In article <408719ff$1@news.povray.org>,
 Dan P <dan### [at] yahoocom> wrote:

> What you are describing is called the "albedo" of an object. This 
> website[1] defines albedo as, "the fraction of light that is reflected 
> by a body or surface." This site contains some albedos that illustrate 
> your point:

Yes, I know. I mentioned this in some of the messages I posted 
previously. Such as the one a couple steps up this thread posted in 
response to one of your messages. Which you replied to. It'd help if you 
read them first...

The Moon's albedo varies drastically with angle because of glass beads 
in the regolith (surface debris formed by impacting bodies...lunar dirt, 
basically) which tend to reflect light back in the direction it came 
from. The apparent albedo from earth is usually closer to 7%, but it 
reaches about 12% at full moon. It'd be interesting to simulate this in 
POV...


> The Earth is 21% brighter than the moon (as you've said), probably 
> because of all the water on the surface and in the clouds. Venus is 43% 
> brighter because it has a lot more clouds to reflect the light. Venus 
> has been so bright to us that people have mistaken it for the light of 
> an on-coming train!

Venus is also closer to the Sun, about 0.7 AU, which means it intercepts 
twice as much sunlight. Approximating the Sun as a point source. ;-)
Still, I think you'd have to be pretty confused to mistake it for a 
train light.

-- 
Christopher James Huff <cja### [at] earthlinknet>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: <chr### [at] tagpovrayorg>
http://tag.povray.org/

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"Christopher James Huff" <cja### [at] earthlinknet> wrote in message

> The Moon's albedo varies drastically with angle because of glass
beads
> in the regolith (surface debris formed by impacting bodies...lunar
dirt,
> basically)

   Glass beads?  Seriously, is this a known fact? I can see that it
could be, because sand (silica) as we know it, will form into the same
glass beads under intense heat here on earth.

   Interesting, and I hadn't heard of 'albedo' before now.

   ~Steve~





> Christopher James Huff <cja### [at] earthlinknet>
> http://home.earthlink.net/~cjameshuff/
> POV-Ray TAG: <chr### [at] tagpovrayorg>
> http://tag.povray.org/

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In article <40880ec5@news.povray.org>, "St." <dot### [at] dotcom> wrote:

>    Glass beads?  Seriously, is this a known fact? I can see that it
> could be, because sand (silica) as we know it, will form into the same
> glass beads under intense heat here on earth.

We've been there, remember? ;-)
There are some micrographs on the net of samples brought back by the 
Apollo missions...here's a page with some good ones from Apollo 17:
<http://www.union.edu/PUBLIC/GEODEPT/COURSES/petrology/moon_rocks/74220.h
tm>
Similar glass beads are found here on Earth around volcanos and impact 
craters. Impact-melted rock or magma gets blasted into the sky and 
solidifies into more or less spherical shapes before it lands.

-- 
Christopher James Huff <cja### [at] earthlinknet>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: <chr### [at] tagpovrayorg>
http://tag.povray.org/

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Among other things, Christoph Hormann wrote:

>> (higher = brighter)
>> Venus: 0.76
>> Earth: 0.33
>>  Moon: 0.12
>> 
>> The Earth is 21% brighter than the moon (as you've said), probably
>> because of all the water on the surface and in the clouds. Venus is 43%
>> brighter [...]
> 
> If earth reflects a fraction of 0.33 of the incoming light and the moon
> 0.12 that means the earth surface reflects 2.75 times the amount of
> light the moon surface reflects per surface area.  I don't even want to
> try to imagine how you came to '21% brighter'...

The moon reflects 12%
The earth reflects 33%

33-12 = 21

The earth reflects 21% more than the moon. Now, 21% is a relative measure, 
so the question is 21% of what? Daniel meant 21% of the whole original 
light income, while you're thinking of 21% of the amount of light reflected 
by the moon (which, obviously, is not correct in this case, as you say).

