Fire, Carberation, and Broken Glass

J. Constantinos /
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Last night was a full moon, so we got drunk and burned candles on the fridge. Eventually, we got to that point where you appreciate the small wonders in the world around you (you know that point - it generally comes just before you lose your short-term memory).

I grabbed a digital camera and ran off to the kitchen, and I can't imagine what people thought of the bright flashes and muttered curses that resulted. I did get a couple pictures of what I wanted, though, and now I have a question for you:

In the below picture, I'm blowing a stream of air past a candle flame. Which direction is the stream of air coming from?

So far, most everyone I've asked has answered this one wrong. From the title, you should be able to get where I'm going...

Ready? In this shot, the cameraman (me) was blowing a thin stream of air straight towards the bottle in the background - to the _left_ of the candle flame. If I had been blowing inward from the right, like most people said, then the candle flame would have guttered and spat; instead, it was drawn smoothly towards the stream of air by the Bernoulli effect, or Bernoulli suction force.

So, that's why this is on-topic - the suction force caused by a moving stream of air is exactly what pulls the fuel mixture out of the float bowl of a carburetor and up through the venturi. Whoo! Science!

This suction force - the Bernoulli effect - is also what caused huge panes of glass to rain down on Boston in the seventies. When they first built the giant, glass John Hancock building, they made sure that the huge windows would stand up to the force of the building's air conditioners. What they didn't check was how much suction would be created by the currents of air passing by the building's large, flat sides.

As a result, whenever the wind got above a certain speed, it would create a Bernoulli suction force that neatly popped 400+ pound plate glass windows from their frames. The huge windows would then get caught up by the strong window and hurled across Boston down onto the heads of care-free, disco moped riders below.

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