Text 23736, 49 rader
Skriven 2008-11-13 17:11:46 av Björn Felten (2:203/2)
  Kommentar till text 23730 av Michiel van der Vlist (2:280/5555)
Ärende: Mass of the moon
========================
 BF>>    The distance Earth-Sun relative Earth-Moon is appr. 390:1. So it
 BF>> relates to e.g. putting a lamp 3.9 m from a wall, holding a disk 10 mm
 BF>> from the wall, and then move it to 20 mm, observing the shadow.

 MvdV> That is under the assumption of a point source of light. But the sun is
 MvdV> not a point source, it is a disk with a diameter of appr. half a degree.

   With the 390:1 approximation, that's as good an appr. as it gets.

 MvdV> So there is a core shadow (umbra) that gets narrower at larger distance
 MvdV> and a half shadow (penumbra) that gets wider at larger distance from the
 MvdV> earth.

   True, but that "error" still isn't big enough to be observed with the
naked eye. And we *WERE* talking about visual approximations here,
weren't we?

 BF>> It's impossible to observe the difference with the naked eye. But if
 BF>> you move the disk to e.g. half way between the lamp and the wall, you
 BF>> can see it.

 MvdV> At that distance the umbra would not reach the wall...

   If that is so, I suggest that you change your light bulb to something
with a more solar alike caracteristic. My light bulbs have no problems
showing a fairly sharp shadow. Did you forget to remove the shade from
the armature? :)

 MvdV> Don't you find it amazing that the Greek already figured this out?
 MvdV> Without telescopes and without Wikipedia. ;-)

   What I find most amazing is, that for about 2000 years now, mankind
has survived and even evolved, despite the fact that the Christian
fanatics managed to keep us all in the Dark Ages for most of this time.

   How stupid can anyone person be, accepting that religious fanatics,
like the Christians, deprive them (and even burn books about it) from
their forefather's intellectual property?

   AND THOSE IGNORANT BASTARDS STILL DEFEND ALL THIS CRAZY INTELLECTUAL
PROPERTY HYPE!?!?!?!

   Well, you get the politicians you deserve. If you are so stupid you
even defend the four-letter media organisations' right to bully you, you
can fucking well have it. I'm soon on the brink of giving up --
considering what we see happening even in Sweden nowadays.

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