Is the Earth Really Spinning? (honest question)

  • 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

    Any specific time lapses, just not a link to a google search?

    Perhaps it is a joke from your side but you are right. Any point of view is ok. The question is, what for a coordinate system is good for calculations one want to do. Having an satellite in the earth's orbit the earth could be this coordinate system. Flying to Mars perhaps it would be better you use a coordinate system with the sun in its origin. Directing a telescope to some nebulus it would be better to use coordinates with a galactic centre.

    @Hohmannfan : Sorry, I thought it would be better to see a collection versus one particular photo; there seems to be a commonness for the most part (for each link).

    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:

    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.

    I appreciate all the comments. I'm trying to take them all in.

    Nice question. Shows some critical thinking.

  • 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:


    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.

    The Foucault pendulum is a classic test that verifies the rotation of the earth.

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Content dated before 7/24/2021 11:53 AM