Author Archives: John F. Lindner

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 … Continue reading →
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The Shape In dimensionless coordinates, with the [latex]z[/latex]-axis pointing down, Norton’s dome has the shape [latex display=”true”] z = \frac{2}{3}s^{3/2},[/latex] where [latex]s[/latex] is the arc length along the dome. If [latex]ds^2 = dx^2 + dz^2[/latex], then [latex display=”true”] x = \int dx … Continue reading →
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I ran up the stairs to the Studio Art Crit space. Justine was already rolling out the treadmill, so I climbed to the old running track and let down both ends of the steel cable, one end connected to the … Continue reading →
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Mercury has the most noncircular or eccentric orbit of any non-dwarf planet in the solar system. This eccentricity may have trapped Mercury in a 3:2 spin-orbit resonance, where it rotates three times for every two revolutions. When nearest Sol at … Continue reading →
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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 … Continue reading →
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I was supervising Jr IS, but as I circulated around the lab, I watched the clock. Everyone was working quietly. Just before launch, I snuck back to my office and closed the door. The SpaceX Falcon Heavy was surrounded by … Continue reading →
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In 1969, Hans Freudenthal posed a puzzle that Martin Gardner would later call “The Impossible Problem”. Below is a 2000 version due to Erich Friedman. I have secretly chosen two nonzero digits and have separately told their sum to Sam … Continue reading →
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The kilogram is the only metric unit still defined by an artifact. The International Prototype Kilogram, IPK or “Le Grand K”, is a golf-ball-sized platinum-iridium cylinder in a vault outside Paris. This year I expect the General Conference on Weights … Continue reading →
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On Wednesday, September 13, 1989, I met with newly elected Physics Club officers Tom Taczak ’91, Dennis Kuhl ’90, Doug Halverson ’91, and Karen McEwen ’90 in Westminister House. I wrote in my diary, “first phys club meeting w. officers goes well”. That year … Continue reading →
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One of my favorite illustrations is the cannon thought experiment from volume three of Isaac Newton‘s Principia Mathematica. Johannes Kepler argued that planets orbit elliptically with Sol at one focus. Galileo Galilei argued that terrestrial bodies fall parabolically in space … Continue reading →
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