First idle thought: I have raised this question before but have never received a satisfactory answer. Can anybody explain to me how friction works? When I put on an undershirt in the morning, it slides easily over my body, but if I try putting it on after a shower and I am still a little bit damp it sticks to my skin. This, I take it, is a consequence of friction. But how does friction work? Why does a little water on my skin make the fabric of the undershirt catch and not fall effortlessly down?
Second idle thought: I met Noam Chomsky roughly 70 years ago when he came to Harvard to take up a Junior Fellowship. He was then a young, slender, clean-shaven handsome man, and he remained that way, at least to my way of thinking, over the next 65 years or so. When people asked me how I thought I differed from Chomsky, I would reply jokingly that he was better looking than I. But several years ago – I am not sure quite when – Noam stopped shaving and very quickly grew a full beard, so that in recent YouTube posted interviews, he looks like an old rabbi from an East European shtetl. Does anybody know why he did that? The difference is really quite striking.
Third idle thought: every night Susie and I eat at the bar in the Pub, which is one of the three dining venues here at Carolina Meadows. We are usually joined by retired general Jim Anderson, whom I have mentioned here before. The three of us were all born in 1933, so all of us turn 90 this year – Susie on January 16, Jim on April 3, and I on December 27. If I were to tell you that I had dinner last evening at a restaurant with three 90-year-olds, Your natural reaction would be how strange it was to be at the same counter with three such ancient characters, and yet that is not the way it feels to me at all. What unites us is not our age but the fact that we all like oysters. On Friday evenings, Carolina Meadows serves oysters on the half shell and they have a limited supply, so the three of us arrive early and among us eat almost half of all the oysters they have secured for the evening. The fact that we are all or about to be 90 does not come into it. It is very strange.
All of this is what I think about as I wait impatiently to find out what the Fulton County District Attorney means by the word "imminently."
I will take a stab at all three questions. (I am actually impressed that Prof. Wolff admits to having idle questions, which is quite humanizing.)
ReplyDelete1. Water, your epidermis and the fabric of your shirt have different coefficients of friction. This is not an explanation of why this is so, but only a report of empirical observation. Here is my take on why it is so (I used to be a chemistry major) The water is an inorganic molecule, composed of hydrogen and oxygen; your epidermis and the fabric of your garment are composed of organic molecules, which by definition include carbon molecules. The oxygen molecule in water is more electronegative than the hydrogen molecules (i.e., electrons tend to gravitate to the oxygen molecule). This results in the oxygen end of the molecule having a slightly negative charge, and the hydrogen end a slightly positive charge. This structure allows water molecules to line up hydrogen to oxygen, and oxygen to hydrogen. It is this structure which determines that water freezes at the temperature it does, and causes it to expand upon freezing, ice cubes and ice bergs to float on water – the expansion makes the ice cubes and ice bergs have a lower density than water itself, hence the floating. When you put on your garment on dry epidermis, the carbon molecules in the garment and the carbon molecules in your epidermis are sufficiently similar so as not to create much friction, which is just the resistance of motion; whereas the positive and negative charges on either side of a water molecule interacting with the carbon molecules in the garment retard motion, i.e., increase friction. I think I got this correct.
2. As men get older, the hair on their head tends to thin, and some of us even go bald. However, our testosterone continues to allow our facial hair to grows. Some of us grow a beard to compensate for the loss of hair on our head. Also, on some of us, a beard makes us look wiser and more scholarly. For others, once you reach a certain age and are retired, you never feel the need to shave every day before going to work. Since I work at home, I go without shaving for three to four days, and save a lot of time, which I can devote to reading this blog and writing comments, in addition to my legal research and writing, playing chess and watching movies. I have no idea whether any of these explanations apply to Prof. Chomsky, and if I had his telephone number or email address, I would contact him and ask him what his explanation is. Assuming he took the call, or did not delete the email, he would probably tell me to mind my own business.
