It wasn't a statement, it was a very flippant joke. His tongue was so far into his cheek that he practically had a speech impediment.
Have you actually seen the video?
He was clearly not serious, and the keynote is the one time that Apple "lets go" a bit and responds to the flak it faces all the time, and even then it's pretty softball stuff.
They had a couple of digs at the concept that Apple users are all sheep, and a quick one about malware, and one about the fact that only a minority of Android users are on the latest version.
The reaction of the press and Android fans seems to have been to take everything Tim Cook said as if he was deadly serious. I'd say "they missed the joke" but it seems like they're wilfully missing it in order to bash Apple some more, so I guess it's a day with a Y in it.
It's hilarious to see just how butthurt the Andoid faithful get over a flippant comment in the keynote.
Cook's comments were a clear and obvious joke, framed in the context of the change in Apple's user base. It's no different to any of the jokes told around here about Apple or its users. He was clearly not serious. The keynote also featured a video message schtick of a bad hair day being corrected with a hedge trimmer - are we meant to take that totally seriously too?
Apple and its users get a seriously large amount of vitriol thrown at them on a day to day basis, so they throw in a few jokes about people buying Android phones "by mistake!" and the Apple haters start frothing.
So, just to be clear on this - you think that any one who uses an Apple product is delusional? That is your suggestion, yes?
Easy to pass off the blame on the faceless Apple, when the control over where your app is sold is a developer decision, unless specific legal issues are encountered (music rights, sponsorship, legality of particular content in certain countries etc), which are clearly spelled out in Apple's documentation.
So, how is it their fault again, or did you get caught in a little white lie because you weren't expecting people to actually argue with you and point out inconsistencies in your argument?
It's not about gas vs. diesel (or electric). It's about variant designs sold in the U.S. vs. Europe. They don't sell exactly the same car. Even with the same fuel type (though they might beef up the U.S. engine to handle the extra weight), U.S. cars tend to do a little more poorly on mileage due to the weight of the extra safety features.
They also do more poorly in comparison because your gallon is smaller than the one used in the UK.
Take any quoted MPG figure from Europe and divide by 1.2 to see the equivalent figure in US MPG.
The irony here is that FCVs _are_ electric vehicles. I'm not sure why they think that a fuel cell is so much better than a battery, but hey. I'm interested to see real-world well-to-wheel comparisons of the H2 that is in the fuel stations and local electricity.
They think it's much better than a battery because that's what every Tom, Dick and Harry on the street says when you bring up electric cars - "but I need to tow my boat 800 miles per week! electric is doomed for everyone!"
You can refuel a hydrogen car very quickly - at a similar rate to a gasoline car, and the general idea is well ingrained (plug a pump nozzle into a filling point, dispense fuel per unit volume/mass then pay for it).
With current technology you can overcome one of the primary problems, the low energy density of H2, by using a large pressure vessel that weighs about 100 kg (220 pounds) to store enough hydrogen to give you an equivalent range to a gasoline engine. In exchange for that weight, you're losing some of the heavier components of the ICE drivetrain like the gearbox, and the engine itself can also be lighter (although current fuel cells have been designed to fit into a similar footprint to gasoline engines).
Production is obviously difficult - the current bulk H2 production is steam reforming of methane, which is obviously a fossil fuel dependent process (although perhaps biomass could be used instead, but that's a long way off viable scale), or bulk electrolysis of aqueous potassium hydroxide which is heavily dependent on electricity costs.
There are a few things in the works to improve all of these areas, but it's not as doomed as people make out. Catalytic water splitting is something we are working on, but there are major challenges to it (namely that replicating enzymes from scratch is hard work) that has the potential to make localised H2 production as easy as letting sunlight fall on your tank of water (metaphorically).
The other benefit of H2 fuel cells over pure electric is that you can more easily scale them to bigger vehicles like busses and trucks. As you scale up the energy storage device of H2 vs EV (the H2 tank or the battery), the mass of the battery scales with the size pretty linearly whereas the hydrogen pressure vessel doesn't - you get more volume per unit mass of tank as you make it bigger, making it more efficient for very large vehicles.
