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Some ignorance from Hume...

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Humeanist	Some ignorance from Hume...	Lead	[-]
Posts: 12896 (08/12/2002 12:32:53) Reply Quote More My Recent Posts Message Me Connection Blocking Invite Ignore User's Posts Report Post	Tags : None ... why does fabric look darker when it's wet? Heaven is better than the best thing you can possibly imagine. Picture countless rows of pews stretching from one end of infinity to the other, with myriad blessed souls mumbling, "Lord I Lift Your Name on High" for the 11 trillionth time, some banging their heads on the pew in front in their enthusiasm, and reflecting that there are no fewer days to sing God's praise than when they'd first begun and even that doesn't match it. - "Rev Gerard Ambulance"
Andy49	Re: Some ignorance from Hume...	#1	[-]
Posts: 963 (08/12/2002 13:04:20) Reply Quote More My Recent Posts Message Me Connection Blocking Invite Ignore User's Posts Report Post	Easy seen you've never been to a wet-T-shirt competition. "When shit becomes valuable, the poor will be born without assholes." Henry Miller
Rosy With A Why	Hmmm ...	#2	[-]
Posts: 5383 (08/12/2002 13:40:47) Reply Quote More My Recent Posts Message Me Connection Blocking Invite Ignore User's Posts Report Post	I was going to suggest that perhaps water particles absorb some light, but then I started to think about what water does on its own. I haven't got a clue! "Ninety per cent of most magic merely consists of knowing one extra fact." Terry Pratchett "An atheist is a man who has no invisible means of support."Sir John Buchan
OmniRev Doohickey Jones	Damn, nothing at the Straight Dope archives	#3	[-]
Posts: 11727 (08/12/2002 17:31:12) Fascist Moderator Reply Quote More My Recent Posts Message Me Connection Blocking Invite Ignore User's Posts Report Post	If we can't get it answered, perhaps we should submit it there? How are we supposed to take control of the planet if we cannot even conquer Office Depot? Turkey Pot Pie on wasting EAC supplies.
zimbrabim	Re: Hmmm ...	#4	[-]
Posts: 1891 (09/12/2002 14:56:07) Reply Quote More My Recent Posts Message Me Connection Blocking Invite Ignore User's Posts Report Post	I was wondering about that, too. Then I read this. Water has an albedo of 0.2, so 80% is absorbed or scattered internally. Most materials will have a higher albedo, so they look darker when wet. Also, the scattering of reflected light by wet material will probably be less random. Since you've got a least in part a flat surface from the water, more light will get scattered away from the prevailing light source (angle of incidence and all that), so while it looks darker in most directions, if you look at it while looking towards the light source, it may appear shiny.
AdrianBarnett	Re: Hmmm ...	#5	[-]
Posts: 12285 (09/12/2002 16:20:47) Grand Pooba of Atheism Reply Quote More My Recent Posts Message Me Connection Blocking Invite Ignore User's Posts Report Post	Not sure about all that... :) [quote] Water has an albedo of 0.2, so 80% is absorbed or scattered internally. Most materials will have a higher albedo, so they look darker when wet. [/quote] If that was true, wouldn't a clear glass of water look quite dark? :) [quote] so while it looks darker in most directions, if you look at it while looking towards the light source, it may appear shiny. [/quote] True, but that doesn't account for the same phenomena under a diffuse light source. I'd suspect it's something to do with the different properties of the wet vs. dry material itself, rather than just the water. It may help to open up the surface (in a porous substance) exposing a greater surface area which can absorb light. Or maybe the thin surface coating of water allows more chances for the material to absorb the light due to internal reflection within the surface layer? Also, because the water will flood any openings in the material it will allow light to be transmitted deeper into the material by acting as a light-guide, so light which would normally have reflected straight back will penetrate further and get absorbed. Or, it could just be magic. :) "If your idea was an oiltanker, it just sank off the coast of Spain and polluted a lot of stuff." - mattg to Orb Come and chat in my Atheist message board, or explore my Atheist website. ADRIAN BARNETT
zimbrabim	Re: Hmmm ...	#6	[-]
Posts: 1891 (09/12/2002 17:33:33) Reply Quote More My Recent Posts Message Me Connection Blocking Invite Ignore User's Posts Report Post	No, it wouldn't look dark, because most of the 80% which isn't reflected goes through without being absorbed - unless we're talking about a very big glass, of course. Internal reflection probably does play quite a big part, though. I'm afraid I'm not sure what you mean with the points about surface area and light guides...
chimesmith1	Knapp	#7	[-]
Posts: 711 (18/12/2002 15:11:29) Reply Quote More My Recent Posts Message Me Connection Blocking Invite Ignore User's Posts Report Post	The surface of most materials is covered with fine fibres that 'stick up' at all sorts of angles so can reflect more light. When wet the knapp lies flat. This was just off the top of my head but it makes sense to me (so is probably wrong). ______________________________________ 'Religion is the emulation of the adult by the child. Religion is the encystment of past beliefs: mythology, which is guesswork, the assumptions of trust in the universe, those pronouncements which men have made in search of personal power, all of it mingled with shreds of enlightenment. And always the ultimate unspoken commandment is "Thou shalt not question!" But we question. We break that commandment as a matter of course. The work to which we have set ourselves is the liberating of the imagination, the harnessing of imagination to humankind's deepest sense of creativity.' Frank Herbert. No saviour from on high delivers No faith have we in prince or peer Our own right hand the chains must shiver Chains of hatred, greed and fear The Internationale
Humeanist	That makes sense to me!	#8	[-]
Posts: 12896 (19/12/2002 19:20:46) Reply Quote More My Recent Posts Message Me Connection Blocking Invite Ignore User's Posts Report Post	So - as you say - therefore it is probably wrong. Heaven is better than the best thing you can possibly imagine. Picture countless rows of pews stretching from one end of infinity to the other, with myriad blessed souls mumbling, "Lord I Lift Your Name on High" for the 11 trillionth time, some banging their heads on the pew in front in their enthusiasm, and reflecting that there are no fewer days to sing God's praise than when they'd first begun and even that doesn't match it. - "Rev Gerard Ambulance"

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