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Imaginary time is a mathematical representation of time that appears in some approaches to special relativity and quantum mechanics. It finds uses in certain cosmological theories. Mathematically, imaginary time is real time which has undergone a Wick rotation so that its coordinates are multiplied by the imaginary unit i .
In physics, sometimes units of measurement in which c = 1 are used to simplify equations. Time in a "moving" reference frame is shown to run more slowly than in a "stationary" one by the following relation (which can be derived by the Lorentz transformation by putting ∆x′ = 0, ∆τ = ∆t′):
Symbol Name Meaning SI unit of measure nabla dot : the divergence operator often pronounced "del dot" per meter (m −1) : nabla cross : the curl operator often pronounced "del cross"
A branch of physics that studies atoms as isolated systems of electrons and an atomic nucleus. Compare nuclear physics. atomic structure atomic weight (A) The sum total of protons (or electrons) and neutrons within an atom. audio frequency A periodic vibration whose frequency is in the band audible to the average human, the human hearing range.
Classical mechanics is the branch of physics used to describe the motion of macroscopic objects. [1] It is the most familiar of the theories of physics. The concepts it covers, such as mass, acceleration, and force, are commonly used and known. [2] The subject is based upon a three-dimensional Euclidean space with fixed axes, called a frame of ...
In physics, there are equations in every field to relate physical quantities to each other and perform calculations. Entire handbooks of equations can only summarize most of the full subject, else are highly specialized within a certain field. Physics is derived of formulae only.
Kepler's 3rd law of planetary motion states, the square of the periodic time is proportional to the cube of the mean distance, [4] or , where a is the semi-major axis or mean distance, and P is the orbital period as above.
In physics, equations of motion are equations that describe the behavior of a physical system in terms of its motion as a function of time. [3] More specifically, the equations of motion describe the behavior of a physical system as a set of mathematical functions in terms of dynamic variables. These variables are usually spatial coordinates ...