Okay, this was interesting: the Leidenfrost Effect and medieval law

>> Tuesday, June 15, 2010

Sort of a random topic, but I thought this was kind of interesting: going through RSS feeds the other night, I stumbled across this item at Kottke, featuring this video edit of the Mythbusters dipping their hands in molten lead:

The reason they can do this is the Leidenfrost Effect; from Wikipedia (in case you can't watch the Mythbusters video right now):

The Leidenfrost effect is a phenomenon in which a liquid, in near contact with a mass significantly hotter than the liquid's boiling point, produces an insulating vapor layer which keeps that liquid from boiling rapidly.... The effect is also responsible for the ability of liquid nitrogen to skitter across lab floors, collecting dust in the process. It has also been used in some potentially dangerous demonstrations, such as dipping a wet finger in molten lead or blowing out a mouthful of liquid nitrogen, both enacted without injury to the demonstrator.

It is named after Johann Gottlob Leidenfrost, who discussed it in A Tract About Some Qualities of Common Water in 1756.

Now, what I found most fascinating about this, frankly, isn't the physics demonstration (which is undeniably trés cool), but that it immediately reminded me of Charles Mackey's classic, Extraordinary Popular Delusions And The Madness Of Crowds.

If you haven't read Extraordinary Madness, it remains a fascinating and relevant work a century-and-a-half after publication. Rambling in scope, Mackey fills out a history of early economic bubbles and crises with thoughts on everything from religious manias to fads in pop music (it turns out, if you didn't know, that a stupid song becoming inordinately, inescapably popular and then abruptly vanishing like it never existed when everybody was sick of it is something that happened as much in the 19th Century as now).

In his fifteenth chapter, "Duels And Ordeals.", Mackey talks about--well, the chapter title is pretty self-explanatory. In its earliest phases, the legal system (such as it was) resolved disputes by letting people beat each other up or by engaging in casual torture under the theory that if God thought somebody was innocent, they'd live or at least not lose a limb; Mackey thinks this was really stupid and says so. He also describes some of the trials by ordeal used to determine guilt or innocence before they invented lawyers:

By the fire-ordeal the power of deciding was just as unequivocally left in their [the clergy's] hands. It was generally believed that fire would not burn the innocent, and the clergy, of course, took care that the innocent, or such as it was their pleasure or interest to declare so, should be so warned before undergoing the ordeal, as to preserve themselves without any difficulty from the fire. One mode of ordeal was to place red-hot ploughshares on the ground at certain distances, and then, blindfolding the accused person, make him walk barefooted over them. If he stepped regularly in the vacant spaces, avoiding the fire, he was adjudged innocent; if he burned himself, he was declared guilty. As none but the clergy interfered with the arrangement of the ploughshares, they could always calculate beforehand the result of the ordeal. To find a person guilty, they had only to place them at irregular distances, and the accused was sure to tread upon one of them. When Emma, the wife of King Ethelred, and mother of Edward the Confessor, was accused of a guilty familiarity with Alwyn, Bishop of Winchester, she cleared her character in this manner. The reputation, not only of their order, but of a queen, being at stake, a verdict of guilty was not to be apprehended from any ploughshares which priests had the heating of. This ordeal was called the Judicium Dei, and sometimes the Vulgaris Purgatio, and might also be tried by several other methods. One was to hold in the hand, unhurt, a piece of red-hot iron, of the weight of one, two, or three pounds. When we read not only that men with hard hands, but women of softer and more delicate skin, could do this with impunity, we must be convinced that the hands were previously rubbed with some preservative, or that the apparently hot iron was merely cold iron painted red. Another mode was to plunge the naked arm into a caldron of boiling water. The priests then enveloped it in several folds of linen and flannel, and kept the patient confined within the church, and under their exclusive care, for three days. If, at the end of that time, the arm appeared without a scar, the innocence of the accused person was firmly established

And even more revealing, in a related footnote Mackey adds:

Very similar to this is the fire-ordeal of the modern Hindoos, which is thus described in Forbes's "Oriental Memoirs," vol. i. c. xi.—" When a man, accused of a capital crime, chooses to undergo the ordeal trial, he is closely confined for several days; his right hand and arm are covered with thick wax-cloth, tied up and sealed, in the presence of proper officers, to prevent deceit. In the English districts the covering was always sealed with the Company's arms, and the prisoner placed under an European guard. At the time fixed for the ordeal, a caldron of oil is placed over a fire; when it boils, a piece of money is dropped into the vessel; the prisoner's arm is unsealed, and washed in the presence of his judges and accusers. During this part of the ceremony, the attendant Brahmins supplicate the Deity. On receiving their benediction, the accused plunges his hand into the boiling fluid, and takes out the coin. The arm is afterwards again Sealed up until the time appointed for a re-examination. The seal is then broken: if no blemish appears, the prisoner is declared innocent; if the contrary, he suffers the punishment due to his crime." * * * On this trial the accused thus addresses the element before plunging his hand into the boiling oil:—"Thou, O fire! pervadest all things. O cause of purity! who givest evidence of virtue and of sin, declare the truth in this my hand!" If no juggling were practised, the decisions by this ordeal would be all the same way; but, as some are by this means declared guilty, and others innocent, it is clear that the Brahmins, like the Christian priests of the middle ages, practise some deception in saving those whom they wish to be thought guiltless.

Notice that in the Indian version Mackey describes, the hand is washed before being immersed.

Obviously, some of these trials aren't situations where the Leidenfrost Effect might occur. But with regards to the trials in which it potentially came into play--e.g. the Indian trial in which the hand is wet and then immersed in boiling oil--it certainly seems possible, doesn't it? It seems impossible to me that this is a novel observation--surely somebody in the past 254 years has suggested this; still, it's fun to think about, isn't it?

Mackey published Extraordinary Madness in 1841; the Leidenfrost Effect was described in 1756 and seems to have been reasonably well-known to engineers of Mackey's era; nonetheless, Mackey hypothesizes that fraud may have been at play when those undergoing ordeals to prove their innocence managed to grab a coin from a pot of boiling oil or water. One wonders how it escaped Mackey's notice, as thorough and wide as his work was.

The Leidenfrost Effect would explain, for one thing, why some people survived ordeals unscathed and others fried a limb. As the Mythbusters discovered, variations in the temperature of the melted lead had a profound effect on whether the Leidenfrost Effect actually occurred; in insufficiently hot molten lead, ironically enough, a test sausage was cooked more than it would be in lead hot enough to trigger the effect.

One might also speculate that Mackey was partly right about Church fathers engaging in some fraud: perhaps someone suspected of being actually guilty was allowed to put a dry hand in the pot (ouch) or a pot wasn't sufficiently heated (again, ouch). Meanwhile, an innocent party might be subtly (or not-so-subtly) encouraged to move a little faster, before the protective steam layer between their limb and the hot substance completely boiled away and vanished.

The thing about this speculation is that physics seems to me a bit more likely than either God or fraud. One issue I always had with Mackey's thoughts on ordeals was that fraud seemed a bit too pat--you can't disregard the possibility altogether (Uri Geller has convinced plenty of rational, intelligent, educated people that he has telespoonesis), but one imagines that, surely, someone would notice something a bit off about that pot of oil or hot lead if it were a con, or that somebody would helpfully screw it up ("Hey, this kettle isn't hot at all, let me throw some more coals on!"). But it turns out you don't need a miracle or deception, which is pretty awesome, really.

All you need is steam.


Nathan Tuesday, June 15, 2010 at 9:19:00 AM EDT  

Tell the truth. You thought of the word "telespoonesis" ages ago and you've just been waiting for an excuse to use it ever since.

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