you see?

Some people see two strings crossing in an X

others see two strings making a V

some see two parallel strings.

Look as close as you can then look far away.

When you look close notice how the string seems to be two strings crossing in an X near your face. When you look far away notice how the crossing point moves away eventually becoming a V or even two nearly parallel strings.

What's Going On?

Close your left eye, look at the string with your right eye.

Switch back and forth from one eye to the other rapidly, notice that each eye sees the string in a different place.

When you look with both eyes you see two strings because the string is so close to your eyes that your brain cannot fuse the images into one three dimensional perception.

Each eye looks inward toward the string as you focus close to your face, this makes you perceive an X.

As you look further away your eyes point more parallel to each other, the crossing point of the perceived X moves further away.

Going Further

Some people have a strong master eye and a weaker slave eye, they will see one clear string and either a ghostly second string or no string at all.

 Scientific Explorations with Paul Doherty © 2011 5 May 2011