Category Archives: Physics

Dancing water droplets in an air bubble inside a water bubble in space

Smarter Every Day 160: The WALKING WATER Mystery (in SPACE and SLOW MOTION!). (YouTube, 12min)

Destin Sandlin explains why you often see water droplets dance or bounce on the surface of water instead of coalescence occurs.

This video features astronaut Don Pettit, who did a cool experiment in space: He attached a big water bubble to a speaker, then inserted an air bubble into it. When he played cello music (by Yo-Yo Ma) through the speaker, little water droplets would detach from the water and bounce around inside the air bubble. You can see it in the above video starting right here.

Schiaparelli Mars lander hit the planet hard — and possibly exploded.

NPR the two-way: Schiaparelli Mars Lander May Have Exploded On Impact, European Agency Says.

“”Estimates are that Schiaparelli dropped from a height of between 2 and 4 kilometers, therefore impacting at a considerable speed, greater than 300 km/h [186 mph]. The relatively large size of the feature would then arise from disturbed surface material. It is also possible that the lander exploded on impact, as its thruster propellant tanks were likely still full.””

From a catastrophe to a new theory

Physics Girl: The Ultraviolet Catastrophe.

“How did the field of quantum mechanics come about in the first place? The Rayleigh-Jeans catastrophe, also known as the ultraviolet catastrophe was a prediction by the Rayleigh-Jeans law that a blackbody would radiate infinite amounts of ultraviolet light. It wasn’t until Max Planck came along and predicted that light came in packets or quanta that the field of quantum mechanics emerged and unintentionally solved the ultraviolet catastrophe.”

Das Dreikörperproblem

… musste ich in meinem dritten Semester an der Uni für den Schein in theoretischer Physik Mechanik programmieren. Das sah natürlich längst nicht so schick aus wie diese Website, und davon abgesehen hatte ich einen Fehler im Programm, den ich erst nach mehreren Tagen gefunden habe – es war ein Vorzeichenfehler.

PhET Interactive Simulations, University of Colorado: My Solar System. (Flash)

You can simulate the orbits of two, three or four objects and change the mass, initial position and velocity for each one individually. Try to find stable or chaotic orbits!

“Hahn: If they have really got it, they have been very clever in keeping it secret.”

German History in Documents and Images: Transcript of Surreptitiously Taped Conversations among German Nuclear Physicists at Farm Hall (August 6-7, 1945).(PDF)

“At the beginning of the war, Germany’s leading nuclear physicists were called to the army weapons department. There, as part of the “uranium project“ under the direction of Werner Heisenberg, they were charged with determining the extent to which nuclear fission could aid in the war effort. (Nuclear fission had been discovered by Otto Hahn and Lise Meitner in 1938.) Unlike their American colleagues in the Manhattan Project, German physicists did not succeed in building their own nuclear weapon. In June 1942, the researchers informed Albert Speer that they were in no position to build an atomic bomb with the resources at hand in less than 3-5 years, at which point the project was scrapped.

After the end of the war, both the Western Allies and the Soviet Union tried to recruit the German scientists for their own purposes. From July 3, 1945, to January 3, 1946, the Allies incarcerated ten German nuclear physicists at the English country estate of Farm Hall, their goal being to obtain information about the German nuclear research project by way of surreptitiously taped conversations. The following transcript includes the scientists’ reactions to reports that America had dropped an atomic bomb on Hiroshima. The scientists also discuss their relationship to the Nazi regime and offer some prognoses for Germany’s future. As the transcript shows, Otto Hahn was especially shaken by the dropping of the bomb; later, hecampaigned against the misuse of nuclear energy for military purposes.”

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