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

1) Water condensed onto grass and other objects near the ground, the temperatures of which have fallen below the dewpoint of the surface air due to radiational cooling during the night, but are still above freezing.
2) Moisture in small drops on a surface.

O.E. deaw, from P.Gmc. *dawwaz, O.H.G. tow, Gk. thein, "to run," thoos "quick," PIE base *dheu- "to run, flow" (cf. Pers. dav-, davidan "to run," Skt. dhav- "to run, flow," dhavati "flows, runs").

Šabnam, from šab→ night + nam "moisture; dew; wet," Mid.Pers. namb, nam, Av. napta- "moist," nabas-câ "cloud," nabah- "sky," Skt. nábhas- "moisture, cloud, mist, sky," Gk. nephos "cloud," L. nebula "mist," PIE base *nebhos- "moisture, cloud, mist."

A hollow tube that extends out in front of the objective lens (refractors) or corrector lens (Schmidt-Cassegrains). It shields the exposed optics from wide exposure to the cool ambient air, slowing heat loss and preventing dew formation. Reflector telescopes do not need dew caps because the main mirror rests at the bottom of the tube, which acts as a dew shield.

→ dew + cap, from O.E. cæppe "hood, head-covering," from L.L. cappa "a cape, hooded cloak."

Kolâhak, from kolâh "cap," see below, + similarity suffix -ak. Kolâh "cap," cf. L. celare "to hide, conceal," occulere "to dissimulate," Gk. kalyptein "to cover," kalia "hut, nest," Skt. cala "hut, house," Goth. hilms "helmet," huljan "cover over," hulistr "covering," E. hull "seed covering," from O.E. hulu, from O.H.G. hulla, hulsa, O.E. hol "cave;" PIE base *kel- "conceal." Šabnam→ dew.

The temperature to which a given air parcel must be cooled at constant pressure and constant water vapor content in order for saturation to occur.

→ dew; → point.

Insulated bottle containing a cryogenic fluid. The electronic detectors operated at very low temperature are mounted inside a dewar.

Named after its inventor Sir James Dewar (1842-1923), Scottish chemist and physicist.

A rainbow formed in the small drops often found on grass in early morning. While the name implies that those drops are dew, that is probably rarely the case. Rather, the drops are usually the result of guttation (the water exuded from leaves as a result of root pressure) rather than dew.

→ dew; → bow.

In → quantum gravity, an equation that describes the → wave function of the → Universe. It is an adaptation of the → Schrodinger equation but includes the curved space attributes of → general relativity.

Named after American theoretical physicists John Archibald Wheeler (1911-2008) and Bryce Seligman DeWitt (1923-2004).