Building a light travelling clock @Marbslab

Uploaded September 2024 | Updated September 2026, 3 days ago

#clock #planets #solarsystem #carlsagan #4017
This clock shows how long it takes light to travel from the Earth to other planets and the sun. I got the idea from the first of six Christmas lectures Carl Sagan gave at the Royal Institution in 1977. A clock like this is shown there in large format. You can find the link to the video here: youtube.com/watch?v=aAxvxIOwnWMIf you haven't seen the lectures yet, I recommend watching them all. The model of the Titan III-Centaur main rocket that sent the interstellar probes, Voyager 1 and Voyager 2 into space, is slightly shorter than scaled in the video. The reason is that otherwise, the clock wouldn't fit on my bookshelf.

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$Powering a Geissler tube by hand #wimshurst #geissler #helium In this video, I show you how to operate a Geissler tube with a Wimshurst machine. The Wimshurst machine is from AliExpress, and the Geissler tube is from eBay. Geissler tubes are filled with various gases at low pressure, with metal electrodes at each end. A high voltage of several thousand volts is applied between the electrodes. The high voltage ionizes the gas, causing it to give off light by fluorescence in a glow discharge. The color of the light depends on the gas used. To give it a vintage look, I made a new base from lime wood and tube holders from turned wood. I also made the brass wire connections myself and paid attention to other historical details. My Geissler tube is filled with helium. I checked this with a diffraction grating by looking at the spectral lines.$

Experimental determination of Plancks constant using LEDs