Category Archives: Physics

Atmospheric optics

I love me some sun dogs and halos.

The Washington Post: The story behind an incredible sky scene in New Hampshire. “This was the surreal scene Saturday morning at Franconia Notch in New Hampshire. Steve LeBaron of the New Hampshire Department of Transportation’s Highway Design Bureau captured a stunner of a sky atop Cannon Mountain while skiing.”

Link via MetaFilter.

From the Earth to Space

Astronomy Picture of the Day: Rocket Launch as Seen from the Space Station. (YouTube, 1:37min) “Video Credit: ISAA, NASA, Expedition 57 Crew (ISS); processing: Riccardo Rossi (ISAA, AstronautiCAST); music: Inspiring Adventure Cinematic Background by Maryna.”

“Have you ever seen a rocket launch — from space? A close inspection of the featured time-lapse video will reveal a rocket rising to Earth orbit as seen from the International Space Station (ISS). The Russian Soyuz-FG rocket was launched ten days ago from the Baikonur Cosmodrome in Kazakhstan, carrying a Progress MS-10 (also 71P) module to bring needed supplies to the ISS. Highlights in the 90-second video (condensing about 15-minutes) include city lights and clouds visible on the Earth on the lower left, blue and gold bands of atmospheric airglow running diagonally across the center, and distant stars on the upper right that set behind the Earth. A lower stage can be seen falling back to Earth as the robotic supply ship fires its thrusters and begins to close on the ISS, a space laboratory that is celebrating its 20th anniversary this month.”

“We’re changing a mass realization system that we’ve had for 129 years”

NPR Science: Say Au Revoir To That Hunk Of Metal In France That Has Defined The Kilogram.

“The world is about to say au revoir to Le Grand K, a cylinder of platinum and iridium that has long reigned over the world’s system of weight measurement.

Le Grand K was forged in 1879 and is held in a locked vault outside Paris — revered and kept under lock and key because its mass, a little over 2 pounds, is the official definition of the kilogram.

But this is will soon change. On Friday, the international General Conference on Weights and Measures will meet in Versailles, France, to vote on whether to redefine the kilogram.

The vote is expected to be unanimous, a mere formality after years of work. Going forward, the world’s system of mass measurement will not be based on some special hunk of metal, but rather on unalterable features of the universe — such as the speed of light, time and Planck’s constant, a number that helps scientists figure out the energy of a photon of light, given its wavelength.”

Minkowski-Diagramme verstehen

Universalthinker: Minkowski-Diagramm 🚀 Spezielle Relativitätstheorie veranschaulicht! (YouTube, 25:30min)

“Möchtest Du spezielle Relativitätstheorie ohne Formeln verstehen, aber Du bist mit der populärwissenschaftlichen Erklärung nicht befriedigt? Dann sind Raum-Zeit-Diagramme (hier: Minkowski-Diagramme) genau das Richtige für Dich! Damit kannst Du alle Phänomene der speziellen Relativitätstheorie (Zeitdilatation, Längenkontraktion) veranschaulichen. Worum geht es im Video genau? In Kurzen Abschnitten wird Dir Folgendes näher gebracht: [22 Punkte]”

Passend dazu gibt’s beim Universaldenker (aka Alexander Fufaev) auch Minkowski-Diagramm: so veranschaulichst Du Relativitätstheorie.