This is basically a long-winded way of saying that there are benefits to both technologies and that it shouldn't be either/or - they should complement each other in the same way that gasoline and diesel power trains do.
Its us the consumer who ends up picking up the tab for the legal bills, and in the end we just find out what we all knew already, they all steal each others ideas. Thanks Apple.
Untrue. By default you have Play, Google's curated app store. You can install other app stores or side load, but the default is just Play.
With great power comes great responsibility and all that. Besides which Apple's App Store isn't devoid of malware either, it's just a different kind of malware. My girlfriend is Chinese and there are a lot of Chinese apps, presumably not even visible in the western version of the store, that look extremely iffy. They ask you for random personal details, direct you to nasty looking web sites, and have masses of rip-off in-app purchases and pay-to-win scenarios.
You realise if an Apple user tried to spin that line in a story where 99% of malware was targeted at iOS they would be down modded into the ground, right?
"Here's tangible, documented proof of 99% of malware being on Android, but hey, some Chinese apps on iOS 'look a bit suspicious' so Apple is bad too!"
Oh, I don't know. Just pick any random slashdot thread where a security vulnerability in an Apple product is mentioned. Those comments seem to rely pretty heavily on "it's about security, not marketshare" when the tables are reversed.
If it's good for the goose, it's good for the gander.
I'll just leave the final conclusion from the paper:
"Although this experimental setup is a special example of a siphon, liquids with low or near-zero tensile strengths can be easily demonstrated to function in siphons at a normal positive pressure. It is therefore concluded that whereas cohesion does have a part to play in most siphons, the underlying principle is most readily explained in terms of gravity and hydrostatic pressure differential without regard to the mechanism of atmospheric pressure or cohesive force."
I'm aware that there's no "negative pressure" - I use the term when talking about suction. i.e., the delta between the static pressure and that produced at the face of the pump. These values are always positive (even for UHV turbo pumps), but the delta is frequently given negative.
But, ignoring that, you're telling me that, at the base of any column of liquid the hydrostatic pressure is equal to the atmospheric pressure? I'm not even sure if you're trolling. If you are, it's expertly done, sir.
Take two tanks of water sitting on the earth, both with open tops. They are both 1 metre on each side, both are 2 metres tall. One of them is half full, the other is full (i.e., one is filled to 1 metre deep, the other is full to 2 metres deep). What is the pressure at the bottom of each tank? What is the atmospheric pressure above the tank?
rho, g, h - the density of the fluid, gravity and the depth of the fluid.... not atmospheric pressure.
That's where hydrostatic pressure comes from.
You could build a siphon to the edge of space and back down again if your hydrostatic pressure was high enough - i.e., the depth of the water in the source reservoir would have to be extremely deep.
The only time that atmospheric pressure is involved in moving water uphill with a limit is if you have a pump at the top. It lowers the pressure in the pipe and sucks the water up, but the change in pressure is therefore between zero and whatever is acting on the surface of a liquid. A siphon does not work that way.
Sucking a column of water involves creating low pressure for the liquid to flow to (pumping water upwards, sucking on a straw etc). The limit there is the difference between zero pressure and the pressure at the source - i.e., atmospheric pressure. What you seem to be missing is that siphons do not work by suction. They work due to gravity and hydrostatic head.
You can create a siphon as high as the hydrostatic head in the source reservoir can provide - this is a function of gravity, fluid density and the depth of the fluid. Atmospheric pressure is not involved.
Surface tension plays a small role, but it is not essential. The two primary drivers are gravity and the hydrostatic pressure. Period.
I'm not saying it's about hiding something, just about demonstrating up to the level where the thing will work. I don't know how strong the surface tension is exactly. What I do know, is that atmospheric pressure is sufficient to have a siphon that's 10 meters tall and I very much doubt that surface tension comes even close to that value. I'm sure your friend would be able to calculate how high it goes, but I doubt that's more than a few cm high.
