Special relativity takes the constancy of the measured speed of light in all reference frames as its core postulate, maintaining theoretical self-consistency through time dilation and length contraction. However, length contraction has long lacked direct experimental verification and exists only as a mathematical supplementary assumption. In contrast, time dilation and gravitational clock frequency shifts have been rigorously confirmed by numerous observations, including GPS systems, atomic clock flight experiments, and lunar laser ranging. The theory of local time freedom proposed in this paper asserts that space is an objective flat three-dimensional structure with no real length contraction, and time is essentially the local evolution rate of a material system, jointly determined by the system coupling coefficient and the intrinsic recursive phase-locking coefficient . The weak gravitational environment on the Moon causes the local atomic clock to run faster than on Earth; under the premise of rigid length invariance, the locally measured one-way speed of light on the lunar surface will be significantly smaller than the speed of light constant measured in the Earth reference frame. Meanwhile, quantum mechanics and quantum field theory are entirely built on a flat three-dimensional spatial framework. No traces of length contraction have been observed in quantum superposition, entanglement, atomic energy level structures, or optical frequency standards, which only reflect changes in system evolution rates. This is naturally consistent with the theory of local time freedom, providing independent theoretical support at the fundamental level. All existing satellite and ground-based speed-of-light measurements rely on Earth clock synchronization, round-trip optical paths, or presuppositions of the constancy of the speed of light, and thus lack decisive power. This paper proposes an independent one-way speed-of-light measurement on the lunar surface: using a rigid vacuum optical path on the Moon as the length standard and a lunar cold atomic clock as the independent time standard, without Earth clock synchronization, round-trip averaging, or theoretical presuppositions, to directly test the physical reality of length contraction. This experiment is falsifiable and reproducible, serving as a crucial decisive test for connecting macroscopic gravity and microscopic quantum systems and reconstructing the fundamental understanding of space and time.
jingkai cheng (Fri,) studied this question.