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A Better Table
The periodic table of the elements is almost as old as The College of Wooster, and I am a big fan. As we approach next year’s sesquicentennial of Dmitri Mendeleev‘s 1869 periodic table, I present a modest addition to the over 600 known periodic tables, which include , , and even designs! I wanted the…
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Math Grenade
I just bought a new calculator. New to me, that is, but older than me. Inspired by the 1600s Gottfried Leibniz stepped cylinder and the 1800s Thomas de Colmar arithmometer, the Curta mechanical calculator design was developed by Curt Herzstark while imprisoned in the Buchenwald concentration camp during World War II. Curta calculators were manufactured between…
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Optical Tweezers
A focused light beam can trap a small particle, such as a micron-sized latex sphere (or biological cell). If the sphere is much larger than the light’s wavelength, ray optics suffices to explain the trapping. Light bends as it passes through the sphere, as in Fig. A. The piconewton forces (red and blue arrows) on…
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Dr. Rendezvous
Edwin Aldrin earned his PhD from MIT in 1963 with a thesis titled, “Line-of-sight guidance techniques for manned orbital rendezvous”. Just three years later in 1966, Aldrin was the pilot of Gemini XII, the last flight of the Gemini program, a critical precursor to the Apollo moon program. Aldrin and his commander James Lovell were…
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Saturnday
Ancient cultures everywhere observed seven “wanderers” move against the apparently fixed stars of the night sky: our star the sun, our natural satellite the moon, and the brightest planets Mars, Mercury, Jupiter, Venus, and Saturn. In many languages, these wanderers became the basis for the names of the seven days of the week; for example,…
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Anholonomy
A falling cat’s twisting returns its shape to normal but rotates its body to land feet down. Earth’s spin returns a Foucault pendulum to its initial position in one day but rotates its oscillation plane. Parallel parking cyclically rotates a car’s front wheels but shifts the car sideways. These are examples of nonholonomic motions or…
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Norton’s Dome
Norton’s Dome is a fascinating counterexample in classical mechanics: A frictionless mass balanced at the dome’s top can remain there forever — but can also spontaneously slide down! A mass slides down Norton’s dome from rest and then is kicked back up to rest. The Shape Norton’s dome has a cubed square root profile: if…
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Moon Dance
I ran up the stairs to Studio Art. Justine was already rolling out the treadmill, so I climbed another flight of stairs to the old running track and let down both ends of the steel cable, one end connected to the harness and the other to the sandbag counterweight. Our reduced gravity rig was basically…
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On Mercury One Day Lasts Two Years
Mercury has the most noncircular or eccentric orbit of any nondwarf planet in the solar system. This eccentricity has trapped Mercury in a 3:2 spin-orbit resonance, where it rotates three times for every two revolutions. When nearest Sun at perihelion, Sun’s tidal forces are greatest, Mercury’s spin and orbit (or rotation and revolution) nearly match,…
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Dynamo
Stationary electric charges generate radial electric fields, and electric fields push positive charges (and pull negative charges). Moving charges also generate circulating magnetic fields, and magnetic fields deflect moving charges perpendicular to both the fields and their motions. All of electromagnetism follows. In particular, spin a conducting disk in a perpendicular magnetic field, and connect its axle to its…
Author: John F. Lindner
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Nice post, John! Thanks for writing these. I always enjoy them.
David Smith’s ein stein is an awesome shape!
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Thanks, Mark! I enjoy reading your posts as well.