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When you spill a bit of water onto a tabletop, the puddle spreads—and then stops, leaving a well-defined area of water with a sharp boundary.
There's just one problem: The formulas scientists use to describe such a fluid flow say that the water should just keep spreading endlessly. Everyone knows that's not the case—but why?This mystery has now been solved by researchers at MIT—and while this phenomenon might seem trivial, the finding's ramifications could be significant: Understanding such flowing fluids is essential for processes from the lubrication of gears and machinery to the potential sequestration of carbon dioxide emissions in porous underground formations.
The new findings are reported in the journal Physical Review Letters in a paper by Ruben Juanes, an associate professor of civil and environmental engineering, graduate student Amir Pahlavan, research associate Luis Cueto-Felgueroso, and mechanical engineering professor Gareth McKinley.
"What's striking here," Pahlavan adds, is that "what's actually stopping the puddle is forces that only act at the nanoscale." This illustrates very nicely how nanoscale physics affect our daily experiences, he says.
http://phys.org/news/2015-07-puddles-simple-everyday-phenomenon-unexplained.html
[Abstract]: http://journals.aps.org/prl/accepted/18079Y1aO511194cd818964075d4bced72a095c9f
[Also Covered By]: http://www.sciencedaily.com/releases/2015/07/150708123326.htm
Original Submission
(Score: 0) by Anonymous Coward on Friday July 10 2015, @04:50PM
Which is also the reason you can overfill a glass without spilling over. Basic physics 101.
(Score: 3, Touché) by wonkey_monkey on Friday July 10 2015, @05:58PM
Yeah, well, turns out it's not as simple as you think it is.
systemd is Roko's Basilisk
(Score: 2) by bob_super on Friday July 10 2015, @07:52PM
Physics are easy. See my plans to build a 200km-long solar-powered slingshot to get us to Mars.
(Score: 2) by deimtee on Friday July 10 2015, @10:19PM
It needs to be a lot longer or the G forces would kill you .
Assuming you have some on-board delta-V (you are going to need it) then your exit speed needs to be at least 15 km/s.
That would require an acceleration of approx 560 m/s², or near enough to 60 G.
If you cough while drinking cheap red wine it really cleans out your sinuses.
(Score: 2) by bob_super on Friday July 10 2015, @10:25PM
While I made the mistake of typing slingshot when i was thinking sling, you seem to have missed the k in 200km...
(Score: 3, Interesting) by deimtee on Friday July 10 2015, @10:59PM
No I didn't. Unless the m in 200km refers to miles not metres.
Do the math.
And if you meant a rotational sling with a radius of 200km, the the centripetal force just before release would be 115 G.
Seems high doesn't it. But you are doing more than twice orbital velocity in a circle less than one fortieth the size...
Getting to Mars is tough.
If you cough while drinking cheap red wine it really cleans out your sinuses.
(Score: 2) by bob_super on Friday July 10 2015, @11:47PM
Note to self: a linear acceleration of 270km/h per km is a lot more interesting when that last km is covered in 66ms
> Getting to Mars is tough.
Yup, that was my original point
(Score: 2) by Dunbal on Saturday July 11 2015, @12:01AM
Nah, getting to orbit is tough. Mars is just a tiny little bit on top of that, depending on the orbit you pick.
(Score: 2) by deimtee on Saturday July 11 2015, @12:33PM
Getting to orbit is halfway to Mars. If gettting to orbit is tough, then getting from Orbit to Mars is equally tough.
If you cough while drinking cheap red wine it really cleans out your sinuses.
(Score: 2) by tangomargarine on Friday July 10 2015, @11:36PM
https://en.wikipedia.org/wiki/John_Stapp [wikipedia.org]
The guy who survived a 46.2G deceleration.
"Is that really true?" "I just spent the last hour telling you to think for yourself! Didn't you hear anything I said?"