Directly measuring the one-way speed of light independent of synchronization is a challenging task, as most experiments rely on the assumptions of the isotropy of the speed of light and the Einstein synchronization convention. However, there have been a few attempts to measure the one-way speed of light. Here are four examples, ranked from easiest to perform to most challenging and from most likely to be successful to least:

1. Sagnac interferometer experiment:
The Sagnac interferometer is a device used to measure the rotation rate of a platform by splitting a light beam and sending it in opposite directions around a closed loop. When the light beams recombine, an interference pattern is created. Although the Sagnac effect is not a direct measurement of the one-way speed of light, it can put constraints on the anisotropy of the speed of light. The experiment is relatively easy to perform, and the results obtained are usually reliable.

2. Stellar aberration:
Stellar aberration is a phenomenon in which the apparent position of a star shifts due to the Earth's motion through space. By comparing the observed aberration of a star with the expected value based on the known speed of light, it's possible to place constraints on the one-way speed of light. This experiment relies on astronomical observations, and while it's more challenging than the Sagnac interferometer, it can still provide useful information.

3. Time of flight measurements with ultra-short laser pulses:
By firing ultra-short laser pulses over a long distance and measuring the time it takes for the pulses to travel the distance, it's possible to measure the one-way speed of light. This experiment is quite challenging because it requires precise timing, distance measurement, and the ability to generate and detect ultra-short laser pulses. However, it has the potential to provide a direct measurement of the one-way speed of light.

4. Cosmic microwave background (CMB) radiation experiments:
CMB radiation is the residual radiation from the early universe. By analyzing the spatial distribution and anisotropy of CMB radiation, it's possible to place constraints on the one-way speed of light. This experiment is the most challenging and least likely to provide a direct measurement, as it relies on complex cosmological models and assumptions. However, if successful, it would provide strong evidence for the isotropy of the speed of light in the early universe.
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