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Generalizing Coulomb’s Law
The forces between two electric charges in arbitrary motion are complicated by velocity, acceleration, and time-delay effects. The forces need not even lie along the line joining the two charges! Suppose a source charge is at position with velocity and acceleration , and a test charge is at position with velocity and acceleration . Let…
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Triple EVA
Since the mid 1960s, all space walks or extra-vehicular activities (EVAs) have involved just one or two astronauts — except once. In May 1992, on the STS-49 mission, the crew of the space shuttle Endeavour was attempting to rescue a stranded communications satellite, Intelsat 603. After repeated two-person EVAs failed to capture the satellite, NASA and the…
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5-Color Theorem
On 1852 October 23, Francis Guthrie noticed that he needed only 4 colors to color the counties of England so no two bordering counties shared the same color. This works for any map, but only in 1976, and with the aid of a computer, did Kenneth Appel and Wolfgang Haken finally prove the 4-color theorem. Here I outline…
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Compton Generator
Long before he won the Nobel Prize in Physics, and while still a Wooster undergraduate, Arthur Compton realized a third way to demonstrate Earth’s spin (after pendulums and gyroscopes). Compton reported his results in a manuscript submitted to the journal Science on 1913 January 13 and published as “A Laboratory Method of Demonstrating the Earth’s Rotation”,…
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Analemma
Photograph the sky at the same time each day for a year and Sun will appear to execute a figure-8 path called an analemma, which is often inscribed on Earth globes and can be used as an almanac, as by Tom Hanks‘ character Chuck Nolan in the movie Cast Away. The 2D animation below illustrates…
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Perseverance, Ignition, Breakeven
Overcoming decades of enormous physics and engineering challenges, and despite persistent pessimism, skepticism, and criticism, the National Ignition Facility has achieved an historic milestone for controlled nuclear fusion, a target energy gain factor of . Last week, NIF focussed the world’s most powerful laser pulse on a small gold cylinder that converted the incident ultraviolet light into x-rays and caused an enclosed…
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Distant Retrograde Orbit
The Artemis 1 mission’s Orion spacecraft has successfully entered and exited a distant retrograde orbit about Moon. DRO is a stable and easily accessible orbit requiring a low velocity change . In DRO, Earth‘s non-negligible gravity contributes to a 3-body problem that makes the inertial space orbit non-Keplerian: an ellipse centered — not focussed — on Earth.…
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Artemis Is the Sister of Apollo
I stayed up late last night and early this morning to watch the successful uncrewed launch of Artemis 1. In Greek tradition, Artemis was the twin sister of Apollo, and the Artemis program hopes to return humans — including the first woman — to Moon as preparation for sending them onward to Mars. As a child…
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Zero-G Indicator
When Crew 5 rocketed to orbit last week aboard the SpaceX Dragon “Endurance” bound for the International Space Station, I was curious to see their zero-gravity indicator. A tradition SpaceX crews have adopted from Russian cosmonauts, the zero-g indicator is usually a stuffed animal whose first float announces the free-fall of Earth orbit. Was that a plush Einstein doll?…
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For the dinosaurs!
The dinosaurs didn’t have a space program, but we do. I just watched live the first kinetic-impact asteroid-redirection test as NASA’s Double Asteroid Redirection Test spacecraft collided with the asteroid-moon Dimorphos of the asteroid Didymos. Below is the last image DART transmitted, truncated by the impact itself! The goal is to measurably change the speed…
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.