] 3 1 Ja n 20 02 Speed of light measurement using ping

We report on a very simple and inexpensive method for determining the speed of an electrical wave in a transmission line. The method consists of analyzing the roundtrip time for ethernet packets between two computers. It involves minimal construction, straightforward mathematics and displays the usefulness of stochastic resonance in signal recovery. Using basic electrical properties of category-five cable students may use their measurements to determine the speed of light in the vacuum to within a few percent. I. INTRODUCTION: With the now ubiquitous network and computer hardware in American secondary schools, high school and college students have become quite familiar with the internet. But the fact that signals on the internet cables typically move at hundreds of millions of meters per second (about 2/3 of the speed of light) is completely lost in the page download-and-rendering time that students experience. This laboratory experience grew out of a desire to leverage the now ubiquitous computer and network resources in schools for a simple, cheap, quality laboratory in which students measure one of the most consequential natural constants, the fantastic speed of light. The measurement of the speed of light [1] has a history that students generally find interesting [2]. There are the early speculations about light of the philosophers followed by the failed attempts of the giants of physics, Galileo and Newton. The first measurement of the speed of light was by Danish Astronomer Olaus Roemer in 1675 who used the moons of Jupiter as a clock. He determined the speed to be some 3/4 of its (now defined) speed, and a more accurate (about 5%) measurement had to wait half a century until British Astronomer James Bradley in 1728 determined it using the aberration of light from distant stars caused by the change in the orbital velocity of the Earth over the course of the seasons. The first non-astronomical measurement of light's speed is due to French physicist Jean-Bernard-Léon Foucault in 1849 using the (now classic) quickly rotating mirror setup used later notably by American physicist Albert Michelson. Foucault's measurement was within a percent of the modern (defined) value. This time period was one of intense scientific scrutiny of electricity and magnetism. In 1856 German physicists W. Weber and F. Kohlrausch used Leyden jars and a ballistic galvanometer to determine a ratio of electric and magnetic coupling strengths that has the dimensions of speed, and, intriguingly, found that speed to …