X-ray vision

In my previous post, I made reference to x-ray vision. The typical view of x-ray vision is that it lets you see through or inside something. Let's clear up how x-rays actually work.

X-rays let you see through your skin and look at your bones. This is true. What happens is that the x-ray go through your soft skin that is mostly made up of light elements. Carbon, oxygen and hydrogen are probably the three most abundant elements in your skin. They have atomic masses of 12, 16 and 1 amu, respectively. The x-rays react very weakly with the light elements and hit the x-ray film. Your bones are made up of many of those same elements, but also one more: calcium! Calcium has an atomic weight of 40, so it stops a lot more of the x-rays, leaving a white spot on the film. Ta-da! You can now see your bones.

The problem is in adapting this to other uses, like Superman's x-ray vision. It only works if you're looking through something made of light elements, to see something made of heavy elements, which has a film behind it. But apparently Superman can shoot x-rays out, which travel through walls (note: sheetrock is made of gypsum, which is made of . . . . calcium! (and sulfate ions, and water)) (also, cement or cinderblock is pretty good at stopping x-rays, because cement is made from limestone, which is made of . . . . calcium carbonate!) bounces off of soft people, goes back through the walls and then is processed by his hi-tech x-ray eyes. It just doesn't work.

So, even with fancy x-ray equipment, Julia would have been hard pressed to identify the sugar and paper sucker inside the paper bag. (Sugar is made of carbon, hydrogen and oxygen, and sadly, no calcium.) We're down to exceedingly impressive spelling skills and ESP as the top two explanations. And ESP isn't looking too likely.

Or maybe it was ghosts.