High School Mathematics-Physics SMILE Meeting
12 October 1999
Notes taken by Porter Johnson [IIT]


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:

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:

Next Meeting [in a more phenomenology-friendly venue, perhaps?] 26 October 1999 See you then and there.