Physicist demonstrates dictionary definition was dodgy
It is the defining moment that demonstrates a QUT physicist was correct in pointing out a 99-year-old mistake to one of the world’s most authoritative dictionaries.
QUT Senior Lecturer in Physics, Dr Stephen Hughes, sparked controversy over how a humble siphon worked when he noticed an incorrect definition in the prestigious Oxford English Dictionary.
In 2010, eagle-eyed Dr Hughes spotted the mistake, which went unnoticed for 99 years, which incorrectly described atmospheric pressure, rather than gravity, as the operating force in a siphon.
Dr Hughes demonstrated the science of siphons in a paper published yesterday in Nature Publishing Group journal Scientific Reports.
For Exploring the boundary between the siphon and barometer in a hypobaric chamber, Dr Hughes conducted an experiment in a hypobaric chamber, which simulates the effects of high altitude, at the Institute of Aviation Medicine at the Royal Australian Air Force’s Base Edinburgh in South Australia.
A siphon 1.5 metres high was set up in the chamber and when the pressure was reduced to an altitude of 40,000 feet a waterfall appeared at the top, but the water flow remained nearly constant.
At 41,000 feet, the siphon broke into two columns of water and, when returned to 40,000 feet, it reconnected as if nothing had happened.
Atmospheric pressure at 40,000 feet, which is more than 10,000 feet higher than Mount Everest, is about 18 per cent of the sea level value.
For the experiment, two buckets, one higher than the other and connected by tubing, were set up and a pool pump returned water from the lower bucket to the higher bucket.
“The fact that the water level in the upper and lower buckets is constant indicates that atmospheric pressure is not pushing water into the siphon,” Dr Hughes said.
“The stable water surfaces act like energy barriers between the atmosphere and siphon. For energy to be transferred from the atmosphere to the water the water level would have to go down, since the amount of energy transferred is equal to force times distance.
“If the water level is constant the distance is zero and therefore no energy can be transferred.”
Dr Hughes, whose previous research has taken him to Bhutan to examine how siphoning could prevent inland tsunamis, said siphons had been used since ancient times but how they work was still debated.
“If you think of a car, atmospheric pressure is like the wheels, it enables it to work. But gravity is the engine,” he said.
“It is gravity that moves the fluid in a siphon, with the water in the longer downward arm pulling the water up the shorter arm.”
The Oxford English Dictionary corrected the error and removed the reference to atmospheric pressure after Dr Hughes pointed it out. However, he said the new entry “unfortunately remains ambiguous”.
“This definition still leaves the question open as to how a siphon actually works,” Dr Hughes 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.
“I hope these findings are a useful contribution to the debate about how siphons work and will enable people to make more effective use of them.”
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This is above my head, actually Anthony, so mistakes do happen and can be corrected by more modern research methodology. And taking into account some of the physics presented by alarmists, maybe they should revise their methodology too.
It is difficult to comment on this article due to lack of precision in
Specification of conditions.
Where are the inlets and outlets located in the two buckets. I assume that
Both tube outlets are located below the water surface.
What is meant by the statement that “flow splits into two columns”. Diagrams
Showing what happens here would be useful.
The OED is not a science textbook, as anyone reading it can plainly see. Well, plainly with the little magnifying glass that comes with it.
From Wankerpedia: “…Specifically, Pascal demonstrated that siphons work via atmospheric pressure (as Torricelli had advocated), not via horror vacui, via the following experiment…”
Empirical results from this engineer’s experience suggest that gravity will facilitate the entry of gasoline into my mouth if I fumble things a little. Gawd, how did anyone ever get on the atmo pressure kick? Some academic?
@jim.says April 24, 2014 at 10:50 pm
The descriptions to which you refer are puzzling as ypu point out, but if you follow the “paper” link [ http://www.nature.com/srep/2014/140422/srep04741/full/srep04741.html ] it goes into a much better explanation along with clarifying diagrams.
Here’s the paper.
Remember the water barometer? A siphon will not work if the height of the water column in the rise to the crest of the U is greater than 10 metres.
From the paper “Between 40 000 and 41 000 feet (17.87 kPa, 0.17 atm) the waterfall stopped and the siphon split into two columns” So it appears the author implies that SOME atmoshperic pressure is required to run a siphon(?)
One wonders what happens with a siphon of, say, two reservoirs of mercury at low pressure.
An error in the One True Dictionary! It is a sign of the End Times. We’re doomed.
The application to glacial lakes and prevention of inland tsunamis is brilliant. There is a lot of academic research into GLOFs (and a lot of environmentalist moaning about it), but this is the best practical solution I have seen, and generates electricity as an extra.
