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Sun, Moon and Earth's shadow.
06-17-2014, 10:18 AM
Post: #1
Sun, Moon and Earth's shadow.
Today was one of those days.
The Sun to my left and Moon to the right, its lower portion partially masked by earth's shadow. Each was at about 45 degrees elevation approx. From my point of view, the moon is in full view of the Sun, yet the Earth somehow gets in the way, to cast its shadow on the lower half of the moon.

I think I understood it once.

Answers on the Net are too lengthy and I don't know enough of this physics/astronomy.
Could anyone give me a nice short explanation please ? A picture would be nice.

Progress might have been all right once, but it has gone on too long -- Ogden Nash
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06-17-2014, 06:52 PM
Post: #2
RE: Sun, Moon and Earth's shadow.
[Image: 800px-Moon_phases_en.jpg]


I heard that the moon was made of cheese??? Any info on that?
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06-18-2014, 12:30 AM
Post: #3
RE: Sun, Moon and Earth's shadow.
The expert on cheese here would know. Big Grin

Thanks LZA for the pic. But some reading material would help me a lot.

I think I found a partial explanation to my question. But I wonder where the moon's gone today. Thought I saw it yesterday morning or was it evening. Hope I didn't dream it. Blush
http://www.atoptics.co.uk/atoptics/sunflat.htm
So this means, due to refraction of light rays, the Sun and I suppose the moon too, are "lower" than we perceive it (especially when at the horizon).

The following page makes for a wonderful read. It is particularly useful as it is written in the context of the next few days. Remarkable exposition.
http://mathisencorollary.blogspot.in/201...-moon.html

Here's a look at a full moon seen from the ISS. A related term to read and understand is "differential refraction"
http://www.atoptics.co.uk/atoptics/issmoon2.htm

From: http://www.digplanet.com/wiki/Atmospheric_refraction
Quote:Atmospheric refraction of the light from a star is zero in the zenith, less than 1′ (one arc-minute) at 45° apparent altitude, and still only 5.3′ at 10° altitude; it quickly increases as altitude decreases, reaching 9.9′ at 5° altitude, 18.4′ at 2° altitude, and 35.4′ at the horizon (Allen 1976, 125); all values are for 10 °C and 101.3 kPa in the visible part of the spectrum.

/still learning

Progress might have been all right once, but it has gone on too long -- Ogden Nash
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06-19-2014, 08:08 AM
Post: #4
RE: Sun, Moon and Earth's shadow.
talking about ISS,on a side note ,are you guys familiar with this?



consistency is the hobdob
of small minds[
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06-19-2014, 09:12 AM
Post: #5
RE: Sun, Moon and Earth's shadow.
It took a few minutes to connect but that's pretty neat, and best on full screen. I could watch that for hours, nice share sj. Smile

"everyone wants to win but no one wants to drink a bucket of sj's piss" - bob5695
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06-19-2014, 09:33 AM
Post: #6
RE: Sun, Moon and Earth's shadow.
bit off topic,but here's some more,you might have to become a member,well worth it

http://www.ustream.tv/explore/all

consistency is the hobdob
of small minds[
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06-19-2014, 09:53 AM
Post: #7
RE: Sun, Moon and Earth's shadow.
No registration required, I just tried the nasa tv and the decorah eagles cam with no probs. Yay

"everyone wants to win but no one wants to drink a bucket of sj's piss" - bob5695
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06-19-2014, 06:35 PM
Post: #8
RE: Sun, Moon and Earth's shadow.
(06-17-2014 10:18 AM)radiobox Wrote:  From my point of view, the moon is in full view of the Sun, yet the Earth somehow gets in the way, to cast its shadow on the lower half of the moon.

you also have to take perspective into consideration. just because part of the moon is obscured in darkness, does not mean that the earth's shadow is causing it.

[Image: 640px-Disco_Ball3.jpg]

in the image, you can see a bright reflection on the disco ball from a light source that is not visible in the picture, but presumed to be located in the background and to the left of the ball. this light source is illuminating half of the disco ball, however, you cannot see the entire illuminated side... all you can see is 1/10th of the illuminated side and 9/10ths of the dark side.

so, in the following example, what you are seeing is sort of like this:

[Image: Dpwlrr8.png]

you are on the other side of the planet looking at the moon... half the moon is illuminated but from your perspective, all you can see is a crescent.

"Yeah. I understand the mechanics of it, shithead. I just don't understand how this is any less retarded than what I'm suggesting." - Kiley; Housebound.
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06-19-2014, 11:29 PM
Post: #9
RE: Sun, Moon and Earth's shadow.
Nice pics and lovely example. Thanks sporkium. I think that is the answer !

Thanks sj for that info. Not connecting yet for me. But going to keep retrying.

Progress might have been all right once, but it has gone on too long -- Ogden Nash
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07-17-2014, 12:16 PM (This post was last modified: 07-17-2014 12:17 PM by radiobox.)
Post: #10
RE: Sun, Moon and Earth's shadow.
"Zigactly" 1 month on, saw the same phenomenon today morning about 9 AM.
Moon at about 45 deg. Sun at 50 deg altitude.

Progress might have been all right once, but it has gone on too long -- Ogden Nash
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