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# Author Archives: John F. Lindner

## Redefining SI

Today the SI (Système international d’unités) base units are redefined. The following are now exact. Memorize these numbers! Cs-133 transition frequency constant [latex]Δν_{\text{Cs}} = 9\,192\,631\,770~\text{s}^{−1}[/latex] defines the second. Then light speed constant [latex]c = 299\,792\,458~\text{m}\cdot\text{s}^{−1}[/latex] defines the meter. Then Planck’s constant [latex]h = 6.626\,070\,15\times … Continue reading →

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## Black Hole Radii

I set the alarm for 8:55 AM. Brutal, but I wanted to watch live the National Science Foundation Event Horizon Telescope news conference. I was expecting the first image of a black hole, and the EHT team did not disappoint. … Continue reading →

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## Black Hole Radii

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## December 22 is the Longest Day

December 22 is the longest day of the year, despite being near the northern hemisphere’s shortest daylight. The sidereal day is the time to rotate 360° with respect to distant stars, about 23 hours and 56 minutes for Earth. The … Continue reading →

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## Relativistic Colors

Metallium, Inc. is attempting to manufacture coins made from as many different metals (and elements) as possible, typically 99 to 99.9% pure. My Metallium coin collection currently includes aluminum, titanium, iron, nickel, copper, zinc, silver, tin, and gold coins. Most … Continue reading →

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## 720° untangles 360° tangles

Despite growing up in three dimensions, as a kid I did not recognize one of 3D’s deep and subtle properties: full rotations tangle, but double rotations untangle! Following physicist Paul Dirac, twist a belt one full turn about its length. … Continue reading →

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## Luna’s Convex Orbit

Luna orbits Earth and Earth orbits Sol (where Luna is Earth’s moon and Sol is Earth’s star, the sun). As a kid, I thought Luna’s solar orbit formed a loopy spirograph pattern. Instead, Luna’s orbit is convex! Neglecting the eccentricity … Continue reading →

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## 1+2+3+… = -1/12?

In quantum electrodynamics, the bare charge of an electron is infinite, but the dressed charge is finite. The bare electron shields itself by polarizing the virtual electron-positron pairs of the nearby quantum vacuum to reduce its coupling at large distances to [latex display=”true”] \infty … Continue reading →

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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 … Continue reading →

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## Math Grenade

I just bought a new calculator. New to me, that is, and 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 … Continue reading →

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