Hi seismometer Mom, I agree with Erich's comments. I have often been a judge for the local science fair, and have seen many versions of paper mache' volcanos (models aka "Close Encounters" providing no science), earthquake "predictions" based on caterpillars (a result of selective hearsay and coincidence), and wooden seismometers crushed by an ever increasing mass of bricks in an attempt to get "results". My usual approach to a fair exhibit is to first try to find an explicit statement of the scientific question of the display. This is the "how do we know ...." or "Why does" or some hypothesis that can be demonstrated by a simple experiment (beans grow faster in an electric field). If there is no question or hypothesis, there can be no scientific test or demonstration of a principle, and therefore, no "results". For a seismograph or seismometer display, the question is "how do we detect the faint ground movement of distant earthquakes". Then I look for some experiment to evaluate the question. Usually the answer is known by science, so showing how we know it is demonstrated by some replication of the physical experiment or, in the case of like math or astronomy, a large poster detailing the logical steps that lead to the conclusion is presented (some have that ring of verbatim Brittanica, especially when a gross error in copying is evident). So for the "how do we know" science display, a demonstration of the core physics is usually presented within the amateur limitations of the student. For a seismometer/seismograph, recording the relative motion of a suspended inertial mass with respect to the moving ground is the key concept. Amplifying the miniscule motion (0.001mm) from a distant quake is more advanced. A comprehensive background poster of earth/core wave propagation is easy to assemble. And a poster with good graphics can detail all the concepts, including wave propagation and quake location without having to build a seismograph. A demo on a map on the table of triangulation of the epicenter location from station S-P travel times represented by using marked tapes is a nice interactive display. A fatal misconception is that some hardware something must be built that should prove or demonstrate the point, (often overlooking the practical alternative of borrowing a professional instrument and then carefully labeling the key components.) This construction then becomes the prime effort of the display even though the student (parent) has not grasped the physics or science involved. Then the display becomes an exhibit of the construction skills of the student (parent), which often blindly copy some article. I have seen beautiful all-wood Lehman type sensors but made with brass cabinet hinges and a brick for a mass with a pencil attached that writes on a tablet placed under the front side. The student got high marks because of the instructions: "slowly slide tablet out while shaking the table"; the principle of the inertial mass was proven, as was the registration of a the waveform passing with time: ie "results". The display even noted that the table shaking was about intensity MM-X, and referred it to a graphic about intensity. However, often the entire point is missed and the "results" are faked; ie."simulated". One seismometer display had a lead pipe hanging on a spring, with the attached pencil writing on a paper cylinder resting on an open clock face (sort of turned by the minute hand). There was a nice tracing of a teleseism, carefully labeled to agree with an attached news clipping. But no current demonstration of how the data was or could be made. (Fair judges often converge on a display that challenges their ability to "make it work", and sometimes make adjustments or add something that does make it work). The value of an exhibit is proportional to the time devoted to it. A good high school project will take about a year, with the last half devoted to building whatever and trying to make it work. Then, in the case of a sensitive seismograph (with a magnification of at least 1000,) you might have to wait a month for a significantly large earthquake to record on it. But I have never seen any seismograph displays involving even rudimentary electronics (moving coil/magnet and amplifier), but this is the midwest rather than California, and although electricity is a high school subject, the practical usefulness of it remains elusive. And a final note: "quick" and "easy" have nothing to do with science. Regards, Sean-Thomas Morrissey St. Louis University. PS: there is a design for a hardware store seismometer using modern electronics that is neither quick (could be done in a devoted month) nor easy (those darn electronics parts) described at: http://www.eas.slu.edu/People/STMorrissey/index.html stmseis.html" The STM-8 Leaf Spring Seismometer: Photos and Report stmfigs.html" The STM-8 Seis: Figures, Schematics, Drawings stmquakes.html" The STM-8 Seis: Recent Quakes, Data __________________________________________________________ Public Seismic Network Mailing List (PSN-L)
Larry Cochrane <cochrane@..............>