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Splash or Plop?

If you drop a rock in a pond, you'll either hear a “splash,” along with a splattering of water, or a discreet “plop” that barely disturbs the surface. Researchers at the LPMCN1 in Lyon have shown that this difference lies in the speed of the rock upon impact.2 Only beyond a certain speed threshold will the rock create a “splash,” a sound produced by the closing of the water cavity after the rock penetrates the surface. Another parameter, the texture of the rock, can influence the way it hits the water. For example, even at high speed, a perfectly smooth glass marble will barely make a “plop,” while the same marble covered by a nano-thin coat of silane will loudly “splash” through the surface. As quirky as it sounds, research into plops and splashes could help researchers control the formation of undesirable water cavities, such as the ones caused by boats when they noisily slice through water waves.

 

1. Laboratoire de physique de la matière, condensée et de nanostructures (CNRS / Université Lyon 1).

2. C. Duez et al., Nature Physics. 3: 180-3. 2007.

 

 

 

SUN: A Heart With a Spin?

The nuclear heart at the center of the Sun spins faster than the rest of the star, suggests a team of European astrophysicians including members from CNRS and the CEA. Published last May in Science,1 these theoretical findings could dramatically alter the way scientists understand the formation of the solar system, the magnetic relationship between Sun and Earth, as well as the dynamics in the heart of the star. The team derived their results from measurements gleaned over ten years of continuous observation of the sun with the GOLF instrument aboard the SoHO Satellite.2

 

1. R. A. Garcìa et al., Science. 316: 1591-3. 2007. 

2. http://sohowww.nascom.nasa.gov/

 


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