posted on Feb, 23 2014 @ 11:05 AM
glass is kinda hard to see
so is any one atom of anything...
at least I can't see them without my glasses on
edit on 22-2-2014 by Danbones because: (no reason given)
That's a good one.
Yes, in some way (and under some circumstances) glass cannot be seen. But a glass surface can certainly reflect heat (IR).
Simple...would kind of fit the criterion.
glass reflects some heat not much though, a thermopane window is like R 1.5
but if you take a horizontally polarized lens
you get light out the other side
add a vertically polarized lens
you get NO light out the other side
add a horizontally polarized lens
you get light out the other side again
so one wouldn't see anything behind two or more pairs of sun glasses unless the polarization is lined up right
dangle a not moving piece of thread in front of a bull frog
no signal from eyeball
move the dangling piece of thread in front of bull frog
signal from eyeball
there are other factors involved beside simple physics
edit on 23-2-2014 by Danbones because: (no reason given)