Dictionaries are pretty solid authorities about what words mean, but they overextended themselves when reaching a bit in the definition for the word siphon. The Oxford English Dictionary and many others have erroneously claimed that atmospheric pressure makes siphons work for 99 years, so Dr. Stephen Hughes did some research to set them straight.
Dr. Hughes noticed that the OED Â misidentified atmospheric pressure as the thing that makes siphons work back in 2010. Really, it’s gravity that causes liquid to flow up the short side of a siphon and down the long side, but the original definition for a siphon read,
A pipe or tube of glass, metal or other material, bent so that one leg is longer than the other, and used for drawing off liquids by means of atmospheric pressure, which forces the liquid up the shorter leg and over the bend in the pipe.
So, Hughes set about helpfully correcting the dictionary, but of course, he needed some proof. So, he tested a siphon inside a hypobaric chamber where he could change the level of atmospheric pressure and see if it had any effect on the siphon. As we’ve all (hopefully) learned, if you’re going to correct someone, you should really be sure you’re right first.
In Hughes’s experiments, the varied air pressure had a small effect on how the water flowed, but it didn’t have any effect on how much water traveled through the siphon over time. So Hughes concluded in a paper, published yesterday in Scientific Reports (that he somehow managed not to title “Neener Neener”), that he is smarter than the dictionary, and gravity is the real driving force.
The OED has changed its definition to remove the reference to atmospheric pressure, but Hughes isn’t fully satisfied with how ambiguous they’ve left the actual driving force behind a siphon. That’s still better than the rest of the world’s dictionaries, as he said,
But at least the reference to atmospheric pressure has been removed. The vast majority of dictionaries of all languages still incorrectly assert that siphons work through atmospheric pressure and not gravity.
Hopefully, the others will come around and change their ways. Sorry, dictionaries, but no book is safe from being proven wrong by science.
(via Phys.org, image via greeblie)
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