Blog Ekkehard Friebe

By Harry H. Mark 
Source: 18th Natural Philosophy Alliance Conference, July 2011

Three pivotal empirical measurements determined the speed of light in relation to a moving observer or its source.
1. Ole Roemer (1644–1710) found that the speed of light from Jupiter’s satellite was lower when an observer on earth was moving away from it, and higher on approach.
2. James Bradley (1693–1762) determined that the speed of light from a star was higher when an observer on earth moved towards its perpendicular incident, and lower on recession.
3. Albert Michelson (1852–1931) examined the speed of light when both the source and the observer were on the same moving earth. Under these circumstances the speed surprisingly did not change.

The experiment was interpreted to mean that the speed of light was not affected by the motion of the earth. However, the results published in the 1881 paper were then amended in a second paper from 1887. In this paper the speed in the perpendicular direction was increased, in the spirit of Bradley’s aberration, and this correction diminished the expected discrepancy by half. The speed in direction of the earth’s motion, in the spirit of Roemer’s data, was however not similarly considered.

All the above data indicated that the speed of light was affected by the speed of the frame of reference.

1. Introduction

Speed is measured in reference to a certain frame, such as the speed v of a train in reference to the stationary earth. The speed of a person moving inside this moving train c in reference to the same earth is than added to that of the train when the motion is in the same direction v?c or subtracted when in the opposite direction v?c. These laws of motion were first published in the 13th century by Nicole Oresme, and are usually termed motions in ‘Inertial Frame of Reference’, ‘Galilean Frame of Reference’ or ‘The Principle of Relativity’ [1].

George Francis FitzGerald (1851–1901) [2-3] and Hendrik Antoon Lorentz [4-6] interpreted the ether drift experiments of Albert A. Michelson [7-8] to mean that the speed of light was always the same whether the frame of reference was stationary or was moving. It was a universal constant. The empirical data available at the end of the nineteenth century are examined in the following article in an attempt to verify whether or not they supported the conclusions derived from them.

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