Fun Fact #4

You can actually measure the width of a piece of hair with a yardstick and a laser light with some simple knowledge of physics. All you do is shine a laser at a piece of hair which will diffract the light, and if positioned correctly, you'll get an interference pattern (see picture) and you can measure the spaces in between each of the spots of light and calculate the width of a piece of hair using:

 [(wavelength)(distance from hair to wall)]/(distance between center and one point of light)=width of hair