How to determine the diameter of Earth?

  • Thread starter oem7110
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  • #1
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We cannot measure the diameter of Earth inch by inch using rulers, and must somehow estimate the distance on Earth, Does anyone have any suggestions on what approach they use to measure the diameter of Earth? and how does this approach apply to measure the diameter of other planets?
Thanks in advance for any suggestions
 

Answers and Replies

  • #2
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Google Eratosthenes, then google 'The Great Arc' and perhaps 'The Prime Meridian through Paris'.
 
  • #3
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And after that, maybe also google Struve Geodetic Arc
 
  • #4
phinds
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how does this approach apply to measure the diameter of other planets?

it doesn't.
 
  • #5
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A planet's diameter may be estimated by occultation, such as studying the cut-off time of a radio signal from an orbiting probe as it swings behind the planet.

Asteroids have been 'sized' by stellar occultation, where many observers watch for a star's cut-off time. From their position on Earth, the asteroid does or doesn't eclipse a background star.
http://www.physorg.com/news/2011-10-faraway-eris-pluto-twin-dwarf.html

Analogy is a solar eclipse, where folk off the centre-line see shorter and shorter eclipses...
 

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