Very simple question

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Anywhere

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Hi,
This is my question :
Do the stars change their place or its fixed and we can not see it sometimes because of the clouds ?
thanks
 
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MeteorWayne

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Well stars (pretty much) stay the same, though over thousands or millions of years their position does change a little. What changes the most is that the earth spins around in 24 hours so stars appear to rise in the east and set in the west. The other thing is that as the earth revolves around the sun; the stars that are highest in the south in January are right next to the sun in July, so we can't see them in the daytime.

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MW
 
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ramparts

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Not even thousands of years, MW! Nearby stars move in the sky enough that, even though we can't tell by the naked eye, our telescopes can make pretty precise measurements. This is called proper motion.

The other effect is that nearby stars will move back and forth in the sky, relative to stars behind them, as the Earth moves around the Sun. This is called parallax. It's a pretty simple geometric effect: try putting your finger a foot in front of your face and closing one eye. Then close that eye and open the other one. Look at your finger. See how it moved? Then close that eye and open the first one again. The finger is back in it's original place. That's the same thing that happens when the Earth moves from one place in its orbit (your left eye) to another, on the other side of the Sun (your right eye), nearby stars move relative to faraway stars.
 
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MeteorWayne

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Of course I'm well aware of both effects you mention ramparts, but I got the impression it was more of a "what do I see when I look up" question based on the cloud reference, so answered it at that level ;)
 
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