Announcements:

• There was a NOVA program on Time Travel on 12 October at 8 pm on Channel 11 [WTTW]. {What did you think of it?}

• Porter Johnson will be the President of the Chicago Section of the American Association of Physics Teachers [AAPT] for the 1999-2000 academic year, running from November to November. Here are the [approximate] spacetime locations of coming [biannual] meetings:

  06 November 1999 [Saturday] 8:30am-3:00pm
  [NEIU] NorthEastern Illinois University
  Contact: Paul Dolan: [773] 794-2539; P-Dolan@neiu.edu

  19-20 April 2000 [Friday-Saturday]
  [Joint Meeting with Illinois AAPT]
  [UIUC] University of Illinois Champ-bana

  11 November 2000 [Saturday]
  [IIT] Illinois Institute of Technology [111 LS]
  Contact: Porter Johnson: [312] 567-5745; johnsonp@charlie.cns,iit.edu

• The 20th International Congress of Theoretical and Applied Mechanics, "Mechanics for a New Millennium", will be held in Chicago 27 August - 02 September 1999. The last conference held in the USA was in 1968, in sunny Palo Alto CA. There will be a Science Teacher's Day at the Congress. Detailed information can be obtained [when available] at the conference website: http://www.tam.uiuc/CTAM2000.

  Contact: Prof Hassan Aref; President ICTAM2000
  Dept of Theoretical and Applied Mechanics, UIUC
  [217] 333-3239; h-aref@uiuc.edu

Bill Colson [Morgan Park HS Mathematics]

The recent NASA fiasco on the rocket landing on Mars [confusing thrusts in "pound seconds and "newton seconds"] was evocative of Bill Blunk's recent lesson on units. It is important to specify the units [with uncertainties] of calculated or measured quantities. It would be simple if everybody used SI metric units for everything; but they don't, and they probably never will. The "never mix units; never worry; just take the SI pledge" approach is ok for self-consistency, but one should not assume that others have the same philosophy. [European torque wrenches wrong-headedly give torques in "kilogram meters"]. Bill's B's assertion "I'll give a ten to anybody who can answer this question", followed by taking ten cents [not ten dollars] out of his billfold, is succinct.

Walter Macdonald [CPS Substitute; Medical Technician]

He demonstrated the versatility of the HP48GX Programmable Calculator, with 128K of internal RAM [random access memory] connection with the software package SPICE48, which allows one to program circuit diagrams[although somewhat tediously, it seems] and to specify the voltage source as DC, sinusoidal AC, sawtooth, or "whatever". The calculator permits display of output currents and such in graphical form, in order to gain insight into the effects of changing resistances, capacitances, and inductances, or switching in diodes. The device is better suited to providing its gentle user with graphical insight, rather than mere numbers.

Walter also commented that the new x-ray machine in his hospital has a digital interface, so that familiarity with PCs/Macs is required in routine usage. Porter observed that the world is "going digital", giving these instances:

• General Motors has described the modern automobile as essentially an electronic device, rather than a mechanical one, as it has always been.
• The hospitals of today seem like, say, the high energy physics labs a few years back, with sophisticated electronics, computer-driven operations, schemes for fast digital tomography [MRI, PET, and CT, and automated EKG monitors, for example], and automated chemical analyses.
• You can buy a car, order merchandise, do banking, find a mate, and pay taxes electronically.

Bill Blunk [Joliet Central HS Physics]

"Everybody knows" that the image on the retina of the eye appears inverted, but that it is difficult to show it directly. He followed up on a suggestion by Earl Zwicker [IIT retired and still flying low!] to do the following direct and simple experiment: Take a bright, small, well-focussed light source [souped-up versions of the Maglite{TM} are readily available [where, Bill??]. First put the light behind your hand and observe that the reddish component goes through [diffuse reflection]. Then, put the light inside your mouth to show that red light penetrates your cheeks. Finally, put the light on your temple just above the nose, close your eyes, turn it on, and notice the reddish image at the BOTTOM of your field of sensation. Although the light surely hits the TOP of the retina [near where you put the light source!], you "see" it at the bottom. Therefore, your brain must invert the image, and you avoid that upside down feeling, unless of course you live in Australia. Bill passed a CLEAN flashlight around the room so we could see it. In a dark room an ordinary flashlight will suffice.

PJ Note: The "pulse-OX monitor" in ERTM and real hospitals is a little [red] laser source- detector that goes over a finger to measure absorption by oxygenated hemoglobin in blood; the O₂ content of blood can be continuously monitored. It is important to attach the "pulse-OX monitor" on the different arm from that of the automated "blood pressure cuff".

Bill saw a t-shirt out west with a bear logo and the phrase "send more tourists; the last one tasted delicious". I shall not reproduce the subsequent fascinating discussion of mores of grizzly bears and their interactions with the human environment.

John Bozovsky [Bowen HS Physics]

He learned in the newspaper that Fall began on 23 September this year [a day late because we are very close to a leap year], and the time for sunrise and sunset were 6:39 am and 6:47 pm, respectively.

Why aren't there exactly 12 hours of daylight? [the finite extent of the solar disk (0.5 degrees) and refraction of light in the earth's atmosphere both make sunrise earlier and sunset later; the latter because light is refracted TOWARD the zenith in both cases]. Calculate both effects yourself [take n=1.001].

Why not at 6:00 am and 6:00 pm? [daylight savings time, and the fact that local solar time in Chicago is not precisely 7 hours behind Zulu Time (Greenwich Mean Time); solar time in Greenwich England, an exurb of London on the South side of the Thames/tims].

