Monday, July 18, 2011

Heat and Light

Benoît Paul Émile Clapeyron, 19th century French Engineer and Physicist is generally credited with developing what we know to be the 2nd law of thermodynamics, and his work has allowed us to evaluate the upper limit of efficiency in an internal combustion engine (hint: combustion engines are not particularly efficient).  But, to my knowledge, there is no historical record of him ever baking a Madeleine cake so, well, he can’t have been all that great.

There’s been quite a lot of fuss about light bulbs lately.  Some people don’t like the new, energy efficient ones because they look weird and take longer to illuminate to full brightness.  It is true that it can be little tricky to attach a lamp shade to the new design (but do we really think this is an unsolvable problem?  Really?), and the new ones don’t generate enough heat to drive an Easy-Bake oven but they do two things well: light up a room and use less energy when they do so.  The shape is actually necessary because, unlike an incandescent bulb where the light emanates from a white-hot filament (typically tungsten; thorium, a radioactive isotope is often produced during the fabrication of tungsten filaments – oops!), the new bulbs generate light at the surface of the bulb only and you get more light out when the surface area is higher – which it is in the curly shape.  But there’s a little more to it than that.  The bulb is really a twisted fluorescent lamp in which UV light from excited gas atoms inside the tube excites a fluorescent compound painted onto the surface of the bulb.  In fluorescence, typically higher energy light goes in (in this case UV) and lower energy light comes out (in this case visible/white light).  It sounds weird that you put in one kind of light to get another kind but you can see lots of examples – black lights, which emit ultraviolet light, will cause fluorescent paints to “glow” in the dark (next time you’re in a disco, make sure that you brush your teeth and wear something brightly colored – it will be dark, but you’ll see what I’m talking about.).

We need both, sure, but there’s a time for each.  Light informs, illuminates, opens the doors and reveals the details for all to see.  Heat, not so much.

Less heat.  More light.  Please.  The good news is that reasonable people seem to be leaving the drama to Broadway, and Glee (here is a recent NY Times story on the subject).