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Sunday, March 13, 2016

March 13: Planet Uranus Discovered (1781)

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Uranus, one of the bigger planets, was discovered on this day in 1781. How does it stack up in diameter compared to the other planets?

Planets’ Diameters


  • Measuring tape
  • String
  • Ruler
  • Sidewalk chalk


  1. What is the diameter of each planet in our Solar System? Check out to find out.
  2. This is best done outside in a space where you can use sidewalk chalk, but could also be done indoors with string and tape.
  3. Try different scales depending on space, but to offer some perspective, if 1 inch equals 1000 miles, Mercury is only three inches across while Jupiter is nearly three feet!
  4. To mark a planets’ diameter with chalk, measure a piece of string to HALF the diameter of the planet.
  5. Once a piece of string is cut to length, one person needs to hold one end steady while a second person holds the other end.
  6. Keeping the string tight, the second person rotates around the first person, tracing a circle with the chalk as he/she moves. This represents the planet’s diameter.
  7. Repeat for each planet.
Source(s): Toolbox Training’s book 100 Science Activities for Kids (activity F10).

Check out the full March calendar. It includes floating holidays, specialty weeks, and specialty months.