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  2. M-theory - Wikipedia

    en.wikipedia.org/wiki/M-theory

    M-theory is a theory in physics that unifies all consistent versions of superstring theory. Edward Witten first conjectured the existence of such a theory at a string theory conference at the University of Southern California in 1995. Witten's announcement initiated a flurry of research activity known as the second superstring revolution.

  3. Dimensional analysis - Wikipedia

    en.wikipedia.org/wiki/Dimensional_analysis

    Dimensional analysis. In engineering and science, dimensional analysis is the analysis of the relationships between different physical quantities by identifying their base quantities (such as length, mass, time, and electric current) and units of measurement (such as metres and grams) and tracking these dimensions as calculations or comparisons ...

  4. Engineering drawing abbreviations and symbols - Wikipedia

    en.wikipedia.org/wiki/Engineering_drawing...

    In a feature control frame (FCF), the ⌀ symbol tells you that the tolerance zone for the geometric tolerance is cylindrical. Abbreviations for "diameter" include ⌀, DIA, and D. D. diameter; delta. Abbreviations for "diameter" include ⌀, DIA, and D. For delta usage, see for example "delta notes". DIA[2] diameter.

  5. Engineering drawing - Wikipedia

    en.wikipedia.org/wiki/Engineering_drawing

    v. t. e. An engineering drawing is a type of technical drawing that is used to convey information about an object. A common use is to specify the geometry necessary for the construction of a component and is called a detail drawing. Usually, a number of drawings are necessary to completely specify even a simple component.

  6. Spin–lattice relaxation - Wikipedia

    en.wikipedia.org/wiki/Spin–lattice_relaxation

    It is characterized by the spin–lattice relaxation time, a time constant known as T 1. There is a different parameter, T 2 , the spin–spin relaxation time , which concerns the exponential relaxation of the transverse component of the nuclear magnetization vector ( perpendicular to the external magnetic field).

  7. Half-life - Wikipedia

    en.wikipedia.org/wiki/Half-life

    Half-life (symbol t½) is the time required for a quantity (of substance) to reduce to half of its initial value. The term is commonly used in nuclear physics to describe how quickly unstable atoms undergo radioactive decay or how long stable atoms survive. The term is also used more generally to characterize any type of exponential (or, rarely ...

  8. Introduction to M-theory - Wikipedia

    en.wikipedia.org/wiki/Introduction_to_M-theory

    It did this by asserting that strings are an approximation of curled-up two-dimensional membranes vibrating in an 11-dimensional spacetime. According to Witten, the M could stand for "magic", "mystery", or "membrane" according to taste, and the true meaning of the title should be decided when a better understanding of the theory is discovered. [5]

  9. Time in physics - Wikipedia

    en.wikipedia.org/wiki/Time_in_physics

    t is the time between these same two events, but as measured in the stationary reference frame; v is the speed of the moving reference frame relative to the stationary one; c is the speed of light. Moving objects therefore are said to show a slower passage of time. This is known as time dilation.