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Retrofuturism - Anachronistic Technology and HAM Radio
The figure above may seem rather silly. It shows WordPerfect 8.0 for UNIX running - roughly the equivalent of WordPerfect 4.2 for MSDOS - mid to late 1980s. WordPerfect 6.0 for MSDOS is shown running in the DOSBOX, an emulator for MSDOS - late 1990s). Finally WordPerfect X.13 is shown running in a virtual machine that is running Windows 7. All of these are running under Linux Mint 21.x. The laptop on which they are running is an old ASUS X55U, with motherboard manufactured in 2013.
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What is the Aurora?
The aurora borealis or Northern Lights is an atmospheric phenomenon that occurs in the northern hemisphere of the planet. It also occurs in the southern hemisphere where it is known as the aurora australis. Aurora are known to exist on comets, brown dwarfs, other planets and on some moons. Aurora are caused by solar wind interacting with magnetic fields and atmospheric particles. Atmospheric particles become energized and form what is known as plasma. Plasma is energized or ionized gas. It is the fourth state of matter and has been so identified since about 1972. Yes, your high school teachers who taught you the three states of matter were...well...not current in their physics. You see plasma every day when you see the sun, an operating fluorescent light or an operating neon light.
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The Wagon-wheel Effect, Stroboscopic Effects and Aliasing
Sometimes in movies one sees a stagecoach rambling through the countryside with some notorious highwayman (such as Dick Turpin) in hot pursuit. The wheels appear to be going in the opposite direction at a very slow speed or not turning at all. Images of any rotating object, including helicopter rotors or aircraft propellers, show this. This phenomenon was mentioned one morning by YARS members during coffee and I decided to write an article about it. One of our members mentioned a "stroboscopic effect" where, with a strobe light flashes at a sampling rate close to the period of motion causes this effect. For example if a light flashes at 60 flashes per second (60 Hz) and the rotating object is rotating 60 revolutions per second (60 Hz), then the object will appear to be stationary. If the object rotates at 61 revolutions per second, it will appear to slowly appear to move backwards. At 50 revolutions per second it will appear to rotate slowly forwards.
This effect can be used to measure the speed of moving objects simply by observing them. It can also lead to irritation by persons sensitive to the effects, sometimes called "flicker". This has nothing to do with a phenomenon called "rolling shutter" - which is merely a time delay artefact in a digital camera caused by how the camera scans an object over time, line by line (see https://www.youtube.com/watch?v=dNVtMmLlnoE ).
Read more: The Wagon-wheel Effect (Nyquist Frequency and Aliasing)