"Graham." wrote in message
...

When I was a child, in my grandfather's bookcase there was a copy of
"Science Advances" by JBS Haldane.
If you aren't familiar with Haldane he's well worth a Google.

The most memorable concept in that book for me, other than his "Come
the revolution" Marxist style, was a few paragraphs on polarized
headlamps.

The idea had been proposed by the inventor of Polaroid sheet
polarizers , Edwin Land.

Basically the idea is we all drive about using un-dipped headlights
with the lights, and windscreens polarized with a 90deg differential.

I know it is said that it takes a genius to think of an idea that
later seems obvious, but in this case I really feel that if Land
hadn't thought of it, I would have, and I expect many here would say
the same.

Here's an good article on the subject

http://www.polarization.com/land/land.html

and here is the Haldane's book see page 183
http://www.archive.org/stream/scienc...ge/n7/mode/2up

So this issue must have been considered time and time again, yet
always rejected for mainstream use. Why?

I imagine one of the problems is that the polariser on the windscreen will
cut out quite a lot of light, so it will be harder to see reflections off
distant objects - so you need even brighter headlights to compensate. All
other (unpolarised) lights would need to be brighter as well to compensate
for losses in the polarising filter on the windscreen.

Hell, they can then even turn all the street-lighting off!
(As they seem to be doing so anyway).

Actually this would not necessarily be a good idea. Sometimes it is better
to have constant illumination of the road ahead from lots of lights dotted
along the road, rather than rely on lights projecting forwards from you car,
which illuminate by inverse square law: objects close too will be very
bright and objects further away will be less bright. Providing that glare
from overhead lights as you pass each one isn't a problem, I prefer constant
illumination to light which is less good on distant objects.