An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

Physics: A vector quantity that specifies the change of position of a body or particle from the mean position or position of rest.
Geology: The offset of rocks caused by movement along a fault.

From displace, from → dis- + place + -ment.

Jâ bé jâyi, noun of jâ bé jâ literally "place to place," from jâ "place," from Mid.Pers. giyag "place," O.Pers. ā-vahana- "place, village," Av. vah- "to dwell, stay," vanhaiti "he dwells, stays," Skt. vásati "he dwells," Gk. aesa (nukta) "to pass (the night)," Ossetic wat "room; bed; place," Tokharian B wäs- "to stay, wait;" PIE base ues- "to stay, live, spend the night."

In electromagnetism, a quantity which is not a real current (movement of charge), but has the units of current and has an associated magnetic field. The physical meaning of this displacement current is that a changing electric field makes a changing magnetic field.

→ displacement; → current.

In → analytical mechanics, any infinitesimal change in the configuration of a material system, consistent with any constraints acting on the system at a given instant. If the constraints are stationary (→ scleronomous), then the actual displacement of the system, in an infinitesimal length of time dt, coincides with one of its virtual displacements. In the case of time-dependent (→ rheonomous) constraints, the actual displacement of the system does not coincide with any of the virtual ones, since the conditions imposed by the constraints vary during the time dt.

→ virtual; → displacement.

The wavelength corresponding to the maximum emissive power of a black body is inversely proportional to the absolute temperature of the body: λ_max.T = 0.29 cm-deg. Wien's law explains why objects of different temperature emit spectra that peak at different wavelengths. Hotter objects emit most of their radiation at shorter wavelengths; hence they will appear to be bluer. Wien's law was an early attempt to describe the → blackbody radiation. The law closely approximated the true shape of the blackbody spectrum at short wavelengths, but ultimately failed because it relied solely on classical physics. It was superseded by → Planck's radiation law, which correctly describes the blackbody spectrum at all wavelengths.

After the German physicist Wilhelm Wien (1864-1928), who found the law in 1896. He was awarded the 1911 Nobel Prize in physics; → displacement; → law.