Talking about percents can easily be ambiguous. We often hear in the news 
things like "this year the inflation has been 0.5% higher than last 
year's", meaning that it was 1% last year and 1.5% this year (and not 
1.005%).

-- 
light_source{9+9*x,1}camera{orthographic look_at(1-y)/4angle 30location
9/4-z*4}light_source{-9*z,1}union{box{.9-z.1+x clipped_by{plane{2+y-4*x
0}}}box{z-y-.1.1+z}box{-.1.1+x}box{.1z-.1}pigment{rgb<.8.2,1>}}//Jellby

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Christoph Hormann wrote:

> Dan P wrote:

<snip:description of albedo />

>> The Earth is 21% brighter than the moon (as you've said), probably 
>> because of all the water on the surface and in the clouds. Venus is 
>> 43% brighter [...]
> 
> 
> What?
> 
> I don't know where you learned math but this can't be meant seriously.
>
> If earth reflects a fraction of 0.33 of the incoming light and the moon 
> 0.12 that means the earth surface reflects 2.75 times the amount of 
> light the moon surface reflects per surface area.  I don't even want to 
> try to imagine how you came to '21% brighter'...

I just subtracted the percentages, 0.33 - 0.12. I'm saying that, on a 
scale of 0 to 1 (0% to 100%), the value 0.33 (33%) is (0.33 - 0.12) = 
0.21 (21%) more than 0.12 (12%). You're thinking I said "times". You're 
right; 0.33 / 0.12 = 2.75, which is another way to think of it. However, 
I also compared the brightness of Venus, so we are not comparing two 
albedos, but instead, a set of albedo values, bound within the range of 
  0 < x < 1 (exact 0 and 1 are impossible because a surface cannot 
reflect 0 light in reality and no surface can reflect all light, not 
even a mirror).

Try substituting the word "brighter" with "more bright" and it may sound 
more clear.

> Christoph

-- 
Respectfully,
Dan P
http://<broken link>

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Jellby wrote:

> Among other things, Christoph Hormann wrote:
>
<snip />

> 3-12 = 21
> 
> The earth reflects 21% more than the moon. Now, 21% is a relative measure, 
> so the question is 21% of what? Daniel meant 21% of the whole original 
> light income, while you're thinking of 21% of the amount of light reflected 
> by the moon (which, obviously, is not correct in this case, as you say).
> 
> Talking about percents can easily be ambiguous. We often hear in the news 
> things like "this year the inflation has been 0.5% higher than last 
> year's", meaning that it was 1% last year and 1.5% this year (and not 
> 1.005%).

Thanks Jellby! I just read this after writing the other message so I'm 
not trying to be redundant; I'm not trying to repeat myself. :-P
-- 
Respectfully,
Dan P
http://<broken link>

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Christopher James Huff wrote:

> In article <408719ff$1@news.povray.org>,
>  Dan P <dan### [at] yahoocom> wrote:
> 
>>What you are describing is called the "albedo" of an object. This 
>>website[1] defines albedo as, "the fraction of light that is reflected 
>>by a body or surface." This site contains some albedos that illustrate 
>>your point:
> 
> Yes, I know. I mentioned this in some of the messages I posted 
> previously. Such as the one a couple steps up this thread posted in 
> response to one of your messages. Which you replied to. It'd help if you 
> read them first...

... perhaps I am misreading this message. Are you feeling threatened by 
my explanation of albedo, which is causing you to become confrontational?

> The Moon's albedo varies drastically with angle because of glass beads 
> in the regolith (surface debris formed by impacting bodies...lunar dirt, 
> basically) which tend to reflect light back in the direction it came 
> from. The apparent albedo from earth is usually closer to 7%, but it 
> reaches about 12% at full moon. It'd be interesting to simulate this in 
> POV...

I'd like to see that too!

