# Circles

When I was a child I fell in love with the idea of thermostats. The lowly thermostat was, I came to understand, the perfectly minimal example of an actual working robot. When the temperature went up, a sensor triggered the thermostat to produce cool air. When the temperature went down, the sensor triggered the thermostat to produce warm air. It was simple, but intelligent.

It was a robot in my house. What more could any kid ask for?

When I was a child there were also mechanical men. They were on TV, in movies, and in exhibitions, and they were called robots. But I understood that these were not robots at all — they were simply puppets dressed to look like robots. The thermostat, humble though it may be, was the real thing.

And then I discovered it had cousins, like the governor of a steam engine. If a steam engine runs too hot, its governor spins faster, and the two steel balls it carries are flung outward through centripetal force. This movement causes a lever to be pulled downward, which partly closes a throttle, thereby cooling the engine down.

My grandparents owned an old telephone they never used, which I was given to play with and take apart. I found an electromagnet inside, which pulled upon a spring metal bar which held a clapper that rang a bell. But as the clapper moved toward the magnet, an electrical connection was broken, and the bar snapped back. This reconnected the electric circuit, and the cycle began anew.

The phone ringer didn’t look anything like the thermostat, or the steam engine governor, but I knew they were all cousins.

And then one day I learned the truth about circles.

More tomorrow.

## One thought on “Circles”

1. There are simple machine I want to show my students (7 to 10 year-old) to understand basic things. But I found it difficult nowadays.

When I wanted to talk about equality, I looked for a (balanced) scale. But if I visit to the amazon, all the scales are digital. It just tell this weight is 108g or whatever, but it is just a magic. No understanding helper.

I looked for flea markets in Berlin and I signed up ebay to find a scale. It was possible, but I started to wonder how the children understand the world now.

There is a good mathematics interactive tool like this