An Optical System for Comparing the Speeds of Starlights

Abstract

The constancy of the speed of light is the second hypothesis of Einstein’s special relativity theory proposed in 1905. Since then science and technology have advanced very much, which can be used to reexamine the century old hypothesis. We proposed a novel method and implemented an optical system accordingly to compare the speed of starlight with the well-known speed of light from a terrestrial source, c. The system consists of a transmitter and a receiver. The transmitter modulated starlight, terrestrial red and infrared lights into pulses simultaneously. After travelling a distance, these pulses were detected by the receiver. A high speed oscilloscope is used to record the arrival times of these pulses, where the terrestrial infrared pulse and the red pulse are used as the trigger and the reference signals. During the measurement, we employed a terrestrial white light travelling along the exact path of the starlight to calibrate the system. We also carefully reduce the errors during the measurement and the data processing, and get some results in these years. We find that comparing with the terrestrial white light pulse, the starlight pulses arrived at the receiver with various degrees of delays. The values of the time delays are likely related to the relative radial velocities of the stars. The result implies that the measured apparent speed of starlight is not constant.