Author Archives: John F. Lindner

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, [latex display=”true”]\log xy = \log… Continue reading →

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 70 milliarcseconds. (For comparison, Earth’s moon subtends 31 arcmin… Continue reading →

Although a child of the Apollo program, I was gripped by Alfred Lansing‘s 1962 book Shackleton’s Valiant Voyage, which tells a great true story from the heroic age of Antarctic exploration. In the 1910s, shortly after Roald Amundsen and Rob… Continue reading →

The Webb telescope has 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 animation, a star (red) and planet (cyan) orbit their common center of … Continue readin… Continue reading →

A liquid-fueled rocket engine is a turbopump, plus some miscellaneous other stuff. Gas generator engines burn a little fuel to drive a turbine, which turns a centrifugal pump, which rapidly pushes the fuel and oxidizer propellants to the combustion cha… Continue reading →

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 … Continue read… Continue reading →

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…. Continue reading →

Launched just last month, Lucy will be the first spacecraft to visit Jupiter’s trojan asteroids, rocky swarms that orbit about 60 degrees ahead and behind Jupiter in its orbit. Hal Levinson, Lucy’s Principal Investigator, has described Lucy… Continue reading →

In four dimensions, you can’t tie your shoelaces, because 4D knots don’t work. Any 1D curve in 4D space can be continuously deformed to the unit circle, which is an unknot. The animation below demonstrates how to undo a trefoil knot …… Continue reading →

She’s not looking up at the sky; she’s looking down at it. I am excitedly following the Inspiration4 spaceflight and its crew of four enthusiastic and diverse private citizens: Jared Isaacman, Hayley Arceneaux, Christopher Sembroski, and Si… Continue reading →