I am a home brewer and trying to siphon a batch of fresh beer or cider can have the same problems: a broke siphon. Very common.
I would imagine at 40K Feet, the water is outgassing and vaporizing and the agitation of the return pump is not helping.
I now use gravity feed from the primary fermentation tank into a set of five gallon soda (Cornelius) kegs and transfers after that are done with positive-pressure CO2.
Yaaay CO2 — what can’t it do?
I wonder…
Given this from the AGWers:
“Because of the small atmospheric pressure on Mars (less than one hundredth that on Earth), the spectral absorption lines of carbon dioxide on Mars are very narrow, and therefore act like a picket fence that lets most of the thermal radiation emitted by the Martian ground surface to escape directly out to space. This does not happen on Earth because of the atmospheric pressure that is exerted by the radiatively inactive nitrogen and oxygen, causing the spectral absorption lines of carbon dioxide and water vapor to be greatly broadened, making them more effective absorbers of thermal radiation. And, for comparison, it is the extremely high pressure on Venus that makes the carbon dioxide absorption of thermal radiation particularly efficient in the Venus greenhouse effect. On Mercury, there is no tangible atmosphere, and hence there is no opportunity for the greenhouse effect to operate.” {emphasis mine}
[Source: “Greenhouse Effect,” Andrew A. Lacis, NASA Goddard Institute for Space Studies New York, NY USA, p. 277; Link: http://cdn.intechopen.com/pdfs/32352/InTech-Greenhouse_effect.pdf%5D
A BONAFIDE QUESTION — Please, if you can, I would sure like to know the answer.
My Question:
What are the implications of this article for the AGWer’s CO2 driven greenhouse effect speculation? That is, does the fact that (assuming that Dr. Stephen Hughes is correct) gravity is the driver and atmospheric pressure only the relatively passive enabler of a siphon…
… make the above-quoted AGW conjecture even more implausible than we already know it to be? Or is Dr. Hughes’ gravity finding completely unrelated to CO2 greenhouse effect conjecture?
THANK YOU FOR HELPING ME!
Janice
(bedtime, here in PST land, so, I’ll acknowledge any help later zzzzzzzzzzzzzzzzz)
Experimental proof that siphons don’t run on atmospheric pressure, which is common sense to me! It also explains the “breaking into two columns” thing:
If you reduce the atmospheric pressure further the water will eventually boil and stop the syphon!
Thanks to TerryS for the link
“Figure 3 | Plot of flow versus time with the siphon at 39 000 feet and then
at 40 000 feet with the waterfall present. The pressure in the chamber was
reduced between points A and B over a period of about a minute. Flow
reduced but then recovered slightly.”
This is an awful set of results for a supposedly controlled lab experiment. It’s a farce.
His results (apparently a single run) indicate that pressure did have some effect. He then bushes that aside and publishes what he ‘knows’ to be the right answer.
If I got results like that I’d be embarrassed to present it as an under-grad project , let alone try to publish it.
Yet more proof that peer-reviewed science is now screwed. You can publish almost anything.
I thought it was the ether doing it.
“At 41,000 feet, the siphon broke into two columns of water and, when returned to 40,000 feet, it reconnected as if nothing had happened.”
This poorly explained bit seems to refer to the fact that a vapour bubble appeared in the syphon tube at low pressure.
The path of the syphon was so poorly designed ( well in fact it wasn’t designed at all) that this effect was poorly accounted for. This experiment should have been redesigned and re-run, not published.
Dr Stephen Hughes is a “Senior Lecturer in Physics” . Well if that is the state of work produced by those teaching hard science subjects in universities these days no wonder we are such a mess with climate science.
We are about to witness the fall of our science based civilisation and the dawn of a new dark age is upon us.
It’s worse than we thought.
Australian ex-PM, ju-LIAR Gillard, prompted the Macquarie Dictionary to redefine the word “misogynist” to reflect her broad and untruthful attack on the now PM of Australia, Mr Tony Abbott. Dictionaries will change definitions for the least plausible reasons in some cases.
I really don’t see the need to do an experiment on this in the first place. It is absolutely obvious that the difference in atmospheric pressure at the water surface in the top vessel is only infinitesimally different to that at the water surface in the lower one. There is NO air pressure difference to do anything.
The pressure difference in the tube between the two ends , which drives the flow, is due to the pressure head of the water column.
Jeezus , this is high-school science , you don’t need a hypobaric chamber.
Janice Moore: My Question:
What are the implications of this article for the AGWer’s CO2 driven greenhouse effect speculation?
===
The main implication is that peer-review science is screwed and those teaching science , even at university level in hard science subjects, no longer seem capable of doing a basic lab experiment.
