Astronomy/the sun


Dear Brad, could you please tell me why the sun appears to move up and down in an arch across the sky during the day, rather than in a straight line from side to side? Thanks for your help.

Hi Liz,

The combination of the Earth's tilt, its motion around the Sun, and the rotation of the Earth all combine to make the Sun appear to move through our sky.  Since the Earth spins (the reason we have daytime and nighttime) around not perfectly straight up and down, but at an angle, the Sun appears to move in arch's across the sky.  However, where you live (north or south) will depend on how it looks.  

I hope this helps.



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Brad Tucker


I'm happy to answer any general questions about Astronomy, Astrophysics, and Cosmology. I'm also happy to take general, specific, and detailed questions related to supernovae, Baryonic Acoustic Oscillations, the Cosmic Microwave Background, dark matter, dark energy, and the Big Bang Theory. I'm also happy to chat about Astronomy/Astrophysics education and careers, and philosophy and science.


I am a professional research astronomer/astrophysicist/cosmologist. My research focuses on studying supernovae and using them to measure the properties of the Universe, such as how fast it is growing and what it is made of. I also frequently give talks to school groups and the public, and am a regular guest on various radio stations.

Current Research Fellow at Mt. Stromlo Observatory, the Australian National University, and in the Department of Astronomy, University of California, Berkeley.

Lots of journals, including the Astrophysical Journal, the Astronomical Journal, and Nature. I am currently in the middle of writing my first popular book.

B.A. Philosophy, University of Notre Dame, Notre Dame, IN USA B.A. Theology, University of Notre Dame, Notre Dame, IN USA B.Sc. Physics, University of Notre Dame, Notre Dame, IN USA Ph.D. Astrophysics, Mt. Stromlo Observatory, the Australian National University, Canberra, ACT, Australia

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