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Why does the moon appear stationary on some nights and on others you can clearly see it moving?

 
 
Reply Sun 25 Aug, 2019 11:53 am
Hi. I am just a bit curious about this.

We know the moon rotates around the earth. Why does it appear to be stationary on some nights, and on other nights you can clearly see it move if you stay still enough to notice?

On the nights when the moon appears stationary, the moon seems to follow you, no matter where you move on the ground.

On nights when you can clearly see the moon move if you stay still enough to notice, the moon appears to be darting across the sky at a certain rate. This seems to be very noticeable when it's windy out, but not always. You can see the moon moving on some nights even if the clouds aren't.

Please help- thank you.

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Type: Question • Score: 5 • Views: 365 • Replies: 14
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hightor
 
  1  
Reply Sun 25 Aug, 2019 12:12 pm
@JGoldman10,
The moon's apparent "movement" is a result of the earth's rotation. I can assure you that even when you think it's 'darting across the sky" it's not "moving" any faster than when it appears to be "stationery".
JGoldman10
 
  -2  
Reply Sun 25 Aug, 2019 12:50 pm
@hightor,
I just found this:

https://www.space.com/24871-does-the-moon-rotate.html :

"Why does the moon appear stationary?

The moon orbits the Earth once every 27.322 days. It also takes approximately 27 days for the moon to rotate once on its axis. As a result, the moon does not seem to be spinning but appears to observers from Earth to be keeping almost perfectly still. Scientists call this synchronous rotation."

Yes, the moon appears to move across the sky sometimes because of the Earth's rotation: https://www.ifa.hawaii.edu/users/gruff/default/Astrolab/18Orientation.htm
https://brainly.in/question/1487811

The Earth performs two circular movements- revolution and rotation. It rotates on its axis and it revolves around the sun. We know the moon revolves around the sun. What's keeping the moon from being thrown out of whack when the Earth revolves around the sun?
maxdancona
 
  1  
Reply Sun 25 Aug, 2019 02:26 pm
@JGoldman10,
I just looked this up to get the numbers roght... the moon is in an elliptical orbit. When it is closest to the Earth its apparent motion measured by the background stars os aboit 12% faster. Parr of this is because it is closer to is, and part is because it is actually moving faster at that time.

hightor
 
  1  
Reply Sun 25 Aug, 2019 02:52 pm
@maxdancona,
But I've never seen it "darting across the sky" as the OP reported — how would you explain that?

(And, my apologies for misspelling "stationary".)
maxdancona
 
  1  
Reply Sun 25 Aug, 2019 06:08 pm
@hightor,
I don't know.... there are some optical illusions related to the size of the moon. People report the moon seems much larger when it is closer to the horizon. You can measure it's radial distance by holding out a pencil at arms length when it seems particularly large, then do the same later in the night... and you can't see that it hasn't actually changed size.

I wonder if this is related.

chai2
 
  2  
Reply Sun 25 Aug, 2019 06:26 pm
Well it’s obvious that the wind moves the moon.

That, and when you turn your back, it sometimes whirls around really really fast, but stops when it sees you looking.

nacredambition
 
  2  
Reply Sun 25 Aug, 2019 09:06 pm
@chai2,
Quote:
Well it’s obvious that the wind moves the moon.


Correct, the movement is inversely proportional to the whistling in the wind (a bit like ping into the wind).

The wind moves the moon which moves the tides which moves the wind in the celestially majestic symphony of creation and perpetual motion. When I ptole my syzygy about it she said I was barking madly up the wrong perigee.

I still don't like the way it follows me around but that's lunacy for you, declining to be predictable.
0 Replies
 
laughoutlood
 
  1  
Reply Mon 26 Aug, 2019 12:13 am


Moon giver, wider than a smile
I'm skirting you in style someday
Oh, seam breaker
You heart maker
Your inner light bending is going astray

Two drifters off to see the twirled
There's such a lot of world to see
Eyeballing the same rainbow's end
Up around the bend
My freckleberry friend
Moon giver and me


0 Replies
 
Jewels Vern
 
  1  
Reply Mon 26 Aug, 2019 12:29 am
@JGoldman10,
Magnets.
0 Replies
 
Olivier5
 
  1  
Reply Mon 26 Aug, 2019 01:41 am
@JGoldman10,
Quote:
We know the moon revolves around the sun.

Around the earth, rather.
0 Replies
 
hightor
 
  1  
Reply Mon 26 Aug, 2019 03:10 am
@maxdancona,
OP reported:
Quote:
This seems to be very noticeable when it's windy out, but not always. You can see the moon moving on some nights even if the clouds aren't.


This makes me think that it is indeed the clouds that are moving and the illusion is thinking they are stationary. It's uncommon for the clouds not to move as there are always winds high up in the atmosphere even if it seems to be still on the ground. While yes, the moon appears to be traveling across the sky but this will occur at a much slower rate than any cloud movement. But if you don't think the clouds are moving at all it does look like the moon is "moving" more quickly than usual.
chai2
 
  2  
Reply Mon 26 Aug, 2019 08:43 am
@hightor,
Unfortunately, you're explaining this common sense thing to an OP that takes delight in being obtuse and dense.
0 Replies
 
coluber2001
 
  1  
Reply Mon 26 Aug, 2019 03:15 pm
I think if you stare at an object long enough it appears to be moving, and that can be explained by your eye movement.

Also in the same astronomical vein, if you look a little bit away from a star it appears to be brighter. That's because you're using the rods in your eye which are situated marginally on your retina. So if you look at a star and then look away from the Star a little bit and then back it's very noticeable and appears to be blinking.
0 Replies
 
JGoldman10
 
  0  
Reply Mon 26 Aug, 2019 08:11 pm
@hightor,
That's probably a slight exaggeration. A few times when I was outside of my home and I looked up at the sky, stayed still and looked up at the moon. The moon appeared to be moving. The moon appeared to be moving when there were clouds out, whether the clouds were moving or not.

The moon was moving something like in the video at this link:

https://www.shutterstock.com/video/clip-27828760-cloudy-night-moving-moon-sky

But it wasn't that dark out.
0 Replies
 
 

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