Measuring the eccentricity of the Earth's orbit with a nail and a piece of plywood

Thierry Lahaye (1)

1 Atomes Froids (LCAR)

I describe how to obtain a rather good experimental determination of the eccentricity of the Earth's orbit, as well as the obliquity of the Earth's rotation axis, by measuring, over the course of a year, the elevation of the Sun as a function of time during a day. With a very simple 'instrument' consisting of an elementary sundial, first-year students can carry out an appealing measurement programme, learn important concepts in experimental physics, see concrete applications of kinematics and changes of reference frames, and benefit from a hands-on introduction to astronomy.

Thierry Lahaye. Measuring the eccentricity of the Earth's orbit with a nail and a piece of plywood. European Journal of Physics, 2012, 33 (5), pp.1167-1178. ⟨10.1088/0143-0807/33/5/1167⟩. ⟨hal-00911357⟩