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Most people consider it common knowledge that the Sun's "movement" in the sky is only perceived due to the Earth's "spin and movement".

Based on this, you'd think that the stars in the night sky (when viewed with time lapse photography) would take a path in the sky similar to the sun. After all, both the sun and stars are practically stationary over the course of one day, given their accepted distances from the earth.

Yet, time lapse photography shows this is not the case.

Compare these photos:

1) Time Lapse of Sun

2) Time Lapse of Stars

3) Time Lapse of Moon

If the Earth's spin is the primary reason for "movement" of things (farther than clouds in the sky), then why do the sun and moon move through the sky in a similar fashion that is totally different from the sky-path of the stars? The Earth is said to spin around 360 degrees every 24 hours. It seems to me that everything in the sky should move in one direction where I live (Texas).

To me (in Texas), it seems the stars should sweep from horizon to horizon over the course of the Earth's night-spin (like the sun and moon do). Yet, the time lapse photos show circular paths in the sky for the stars. That would make sense at the poles, but not in Texas!?

-Lonnie Lee Best

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    $\begingroup$ Any specific time lapses, just not a link to a google search? $\endgroup$ – Hohmannfan Feb 12 '16 at 16:41
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    $\begingroup$ I've seen lots of day and night time lapses, and they seem to show the same sort of motion to me (provided the viewpoints and lens angles don't change). If you want other evidence of Earth's spin, try one of these: en.wikipedia.org/wiki/Foucault_pendulum $\endgroup$ – Andy Feb 12 '16 at 17:34
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    $\begingroup$ It's a question of time frame. The star time lapse pictures you see are showing closer to 24 hours, an entire spin around the north celestial pole, where as the sun and moon time lapse pictures are only showing a few hours worth of lapse. In locations where the sun/moon remain up for 24 hours, you would see a pattern similar to that of the stars. $\endgroup$ – barrycarter Feb 12 '16 at 18:24
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    $\begingroup$ I appreciate all the comments. I'm trying to take them all in. $\endgroup$ – Lonnie Best Feb 12 '16 at 20:24
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    $\begingroup$ Nice question. Shows some critical thinking. $\endgroup$ – Jan Doggen Aug 29 '18 at 9:31
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You are already starting to get it.

That would make sense at the poles

What about one meter from the poles?
Or a kilometre?

As long as you can see the celestial pole in the sky, you can see the stars revolve around it at night.

Let us see if you are able to see the celestial pole.

Texas was about 30 degrees north last time I checked:

you can!

That explains the circular movement of the stars, the Sun and the Moon.

This is true for all locations on the Earth, except for the equator:

cannot

Is the Earth spinning? That depends, you can always choose a frame of reference that suits you. However, only one of them are non-rotating, the Inertial frame. In all the others we have fictitious forces acting, like centrifugal or Coriolis forces.

We can test if the Earth rotates by watching a pendulum throughout a day. The pendulum would then seem to slowly rotate during this period of time, meaning some fictitious "force" is acting on it. That means that we are located in a rotating frame of reference, and thus the Earth rotates.

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There's quite a simple answer to this that no-one seems to have focused on; The photos showing a starwheel effect are taken by pointing the camera at the celestial North Pole (roughly in the direction of Polaris in Ursa Minor). The stars in that part of the sky appear to rotate around the pole and never set (viewed from Texas). This makes a good photo.

The Sun and Moon are never anywhere near the pole. They are found on the ecliptic, which is roughly above the Earth's equator. Viewed from Texas, that's south of you, so as the Earth turns, the Sun and Moon follow an arc across the sky that reaches its highest point due South.

In the image searches, there are a few photos showing Sun/Moon like paths (i.e., low arcs) for stars as well. Those are stars near the ecliptic. The photos aren't so striking as the circumpolar stars, which is why there are more of those.

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  • $\begingroup$ "They move around on the ecliptic" ... on the timeframe of weeks and months. But on the timeframe of a single night/day they perform the exact same motion as any star. $\endgroup$ – AtmosphericPrisonEscape Aug 29 '18 at 15:56
  • $\begingroup$ @AtmosphericPrisonEscape: Sure - I'll tweak it make it clearer.. $\endgroup$ – Oscar Bravo Aug 30 '18 at 6:10
  • $\begingroup$ Look at youtube.com/watch?v=8CyG2zc8HkU for star trails at the equator... $\endgroup$ – DJohnM Sep 24 '18 at 23:20

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