APOD
Astronomy Picture of the Day
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.
Solar System Ball Drop
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 famous solar system bodies , assuming no air resistance . The force of gravity depends on the mass of the attracting object , with higher masses pulling down with greater forces . But gravitational force also depends on distance from the center of gravity , with shorter distances causing the ball to drop faster. Combining both mass and distance, it might be surprising to see that Uranus pulls the ball down slightly slower than Earth , despite containing over 14 times more mass. This happens because Uranus has a much lower density, which puts its cloud tops further away from its center of mass . Although the falling ball always speeds up, if you were on the ball you would not feel this acceleration because you would be in free-fall . Of the three planets mentioned, the video demonstrates a ball drops even faster on Jupiter than either Earth and Uranus.
| Date | August 25, 2021 |
|---|---|
| Credit | Video Credit & Copyright: James O'Donoghue ( JAXA ) & Rami Mandow ( Space Australia ); Text: James O'Donoghue |
| Authors & editors: | Robert Nemiroff (MTU) & Jerry Bonnell (UMCP) |
| A service of: |
ASD at NASA / GSFC, NASA Science Activation & Michigan Tech. U. |