Surface tension is not the major driving force, as is very apparent from the experiments (and because the surface tension of the ionic liquid is lower).
It is clear that the hydrostatic pressure and gravity are what drive the siphon, not atmospheric pressure.
How exactly can atmospheric pressure drive a siphon that is 10m tall? Tell me, what is the pressure at the inlet of the siphon and at the exit? What's the difference in pressure between these two points?
No, it seems clear that you don't understand the forces that make a siphon work and you're just trying to "common sense" it in the fact of actual scientific experiments that demonstrate that atmospheric pressure is not involved at all.
The video was giving a layman's description of cations and anions - i.e., the components of an ionic liquid.
The actual measured scientific data demonstrates that the ionic liquid used has a lower surface tension than water - most liquids do, since water is one of the most cohesive liquids there is. That's just a measurable fact.
Water hydrogen bonds, and the physical properties of water are very strange, but it evaporates in outer space because the vapour pressure is higher than that of the ionic liquid. There are a number of factors that go into the resulting vapour pressure, of which cohesion is one. The properties of the ionic liquid give it a near-zero vapour pressure, but a lower surface tension (and cohesion) than water. It's just how it turns out.
Hydrostatic pressure is the pressure exerted on a fluid by the weight of the fluid above it - it's why the pressure at the bottom of the sea is high - there's a large amount of water above pressing down. The hydrostatic pressure at the bottom of the siphon reservoir is created by the weight of the liquid pressing down. The deeper that reservoir is, the higher the hydrostatic pressure will be, and the higher you will be able to siphon. The level of the surface of the liquid above the opening, along with gravity, determines the hydrostatic pressure (assuming that the pressure of the gas or lack thereof above the liquid is fixed - i.e., in a vacuum it is zero, for a normal siphon it is close enough to equal to not matter, but ever so slightly higher at the lower siphon exit).
It's not that much more cohesive than water - in fact, it is less. The surface tension of the ionic liquid used is less than that of water, yet the siphon still works.
The fluid breaks up due to a lack of hydrostatic pressure if you change the elevation too much - with more liquid in the reservoirs, you could siphon across a larger height without breakup of the fluid.
Here's the conclusion of the paper:
"Although this experimental setup is a special example of a siphon, liquids with low or near-zero tensile strengths can be easily demonstrated to function in siphons at a normal positive pressure. It is therefore concluded that whereas cohesion does have a part to play in most siphons, the underlying principle is most readily explained in terms of gravity and hydrostatic pressure differential without regard to the mechanism of atmospheric pressure or cohesive force."
Well, the siphon is limited in size to hit in the ultra high vacuum box.
I know you probably can't read the paper the video is based on (since it's paywalled), but you're making assumptions. The ionic liquid used in that experiment has a *lower* surface tension than water - there's a detailed section of the paper that discusses this, and they also measured surface tension data at a range of temperatures and under varying pressures.
Tell me, how big do you think you can (affordably) make a chamber that you can pump down to 10^-5 mbar? The reason that the siphon is that size is not because they're trying to hide anything, just that the box is a certain size.
(disclaimer: I know the guys in the video personally).
I argue that that with atmospheric pressure you get a much more generally usable siphon.
No, you're arguing that an atmosphere is *required* for a siphon to work when it clearly does not.
The use of an ionic liquid to prove that is not an extreme corner case, it's simply making use of the properties of a particular substance to test a hypothesis.
Elemental sodium is very rare on the earth's surface, but I wouldn't call an experiment to test how it reacts with water or with air to be an extreme corner case - there's no doubting that it's a controlled experiment. You can't dismiss the results of the experiment because you think it is too niche. It's one of several experiments carried out into the function of a siphon and the conclusions are not drawn just from that one case.
That is what has been done here, along with other measurements using different liquids and conditions to determine how a siphon works and the variables that affect it. It has been determined through multiple experiments by different groups that an atmosphere is not needed. While it has an effect on the liquid that you are siphoning in terms of its physical properties, it has no function in the mechanism of the siphon itself as expected.
