Problem: Group (mathematics):

Lie groups are of fundamental importance in modern physics: Noether's theorem links continuous symmetries to conserved quantities. Rotation, as well as translations in space and time are basic symmetries of the laws of mechanics. They can, for instance, be used to construct simple models—imposing, say, axial symmetry on a situation will typically lead to significant simplification in the equations one needs to solve to provide a physical description.v[›] Another example are the Lorentz transformations, which relate measurements of time and velocity of two observers in motion relative to each other. They can be deduced in a purely group-theoretical way, by expressing the transformations as a rotational symmetry of Minkowski space. The latter serves—in the absence of significant gravitation—as a model of space time in special relativity. The full symmetry group of Minkowski space, i.e. including translations, is known as the Poincaré group. By the above, it plays a pivotal role in special relativity and, by implication, for quantum field theories. Symmetries that vary with location are central to the modern description of physical interactions with the help of gauge theory.

What connects continuous symmetries to conserved quantities?
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A: Noether's theorem


Problem: By 3400 BCE, the Sahara was as dry as it is today, due to reduced precipitation and higher temperatures resulting from a shift in the Earth's orbit. As a result of this aridification, it became a largely impenetrable barrier to humans, with the remaining settlements mainly being concentrated around the numerous oases that dot the landscape. Little trade or commerce is known to have passed through the interior in subsequent periods, the only major exception being the Nile Valley. The Nile, however, was impassable at several cataracts, making trade and contact by boat difficult.
By What time period was the Sahara dry like it is today?
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Answer: 3400 BCE


Q: What is a question about this article? If the question is unanswerable, say "unanswerable".
Since October 2004, the iPod line has dominated digital music player sales in the United States, with over 90% of the market for hard drive-based players and over 70% of the market for all types of players. During the year from January 2004 to January 2005, the high rate of sales caused its U.S. market share to increase from 31% to 65% and in July 2005, this market share was measured at 74%. In January 2007 the iPod market share reached 72.7% according to Bloomberg Online.
What share of the US digital music player market does iPod hold?
A: 90%


Context and question: The status of "language" is not solely determined by linguistic criteria, but it is also the result of a historical and political development. Romansh came to be a written language, and therefore it is recognized as a language, even though it is very close to the Lombardic alpine dialects. An opposite example is the case of Chinese, whose variations such as Mandarin and Cantonese are often called dialects and not languages, despite their mutual unintelligibility.
What language are Mandarin and Cantonese sometimes considered dialects of?
Answer: Chinese


Question: where the uncertainty is given as the standard deviation of the measured value from its expected value. There are a number of other such pairs of physically measurable values which obey a similar rule. One example is time vs. energy. The either-or nature of uncertainty forces measurement attempts to choose between trade offs, and given that they are quanta, the trade offs often take the form of either-or (as in Fourier analysis), rather than the compromises and gray areas of time series analysis.
Is there an answer to this question: What forces measurement attempts to choose between trade-offs, in quanta?

Answer: either-or nature of uncertainty


Question: As many as five bands were on tour during the 1920s. The Jenkins Orphanage Band played in the inaugural parades of Presidents Theodore Roosevelt and William Taft and toured the USA and Europe. The band also played on Broadway for the play "Porgy" by DuBose and Dorothy Heyward, a stage version of their novel of the same title. The story was based in Charleston and featured the Gullah community. The Heywards insisted on hiring the real Jenkins Orphanage Band to portray themselves on stage. Only a few years later, DuBose Heyward collaborated with George and Ira Gershwin to turn his novel into the now famous opera, Porgy and Bess (so named so as to distinguish it from the play). George Gershwin and Heyward spent the summer of 1934 at Folly Beach outside of Charleston writing this "folk opera", as Gershwin called it. Porgy and Bess is considered the Great American Opera[citation needed] and is widely performed.
Is there an answer to this question: When did Gershwin and Heyward write their folk opera?

Answer:
summer of 1934