4/35    Does aluminum foil or white sheets of paper reflect more light, if the
        direction of the reflected light is not important?  -- yuen
        \_ Are you talking about strictly visible light?  IR?  UV?
           \_ I'm interested in daylight (5500K).  -- yuen
        \_Christ, get a clue. Get a strong light source and a dark wall.
          Hold up a sheet of paper and a sheet of tin foil that are the
          same size. Measure the size of the square of reflected light.
          Estimate the intensity in a small area, and multiply by the
          entire area of the reflected light. Very simple. Any fourth
          grader could do it.
        \_ WAG (wild-ass-guess): Metal over paper any day.  However, to test,
           put some paper and aluminum foil out in the sun for a few hours.  See
           which is warmer.
           \_ This is incorrect advice.  Just because something 'feels' warmer
              does not mean it is.  For instance, titanium watches feel
              neutral on your hand, but steel watches feel cold (when you first
              put them on).  However, both are at the same (room) temperature.
              The subjective sensation of coldness can often be caused by the
              _rate_ of heat transfer, not the actual temperature.  In the case
              of watches, steel has a greater heat transfer rate, so it absorbs
              more heat from the human skin in the same amount of time than
              titanium.  These rapid temperature changes is what the human
              skin's thermal receptors are most sensitive to.
                -- motd physics god
              \_ i knew this, too. - motd physics weenie
           \_ as tom pointed out on wall, this won't work for another
              good reason: paper transmits light, aluminum doesn't.
              so you need to check the temperature as well as the trasmitted
              light. -ali
        \_ take both into a dark room and flash a flashlight at them...
           have it reflect against a wall.  seems like a logical
           test *shrug*
           \_ this doesn't take into consideration the fact that aluminum
              is specular and paper diffuse. the pattern on the wall will
              look different. you need to add the TOTAL amount of energy
        \_ Who cares?
              reflected everywhere on the wall, not just look at the intensity
              at one point on the wall. the only good quick way i can think
              of this is to point a thin laser at the paper, measure the
              reflected intensity at some angle, and scale to the rest of the
              hemisphere, and do the same with aluminum, but measure the
              reflected intensity near the surface normal. -ali
        \_ The two sides of my foil differ. Which side you talking 'bout?

        \_ If you want to grow pot, don't use aluminum foil. _Very_ hard to keep
         flat enough to reflect light.
        \_ I think of it this way - mirrors are made of melted metal (I don't
           know which) poured over the back of glass. Mirrors are *very*
           reflective. I believe that part of the reason is that the glass
           holds the metal flat. Put paper on the back of glass, and you
           don't get anything particularly reflective. If my life depended
           on it, I'd choose aluminum.