Why No One Has Measured The Speed Of Light

TL;DR

No one has ever measured the one-way speed of light, and it is uncertain whether it is the same in all directions or varies depending on the direction. This raises questions about the concept of simultaneity and challenges our understanding of the universe.

Transcript

• This video was sponsored by KiwiCo. More about KiwiCo at the end of the show. I know what you're thinking. - Clickbait! - No one has measured the speed of light, that's ridiculous. The speed of light is exactly 299,792,458 meters per second. We are so sure of it that since 1983, we've actually used the speed of light to define how long a meter is... Read More

Key Insights

• 🙂 The one-way speed of light has never been measured experimentally, and the conventional belief in its constancy is based on a convention set by Einstein.
• 🤨 The inability to measure the one-way speed raises questions about the concept of simultaneity and the definition of "now" in different locations.
• 🙂 Occam's razor suggests that it is simpler to assume the same speed of light in all directions, but this remains an unresolved debate in physics.

Questions & Answers

Q: Why is it impossible to measure the one-way speed of light?

Measuring the one-way speed of light requires synchronized clocks, which can only be achieved by knowing the one-way speed. It creates a circular problem with no solution.

Q: Can high-speed cameras be used to measure the one-way speed of light?

Although high-speed cameras can capture light passing through objects, they also capture the light's reflection, resulting in the measurement of the two-way speed instead.

Q: How does the assumption of the speed of light being the same in all directions affect GPS synchronization?

GPS synchronization relies on the assumption that the speed of light is the same in all directions. If this assumption is incorrect, the clocks won't be properly synced, leading to inaccurate GPS measurements.

Q: What are some alternative theories concerning the speed of light in different directions?

Some physicists propose that the speed of light may vary in different directions, possibly ranging from a few percent slower to being halved in one direction and instantaneous in the other.

Summary & Key Takeaways

• The speed of light is well-defined for round trips, but measuring the one-way speed of light is impossible due to the need for synchronized clocks, which requires knowing the one-way speed.

• Various proposed methods, such as using high-speed cameras or fiber optic cables, fail to measure the one-way speed as they inadvertently measure the two-way speed.

• The conventional belief that the speed of light is the same in all directions is a convention rather than an experimentally verified fact, and alternative theories suggest that the speed of light may vary in different directions.