Why No One Has Measured The Speed Of Light

The video begins by questioning the commonly accepted speed of light, stating it has never been directly measured in one direction due to the complexities of synchronizing clocks over distances. It explains the historical context of defining the speed of light as 299,792,458 meters per second, which since 1983 has been used to define the meter. The video discusses the difficulty in measuring the speed of anything without a direct comparison, illustrated by an analogy of measuring a baseball's speed. It also introduces the concept of measuring the speed of light using a round trip to avoid synchronization issues, referencing historical experiments by Hippolyte Fizeau that got close to the current accepted value of light's speed. However, it raises the point that all known measurements are of the round-trip speed of light, not the one-way speed, leading to philosophical and practical questions about the true nature of light's velocity.

This section delves into the hypothetical scenario where the speed of light might differ depending on its direction, challenging the symmetry of space-time and questioning the universality of light's speed. It explores the idea that the universe might have a preferred direction, which could lead to asymmetries, like the matter-antimatter imbalance. The video covers Einstein's 1905 paper on the electrodynamics of moving bodies, where he introduces the convention of light's speed being constant in all directions as a definition rather than an empirical fact. This convention, known as the Einstein synchronization convention, is critical for the concept of simultaneity but is not verifiable through direct measurement. This raises intriguing questions about the nature of light, simultaneity, and the fundamental laws of physics, suggesting that our understanding of the universe might be based on conventions rather than absolute truths.

The video presents a thought experiment involving communication between Earth and Mars to illustrate the practical difficulties of measuring the one-way speed of light and the implications for synchronizing clocks over vast distances. It explains how reliance on the Einstein synchronization convention could lead to a mismatch in perceived simultaneity, potentially causing a 10-minute discrepancy in timekeeping between Earth and Mars. This segment highlights the foundational role of assumptions in our understanding of physics and the limits of our current methodologies to distinguish between different models of light's behavior. The discussion extends to the broader implications for GPS technology and the fundamental nature of simultaneity, emphasizing the philosophical and practical challenges inherent in the current conventions used to measure and understand the speed of light.

The final part of the video discusses the implications of the inability to measure the one-way speed of light directly, suggesting that it may not even have a well-defined value. It considers how this limitation affects the concept of simultaneity and our understanding of the universe. The video argues that while the roundtrip speed of light is universally accepted as 'c', the one-way speed remains a subject of debate, potentially influencing future scientific breakthroughs in physics. The segment concludes with a promotion for KiwiCo, highlighting the educational value of their projects for children and the importance of fostering curiosity and learning through hands-on activities. This sponsorship underscores the video's theme of exploring and questioning the boundaries of scientific knowledge.