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Alien Suns Reversing in Exoplanet Skies
Not only can suns stand still in the sky, from some exoplanets their motion can apparently reverse! Wooster physics-math double majors Xinchen (Ariel) Xie ’21 and Hwan (Michelle) Bae ’19 and I just published an article elucidating these apparent solar reversals. Michelle and I began studying the architecture of daylighting terrestrial buildings for energy efficiency as part…
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Black Hole Above the Fold
When grocery shopping, I normally just glance at the newspapers in the newsstand. However, this morning, I was excited to see “above the fold” of the Wall Street Journal a large reproduction of the first image of the supermassive black hole Sagittarius A* at the center of our Milky Way galaxy! The Event Horizon Telescope team…
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Slide Rule Examples
Slide rules were widely used in engineering, science, and mathematics until the early 1970s, including during the Gemini and Apollo space programs. Although rendered largely obsolete by the advent of inexpensive electronic calculators, their descendants continue to have specialized applications, such as backup flight computers. Buzz Aldrin and a floating slide rule during Gemini 12 on…
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Slide Rule Theory
Slide rules were the analog computers that ruled science and engineering for 400 years. Their brilliant innovation was using logarithms to convert multiplication and division to addition and subtraction, and Slide rules feature logarithmic scales that slide past each other. For straight slide rules, logarithms of the numbers are proportional to their distances along them.…
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Diffraction Limited
Yesterday, Webb optical telescope element manager Lee Feinberg said “We made the right telescope” while reporting that its focus has reached the diffraction limit of 0.7 arcseconds at the infrared wavelength of 2 microns. (For comparison, from Earth, Luna subtends 31 arcminutes, which is about 1/2°.) Unlike the Hubble space telescope, whose primary mirror was…
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Shackleton’s Valiant Voyage
Although a child of the Apollo program, I was gripped by Alfred Lansing‘s 1962 book Shackleton’s Valiant Voyage, a great tale of endurance, leadership, and survival and an inspiring true story from the heroic age of Antarctic exploration. In the 1910s, shortly after Roald Amundsen and Robert Scott separately reached the south pole, Ernest Shackleton organized an expedition…
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Halo Orbit
The Webb telescope has fully deployed and arrived at its halo orbit about the second Earth-Sun Lagrange point. But how can it orbit an empty point in space? In the accompanying animated sequence of inertial space diagrams, a star (red) and planet (cyan) orbit their common center of mass (cross). The inward force to pull…
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Merlin & Raptor
The turbopump is the heart of most liquid-fueled rocket engines. Gas generator engines tap off and burn a little propellant to drive a turbine, which turns a centrifugal pump, which rapidly pushes the fuel and oxidizer to the combustion chamber, after the cryogenic fuel first circulates around the rocket nozzle to cool it. The combustion generates supersonic exhaust out…
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Astronomy Christmas Gift
I awoke early this Christmas morning to watch the successful launch of the James Webb Space Telescope. I remember the genesis of the telescope a quarter of a century ago when it was called the Next Generation Space Telescope. (The telescope’s name is controversial, and I would have preferred an astronomer’s name.) Its development has…
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Burning Plasma
In August I received an urgent email from my brother with the title “Fusion”. The National Ignition Facility (NIF) had created a burning plasma — a star on Earth — a major milestone on the long road to controlled nuclear fusion. A plasma is an ionized gas, but in this context “burning” does not mean chemically…
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.