What is it about?

The measurement of the speed of light, c, is routinely performed by using the speed of light to measure itself. This creates a conundrum since to measure light speed, you need to know light speed. This problem was 'solved' by assuming light speed is constant in all directions and using roundtrip measurements to define light speed in one direction. This work proposes to measure the speed of light by comparing light speed to the speed of various mass objects running at different velocities. Since the conversion of energy to velocity is nonlinear, due to relativistic effects, using multiple mass object speeds allows verification of the underlying assumptions on light speed. This allows measurement of the directional speed of light.

Featured Image

Why is it important?

This is important because the basis for all our physics is that light speed is the same in every direction though it never has been directly verified experimentally. An asymmetry in light speed will have dramatic effect on our interpretation of the universe. While this author believes that in our corner of the universe light speed is most likely independent of direction, it is still important to measure it, to verify it.


The special theory of relativity come into the measurement of light speed in very subtle ways. This work recognizes this and attempts to address, via this new method, these issues by keeping all clocks and measurements in the same inertial frame, thus reducing the likelihood that STR effects don't prevent an experimental estimation of the one-way speed of light.

Doug Baney
Keysight Technologies

Read the Original

This page is a summary of: Massive object velocity method for clock synchronization, AIP Advances, December 2022, American Institute of Physics, DOI: 10.1063/5.0128188.
You can read the full text:



The following have contributed to this page