A Light Experiment
Why do we wear white clothes in extreme heat and dark clothes in the winter? To this question every one will answer that white clothes absorb less heat than black, and that we therefore feel the rays of the sun less.
Quite true; and yet, how is it that Polar bears and other Arctic creatures exposed to such extreme cold are clothed in white?
The fact is that not only does white absorb less heat, but it serves to retain heat, and a white coat preserves the natural warmth in the animal’s body. This is exemplified by the following experiment, for which only a tumbler is required.
Choose a glass with the lower part faced, as in [Fig. 12]. Color these faces black and white alternately, a little India ink serving for the former and some crushed chalk and water for the latter.
With a very small knob of wax fasten a pin to each face, as shown in the figure. Having done this place a lighted candle within the glass.
The heat, striking the interior equally, is modified by the colors painted on the outside to such an extent that after some little while the wax supporting the pins of the BLACK faces is melted, whilst the pins on the white parts remain unaffected. This shows very clearly that the white prevents the escape of internal heat, as surely as it prevents the penetration of external warmth.