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BooJumMan
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Yes of course, I meant from our perspective "full". Just questioning the question to answer correctly.
"I ask why on most days we see only part of the moon".
Part of the moon...as it part lit (phases), or just always the same area/side of the moon?
If why we only see the same "side" of the moon, it is because the rotation/spin of the moon is equal to the orbital velocity of the moon around the
earth. Or is that still not what you're looking for? Ha. Sorry I'm a aerospace engineer and love physics and space, and just don't know what "part"
refers to. 
[Edited on 5-10-2016 by BooJumMan]
In that pre-Google Earth and social media epoch, The Code was adhered to. It was based on a simple verity: if a locale had been transformational for
you, and you had put the hard yards in to get there and to learn it, to know it, why in god�s name would you broadcast the news, thus ruining the
future experience not only for yourself, but for future adventurers?
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SFandH
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Always? Not during a lunar eclipse, when it is in the earth's shadow.
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4x4abc
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damn - you are good!
Harald Pietschmann
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4x4abc
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Quote: Originally posted by BooJumMan  | Yes of course, I meant from our perspective "full". Just questioning the question to answer correctly.
"I ask why on most days we see only part of the moon".
Part of the moon...as it part lit (phases), or just always the same area/side of the moon?
If why we only see the same "side" of the moon, it is because the rotation/spin of the moon is equal to the orbital velocity of the moon around the
earth. Or is that still not what you're looking for? Ha. Sorry I'm a aerospace engineer and love physics and space, and just don't know what "part"
refers to.
[Edited on 5-10-2016 by BooJumMan] |
I had already noticed my careless language and corrected the original question:
Why do we see only part of the moon illuminated by the sun most days?
Like in the image above, we also see the part that is illuminated by earth.
And like any other object in the universe, we never see more than 1/2.
Harald Pietschmann
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woody with a view
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Is it because the sun provides the light and the shadows play tricks on our perception of said light?
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4x4abc
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here is the easiest approach:
we have 3 things - a source of light (the sun), an object (the moon), an observer on earth (you and I)
earth rotates once around itself towards the east in 24 hours
the moon orbits earth eastward and it moves a little faster than earth
therefore the moon has a different position in the sky every day
that makes the angles between the 3 change every day
the answer: we see only part of the lit moon from our perspective due to the changing angles between moon and earth.
the easy one:
full moon
from our prospective sun and moon are 180 degrees apart (we are in the middle - all 3 are in one line
sun sets, full moon rises
lets assume it's a perfect day night balance, 6 am sun up, 6 pm sun down
then the full moon will be visible the entire night of 12 hours
the next day the almost full moon (waning) will rise at about 7 pm - about one hour (exact 53 min) darkness, 11 hours 7 minutes moonlight
skip to (third quarter) half moon,
half moon will rise at exactly 12 am (6 hours of darkness before, followed by 6 hours of moonlight)
moon will be lit from the bottom at 12 am, because the sun is in the south below the horizon
at 6 am the moon will be exactly in the south (90 degree angle to the sun)
lit from the left because the sun rises at this time in the east
moon will be visible in the day sky until 12 noon
new moon: entire night will be in darkness
moon is between earth and sun (0 degrees angle)
waxing crescent moon (2 days old): visible right before the 6 pm sunset - and a little after sunset, rest of the night will be in total darkness
first quarter half moon:
moon rises at 12 pm
at 6 pm the moon will be exactly in the south
90 degree angle to the sun setting in the west
moon will be 6 hours in the night sky, rest of the night is dark
when the moon sets at 12 am, it will be lit from the bottom
[Edited on 5-10-2016 by 4x4abc]
[Edited on 5-10-2016 by 4x4abc]
Harald Pietschmann
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wessongroup
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I'll never look at the moon the same
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4x4abc
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we do a campfire game on occasion
10 feet away from whoever is watching put a water melon on a tripod (apple works as well)
someone shines a flashlight onto the melon
flashlight behind audience = full moon (melon)
flashlight right of audience (90 degrees) = 1st quarter half moon (melon)
flashlight left of audience (90 degrees) = 3rd quarter half moon (melon)
and anything in between
here is a 1st quarter half apple:
https://carlosnpainter.smugmug.com/Travel/2014-04-13-Pily-an...
Harald Pietschmann
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Barry A.
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| Quote: Originally posted by 4x4abc | we do a campfire game on occasion
10 feet away from whoever is watching put a water melon on a tripod (apple works as well)
someone shines a flashlight onto the melon
flashlight behind audience = full moon (melon)
flashlight right of audience (90 degrees) = 1st quarter half moon (melon)
flashlight left of audience (90 degrees) = 3rd quarter half moon (melon)
and anything in between
here is a 1st quarter half apple:
https://carlosnpainter.smugmug.com/Travel/2014-04-13-Pily-an...
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Great demo, Harald!! Love it.
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