A while back I moved into a new office building at Sun Microsystems. This was good in that it gave me an excuse to discard all the flotsam and jetsam I had not yet unpacked from the previous such move. You should move your office every three years for that reason alone. Not me, you. But my move was bad in that there were a few things about the new office that didn't suit me.
Number one on the list was the motion sensor connected to the lights. All modern U.S. office buildings have power-saving features in the lighting, heating, and ventilation. These building services are usually installed in a false floor at the top of a building, but that's another storey[4] . Improving the energy efficiency of buildings is part of the U.S. government's Energy Star program. Energy Star is the reason that the photocopier is always off when you go to use it. There are Energy Star power management guidelines that apply to desktop computers, too. At that time, I was responsible for Sun's desktop power management software in the Solaris kernel, so I know how essential it is to allow users to retain control over power-saving features. Apparently, our building designers did not appreciate this.
The light in my new office was wired up to a motion sensor, and it would automatically switch itself off if you didn't move around enough. This was something of a nuisance as there are long periods in the day when the only thing moving in my office are my fingertips flying over the keyboard. Periodically, my office would be plunged into darkness, a sharp transition which spoils my concentration. And concentration is very important to programmers.
After that unpleasant business with the glitter booby trap[5] I installed in the VP's office, it would have been futile to ask the facilities guys to replace the motion sensor with a regular switch. So I considered other alternatives. A gerbil on an exercise wheel? They're high maintenance, noisy, smelly, and they keep erratic hours. One of my colleagues suggested installing folks from the marketing department in my office and having them flap their arms intermittently, thus getting some productive use out of them. I did consider it, but they have many of the same disadvantages as the gerbil, and are not so easy to train.
The final answer was one of those kitschy dippy bird things. I position it next to the sensor and dip the beak in the glass of water in the morning. It continues to rock backwards and forwards for a good long time, and everyone is happy. I plan to camouflage the dippy bird with a water lily in a dish, which motivates the housekeeping staff to keep the water level topped up. That makes it zero maintenance from my perspective and the closest we'll get to perpetual motion, and furthermore the lights no longer go out on me.
How do dippy birds work?
Dippy birds work on the same general principle as the steam engine, but with less splendor.
The bird is essentially two balanced globes connected by a small tube, with the lower globe full of a very volatile (easy to evaporate) liquid. You start it going by tipping the upper globe forward into a glass of water, and releasing it back upright.
Water evaporation from the surface of the upper globe soon cools it, cooling the air inside too, thus dropping its pressure. The lowered air pressure in the upper globe sucks some of the fluid up the tube from the lower globe. That change in delicate weight distribution causes the bird to tip forward, and dunk its beak in the water.
Now that the bird is tipped forward, the bottom of the tube comes out of the volatile liquid. A bubble of normal pressure air will travel up the tube, thus releasing the column of fluid to the bottom of the bird. That weight change in turn makes the bird bob upright again. Why does the liquid have to be volatile? So it doesn't inhibit the tiny cooling effect of water evaporation from a surface.
As the water droplets left on its beak start to evaporate, the pressure in the higher globe drops again, and the cycle repeats until the water source is used up.
You can get a dippy bird of your own (see Figure 13-6) from Edmunds Scientific at www.edsci.com. Don't forget about the glitter trap, either. Email me your results!