>>The Earth is 21% brighter than the moon (as you've said), probably 
>>because of all the water on the surface and in the clouds. Venus is 43% 
>>brighter because it has a lot more clouds to reflect the light. Venus 
>>has been so bright to us that people have mistaken it for the light of 
>>an on-coming train!
> 
> Venus is also closer to the Sun, about 0.7 AU, which means it intercepts 
> twice as much sunlight. Approximating the Sun as a point source. ;-)

Well, true; the amount of light that hits a surface does not change its 
albedo, though, but I see your point; I shouldn't have used "brightness" 
there without saying "all things being equal".

 > Still, I think you'd have to be pretty confused to mistake it for a
 > train light.

Indeed. People get like that, though.
-- 
Respectfully,
Dan P
http://<broken link>

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In article <40885de1$1@news.povray.org>,
 Dan P <dan### [at] yahoocom> wrote:

> > Yes, I know. I mentioned this in some of the messages I posted 
> > previously. Such as the one a couple steps up this thread posted in 
> > response to one of your messages. Which you replied to. It'd help if you 
> > read them first...
> 
> ... perhaps I am misreading this message. Are you feeling threatened by 
> my explanation of albedo, which is causing you to become confrontational?

No, I'm being annoyed by the way you explained something to me as if I 
knew nothing about it, immediately after I wrote about it, and you are 
doing so in a reply to the message in which I wrote about it. (Well, it 
was actually in a reply to my reply to your reply to the message in 
which I wrote about relative albedos of the Earth and Moon.)

It means you either didn't read what I wrote before responding (mainly 
frustrating), or are for some reason pretending I didn't write it or 
even know about it (slightly insulting).

-- 
Christopher James Huff <cja### [at] earthlinknet>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: <chr### [at] tagpovrayorg>
http://tag.povray.org/

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Christopher James Huff wrote:

> In article <40885de1$1@news.povray.org>,
>  Dan P <dan### [at] yahoocom> wrote:
> 
>>>Yes, I know. I mentioned this in some of the messages I posted 
>>>previously. Such as the one a couple steps up this thread posted in 
>>>response to one of your messages. Which you replied to. It'd help if you 
>>>read them first...
>>
>>... perhaps I am misreading this message. Are you feeling threatened by 
>>my explanation of albedo, which is causing you to become confrontational?
> 
> No, I'm being annoyed by the way you explained something to me as if I 
> knew nothing about it, immediately after I wrote about it, and you are 
> doing so in a reply to the message in which I wrote about it. (Well, it 
> was actually in a reply to my reply to your reply to the message in 
> which I wrote about relative albedos of the Earth and Moon.)

Ah, I traced back in the thread and saw you used the word "albedo"; it 
must not have registered in my head that you used the word and I was 
thinking, "Isn't there a word for that," and looked it up and decided to 
share it to try and add value to the thread.

I don't mean to demean your feelings because, as a human, you have them, 
just like the rest of us, and it is okay to have them. I just ask that 
you consider that, perhaps, you stand back, take a deep breath, and 
think to yourself, "Is this something worth getting so upset over?" 
That, perhaps in my message, I was only trying to add to the 
conversation and not challenge your knowledge.

To base our self worth on our knowledge is both hopelessly frustrating 
and ultimately self-defeating. It is frustrating because we will always 
consider ourselves inferior to somebody and it will drive us mad - often 
we'll even manage to convince ourselves that everybody is inferior to 
us, but deep down, we know that isn't true, and that will tear us up inside.

We will always seek out people who are inferior to us to try and balance 
our feelings of inferiority. Soon, we will become jaded, because there 
is so much knowledge to know and no way we can possibly know it all, no 
matter how much we try, no matter how much we want to, no matter how 
much time we spend on learning. Our drive is not to feel superior, but 
to avoid feeling inferior. Avoidance is in our very nature; we don't 
like to confront and if somebody confronts, we assume that they must be 
really angry. To some of us, this "knowledge thing" is all we have, and 
if we aren't tops at this, we feel we are nothing, which is so tragic, 
because our knowledge and intelligence is such a small part of our human 
existance.

