Friday, November 26, 2010

Science: Common Sense does not equal Science

It seems impossible at first. When you hear that it should be possible your brain tries to cope with an idea that seems contrary to common sense. The idea?

You can build a wind powered car (no batteries or hidden power sources) that can be pushed downwind by the wind and move faster than the wind.
You can build a wind powered vehicle that can have a 10 mile per hour wind behind it and yet travel faster than 10 miles per hour.
It just seems wrong. It can't work... can it? The idea is known as downwind faster than the wind or DFTTW. Until this summer the debate ranged far and wide over whether or not the concept was feasible or possible.

If you think about it for a moment there are hints that it could be possible. For example let's take the example of a sailboat. Now I sailed quite a bit. Mainly in small one or two man sailboats. Sailing away from the wind is no faster than the wind.

If you are sailing south with a 10 knots per hour wind at your back and your sail is set 90 degrees to the wind then you can go no faster than the wind. The sail is acting like nothing more than a giant board sticking into the air and being pushed directly by the wind.

But if the wind is coming from the north at 10 knots per hour and you are sailing east... then the sail isn't just a giant obstacle for the wind. Then the sail is an airfoil or a wing. Then sailboats easily sail faster than the windspeed.

So it is possible for a sailboat to move faster than the wind. The trick is can there be a car or device that can move downwind faster than the wind?

The answer was put to rest (I hope) once and for all this summer when Blackbird set an official record by going 2.8 times faster than its tailwind.

The story of how Blackbird became to be built, and the story of the fights over whether DWFTTW is even possible, are detailed in A Long, Strange Trip Downwind Faster Than the Wind in Wired magazine. Rick Cavallaro's tale includes links to various discussion boards and forums where the issue was (and may still be) hotly debated. He also digs into the history of attempts to prove (with math and physics) and show (with models or cars) that the feat is possible.

It's a wonderful read. Of course now we know it can be done. During the discussions and arguments people were faced with something that didn't seem possible. It seemed wrong. It violated common sense. It didn't seem right.

The world around us doesn't operate based on our common sense notions. Nor does it have to do so. The universe is unexpectedly wonderful and many things that don't seem possible are actually quite simple. The hard part is convincing people of that.

1 comment:

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