Let’s just start with the Mpemba effect. This is totally cool!
Wikipedia, current article.
I came across this from a comment on E-catworld.com in a discussion of Water Behavior Surprises — Freezing at High Temperatures in Carbon Nanotubes
I was familiar with the claimed effect itself, but not the name and the more recent history, particularly the competition. The video of the winner is particularly engaging, that young researcher’s attitude is to be acknowledged and appreciated.
Something is missing from every comment I have seen so far on the effect. (Someone must have said it, I just haven’t found it.) This missing idea is fundamental to why the effect is knee-jerk rejected by most with an understanding of physics. With it in mind, then, the proposed explanations may be much more quickly vetted. I did find comments that more or less hinted at this, but that did not explicitly state it.
When the hotter water cools, it either never catches up, becomes as cool as the cooler water, or it does. If it never catches up, then presumably the cooler water will reach freezing sooner, contradicting the effect. This is the normal expectation. However, suppose it does catch up, consider the point where it is the same temperature. What then? If the apparent result is that the originally hotter water freezes first, there must be some difference between these two containers at the same temperature.
There is no “cooling inertia.” There could be inertia of the air circulation, but it seems unlikely that this could be enough to explain the fairly gross effect. I.e., the increased convection from the hot water would seem to be unable to persist for long, and that effect would decline as the hotter container approached the temperature of the cooler container.
The effect is experimentally confirmed. The Wikipedia article points out the vagueness of definitions. However, the original Mpemba effect was with ice cream, where the difference was simple and readily observable. Ice cream is either a frozen slurry, or it is liquid. In the situation Mpemba described, the difference was blatant.
So, there must be a difference in the two containers (or maybe the immediate environment), even if they have the same temperature. It was of interest to see comment on the Wikipedia article that seems to have assumed that the claim was about separate containers, not two in parallel, cooling at the same time in the same freezer. This all demonstrates our propensity for inventing prosaic explanations, explanations that keep us from confronting a mystery. He thought the hotter container triggered the freezer to turn on, and then hysteresis kept the temperature lower. And he obviously did not research the matter, or he’d have known that this wasn’t reasonable under the experimental conditions described.
We see this all the time with cold fusion, people who encounter the concept, and with no depth of understanding of the experimental record, propose explanations that make sense to them. Sometimes these are proposed with an attitude of “What a bunch of idiots! Can’t they see that [the obvious, blah, blah]?”
(I want to be clear that none of this is an argument for cold fusion. I am interested in how we think and how it is, on the one hand, useful, but, on the other hand. limits us. It could be an argument against pseudoskepticism.)
From the Wikipedia article:
A reviewer for Physics World writes, “Even if the Mpemba effect is real — if hot water can sometimes freeze more quickly than cold — it is not clear whether the explanation would be trivial or illuminating.” He pointed out that investigations of the phenomenon need to control a large number of initial parameters (including type and initial temperature of the water, dissolved gas and other impurities, and size, shape and material of the container, and temperature of the refrigerator) and need to settle on a particular method of establishing the time of freezing, all of which might affect the presence or absence of the Mpemba effect. The required vast multidimensional array of experiments might explain why the effect is not yet understood.
So much for “a reviewer for Physics World” being at all cogent. (To be fair, I don’t have access to the original review. Wikipedia paraphrases can be way off.) The “sometimes” in the review implies that the effect is not consistent. Yes, there may be variables that affect it, that is expected. However, none of the ones the reviewer names would be difficult to control, and much of that has been done, apparently. Obviously, the entire possible parameter space has not been explored, but the reviewer comments, to me, appear totally useless. The Mpemba effect is interesting, “illuminating,” because it is an effect within ordinary experience, so far not clearly or thoroughly understood, and simple to test.
“If” in the reviewer statement implies that the evidence for the reality of the effect is weak. It has not been proposed that hot water always freezes sooner under all conditions, but the difference between frozen and unfrozen ice cream, the original Mpemba effect, is blatantly obvious. It then appears that this works with ordinary water, at least under some known conditions. The reviewer makes the effect itself out to be far more complicated than it is. Yes, in designing controlled experiments, we would want to consider all the variables, but the investigation of an effect would always start with observing it — or not.
How to Fossilize Your Hamster: And Other Amazing Experiments For The Armchair Scientist has some good coverage. It presents some plausible hypotheses, but does not attempt to declare one the true cause. All this is testable.
And then I found that winning answer by Nikola Bregović, more than the summary I had at first. He does fully cover the issue I consider important, above. For some odd reason, in his experimental work, he did not use parallel experiments. Perhaps he only had one thermocouple.
His analysis of a series of proposed mechanisms is thorough and careful. He does not come to a firm conclusion, but does present convection as important. When beakers of water were stirred during cooling, the Mpemba effect disappeared. He ends with the point that the behavior of water
The fact that this effect is not fully resolved to this day, was an indication to me that fundamental problems lie underneath it, but still I did not expect to find that water could behave in such a different manner under so similar conditions. Once again this small, simple molecule amazes and intrigues us with [its] magic.
Palladium deuteride is nowhere near as simple as water. Pseudoskeptics, however, treated the Fleischmann-Pons experiment as if it were simple, and used the difficulty of controlling conditions to generate controlled results as an argument against reality of the Anomalous Heat Effect. When the effect was reported, hosts of prosaic explanations were invented. Indeed, such is part of normal scientific process, but the vituperation and contempt that accompanied all this, still continuing, on occasion, to this day, were utterly unwarranted.
To complete this, the original topic on e-catworld.com was the reported presence of water ice within carbon nanotubes at 100 C.
Inside tiny tubes, water turns solid when it should be boiling
MIT researchers discover astonishing behavior of water confined in carbon nanotubes.
I’m just not surprised, and here is why: I have been looking at the theories of Kim and Takahashi about Bose-Einstein Condensates being possible as explanation for the Anomalous Heat Effect. These are often rejected immediately because BECs occur very close to absolute zero. They are “impossible” at room temperature. However, this misses something. First of all, the requirement for a BEC is not low temperature, per se — and “temperature” refers to the bulk — but low relative momentum of the BEC atoms. Because of the random nature of motion with heat, it will occur that transient BECs form in liquids or gases at much higher bulk temperature, but these will be like ice forming in water above freezing. Any such ice crystals will be transient, necessarily very small, and very difficult to detect. But they must form, that is, bonded water must form. The issue is lifetime. The same with BECs. They must form, but would normally be undetectable. The issue then becomes rate, much more complex. We don’t actually have enough information to calculate the rate without major guesswork. So what can be said is, “It might be possible.” Ruling it out without experimental evidence is simply a failure of imagination.
Because pure liquid deuterium exhibits no AHE, the idea is that the confinement of the palladium lattice or structures in the palladium catalyzes the specific arrangement needed for a BEC, which, from Takahashi’s calculations, need only exist for a femtosecond to collapse with fusion by tunnelling being complete within an other femtosecond.
So with this thinking in mind, that a carbon nanotube may support and maintain water bonding with itself, confined in the tube, at higher temperatures than normal boiling is not in the least surprising. It was only astonishing for a naive consideration. The effect appears to be critically sensitive to the nanotube diameter.
This, again, is not intended as a proof that cold fusion actually occurs. That strong evidence does exist, but it is much more direct.
