transient lunar phenomenon (TLP)
padide-ye mângi-ye gozarâ, ~ mâhi-ye
Fr.: phénomène lunaire transitoire
A short-lived change in the brightness of patches on the face of the Moon. The TLPs last from a few seconds to a few hours and can grow from less than a few to a hundred kilometers in size. They have been reported by many observers since the invention of the telescope. However, the physical mechanism responsible for creating a TLP is not well understood. Several theories have been proposed, among which lunar outgassing, that is, gas being released from the surface of the Moon.
→ transient; → lunar; → phenomenon.
Fr.: théorème de Varignon
The → moment of the resultant of a → coplanar system of → concurrent forces about any center is equal to the algebraic sum of the moments of the component forces about that center.
Named after Pierre Varignon (1654-1722), a French mathematician, who outlined the fundamentals of statics in his book Projet d'une nouvelle mécanique (1687).
A colorless, odorless, tasteless, chemically un-reactive gas, belonging to the → inert gas group, occurring in exceedingly minute amounts in the air; symbol Xe. → Atomic number 54; → atomic weight 131.29; → melting point -111.9°C; → boiling point -107.1°C. Xenon was discovered spectroscopically in 1898 by William Ramsay and M. W. Travers, who obtained it by fractional distillation of an impure sample of liquid → krypton. The lightest → isotopes of xenon (124Xe and 126Xe) are produced during → supernova explosions; intermediate-mass isotopes (127Xe, 128Xe, 129Xe, 130Xe, 131Xe and 132Xe) are produced during the → Asymptotic Giant Branch phase of evolved low- and intermediate-mass stars; the heaviest isotopes (134Xe and 136Xe) are produced during the → merger of → neutron stars.
From Gk. xenon, neuter of xenos "strange," introduced by the discoverers.