“It is gravity that moves the fluid in a siphon, with the water in the longer downward arm pulling the water up the shorter arm.”
_______________________________________________________________________
That’s in fact quite inaccurate too. The longer downward arm can only pull the short arm up to tensile strength of the water column – above that the column breaks if there isn’t atmospheric pressure pushing equally from both sides of the column, making sure it continues to work.
So if we consider water column tensile strength negligible (which is correct for standard siphon sizes), we need to account for four forces – gravity pull on long arm, gravity pull on short arm, atmospheric pressure on long arm end, and atmospheric pressure on short arm end. Difference of gravity pull on long arm and atmospheric pressure on the same end results in decreased pressure at the top of the siphon and motion of the fluid down the long arm, while difference of gravity pull on short arm, atmospheric pressure at short arm end (atmospheric pressure is greater than gravity here) causes the fluid to move up the short arm, compensating decreased pressure caused by long arm.
And while it sure is nice to have Oxford dictionary corrected, many other popular places such as Wikipedia had apparently things right all along.
In common siphons, it IS atmospheric pressure that pushes the liquid up, after gravity has pulled the liquid down on the discharge side and lowered the pressure at the top. Gravity supplies the energy to create a pressure difference. Atmospheric pressure pushes the liquid up into this pressure difference. Even in this experiment Hughes notes that by 41000ft the siphon broke in two and when the atmospheric pressure was increased the water rose back to the top and reconnected. What was pushing the water back up to the top? The atmospheric pressure was pushing the water up as he raised said atmospheric pressure. What pushes the liquid up in a barometer? What pushes the liquid up in a drinking straw? In none of these cases can liquid cohesion explain the rise of the liquid. There is nothing else applying an upward force to the liquid when there is a gas or void at the top. The liquid cohesion theory also fails because in a typical not too tall siphon at near sea level, the liquids and gasses present in all parts of the siphon are at positive absolute pressure, and therefore the molecules are all repelling each other. There is no pulling.
But a siphon of liquid that doesn’t boil in vacuum can work in a vacuum. It has been published for more than a hundred years and has been demonstrated on video at youtube. Atmospheric pressure obviously cannot explain such a siphon. Liquid cohesion must be the explanation for siphons in vacuum. This confuses people because they think that two contradictory explanations can’t both be correct. They feel they have to choose. In fact both explanations are correct because they are not contradictory. A siphon in vacuum must be explained by liquid cohesion. A common siphon at sea level with a bubble at top, separating the two sides, CANNOT be explained by liquid cohesion between two bodies of liquid that AREN’T TOUCHING. There is no reason to believe that siphons can only work by one method.
Dr Hughes stubborn clinging and even compounding the mistake of his 2010 article, is a perfect example of part of the reason why climate scientists won’t change their mind about the effects of CO2. No matter how clear the evidence is, they will dream up any excuse they can to maintain their current belief and avoid the embarrasment of admitting their mistake. This is especially true because as they have said many times, they believe that even if they are wrong about CO2, it is worth it to stop fossil fuel pollution. They don’t even want to know if they are wrong.
Don’t make the mistake they’re making. Seek out your own errors. Be proud when you can overcome your own confirmation bias and admit your mistakes. Being able to admit your mistakes is a precious skill. Practice helps. Don’t dodge tough questions. Also try to account for the fact that you are very unlikely to be able to completely overcome your own comfirmation bias. You are probably wrong about some of the things you think you have lots of evidence and good reason for. I’m just glad there is so much evidence to support and confirm MY current beliefs. Seriously though, lets practice. Maybe Dr Hughes is right. Maybe the climate scientists are right.
“So it appears the author implies that SOME atmoshperic pressure is required to run a siphon(?)”
No, some atmospheric pressure is needed to prevent the water evaporating. Nothing to do with the syphon. Same would apply to mercury (except that the vapour is highly toxic).
If he’d cooled the water to the temperature of the atmosphere at 40,000 ft he would not have had a vapour lock problem. But heck the guy’s only _teaching_ science you would not expect him to actually know how to do it in practice, would you?
Read the paper. Nice didactically. But published in Nature – seriously? Basically, this (somewhat crude) study appears to be a bit of an overkill for showing that cohesive properties of water have some influence on (special situations in) siphoning. I bet there is a close connection between the vapor pressure of water and its cohesive properties… Moreover, pressure differences are still essential in the waterfall case since the ambient pressure is higher than the water vapor pressure in the waterfall region! Finally: no need for a fancy hypobaric chamber! Use a >10m high siphon instead and vary the reservoir-to-apex height to see the waterfall effect – much cheaper!