by neufer » Fri Mar 16, 2012 1:05 pm
alter-ego wrote:Chris Peterson wrote:
In practice, "brightness" is usually casually synonymous with "intensity", are refers to the particle (typically photon) flux.
I've seen, and used, photon flux (photons/second) used for threshold irradiance (photons/[cm
2 sec]) dependencies, but generally speaking, I can't remember when I last saw brightness constants described by photon flux.
Chris is probably thinking more along the lines of source brightness (photons/[steradian sec]) than of than of illumination intensity (photons/[cm
2 sec]) since he often has to remind us that while telescopes can collect photons over an extended apertures and also make extended sources seem closer (by expanding the steradians) they cannot increase the apparent source brightness (#photons per steradian) of those extended sources (e.g., planets, nebulas, galaxies, etc.).
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Note, however, that Webster's Revised Unabridged Dictionary (1828)
says absolutely nothing about photons :
............................................................
BRIGHTNESS, n. briteness. Splendor; luster; glitter.
- 1. Acuteness, applied to the faculties; sharpness of wit; as the brightness of a man's parts. (Sorry ladies.)
............................................................
BRIGHT, a. brite. [Heb. to shine.]
- 1. Shining; lucid; luminous; splendid; as a bright sun or star; a bright metal.
2. Clear; transparent; as liquors.
3. Evident; clear; manifest to the mind, as light is to the eyes.
4. Resplendent with charms; as a bright beauty; the brightest fair.
5. Illuminated with science; sparkling with wit; as the brightest of men.
6. Illustrious; glorious; as the brightest period of a kingdom.
7. In popular language, ingenious; possessing an active mind.
8. Promising good or success; as bright prospects.
9. Sparkling; animated; as bright eyes.
- [list]The Men Who Stare at Goats (2009)
Lyn Cassady (George Clooney): Like all Shaman before him, he had traversed the wilderness. Now he was returning to his people, a changed man. He brought with him his confidential report, which he called: "The New Earth Army manual." The New Earth Army is a banner under which the forces of good can gather. The courage and nobility of the Warrior, blended with the spirituality of the Monk. The Jedi Warrior will follow in the footsteps of the great imagineers of the past: Jesus Christ, Lao Tse Tung, Walt Disney. The role of The New Earth Army is to resolve conflict world-wide. Jedis will parachute into war zones, utilizing sparkly eyes technique, carrying symbolic flowers and animals, playing indigenous music and words of peace...
Bob Wilton (ex-Jedi Warrior Ewan McGregor): What's... What's the sparkly eyes technique?
[/list]
[quote="alter-ego"][quote="Chris Peterson"]
In practice, "brightness" is usually casually synonymous with "intensity", are refers to the particle (typically photon) flux.[/quote]
I've seen, and used, photon flux (photons/second) used for threshold irradiance (photons/[cm[sup]2[/sup] sec]) dependencies, but generally speaking, I can't remember when I last saw brightness constants described by photon flux.[/quote]
Chris is probably thinking more along the lines of source brightness (photons/[steradian sec]) than of than of illumination intensity (photons/[cm[sup]2[/sup] sec]) since he often has to remind us that while telescopes can collect photons over an extended apertures and also make extended sources seem closer (by expanding the steradians) they cannot increase the apparent source brightness (#photons per steradian) of those extended sources (e.g., planets, nebulas, galaxies, etc.).
-------------------------------------------------------------------------
Note, however, that Webster's Revised Unabridged Dictionary (1828) [b][u]says absolutely nothing about photons[/u][/b] :!: :
............................................................
BRIGHTNESS, n. briteness. Splendor; luster; glitter.
[list] 1. Acuteness, applied to the faculties; sharpness of wit; as the brightness of a man's parts. (Sorry ladies.) [/list]
............................................................
BRIGHT, a. brite. [Heb. to shine.]
[list] 1. Shining; lucid; luminous; splendid; as a bright sun or star; a bright metal.
2. Clear; transparent; as liquors.
3. Evident; clear; manifest to the mind, as light is to the eyes.
4. Resplendent with charms; as a bright beauty; the brightest fair.
5. Illuminated with science; sparkling with wit; as the brightest of men.
6. Illustrious; glorious; as the brightest period of a kingdom.
7. In popular language, ingenious; possessing an active mind.
8. Promising good or success; as bright prospects.
9. Sparkling; animated; as bright eyes.
[list][size=125][list]The Men Who Stare at Goats (2009) [/list][/size]Lyn Cassady (George Clooney): [b][i][color=#0000FF]Like all Shaman before him, he had traversed the wilderness. Now he was returning to his people, a changed man. He brought with him his confidential report, which he called: "The New Earth Army manual." The New Earth Army is a banner under which the forces of good can gather. The courage and nobility of the Warrior, blended with the spirituality of the Monk. The Jedi Warrior will follow in the footsteps of the great imagineers of the past: Jesus Christ, Lao Tse Tung, Walt Disney. The role of The New Earth Army is to resolve conflict world-wide. Jedis will parachute into war zones, utilizing sparkly eyes technique, carrying symbolic flowers and animals, playing indigenous music and words of peace...[/color][/i][/b]
Bob Wilton (ex-Jedi Warrior Ewan McGregor): [b][i][color=#0000FF]What's... What's the sparkly eyes technique?[/color][/i][/b][/list][/list]