Check it:

The glass is perfectly clean.
All those specs of "dust?"
They're contrails from radiation particles zooming through the special fluid inside the tank. It's called a "Cloud Tank", and it's used to observe the paths of radioactive materials (not with the accuracy and minuteness of a Cloud Chamber, of course...)

You'll notice they seem to be radiating from that block on the right side of the picture. In that block, is an eraser-sized peice of radioactive ore.

E=mc^2, bitches.