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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