How to determine the diameter of Earth?

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Discussion Overview

The discussion centers on methods for determining the diameter of Earth, exploring various approaches and their applicability to other celestial bodies. Participants share historical methods and modern techniques, as well as their limitations.

Discussion Character

  • Exploratory, Technical explanation, Conceptual clarification

Main Points Raised

  • One participant suggests that direct measurement of Earth's diameter is impractical and asks for alternative methods.
  • Another participant recommends researching Eratosthenes' method, 'The Great Arc', and the Prime Meridian through Paris as historical approaches.
  • A third participant mentions the Struve Geodetic Arc as another relevant historical method.
  • One participant asserts that the methods discussed for measuring Earth's diameter do not apply to other planets.
  • Another participant proposes that a planet's diameter can be estimated through occultation techniques, such as observing the cut-off time of a radio signal from a probe as it passes behind the planet.
  • The same participant draws an analogy to how asteroids can be sized using stellar occultation, where observers note the timing of a star's light being blocked.

Areas of Agreement / Disagreement

Participants present multiple approaches to measuring Earth's diameter, but there is disagreement regarding the applicability of these methods to other planets, with at least one participant stating that they do not apply.

Contextual Notes

Some methods mentioned rely on historical context and may have limitations based on the technology available at the time. The applicability of certain techniques to other celestial bodies remains unresolved.

Who May Find This Useful

This discussion may be of interest to those studying geodesy, astronomy, or the history of scientific measurement techniques.

oem7110
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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
 
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Google Eratosthenes, then google 'The Great Arc' and perhaps 'The Prime Meridian through Paris'.
 
how does this approach apply to measure the diameter of other planets?

it doesn't.
 
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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