by neufer » Thu Jan 06, 2022 5:36 pm
Chris Peterson wrote: ↑Thu Jan 06, 2022 3:27 pm
rstevenson wrote: ↑Thu Jan 06, 2022 3:17 pm
gmPhil wrote: ↑Thu Jan 06, 2022 9:23 am
"about 2 percent illuminated by sunlight" sounds somewhat strange to me - it is 100% illuminated by sunlight!! I presume you mean that about 2% of the sunlight that hits it is reflected...
I’ve always taken that sort of statement as meaning that 2% of the disk of Venus is reflecting sunlight towards us. I may be wrong.
You are not. It's a reference to
phase (not to be confused with
phase angle), which as with the Moon or any other body that shows phases, simply refers to the percentage of the disc that is illuminated from the observer's reference (typically the Earth).
https://www.etymonline.com/search?q=phase wrote:
<<phase (n.) 1705, "phase of the moon, particular recurrent appearance presented by the moon (or Mercury or Venus) at a particular time," back-formed as a singular from Modern Latin phases, plural of phasis, from Greek phasis "appearance" (of a star), "phase" (of the moon), from stem of phainein "to show, to make appear" (from PIE root *bha- (1) "to shine"). Latin singular phasis was used in English from 1660 for each of the aspects of the moon. General (non-lunar) sense of "aspect, appearance, stage of development at a particular time" is attested by 1841. Meaning "temporary difficult period" (especially in reference to adolescents) is attested from 1913.>>
[quote="Chris Peterson" post_id=319666 time=1641482877 user_id=117706]
[quote=rstevenson post_id=319665 time=1641482240 user_id=124801]
[quote=gmPhil post_id=319657 time=1641460990 user_id=130728]
"about 2 percent illuminated by sunlight" sounds somewhat strange to me - it is 100% illuminated by sunlight!! I presume you mean that about 2% of the sunlight that hits it is reflected... :) [/quote]
I’ve always taken that sort of statement as meaning that 2% of the disk of Venus is reflecting sunlight towards us. I may be wrong. :-) [/quote]
You are not. It's a reference to [i]phase [/i](not to be confused with [i]phase angle[/i]), which as with the Moon or any other body that shows phases, simply refers to the percentage of the disc that is illuminated from the observer's reference (typically the Earth). [/quote][quote=https://www.etymonline.com/search?q=phase]
<<phase (n.) 1705, "phase of the moon, particular recurrent appearance presented by the moon (or Mercury or Venus) at a particular time," back-formed as a singular from Modern Latin phases, plural of phasis, from Greek phasis "appearance" (of a star), "phase" (of the moon), from stem of phainein "to show, to make appear" (from PIE root *bha- (1) "to shine"). Latin singular phasis was used in English from 1660 for each of the aspects of the moon. General (non-lunar) sense of "aspect, appearance, stage of development at a particular time" is attested by 1841. Meaning "temporary difficult period" (especially in reference to adolescents) is attested from 1913.>>[/quote]