Daily Archives: November 24, 2008

The Billy Preston Effect

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Will it Go ‘Round in Circles?

Building The Amazing Steam Candle

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This is a variant of the pop-pop engine — if you point the tubes parallel rater than in opposite directions, you’ll get linear propulsion.

At first glance you might think this couldn’t work. Once you hit steady-state, the rate at which water enters and exits the tube has to be equal. Inside the tubes, that means that the momenta must be equal in magnitude, but opposite in direction, meaning no net momentum for the water, and no propulsion for the boat. The effect is a little more subtle — one has to consider what happens at the entrance to the tube. The water exiting will have its velocity vector along the direction of the tube. But the incoming water is drawn from different directions; it only has to have a component of its velocity in the direction of the tube, meaning the ejected water exerts a greater force.

Plasmas Can Be Cool

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Molecular Plasma is Cooler Than You Think

Plasma inside the sun blazes at millions of degrees, but much of the matter between the stars is also plasma, in a colder form. In the lab, cold plasmas have always been made from ionized atoms, but a team reports in the 14 November Physical Review Letters that molecules can also be turned into an ultracold plasma. They created the molecular plasma by cooling a beam of nitric oxide molecules and then hitting it with lasers. They say the technique can work for any molecule that can be vaporized. Ultracold molecular plasmas probably don’t exist in nature, yet they share characteristics with very dense plasmas in the centers of some stars and gaseous planets. On Earth they may be used to explore more complex plasma dynamics, or help researchers create even colder atomic plasmas.