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Author Topic: British scientists make water defy gravity  (Read 2034 times)

paul.fr

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British scientists make water defy gravity
« on: 11/11/2007 01:42:31 »
esearchers achieved the unlikely feat by vigorously vibrating the droplets. The force created when they bulged upwards as the surface they were on dropped was enough to make them trickle up a steep slope.

Small raindrops on windscreens can remain in place due to surface tension, until they grow to a size where this force is overcome by gravity.

Mathematicians have now demonstrated small drops of various different liquids can be made to move up gradients as steep as 85 degrees.

Prof Jens Eggers, from the University of Bristol, said: "This is totally new. It's never been done before, and we're still not totally sure exactly what's happening.

"As the shaking surface rises the drop is compressed, while it bulges upward as the plate falls.

"If the shaking is vigorous enough to overcome the surface tension experienced as the drop is compressed, the drop will tend to lean forward, producing a net force which drives the drop uphill.

"We don't completely understand why this is happening. It means there is a lot of interesting physics and maths to discover."

The basic mechanism is that the drop has greater freedom to bulge upwards when the surface falls than it has to compress when the surface rises creating a force which pushes it uphill.

Prof Eggers and colleague Dr Philippe Brunet discovered the phenomenon accidentally while investigating the properties of corn flour.

They found drops could only be persuaded to move uphill if they were large enough to be able to rock back and forth when vibrated but smaller than about 1mm, otherwise they would break apart.

The research, to be published online this week in Physical Review Letters, will be useful in understanding the small-scale movements of fluids, and may, for example, help police forensic investigators make better use of DNA evidence.

http://www.telegraph.co.uk/earth/main.jhtml?xml=/earth/2007/10/05/sciwater105.xml


 

Offline ukmicky

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British scientists make water defy gravity
« Reply #1 on: 11/11/2007 21:19:02 »
You could vibrate the thames and suck all the water out of the atlantic ;D
 

Offline JimBob

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British scientists make water defy gravity
« Reply #2 on: 12/11/2007 18:18:57 »
What gets me is that the water ONLY moves uphill when energy is added. So what is so unusual about adding energy to get water to move uphill other than a mathematical curiosity of surface tension? Isn't capillary action due to surface tension and intermolecular forces??
 

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British scientists make water defy gravity
« Reply #2 on: 12/11/2007 18:18:57 »

 

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