8A05.30 - Eratosthenes' Measurement of Earth's Radius

Code Number:
8A05.30
Demo Title:
Eratosthenes' Measurement of Earth's Radius
Condition:
Excellent
Principle:
Measuring the Radius of the Earth
Area of Study:
Astronomy
Equipment:
Eratosthenes' Model.
Procedure:

Place the model so that one of the pillars is pointed at the light source and gives no shadow.  Bend the cardboard and show that the other pillar produces a shadow whose size depends on the radius you have produced by bending the cardboard.

References:
  • Clinton Lewis, "A Tale of Two Bridges and a Round Earth", TPT, Vol. 60, #7, Oct. 2022, p. 614.
  • Paul Hewitt, Figuring Physics, TPT, Vol. 58, #8, Nov. 2020, p. 607.
  • Carl E. Mungan, "Sizing Up Earth with a Pair of Sticks", TPT, Vol. 57, #8, Nov. 2019, p. 516.
  • Paul G. Hewitt, "Pair-of-Sticks Hypothesis", TPT, Vol. 56, #9, Dec. 2018, p. 579. 
  • Paul Hewitt, "Solution to the September 2018 Figuring Physics", TPT, Vol. 56, #7, Oct. 2018, p. 483. 
  • "Erratum: to February 'Figuring Physics' Answer", TPT, Vol. 56, #4, Apr. 2018, p. 197.
  • Paul Hewitt, "Answer to February 2018 Figuring Physics", TPT, Vol. 56, #3, Mar. 2018, p. 160.
  • Rondo N. Jeffery, "Observing Earth From Above, Again", TPT, Vol. 52, #2, Feb. 2014, p. 69.
  • J. Mottmann, "The Size of Earth from Seven Miles Up", TPT, Vol. 51, #9, Dec. 2013, p. 555.
  • Seihi Takemae, Peter Kirwin, and Gordon McIntosh, "Reproducing Eratosthenes' Determination of Earth's Circumference on a Smaller Scale", TPT, Vol. 51, #4, Apr. 2013, p. 222.
  • Ronald A. Brown and Alok Kumar, "A New Perspective on Eratosthenes' Measurement of the Earth", TPT, Vol. 49, #7, Oct. 2011, p. 445.
  • Silvia Pugliese Jona, "Eratosthenes' Measurement", TPT, Vol. 48, #2, Feb. 2010, p. 84.
  • Dhevan Gangadharan, "Measuring the Radius of the Earth from a Mountain Top Overlooking the Ocean", TPT, Vol. 47, #8, Nov. 2009, p. 533.
  • Mark L. Biermann and Nicholas A. Nelson, "Using the GPS to Determine the Size of the Earth", TPT, Vol. 38, #6, Sept. 2000, p. 360.
  • D. Rae Carpenter, Jr., "Sight Distance at Sea", TPT, Vol. 31, #9, Dec. 1993, p. 519.
  • Zachary H. Levine, "How to Measure the Radius of the Earth on Your Beach Vacation", TPT, Vol. 31, #7, Oct. 1993, p. 440.
  • Jerry Webb and Roberta Bustin, "Eratosthenes Revisited", TPT, Vol. 26, #3, Mar. 1988, p. 154.
  • Rondo N. Jeffery and Richard G. Hills, "Eratosthenes Remembered on United Airlines Flight 456", TPT, Vol. 25, #8, Nov. 1987, p. 500.
  • Kevin Krisciunas et al., "The First Three Rungs of the Cosmological Distance Ladder", AJP, Vol. 80, #5, May 2012, p. 429.
  • Frank O. Goodman, "Measure the Earth's Radius While Boating on One of its Lakes", AJP, Vol. 61, #4, Apr. 1993, p. 378.
  • Dennis Rawlins, "Doubling your Sunsets or How Anyone Can Measure the Earth's Size with Wristwatch and Meterstick", AJP, Vol. 47, #2, Feb. 1979, p. 126.
  • Jearl Walker, "The Amateur Scientist: How to Measure the Size of the Earth with Only a Foot Rule or a Stopwatch", Scientific American, Vol. 240, #5, May 1979, p. 172.
  • "S-360. Sight Distance at Sea", DICK and RAE Physics Demo Notebook, 1993.
  • Christopher P. Jargodzki and Franklin Potter, "359, Measuring the Earth", Mad About Physics, p. 141, 282 - 283.
  • Jim Glenn, "The Geometers", Scientific Genius: The Twenty Greatest Minds, p. 18 - 19.
  • Robert P. Crease, "Measuring the World: Eratosthenes' Measurement of the Earth's Circumference", The Prism and the Pendulum, p. 2.

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