As has been pointed out, a siphon moves liquid from high to low elevation via an uphill pipe. The outlet of the siphon is at higher pressure than the inlet. If pressure affected the siphon then it would be an inhibitory one - however, this effect is not seen at varying pressure - i.e., you'd expect to see the effect diminish as the pressure dropped if it had an effect at all. The fact that you don't see this at different pressures and that the liquids behave the same regardless of pressure (up to the limit of that particular liquid's vapour pressure) demonstrates that it has no function in the way a siphon works.
Your comparison to a magnet and chain is not relevant. You're introducing new forces (and while ionic liquids contain ions, they're not magnets), and the chain itself is a contiguous object. It "acts like" a siphon, but then a piston driven by steam extends in the same way that a solenoid driven by electricity does. Does that mean the solenoid is driven by pressure because it acts like the steam piston?
Your doubt and intuition versus peer-reviewed science? Hmm. Tough choice.
How do you know it wouldn't work with a 1 metre siphon? You're still claiming you need atmospheric pressure for a siphon to work when it;s demonstrably not the case.
This vacuum experiment works with any liquid that can stay liquid under those conditions - like mercury, for example, although you can't go quite as low.
The two properties you need for a siphon are the cohesion of the liquid (and this is true for the regular water siphon) and gravity, with the latter being the key player. Atmospheric pressure is not needed.
TFA demonstrated that the siphon stopped working when the pressure fell too low because of the properties of the fluid being siphoned, not because a siphon requires atmospheric pressure to work.
An analogy would be that I can demonstrate that F=ma is not true for high values of F and small values of m because air resistance starts to affect the result. This doesn't mean that the equation doesn't work at these values, just that the experiment cannot measure the data under those conditions.
The water siphon experiment is the same - it stops working at low pressure, but not because you need pressure for a siphon to work. It's simply not possible to take data because the water boils off.
The ionic liquid experiment demonstrates that you do not need pressure for it to work at all - since it operates in UHV. The ionic liquid has cohesion in the same way that water does - it just has more of it due to the physical properties of the liquid. However, it is clear that gravity is the most important part, since you can siphon almost any liquid (like gasoline, which has very little cohesion compared to water or an ionic liquid) as long as you have a change in elevation.
There's no "substitution" of weak ionic bonds for pressure, because it's not pressure that is driving the water siphon. There happens to be pressure, purely because there's an atmosphere, but it's not why the siphon works. The water siphon works because of the cohesion of the water and gravity... just like the ionic liquid version under vacuum.
Ionic liquids aren't really "exotic", they're just uncommon to non-chemists. Almost any melted salt is an ionic liquid. If you make it with large, oddly shaped diffuse ions then it tends to be liquid at room temperature. They flow like other liquids. They can be decanted, they have surface tension, they work as solvents. There's no "cheating" or substitution going on. It was just used because it has a low vapour pressure and can thus go beyond the range capable with water.
You could do the same experiment with a liquid metal, such as mercury (convenient) or any other metal that you can keep liquid long enough to test it if you can stop it solidifying, although even mercury has a vapour pressure and will boil off in a high vacuum so you'd have to be careful about repeating the experiment.
No, you do not need any atmosphere at all. This has already been proven (and demonstrated on video!) yet people still seem to think "common sense" prevails.
You just need a liquid that won't boil off under vacuum. The only reason the Nature experiment failed was because the working fluid was water, which boils at low pressure.
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It wasn't a statement, it was a very flippant joke. His tongue was so far into his cheek that he practically had a speech impediment.
Have you actually seen the video?
He was clearly not serious, and the keynote is the one time that Apple "lets go" a bit and responds to the flak it faces all the time, and even then it's pretty softball stuff.
They had a couple of digs at the concept that Apple users are all sheep, and a quick one about malware, and one about the fact that only a minority of Android users are on the latest version.
