Author Archives: John F. Lindner

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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I’ve been fascinated by aperiodic tilings of the plane since Martin Gardner first wrote about them in Scientific American. In the 1960s, Robert Berger discovered a set of 20 426 prototiles or tile-types that can tile the plane but only with no … Continue reading →
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As a kid, I devoured the pages of Popular Science magazine and was fascinated by the quest for human-powered flight: Was a flying bicycle possible? In the mid 1970s, I read that aerospace engineer Paul MacCready had assembled a team … Continue reading →
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There is a fantastic castle in the sky, built in free fall, brick-by-brick. It derives its energy from sunlight and recycles its water. Sealed against a vacuum, its inhabitants float and glide through its passageways as the sun rises and … Continue reading →
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1930s businessman Edgar Kaufmann Sr. and his family lived in Pittsburgh Pennsylvania. Kaufmann owned a rural retreat outside the city and wanted a weekend home there. He assumed his 67-year-old architect would design the home with a good view of … Continue reading →
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