Porter pointed out that short wavelengths are refracted by greater amounts than long wavelengths by air, and thus in the half-second before sunrise and after sunset there is a green flash. A pictogram on an ancient Egyptian pyramid shows a green stripe under the sun---it so happens that atmospheric conditions would favor seeing it there, especially in ancient times, without problems of background illumination. Lord Rayleigh made an expedition/vacation to the Matterhorn [Swiss Alps] to look for it at sunrise [at sunset you may "see green" whether it is there or not]. The science fiction master Jules Verne wrote a short story Le Rayon Vert [the green flash], in which he was more accurate with the physics than in his classics Journey to the Center of the Earth and Voyage to the Moon. [As a rule, scientists seem to love science fiction and loathe para-psychology and astrology. How come?]

Earnest Garrison [Jones Commercial HS; Mail Run 38]

Traditional calorimeters are both expensive and unreliable, and he tried the "SMILE approach" when he found that his new school didn't have any. So, he took a little coffee cup [styrofoam], inserted it into a glass beaker [a big styrofoam cup might have been better]. A styrofoam plate served as a top, with a small hole punched through it to insert the Celsius thermometer. He measured the temperature of simmering water as 102 C, and added water at room temperature. The calculated final temperature was 26.98 C [approximately], and measured at 26 C. The crude, home-made device works better than the gleaming store-bought apparatus!

The final discussion took a non-phenomenological turn, addressing important matters such as the following:

• The 1999 Nobel Prize in Physics went to Tini Veltman and Gerard 't Hooft on using dimensional regularization to prove that non-Abelian gauge theories are renormalizable. That is, in this very intricate fundamental theory, "bare" or "undressed" particles [such as electrons] are the fundamental entities of the theory as formulated, but one can observe only the "fully clothed" particles [real electrons are always enshrouded in photon clouds]. Therefore, very elaborate procedures must be employed to obtain consistent results for observable quantities. The "dimensional regularization" concept involves formulating the theory and calculating things in "d" space-time dimensions, and carefully extirpating the unphysical parts in the limit d--->4. Why? So you don't unwittedly destroy the gauge symmetry of the theory.

  Clear?? If not, consider this observation from the Hunting of the Snark, Fit the Fifth: The Beaver's Lesson by Louis Carroll:

  You boil it in sawdust; you salt it in glue;
  You condense it with locusts and tape;
  Still keeping one principal object in view
  To preserve its symmetrical shape.
  

  Incidentally, one of Tini's students [a friend of mine] was killed in Pan AmTM Flight 192 over Lockerby Scotland several years ago. Alfred Nobel [Swedish dynamite inventor and manufacturer] set up the physics prize in his will for a "device or discovery made by during the last year", but has become more of a "lifetime achievement academy award".

• Why does dew condense on the rear window of a car [away from shelter] preferentially to the front window [close to the shelter]? Presumably, this happens because the rear window is cooler. In vacuum technology one removes noxious substances [such as water] with a "cold trap" on which it will condense [the equilibrium vapor pressure drops off dramatically with temperature]. [Water condensed on the protective outside screen of my new high-tech window, but not on the glass itself during the recent foggy days.]

• One gets fog, heavy dew, and condensation when the temperature of air drops below the "wet bulb" or condensation temperature - 100% relative humidity. By contrast, rain hail, sleet, and snow fall out of clouds when fronts collide ["lake effect" snow looks, feels, and shovels like real snow, but arises from moisture blown from the lake and onto the land]. "Freezing fog" or hoar frost is produced when 100% humidity is reached below 0 C. The spider webs, bushes, and dead flowers look like glittering gossamer "diamond necklaces" in the gleaming sun. This effect [mentioned in "Silas Marner" by [Marian Evans / George Eliot] occurs quite frequently in maritime climates [Seattle, Vancouver, Juneau, England, North Sea Coast, even Holland MI], but occasionally occurs in inland climates [Chicago- Kiev, Minneapolis-Moscow, etc]. The word "hoar", meaning "grayish white" [among other things!] is a cognate of the modern German word "Hehr" [venerable or stately], and was already ancient when Geoffrey Chaucer [Merchant's Tale of The Canterbury Tales, 1386] made the wry comment "I feele me nowhere hoor but on myn heed" [so much for interdisciplinary education and ScrabbleTM words].

• Liquids can be superheated without boiling [the bubble chamber records ionization tracks briefly, since those tracks are little bubbles that soon become big bubbles. Water can easily be reduced to -2 C [28 old-fashioned F] before it begins to freeze if not agitated, and much lower with special handling. A drop of water very hot surface [frying pay] will scoot on a vapor layer for some time before boiling [Leidenfrost: good for "stump the band" but not ScrabbleTM].

• Albert Einstein said that there is no such thing as time; there are only clocks. Indeed developing precise clocks has been important for science, technology, and commerce. He also said that space and time should never be considered separately, but only a composite spacetime, in which the speed of light is the same for all "observation teams". Indeed, the speed of light is no longer "measurable", being defined at the value 299794258 meters/second. However, we can speak freely about "anywhere", but might be "locked up without the key" if we discussed "anywhen". How come space and time are "the same thing, but different"?

• And, what about time travel and alternative futures? Consider these [Space Child's Mother Goose].
  There was a man with a time machine
  Who borrowed a Tuesday all painted green
  His pockets with rockets he would like to jam
  And he said "I have think, so I cannot am".
  

  or

  Probable-possible, my black hen
  She lays eggs in the relative when
  She cannot lay in the positive now
  Because she's not able to postulate how.