3. The fact that you and Susie live in a retirement community makes it more probable that the people you interact with will be over the age of 65. The probability that any two people in any given gathering will have the same birthday actually increases with the number of people in the group. In a group of 23 people, the likelihood that two people in the group will have the same birthday is 50%, and increases as the group gets larger. See https://www.scientificamerican.com/article/bring-science-home-probability-birthday-paradox/#:~:text=This%20is%20known%20as%20the,see%20mathematical%20probab
As long as we are asking idle questions, here is my idle question, which popped into my head as I sit at my computer writing an appellate brief which is due in the 6th Circuit Court of Appeals in Cincinnati by midnight, Monday. As I type, my cat is sitting next to the computer staring at me with this very wise and knowing demeanor, like he is ready to provide me with legal information should I need it. I can understand why Egyptians held cats in such high regard. As I was looking at him a few minutes ago, the following question popped into my head. Tigers, leopards, cheetahs, jaguars are solitary felines. They do not live in groups. Lions, on the other hand, live in prides, with an alpha male lion and his harem of lionesses. How did the different cat species evolve to have different social organizations, and if living in a pride gives lions an evolutionary advantage, why didn’t tigers, leopards, cheetahs and jaguars evolve with the same tendency for social organization?
ReplyDeleteChomsky's wife passed away fifteen years ago and he remarried.
ReplyDeletePerhaps his new wife prefers him with a beard and longer hair.
Professor Wolff,
ReplyDeleteProbably because the shirt fabric contracts in size with the added absorption of the water. If I wear a 2x and get it soaked with water, it will probably be like wearing a size large or medium. Plus, the fabric becomes thicker too. From being a few mm thick it now becomes maybe a few cm thick with the added absorption of water. So it expanded. Also the fabric is no longer pliable when wet as opposed to when the fabric is dryer. And with the added weight of the water your upper body feels heavier. Not to mention wetter and much colder--which the mind focuses on more than anything else. I believe, Professor Wolff, you're looking more for a common sense explanation more than one based on physics.
ReplyDeleteI didn't know until I read Marc's paragraph 2 above that part of the meager amount of testosterone that my 85 year-old body produces is used to grow my beard. I can think of better uses for it.
This is completely off topic but it might interest aaall (and possibly others).
ReplyDeleteI'm reading C. Vann Woodward's classic _The Strange Career of Jim Crow_ and I just read a sentence that sort of astounded me. It's in the chapter "Forgotten Alternatives" where he's talking about alternatives to the rigid, fanatical (Woodward's word) form of legally enforced segregation that triumphed across the South in the 1890s.
One of those alternatives was a conservative (Woodward's word) view that embraced a notion of white supremacy but without advocating either total separation of the races or "Negro degradation." (p.48) He notes in this connection (p.53) that "In a symposium published in the North American Review in 1879, [Wade] Hampton, [L.Q.C.] Lamar, and Alexander Stephens [!] agreed not only that the disfranchisement of the freedmen was impossible, but that even if it were possible the South would not desire it."
In other words, in 1879 Alexander Stephens, author of the infamous "cornerstone" speech and former v.p. of the Confederacy, was arguing that Blacks should vote. It might have been purely self-interested, a result of the somewhat complicated political alignments of the period, but it nonetheless surprises me. (And I think Lamar had also been a strong secessionist, though I might be confusing this Lamar with another one.)
Here is what Feynman says about sliding friction in his lectures on physics
ReplyDelete"it is a truly complicated matter. Both surfaces of contact are irregular, on an atomic level. There are many points of contact where they seem to cling together, and then, as the sliding body is pulled along, the atoms snap apart and vibration ensues; something like that has to happen. Formerly the mechanism of this friction was thought to be very simple, that the surfaces were merely full of irregularities and the friction originated in lifting the surfaces over the bumps; but this cannot be, for there is no loss of energy in that process, whereas power is in fact consumed. The mechanism of power loss is that as the slider snaps over the bumps, the bumps deform and then generate waves and atomic motions and after a while heat in the two bodies. Now it is very remarkable that again empirically this friction can be described approximately by a simple law. This law is that the force needed to overcome friction and to drag one object over another depends upon the normal force ( ie perpendicular to the surface) between the two surfaces that are in contact. Actually, to a fairly good approximation, the frictional force is proportional to this normal force and is a more or less constant coefficient; that is F-muN3
where mu is called the coefficient of friction. Although this coefficient is not exactly constant, the formula is a good emopirical rule for judging approximately the amount of force that will be needed in cetain practical or engineering circumstances. If the normal force or the speed of motion gets too big, the law fails because of the excessive heat generated. It is important to realize that each of these empirical laws has its limitations, beyond which it does not really wor."
