Shadow Analysis Could Spot Terrorists

It couldn't work through non-transparent substances because it's watching your shadow, which is defined by the visible light arround it.

The sun isn't positionally static, so I'd assume it could use other light sources to a limited degree as well. /shrug

Also, a lot of my previous post was just idle speculation on how it would work.

Yes, but the device watching has to be able to see the absence of visible light that is the shadow.

Yes, but the device watching has to be able to see the absence of visible light that is the shadow.

Yeah, I just realized how incredibly stupid that thought process was. Posting at 4am or whatever for the win.

Edit: Okay, that was at 9pm. Nevermind, no excuses there, that was straight failure.

How is that failure? It is how the machine works.