The reaction of the press and Android fans seems to have been to take everything Tim Cook said as if he was deadly serious. I'd say "they missed the joke" but it seems like they're wilfully missing it in order to bash Apple some more, so I guess it's a day with a Y in it.
It's hilarious to see just how butthurt the Andoid faithful get over a flippant comment in the keynote.
Cook's comments were a clear and obvious joke, framed in the context of the change in Apple's user base. It's no different to any of the jokes told around here about Apple or its users. He was clearly not serious. The keynote also featured a video message schtick of a bad hair day being corrected with a hedge trimmer - are we meant to take that totally seriously too?
Apple and its users get a seriously large amount of vitriol thrown at them on a day to day basis, so they throw in a few jokes about people buying Android phones "by mistake!" and the Apple haters start frothing.
So, just to be clear on this - you think that any one who uses an Apple product is delusional? That is your suggestion, yes?
And you believe him?
Easy to pass off the blame on the faceless Apple, when the control over where your app is sold is a developer decision, unless specific legal issues are encountered (music rights, sponsorship, legality of particular content in certain countries etc), which are clearly spelled out in Apple's documentation.
So, how is it their fault again, or did you get caught in a little white lie because you weren't expecting people to actually argue with you and point out inconsistencies in your argument?
http://lmgtfy.com/?q=VLC
It's not about gas vs. diesel (or electric). It's about variant designs sold in the U.S. vs. Europe. They don't sell exactly the same car. Even with the same fuel type (though they might beef up the U.S. engine to handle the extra weight), U.S. cars tend to do a little more poorly on mileage due to the weight of the extra safety features.
They also do more poorly in comparison because your gallon is smaller than the one used in the UK.
Take any quoted MPG figure from Europe and divide by 1.2 to see the equivalent figure in US MPG.
When people spend a lot of money on something, they tend to like it no matter what for a while.
So I have the following formula of trust.
(cost/1000) / 2 = n Months until the 'new car placbo effect' has worn off.
Can I call this your "easy way to dismiss arguments that don't agree with my position" rule?
The irony here is that FCVs _are_ electric vehicles. I'm not sure why they think that a fuel cell is so much better than a battery, but hey. I'm interested to see real-world well-to-wheel comparisons of the H2 that is in the fuel stations and local electricity.
They think it's much better than a battery because that's what every Tom, Dick and Harry on the street says when you bring up electric cars - "but I need to tow my boat 800 miles per week! electric is doomed for everyone!"
You can refuel a hydrogen car very quickly - at a similar rate to a gasoline car, and the general idea is well ingrained (plug a pump nozzle into a filling point, dispense fuel per unit volume/mass then pay for it).
With current technology you can overcome one of the primary problems, the low energy density of H2, by using a large pressure vessel that weighs about 100 kg (220 pounds) to store enough hydrogen to give you an equivalent range to a gasoline engine. In exchange for that weight, you're losing some of the heavier components of the ICE drivetrain like the gearbox, and the engine itself can also be lighter (although current fuel cells have been designed to fit into a similar footprint to gasoline engines).
Production is obviously difficult - the current bulk H2 production is steam reforming of methane, which is obviously a fossil fuel dependent process (although perhaps biomass could be used instead, but that's a long way off viable scale), or bulk electrolysis of aqueous potassium hydroxide which is heavily dependent on electricity costs.
There are a few things in the works to improve all of these areas, but it's not as doomed as people make out. Catalytic water splitting is something we are working on, but there are major challenges to it (namely that replicating enzymes from scratch is hard work) that has the potential to make localised H2 production as easy as letting sunlight fall on your tank of water (metaphorically).
The other benefit of H2 fuel cells over pure electric is that you can more easily scale them to bigger vehicles like busses and trucks. As you scale up the energy storage device of H2 vs EV (the H2 tank or the battery), the mass of the battery scales with the size pretty linearly whereas the hydrogen pressure vessel doesn't - you get more volume per unit mass of tank as you make it bigger, making it more efficient for very large vehicles.
