For 99 Years, Oxford English Dictionary Got It Wrong

http://www.aolnews.com/world/article/oxford-english-dictionary-got-siphon-definition-wrong-for-99-years/19472844

by mikecane • 16 years ago

16 20 16 years ago

Local link that correctly identifies the university Hughes works for - http://www.news.com.au/breaking-news/qut-physics-professor-s...

One of my life dreams is to add a word to the OED. I would definitely be happy with adjusting an existing definition as well !

btilly3• 16 years ago

Both are right.

The force that makes water want to go from one end to the other of the siphon is gravity. However what pushes the water up the siphon is atmospheric pressure. And if the middle of the siphon is too high for atmospheric pressure to push water up to the middle, then the siphon won't work no matter what height differential exists between the two ends.

So both gravity and air pressure are involved.

VBprogrammer2• 16 years ago

I initially doubted you however http://en.wikipedia.org/wiki/Siphon agrees.

Nice catch.

btilly3• 16 years ago

However http://eprints.qut.edu.au/31098/ which was written by the physicist that submitted the correction to the OED claims, contrary to wikipedia, that the tensile strength of water is relevant.

Anyone have the ability to run a siphon and pull the middle up about 50 feet in the air? If atmospheric pressure is key, it should stop working at something like 30 feet high. If tensile strength is key, it should go several times that height.

Edit: I accidentally said that the tensile strength of water was said to be irrelevant, not relevant.

andreyf2• 16 years ago

I was a little surprised that "a siphon with a large leg" works (even tested it out to double check [1]). Could someone explain this to me - surely the weight of the water inside the "large leg" exceeds the weight in the little leg. Why doesn't that make the water move the other way [2]?

1. http://dl.dropbox.com/u/404957/siphon_with_a_large_leg.jpg

2. I realize is impossible because it would end up moving water from a lower reservoir to a higher one, but proof by contradiction doesn't count - I'm trying to understand what's happening at the point of the cap (in [1]).

ars4• 16 years ago

Yes.

The falling water causes a vacuum in the tube, which "pulls" the water up behind it (since water has almost no tensile strength).

And vacuum doesn't really pull, atmospheric pressure pushes.

But fluids that do have some tensile strength could flow without air pressure, so the siphon as a concept is all about gravity.

RK2• 16 years ago

I think that it's actually the hydrostatic pressure at the bottom of the intake that pushes the water up, not the atmospheric pressure. Hydrostatic pressure is essentially only a function of depth: P = rho.g.h. Think about the design of a damn, it needs to be much thicker at the bottom due to higher pressures. You can experiment (or thought experiment) with two cups of water and a tube on the same level. Fill one cup and fill the tube. As long as the depth of one side is greater, and thus the hydrostatic pressure is greater on that side, the siphon will continue until the pressures equal. The difference in atmospheric pressures is almost negligible.

ars4• 16 years ago

The hydrostatic pressure can not push the water higher than the level of the top of the water.

The cup experiment is showing gravity, not hydrostatic pressure. There is more water in the lower tube, so it's heavier than the water on the other side.

anigbrowl• 16 years ago

In other news, scientists say they are 'appalled' to discover that Physical Review Letters does not instill good prose style among its readership, before going on to characterize their emotions with several other superficial and unnecessary adjectives (N > 3).

edge17• 16 years ago

Anyone ever read the history of the OED? It's a fascinating and ill conceived project that took 70 years to actually yield a product (mind blowing when you compare the time and growth of Wikipedia).

If you know a little about it's history, it's pretty easy to see how mistakes were made. Wikipedia has mistakes too.

jackfoxy2• 16 years ago

The first entry doing define: siphon on Google also gets it wrong. I'll look it up in my old Webster's Unabridged when I get home. If Noah got it wrong,it's possible the error dates back to Samuel Johnson.

There have been intervening editors since Noah Webster's time.

jackfoxy2• 16 years ago

Better yet I found Noah Webster's 1828 dictionary online.

http://www.1828-dictionary.com/d/search/word,siphon

A device, consisting of a pipe or tube bent so as to form two branches or legs of unequal length, by which a liquid can be transferred to a lower level, as from one vessel to another, over an intermediate elevation, by the action of the pressure of the atmosphere in forcing the liquid up the shorter branch of the pipe immersed in it, while the continued excess of weight of the liquid in the longer branch (when once filled) causes a continuous flow. The flow takes place only when the discharging extremity of the pipe ia lower than the higher liquid surface, and when no part of the pipe is higher above the surface than the same liquid will rise by atmospheric pressure; that is, about 33 feet for water, and 30 inches for mercury, near the sea level.

It seems the error traces back to Noah (but he correctly points out the receiving side must be at a lower elevation). Johnson's definition is simply "a pipe to convey liquors through".

swernli• 16 years ago

Yes, and children are still taught that Bernoulli's principle is the reason why planes can fly. There are a lot of interesting physics misconceptions that have become widely accepted, but because physics (and perhaps science in general) is not a major focus of our culture, no one really worries about these misconceptions being out there.

Well, no one except the physicists :).

stoney• 16 years ago

I have heard so many different explanations of why planes fly that I doubt that anyone really understands it. There was a memorable moment towards the end of my engineering degree, when after being given yet another explanation of why planes fly a classmate shouted out, "I think we've heard enough theories about whether planes can fly".

Apparently chemists encounter a similar thing when studying chemical bonds - every new academic year you are told that what you learned the previous year was such a gross simplification that it's basically wrong.

For 99 Years, Oxford English Dictionary Got It Wrong

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