Precise Weights for Pocket Change

Shawn,

You asked, "BTW: If you know of some easy-to-obtain object that has a precisely and accurately known mass in the range of 100-500 milligrams, please email me, and I will share it the rest of the community." (See Shawn Carlson, "The Amateur Scientist" Classics: Measuring Micrograms, The Citizen Scientist, 12 November 2004.)

How about newly minted coins? The Canadian mint publishes the weight of our coins, as does the US mint, I assume.

I have used coins with a simple balance and found they worked well for my purposes. Since so many coins, even of the same denomination, may have different weights because of differing alloys used, etc., it's relatively easy to combine them to get a required weight. I stamped their weight on them with an inexpensive metal punch from Harbor Freight, so it's easy to keep track of the various weights.

Grant Fair,
Toronto

Thanks Grant for sharing your note to Shawn. This is a great suggestion. Editor.



Pill Bugs Face-to-Face

Editor,

Pill bugs are a popular lab animal and are used in a traditional animal behavior lab. We here have just created a virtual version of this lab using pill bugs obtained by simply pushing back some local vegetation. They show interesting taxis with various materials. We used 20 pill bugs and a chi-square analysis to determine that if 5 or fewer remain on one side, the result is significant.

Strangely, the animals were not much affected by 0.1 M HCl, but were very strongly repelled by vinegar (5% acetic acid) even though the pH of the vinegar is much higher.

You can keep pill bugs in jars if you provide them with moisture and food. Food can be leaves (pesticide free) that you collect around the house. A moist paper towel will suffice for the moisture.

I find the tendency of pill bugs to roll up very interesting because an ancient crustacean, the trilobite, did just the same thing. Does anyone know if pill bugs are directly descended from trilobites or developed this balling behavior independently? Do other modern crustaceans also curl up?

Harry Keller, PhD
President, ParaComp, Inc.

Readers, if you can answer Harry's questions, please send a note to Backscatter. Thanks. Editor.

Observing Solstices

Editor,

For those who are interested in either observing or determining the winter solstice, the web site at www.solsticeamateur.com provides some interesting insights as to how the ancients probably determined dates. The site links to other sites about ancient solar observatories and gives detailed information relative to its determination using solar observations, including technical guidance and suggestions on "How To Do It In Your Own Backyard."

Gene Dyer

Gene, sorry this is being published after the solstice, but your letter arrived after our December installment. Readers, Gene's suggestion is worth checking out. The next date of interest will be the spring equinox on 21 March 2007. Editor.

Still More About Temperature Conversions

Editor,

In the 1 December 2006 issue of The Citizen Scientist, Bob Warren asks if I can describe how I came to learn of the temperature conversion algorithm. My memory of this is quite fuzzy. I believe that the simplicity of the technique was mentioned to me by a fellow student sometime after September 1959 and before 1961. At this distant point in time I have no recollection of who it was or where he might have learned it. I think I was left to my own devices to recognize that multiplying by 1.8 can be done by multiplying by 2 and subtracting 10%. And, likewise multiplying by 5/9, can be done by dividing by two and adding 10%. And, if the need for accuracy requires it, adding 1% to get an even better approximation, as suggested by another "Backscatter" letter.

The main thing I remember is what a marvelously simple approach it is. I never had to remember when the 32 had to be added or subtracted. It is always add 40 at the beginning and subtract it at the end. The other main thing to remember is that there are more degrees F between freezing and boiling than there are degrees C, in the ratio of 9 to 5.

Thanks to Bob Warren and TCS for popularizing this method. It should be required in high school science, if for no other reason than to remind students that science is really pretty simple if you don't let the teachers snow you.

Having made that somewhat disparaging comment I would like to recognize my late high school physics instructor, Russell E. Smith of East Peoria Community High School, for teaching me that science is fun in spite of nearly every previous teacher (and some who came later as well) who tried to destroy my considerable interest by making it a dull, boring exercise in memorization. Maybe Mr. Wizard deserves some credit, too. Science education could clearly use more Russell Smiths and Mr. Wizards.

James M. Potter, PhD, President
JP Accelerator Works, Inc.
http://www.jpaw.com
Los Alamos, NM 87544

A question about Physics

The FAA has standardized many tests relating to flying. In the test that is given to prospective private pilots there is a section on a acronym called “ANDS.” This acronym stands for accelerate north
decelerate south. It means that when a plane is flying in a east-west direction then the magnetic compass will move in response to acceleration or deceleration. The direction of the motion is given
by the acronym.

My question is why does this effect place? Is there any explanation for it?

Allan Rydberg

Readers, if you can answer Allan's questions, please send a note to "Backscatter." Editor.

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