Harold R. Hay: Solar Pioneer
(Page 12 of 17)
September/October 1976
By Mother Earth News Editors
PLOWBOY: Mr. Hay, has your work with solar energy led you into formulating any other theories or concepts?
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HAY: Oh sure One that I've come up with which you might find interesting is my idea about cool black and warm white.
PLOWBOY: Cool black and warm white?
HAY: Yes. It's become almost holy writ, you know, that black always absorbs the sun's rays and warms up, while white always reflects solar energy and stays cool. We paint the collectors of our solar energy systems black and our barn and factory roofs white for this very reason.
Why then are polar bears white and why do so many tropical animals have a black or a dark tint to their coats? Why are so many Nordic people from far northern Europe light skinned with almost white hair ... while Negroes from equatorial Africa are very, very dark with black hair? If black always absorbs heat it would seem to make more sense for polar bears to be black and for Negroes to live in the arctic zones of the world. They'd stay warmer that way. And if white always reflects heat, tropical animals should be light—not dark—and blonds should hail from the equator. They'd have evolved to stay cooler that way.
But that's not the way nature designed them ... and nature doesn't seem to make the kind of mistake that our conventional theory of black and white tells us it's made. How do we explain this contradiction?
Well I explain it by saying that black does not always absorb the sun's rays and white does not always reflect it in just the way we've been taught to believe. There's also what I call "cool black" and "warm white".
I can best explain cool black by telling you to lay a piece of black metal out in the noon summer sun alongside a thick black coat. And then, an hour later, I want you to go back out and pick them both up. What will happen? Well, of course, you'll burn your hand on the metal ... but the coat will still be cool enough to handle.
Why? Because-even though the surface of the coat is just as hot as the surface of the metal-the fibers immediately below the coat's surface act as insulation instead of a heat sink. So, as fast as the surface of the coat warms up, it radiates its heat right back into the atmosphere.
And that's why tropical animals are darker. That's why people from very hot countries have thick black hair. The sun's rays never get a chance to reflect down through the hair to the skin underneath. Instead, they're absorbed right at the tips of the hair and the resulting heat is quickly carried away by radiation and convection. The outer surface of the body of hair becomes an automatic heat dumping system that is insulated from the skin underneath by the mass of hair in between.
PLOWBOY: And just the opposite holds true, I suppose, for the polar bear?
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