This is basically a long-winded way of saying that there are benefits to both technologies and that it shouldn't be either/or - they should complement each other in the same way that gasoline and diesel power trains do.
Its us the consumer who ends up picking up the tab for the legal bills, and in the end we just find out what we all knew already, they all steal each others ideas. Thanks Apple.
So you agree that Samsung ripped off the iPhone?
Brave comment on slashdot.
no curation for Android
Untrue. By default you have Play, Google's curated app store. You can install other app stores or side load, but the default is just Play.
With great power comes great responsibility and all that. Besides which Apple's App Store isn't devoid of malware either, it's just a different kind of malware. My girlfriend is Chinese and there are a lot of Chinese apps, presumably not even visible in the western version of the store, that look extremely iffy. They ask you for random personal details, direct you to nasty looking web sites, and have masses of rip-off in-app purchases and pay-to-win scenarios.
You realise if an Apple user tried to spin that line in a story where 99% of malware was targeted at iOS they would be down modded into the ground, right?
"Here's tangible, documented proof of 99% of malware being on Android, but hey, some Chinese apps on iOS 'look a bit suspicious' so Apple is bad too!"
Laughable. Truly laughable.
[Citation needed]
Oh, I don't know. Just pick any random slashdot thread where a security vulnerability in an Apple product is mentioned. Those comments seem to rely pretty heavily on "it's about security, not marketshare" when the tables are reversed.
If it's good for the goose, it's good for the gander.
I'll just leave the final conclusion from the paper:
"Although this experimental setup is a special example of a siphon, liquids with low or near-zero tensile strengths can be easily demonstrated to function in siphons at a normal positive pressure. It is therefore concluded that whereas cohesion does have a part to play in most siphons, the underlying principle is most readily explained in terms of gravity and hydrostatic pressure differential without regard to the mechanism of atmospheric pressure or cohesive force."
I'm aware that there's no "negative pressure" - I use the term when talking about suction. i.e., the delta between the static pressure and that produced at the face of the pump. These values are always positive (even for UHV turbo pumps), but the delta is frequently given negative.
But, ignoring that, you're telling me that, at the base of any column of liquid the hydrostatic pressure is equal to the atmospheric pressure? I'm not even sure if you're trolling. If you are, it's expertly done, sir.
Take two tanks of water sitting on the earth, both with open tops. They are both 1 metre on each side, both are 2 metres tall. One of them is half full, the other is full (i.e., one is filled to 1 metre deep, the other is full to 2 metres deep). What is the pressure at the bottom of each tank? What is the atmospheric pressure above the tank?
Look at the equation you just posted.
rho, g, h - the density of the fluid, gravity and the depth of the fluid.... not atmospheric pressure.
That's where hydrostatic pressure comes from.
You could build a siphon to the edge of space and back down again if your hydrostatic pressure was high enough - i.e., the depth of the water in the source reservoir would have to be extremely deep.
The only time that atmospheric pressure is involved in moving water uphill with a limit is if you have a pump at the top. It lowers the pressure in the pipe and sucks the water up, but the change in pressure is therefore between zero and whatever is acting on the surface of a liquid. A siphon does not work that way.
Sucking a column of water involves creating low pressure for the liquid to flow to (pumping water upwards, sucking on a straw etc). The limit there is the difference between zero pressure and the pressure at the source - i.e., atmospheric pressure. What you seem to be missing is that siphons do not work by suction. They work due to gravity and hydrostatic head.
You can create a siphon as high as the hydrostatic head in the source reservoir can provide - this is a function of gravity, fluid density and the depth of the fluid. Atmospheric pressure is not involved.
Surface tension plays a small role, but it is not essential. The two primary drivers are gravity and the hydrostatic pressure. Period.
I'm not saying it's about hiding something, just about demonstrating up to the level where the thing will work. I don't know how strong the surface tension is exactly. What I do know, is that atmospheric pressure is sufficient to have a siphon that's 10 meters tall and I very much doubt that surface tension comes even close to that value. I'm sure your friend would be able to calculate how high it goes, but I doubt that's more than a few cm high.
