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.

Can I call this your "easy way to dismiss arguments that don't agree with my position" rule?

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.

So you agree that Samsung ripped off the iPhone?

Brave comment on slashdot.

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.

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.

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).

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?