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

TL;DR

This paper presents a simple experimental method for first-year students to measure Earth's orbital eccentricity and axial tilt by tracking the Sun's elevation over a year using basic sundial techniques.

Contribution

It introduces an accessible, hands-on approach for students to determine Earth's orbital parameters with minimal equipment.

Findings

Successful measurement of Earth's eccentricity and obliquity

Demonstrates practical application of kinematics and reference frames

Engages students in experimental astronomy

Abstract

I describe how to obtain a rather good experimental determination of the eccentricity of the Earth orbit, as well as the obliquity of the Earth 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.