Surface tension is not the major driving force, as is very apparent from the experiments (and because the surface tension of the ionic liquid is lower).
It is clear that the hydrostatic pressure and gravity are what drive the siphon, not atmospheric pressure.
How exactly can atmospheric pressure drive a siphon that is 10m tall? Tell me, what is the pressure at the inlet of the siphon and at the exit? What's the difference in pressure between these two points?
No, it seems clear that you don't understand the forces that make a siphon work and you're just trying to "common sense" it in the fact of actual scientific experiments that demonstrate that atmospheric pressure is not involved at all.
The video was giving a layman's description of cations and anions - i.e., the components of an ionic liquid.
The actual measured scientific data demonstrates that the ionic liquid used has a lower surface tension than water - most liquids do, since water is one of the most cohesive liquids there is. That's just a measurable fact.
Water hydrogen bonds, and the physical properties of water are very strange, but it evaporates in outer space because the vapour pressure is higher than that of the ionic liquid. There are a number of factors that go into the resulting vapour pressure, of which cohesion is one. The properties of the ionic liquid give it a near-zero vapour pressure, but a lower surface tension (and cohesion) than water. It's just how it turns out.
Hydrostatic pressure is the pressure exerted on a fluid by the weight of the fluid above it - it's why the pressure at the bottom of the sea is high - there's a large amount of water above pressing down. The hydrostatic pressure at the bottom of the siphon reservoir is created by the weight of the liquid pressing down. The deeper that reservoir is, the higher the hydrostatic pressure will be, and the higher you will be able to siphon. The level of the surface of the liquid above the opening, along with gravity, determines the hydrostatic pressure (assuming that the pressure of the gas or lack thereof above the liquid is fixed - i.e., in a vacuum it is zero, for a normal siphon it is close enough to equal to not matter, but ever so slightly higher at the lower siphon exit).
It's not that much more cohesive than water - in fact, it is less. The surface tension of the ionic liquid used is less than that of water, yet the siphon still works.
The fluid breaks up due to a lack of hydrostatic pressure if you change the elevation too much - with more liquid in the reservoirs, you could siphon across a larger height without breakup of the fluid.
Here's the conclusion of the paper:
"Although this experimental setup is a special example of a siphon, liquids with low or near-zero tensile strengths can be easily demonstrated to function in siphons at a normal positive pressure. It is therefore concluded that whereas cohesion does have a part to play in most siphons, the underlying principle is most readily explained in terms of gravity and hydrostatic pressure differential without regard to the mechanism of atmospheric pressure or cohesive force."
Well, the siphon is limited in size to hit in the ultra high vacuum box.
I know you probably can't read the paper the video is based on (since it's paywalled), but you're making assumptions. The ionic liquid used in that experiment has a *lower* surface tension than water - there's a detailed section of the paper that discusses this, and they also measured surface tension data at a range of temperatures and under varying pressures.
Tell me, how big do you think you can (affordably) make a chamber that you can pump down to 10^-5 mbar? The reason that the siphon is that size is not because they're trying to hide anything, just that the box is a certain size.
(disclaimer: I know the guys in the video personally).
I argue that that with atmospheric pressure you get a much more generally usable siphon.
No, you're arguing that an atmosphere is *required* for a siphon to work when it clearly does not.
The use of an ionic liquid to prove that is not an extreme corner case, it's simply making use of the properties of a particular substance to test a hypothesis.
Elemental sodium is very rare on the earth's surface, but I wouldn't call an experiment to test how it reacts with water or with air to be an extreme corner case - there's no doubting that it's a controlled experiment. You can't dismiss the results of the experiment because you think it is too niche. It's one of several experiments carried out into the function of a siphon and the conclusions are not drawn just from that one case.
That is what has been done here, along with other measurements using different liquids and conditions to determine how a siphon works and the variables that affect it. It has been determined through multiple experiments by different groups that an atmosphere is not needed. While it has an effect on the liquid that you are siphoning in terms of its physical properties, it has no function in the mechanism of the siphon itself as expected.
