How to measure the Earth-Sun distance by studying the transit of Venus

Francis Berthomieu, Frédéric Dahringer, Rainer Gaitzsch, Michele Gerbaldi, Alan Pickwick and Rosa M. Ros
EAAE European Association for Astronomy Education- WGSummer School

Introduction.

Description of the method used to calculate the Earth-Sun distance.

A) Background

  1. Parallaxes of the Sun (named as horizontal parallaxes)
  2. Observation from the Earth
  3. A geometrical Problem
  4. Kepler's third law
  5. Final formulae for the Earth-Sun distance.

B) Observational data needed

  1. Distance between observers at points A and B
  2. Distance Db between two observed paths of Venus
    • 2a) Calculation of Db by direct measurement
    • 2b) Calculation of Db by measurement of the chords
    • 2c) Calculation of Db by measurement of the times of transit

C) Results using the observations of 1769

  1. Distance between observers at points A and B
  2. Distance Db between two observed Venus paths
    • 2a) Calculation of Db by direct measurement
    • 2b) Calculation of Db by measurement of the chords
    • 2c) Calculation of Db by measurement of the times of transit.
  3. AND FINALLY the Earth-Sun distance re

D) Observations that you can make in 2004

  1. Single observations that are quick and easy to make
  2. Longer observations that are quite easy to make