Needing not to feel inferior is self-defeating. We will attack anything 
that might make us feel inferior, often forcing others to attack back, 
forcing them to do the very thing we most fear to try and "save face". 
The need is so strong we will actually try to convince others that they 
are inferior by demeaning them, particularly in public. The more 
miserable we get, the more we try to interpret what others say as an 
insult to our superiority, driving us even more mad. We will go out of 
our way to say, "Look at me, I'm better than you," and than brace 
ourselves for anyone else like ourselves that might challenge it. What a 
great place to do this; on newsgroups, where nobody can see the manic 
look in our eyes as we pound away our insults, all the while doing the 
very thing we fear most that others will do to us. Ultimately, we spend 
so much time building our attacks and defenses that we stop spending 
time on learning, deepening our feelings of inferiority, and our madness.

When we get really frustrated, which is inevitable for all and more than 
the reasons I have written, we grasp at any power we have to fight the 
feeling. For many of us, that means control over a computer, which is 
really no more than a really neat pencil! With the Internet, this 
control extends to control over the users of the computer, which are 
people; joy, rapture, we never had that before, drink deeply, 
clickity-clack! We make threats with our fragile power, which we know to 
be insignificant deep down, so we spend time trying to intimidate others 
and convince them not to look behind the big green curtain and see the 
little man.

If there is a better description of a personal hell, please write it!

> It means you either didn't read what I wrote before responding (mainly 
> frustrating), or are for some reason pretending I didn't write it or 
> even know about it (slightly insulting).

You are internalizing me. I am not you. You cannot predict my behavior 
or my intentions based on what you estimate you would do in the same 
situation, even if we do share personality types. We haven't had the 
same needs nor experiences, Christoph.

As a general rule, the overwhelming amount of time, we don't mean to 
insult others. If you feel insulted, consider first that you did not 
understand what the person meant. Then, if you confirm that they 
actually insulting you, beat the crap out of them.
-- 
Respectfully,
Dan P
http://<broken link>

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"Christopher James Huff" <cja### [at] earthlinknet> wrote in message
news:cjameshuff-4EC0B0.15182322042004@news.povray.org...
> In article <40880ec5@news.povray.org>, "St." <dot### [at] dotcom> wrote:
>
> >    Glass beads?  Seriously, is this a known fact? I can see that
it
> > could be, because sand (silica) as we know it, will form into the
same
> > glass beads under intense heat here on earth.
>
> We've been there, remember? ;-)

    Heh, yes, I think I was about 6-7yo, cross-legged, wearing grey
shorts, grey socks, in our sports-hall, watching a black and white TV
when they touched down. A nice memory.  :)


> There are some micrographs on the net of samples brought back by the
> Apollo missions...here's a page with some good ones from Apollo 17:
>
<http://www.union.edu/PUBLIC/GEODEPT/COURSES/petrology/moon_rocks/7422
0.h
> tm>

    Aargh! 404 even when pasting the URL directly.


> Similar glass beads are found here on Earth around volcanos and
impact
> craters. Impact-melted rock or magma gets blasted into the sky and
> solidifies into more or less spherical shapes before it lands.

 Yes, I used to walk our defunct railway lines when I was younger, and
believe that I found samples of magma - I'm not sure, but that was
what I was told. It was a dark substance with a golden
sheen/iridescence to it, but it definitely looked molten and was round
in shape when solidified. It was very 'glassy', and would break in
half very cleanly, leaving a very reflective surface. I don't know if
it was magma, it could have been anything native I guess, but I
wouldn't know what.

   I found many shell fossils too, if that's a clue?

   ~Steve~


>
> -- 
> Christopher James Huff <cja### [at] earthlinknet>
> http://home.earthlink.net/~cjameshuff/
> POV-Ray TAG: <chr### [at] tagpovrayorg>
> http://tag.povray.org/

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