As has been pointed out, a siphon moves liquid from high to low elevation via an uphill pipe. The outlet of the siphon is at higher pressure than the inlet. If pressure affected the siphon then it would be an inhibitory one - however, this effect is not seen at varying pressure - i.e., you'd expect to see the effect diminish as the pressure dropped if it had an effect at all. The fact that you don't see this at different pressures and that the liquids behave the same regardless of pressure (up to the limit of that particular liquid's vapour pressure) demonstrates that it has no function in the way a siphon works.
Your comparison to a magnet and chain is not relevant. You're introducing new forces (and while ionic liquids contain ions, they're not magnets), and the chain itself is a contiguous object. It "acts like" a siphon, but then a piston driven by steam extends in the same way that a solenoid driven by electricity does. Does that mean the solenoid is driven by pressure because it acts like the steam piston?
Your doubt and intuition versus peer-reviewed science? Hmm. Tough choice.
How do you know it wouldn't work with a 1 metre siphon? You're still claiming you need atmospheric pressure for a siphon to work when it;s demonstrably not the case.
This vacuum experiment works with any liquid that can stay liquid under those conditions - like mercury, for example, although you can't go quite as low.
The two properties you need for a siphon are the cohesion of the liquid (and this is true for the regular water siphon) and gravity, with the latter being the key player. Atmospheric pressure is not needed.
Now you're changing your argument.
TFA demonstrated that the siphon stopped working when the pressure fell too low because of the properties of the fluid being siphoned, not because a siphon requires atmospheric pressure to work.
An analogy would be that I can demonstrate that F=ma is not true for high values of F and small values of m because air resistance starts to affect the result. This doesn't mean that the equation doesn't work at these values, just that the experiment cannot measure the data under those conditions.
The water siphon experiment is the same - it stops working at low pressure, but not because you need pressure for a siphon to work. It's simply not possible to take data because the water boils off.
The ionic liquid experiment demonstrates that you do not need pressure for it to work at all - since it operates in UHV. The ionic liquid has cohesion in the same way that water does - it just has more of it due to the physical properties of the liquid. However, it is clear that gravity is the most important part, since you can siphon almost any liquid (like gasoline, which has very little cohesion compared to water or an ionic liquid) as long as you have a change in elevation.
There's no "substitution" of weak ionic bonds for pressure, because it's not pressure that is driving the water siphon. There happens to be pressure, purely because there's an atmosphere, but it's not why the siphon works. The water siphon works because of the cohesion of the water and gravity... just like the ionic liquid version under vacuum.
Ionic liquids aren't really "exotic", they're just uncommon to non-chemists. Almost any melted salt is an ionic liquid. If you make it with large, oddly shaped diffuse ions then it tends to be liquid at room temperature. They flow like other liquids. They can be decanted, they have surface tension, they work as solvents. There's no "cheating" or substitution going on. It was just used because it has a low vapour pressure and can thus go beyond the range capable with water.
You could do the same experiment with a liquid metal, such as mercury (convenient) or any other metal that you can keep liquid long enough to test it if you can stop it solidifying, although even mercury has a vapour pressure and will boil off in a high vacuum so you'd have to be careful about repeating the experiment.
No, you do not need any atmosphere at all. This has already been proven (and demonstrated on video!) yet people still seem to think "common sense" prevails.
https://www.youtube.com/watch?...
No, that "correct" explanation is wrong.
You do not need an atmosphere.
This video demonstrates a high vacuum siphon.
https://www.youtube.com/watch?...
Here's a video of a siphon working in a vacuum (10^-5 mbar) (and also a link to the paper featured as a result of the work).
You *do not* need an atmosphere, or atmospheric pressure to make it work.
https://www.youtube.com/watch?...
You just need a liquid that won't boil off under vacuum. The only reason the Nature experiment failed was because the working fluid was water, which boils at low pressure.
Followup to my post:
https://www.youtube.com/watch?...