Here is a question about this article: Classical statistical mechanics requires the existence of h (but does not define its value). Eventually, following upon Planck's discovery, it was recognized that physical action cannot take on an arbitrary value. Instead, it must be some multiple of a very small quantity, the "quantum of action", now called the Planck constant. Classical physics cannot explain this fact. In many cases, such as for monochromatic light or for atoms, this quantum of action also implies that only certain energy levels are allowed, and values in between are forbidden.
What is the answer to this question: What was realized after Planck's discovery?
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So... that physical action cannot take on an arbitrary value

Here is a question about this article: For the first several decades of disc record manufacturing, sound was recorded directly on to the "master disc" at the recording studio. From about 1950 on (earlier for some large record companies, later for some small ones) it became usual to have the performance first recorded on audio tape, which could then be processed and/or edited, and then dubbed on to the master disc. A record cutter would engrave the grooves into the master disc. Early versions of these master discs were soft wax, and later a harder lacquer was used. The mastering process was originally something of an art as the operator had to manually allow for the changes in sound which affected how wide the space for the groove needed to be on each rotation.
What is the answer to this question: After the 1950s what was a typical recording process?
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So... first recorded on audio tape, which could then be processed and/or edited, and then dubbed on to the master disc

Here is a question about this article: During the night of December 2 and early morning of December 3, 1968, Kerry was in charge of a small boat operating near a peninsula north of Cam Ranh Bay together with a Swift boat (PCF-60). According to Kerry and the two crewmen who accompanied him that night, Patrick Runyon and William Zaladonis, they surprised a group of Vietnamese men unloading sampans at a river crossing, who began running and failed to obey an order to stop. As the men fled, Kerry and his crew opened fire on the sampans and destroyed them, then rapidly left. During this encounter, Kerry received a shrapnel wound in the left arm above the elbow. It was for this injury that Kerry received his first Purple Heart Medal.
What is the answer to this question: What did Kerry's crew destroy?
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So...
sampans