No idea where this should go, but i thought it was quite cool (sorry if this is well-known to phisisists):

 

http://www.as-e.com/products_solutions/z_backscatter.asp

http://www.youtube.com/watch?v=pAldBxgRCdY

 

afaict, it assays materials' ability to scatter x-rays and so measures stuff with low molecular weight (people, drugs, explosives etc) which apparently are more inclined to scatter x-rays, whereas normal x-ray scanners (like you'd find in a hospital) i think measure things based on their x-ray-adsorption, and so measure stuff with a higher molecular weight. or something.

 

apart from thinking that this is interesting/cool/like sci-fi x-ray specs, i have a question: if the backscatter thingy detects matter with 'low atomic weight, such as stuff made from carbon, hydrogen, etc', then why isn't it detecting the petrol in the vehicles tanks?

 

DISCLAIMER: I suck at phisics, so if anyone's reading this who isn't very good at phisics themselves, don't take anything i said above as accurate.

not sure why it doesn't seem to pick up petrol. its says it also picks up radiation. if its dodgy with petrol maybe its dodgy with nukes and thats what they were using in iraq