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Astronomers are to thank for discovery of helium
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הכימאי שניסה להביא שלום ונרצח באושוויץ
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By Katharine Sanderson2021-02-15T10:42:00+00:00
Katharine Sanderson tells the story of a 19th century Russian chemist who made contributions across a range of chemistry
By the time Julia Lermontova successfully defended her thesis in October 1874, the number of women with doctorates in chemistry worldwide could be counted on one hand. In fact, they could be counted on one finger. At Göttingen University in Germany, Lermontova doubled the tally, probably just months behind Lydia Sesemann from Finland, who was the first woman to get a doctorate in chemistry, awarded by the University of Zurich. In a deeply patriarchal and often misogynistic society, Lermontova’s achievement was impressive. She was not only the first Russian woman to be awarded a doctorate for chemistry but also the first woman to do so at a German university.
关于原子钟的10个奇妙事实
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The term atomic clock may conjure up scary, 1950s-horror movie mental images: A Doomsday device, constructed by a lab coat-wearing maniac in a mountain fortress, is ticking away the seconds before it wipes out our entire planet. In reality, though, atomic clocks are one of the more benign inventions to emerge from the explosion oops, maybe not the best word choice of knowledge about the workings of the atom and its parts. That knowledge came in the wake of the World War II Manhattan Project to develop the atomic bomb.
Unlike the bomb, though, atomic clocks don t split atoms and they don t blow up. Instead, they use oscillation that is, the change in the flow of electrical charge in between an atom s nucleus and its surrounding electrons, the same way an old-fashioned grandfather clock might use a pendulum. Because an atom s oscillation involves incredibly small units of time a cesium atom, for example, has a frequency of 9,192,631,770 cycles per second and is extraordi