Astronomy Picture of the Day

   [1]Discover the cosmos! Each day a different image or photograph of our
      fascinating universe is featured, along with a brief explanation
                    written by a professional astronomer.

                               2021 August 25

         IFRAME: [2]https://www.youtube.com/embed/uHhQrplIm8g?rel=0

                           Solar System Ball Drop
      Video Credit & Copyright: [3]James O'Donoghue ([4]JAXA) & [5]Rami
           Mandow ([6]Space Australia); Text: [7]James O'Donoghue

   Explanation: Does a ball drop faster on Earth, Jupiter, or Uranus? The
   featured animation shows a ball dropping from one kilometer high toward
   the surfaces of [8]famous solar system bodies, assuming no [9]air
   resistance. The force of [10]gravity depends on the mass of the
   [11]attracting object, with higher masses pulling down with [12]greater
   forces. But [13]gravitational force also depends on distance from the
   [14]center of gravity, with shorter distances causing the ball to drop
   faster. Combining both mass and distance, it might be surprising to see
   that [15]Uranus pulls the ball down slightly slower than [16]Earth,
   despite containing over 14 times more mass. This happens because
   [17]Uranus has a much lower density, which puts its cloud tops further
   away from its [18]center of mass. Although the [19]falling ball always
   speeds up, if you were on the ball you would not feel this acceleration
   because you would be in [20]free-fall. Of the three planets mentioned,
   [21]the video demonstrates a ball drops even faster on [22]Jupiter than
   either Earth and Uranus.

                       Tomorrow's picture: open space
     __________________________________________________________________

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    Authors & editors: [34]Robert Nemiroff ([35]MTU) & [36]Jerry Bonnell
                                 ([37]UMCP)
          NASA Official: Phillip Newman [38]Specific rights apply.
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                A service of: [40]ASD at [41]NASA / [42]GSFC
                           & [43]Michigan Tech. U.

References

   1. https://apod.nasa.gov/apod/archivepix.html
   2. https://www.youtube.com/embed/uHhQrplIm8g?rel=0
   3. https://www.youtube.com/user/jayphys85/about
   4. https://global.jaxa.jp/
   5. https://twitter.com/CosmicRami
   6. https://spaceaustralia.com/
   7. https://jamesodonoghue.wixsite.com/home
   8. https://nssdc.gsfc.nasa.gov/planetary/factsheet/
   9. https://www.grc.nasa.gov/www/k-12/airplane/falling.html
  10. https://spaceplace.nasa.gov/what-is-gravity/en/
  11. https://m.media-amazon.com/images/I/41NxxwsUPCL.jpg
  12. https://phet.colorado.edu/sims/html/gravity-force-lab/latest/gravity-force-lab_en.html
  13. https://en.wikipedia.org/wiki/Gravity
  14. https://www.grc.nasa.gov/www/k-12/airplane/cg.html
  15. https://solarsystem.nasa.gov/planets/uranus/overview/
  16. https://apod.nasa.gov/apod/ap100713.html
  17. https://solarsystem.nasa.gov/planets/uranus/by-the-numbers/
  18. https://study.com/academy/lesson/understanding-the-center-of-mass-center-of-gravity.html
  19. http://www.stefanom.org/spc/game.php
  20. https://www.grc.nasa.gov/www/k-12/airplane/ffall.html
  21. https://youtu.be/oIMMZl4n-uk
  22. https://apod.nasa.gov/apod/ap190205.html
  23. https://apod.nasa.gov/apod/ap210824.html
  24. https://apod.nasa.gov/apod/archivepix.html
  25. https://apod.nasa.gov/apod/lib/apsubmit2015.html
  26. https://apod.nasa.gov/apod/lib/aptree.html
  27. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search
  28. https://apod.nasa.gov/apod/calendar/allyears.html
  29. https://apod.nasa.gov/apod.rss
  30. https://apod.nasa.gov/apod/lib/edlinks.html
  31. https://apod.nasa.gov/apod/lib/about_apod.html
  32. http://asterisk.apod.com/discuss_apod.php?date=210825
  33. https://apod.nasa.gov/apod/ap210826.html
  34. http://www.phy.mtu.edu/faculty/Nemiroff.html
  35. http://www.phy.mtu.edu/
  36. https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html
  37. http://www.astro.umd.edu/
  38. https://apod.nasa.gov/apod/lib/about_apod.html#srapply
  39. https://www.nasa.gov/about/highlights/HP_Privacy.html
  40. https://astrophysics.gsfc.nasa.gov/
  41. https://www.nasa.gov/
  42. https://www.nasa.gov/centers/goddard/
  43. http://www.mtu.edu/