Richard Feynman The Feynman lectures on physics v1 12-4
Could air pressure be a factor? Skin is porous and one sided. A dry cloth, being porous and two sided, would have pressure equalized on both sides while a wet cloth would have the air between the two surfaces squeezed out proportional to the moisture between the two surfaces.
ReplyDeleteOn the other hand water between two none porous surfaces can act as a lubricant.
LFC, I scanned the article in the NAR and Steven's take is not what the book represents, nor is Lamars.
https://www.jstor.org/stable/25100732?seq=33
aaall
ReplyDeleteI don't think I knew that NAR from 1879 was available on JSTOR. I'll take a look though it may be a while before I get to it.
While I'm certain that _Strange Career_ was criticized (and that Woodward responded to criticisms), to charge him w misrepresentation of the contents of an article is fairly serious. Perhaps it's more a matter of interpretive slant? Anyway I'll take a look at the NAR. Incidentally MLK called _The Strange Career of Jim Crow_ "the historical bible of the civil rights movement."
"In a symposium published in the North American Review in 1879, [Wade] Hampton, [L.Q.C.] Lamar, and Alexander Stephens [!] agreed not only that the disfranchisement of the freedmen was impossible, but that even if it were possible the South would not desire it."
ReplyDeleteL.Q.C. Lamar:
"I was born and bred a slave holder, born and bred among slaveholders ; I have known slavery in its kindest and most beneficent aspect. My associations with the past of men and things are full of love and reverence. In all history never has a heavy duty been discharged more faithfully, more conscientiously, more successfully, than by the slaveholders
of the South."
"The South took him, as he was sent to her, a wild and godless barbarian, and made him such that the North has been able to give him citizenship without the destruction of our institutions. The progress which he made with us as a slave will not be arrested now that he is a freeman--unless party passion and personal ambition insist upon using him as an instrument for selfish ends."
Stephens waves his hands and asserts:
"No State, under this provision of the Constitution, can make any discrimination as to the right of suffrage within its limits, "on account of race, color, or previous condition of servitude "; nor has any State, South or North, within the knowledge of the undersigned, made any such discrimination.
If there have been violations of the right of suffrage on the
part of individuals by intimidation, force, violence, or bribery (which is by no means denied), the remedy under the Constitution is a plain one ; and the undersigned believes that the remedy through the courts would be as strongly enforced in the South as in the North. In elections to Congress each House is the sole judge of the election and returns of its own members. If a State were to pass a law making a discrimination, the State courts as well as the Federal courts would of course hold such a law to be unconstitutional."
That worked out well! (See Cruikshank, Slaughterhouse, Civil Rights Cases, Plessy).
LFC, I was commenting on the NAR article and your post as I haven't read Woodward. If he assigned much weight to the NAR piece then that's a problem as even a cursory reading of the Lamar and Stevens pieces shows some serious problems as well as a certain lack of either candor or perception on their part.
The only way Jim Crow of some sort didn't happen would have involved serious and prolonged federal intervention. Recall that the response of the former slave states to emancipation was the Black laws which were rooted in the earlier slave codes.
aaall,
ReplyDeleteI wouldn't say he assigned the NAR piece great weight -- rather he was citing it as one of a variety of pieces of evidence in the course of making his argument. Since I haven't yet finished the Woodward book and haven't yet read the NAR piece, I don't think I shd comment much further.
Re your reference to Jim Crow "of some sort": there was only one sort of Jim Crow -- total, legally-sanctioned and enforced segregation of the races in virtually every aspect of life -- and it only finally took hold across the entire South in the 1890s, some years after the end of Reconstruction in 1877. That seems to be Woodward's main factual point, though as I say I haven't yet finished the book.
@aaall
ReplyDeleteWould air pressure be a factor? My guess were I Feynman's student would be to suggest that anything that affects the texture of the atoms on a given surface would change friction. That would include temperature which is related to pressure by a formula with closed systems which if I remember right is: P=T/V
I was sort of modeling a suction cup-like situation. If one drags a dry chamois or cloth over an automobile body it glides easily but a wet one will require more force.
ReplyDeleteI was also born on December 27, albeit a bit more recently. Unfortunately, it doesn't fall on a Friday this year.
ReplyDeleteHi Professor Wolff,
ReplyDeleteRegarding Chomsky, he has stopped shaving in order to accrue wisdom points. The beard makes him look much wiser than ever before and suits him quite well. I hope you understand.
Best,
Matt
P.S. I love the Kant lectures.