Marc,

I've been enjoying reading the discussion of window
tinting and transmittence of uv light, etc.  I
disagree on a couple of things, one on principal only.
 Light most definitely does not slow down. You can
always count on light to go exactly the same
speed--ie, the speed of light.

>The light energy hits things inside your van, slows
>down, and gets converted to radiant energy (heat).

>Regarding the experiment, it is pointless.  As I said
>above, as long as there is a net energy input into
your van, there will always be heat buildup. The
amount
>over time (4-6 hours) will come to an equilibrium
>because the vehicle will be giving off as much heat
as >is coming in.

>A better experiment would be to see
>how quickly each van would cool off with the AC on
after having reached that
>high temperature.  The tinted van would win, I'm
sure.

I suspect you are right that after some period of time
(and 6 hours seems reasonable) the vans will be the
same temperature.  But if two materially identical
objects are the same temperature, it will require
equal removal of heat (ie, AC power) to cool them.

The useful experiment, I think, would be to test HOW
LONG it takes each van to heat up.  If a tinted van
takes 6 hours to heat to, say 130, but a non-tinted
van hits 130 in 2 hours, that is a useful result.

Doug Demarest
SLC, UT
86 vanagon

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