In this task you will be given a text passage from a trivia quiz. You should choose the category this question belongs to from these categories: History, Science, Social Science, Fine Arts, Literature. You can only choose one category, so if in doubt, please choose the closest match.

[EX Q]: This rule holds if the operator algebra for some set of observables is non-trivial; that is true because it is derived via the Schwarz inequality applied to the expectation value of the commutator of two observables operators. It formally bounds the product of the dispersions in two observables. An adapted form of this law applies to energy and time; it applies directly to any two components of spin, but it is best known in its application to position and momentum, the product of the standard deviations of which is at least h-bar over two. FTP, name this principle from quantum mechanics that limits the precision of measurements.
[EX A]: Science

[EX Q]: Erwin Finlay-Freundlich proposed one explanation for this phenomenon that claimed its strength should be proportional to the radiation density. A version of this phenomenon in the CMB is known as the Sachs-Wolfe effect, while the quantity that describes the strength of this effect has a value of about 1100 for the surface of last scattering. One version of this effect was measured using the Mossbauer effect in an experiment by Pound and Rebka, and the magnitude of this effect is usually denoted "z. " For 10 points, name this phenomenon, which can be caused by gravity or the Doppler effect, in which the wavelength of an object's light appears longer to an observer.
[EX A]: Science

[EX Q]: The fact that it does not affect the ground state can be derived heuristically from symmetry considerations or explicitly from the Wigner-Eckart theorem. In semiconductor heterostructures, a quantum-confined version of this effect occurs, which results from the enhancement of this effect by excitons. For higher quantum numbers, the energy levels induced by this effect are degenerate, and leading to the commonly observed quadratic form, whose components are proportional to the polarizability tensor. Particularly useful for analyzing molecular rotational spectra, for ten points, identify this effect from atomic physics, which consists of the splitting and shift of a spectral line into several components in the presence of an electric field.
[EX A]:
Science