Why No One Has Measured The Speed Of Light
Veritasium・17 minutes read
The speed of light is a fundamental constant defined as 299,792,458 meters per second since 1983, with Hippolyte Fizeau first experimentally measuring it to be close to the current accepted value. There are ongoing debates and challenges in measuring the one-way speed of light due to its implications on concepts like time, space, and the nature of the universe.
Insights
- The speed of light, crucial for defining the length of a meter, has been established as a constant, with the one-way speed remaining unmeasured due to challenges in synchronization and directional variations.
- Einstein's convention that the speed of light is constant in both directions is a stipulation rather than a verified fact, sparking debates among physicists on its empirical verification and implications for concepts like simultaneity and the fundamental nature of the universe.
Get key ideas from YouTube videos. It’s free
Recent questions
What is the speed of light in meters per second?
The speed of light is precisely 299,792,458 meters per second, defined since 1983 to determine the length of a meter.
Who first experimentally measured the speed of light?
Hippolyte Fizeau in 1849 first experimentally measured the speed of light to be 313,000 kilometers per second, close to the current accepted value.
Why is measuring the one-way speed of light challenging?
Various methods proposed to measure the one-way speed of light, such as using fiber optic cables or synchronized clocks, face obstacles due to the nature of light. Synchronizing clocks for measuring the one-way speed of light presents a paradox, as knowing the speed of light is necessary for synchronization.
What implications arise from differing speeds of light in different directions?
The challenge of measuring the one-way speed of light highlights the fundamental role of the speed of light in defining our understanding of time and space. The implications of differing speeds of light in different directions are illustrated through a scenario on Mars, showcasing the complexities that arise from such variations.
How does the one-way speed of light impact communication between Earth and Mars?
Due to the time difference, a message from Earth to Mars would take 20 minutes but arrive at 12:30 Mars time, causing confusion in communication. Physicists debate the significance of measuring the one-way speed of light, with some accepting the convention while others question its empirical verification and impact on concepts like simultaneity and the nature of the universe.
Related videos
PBS Space Time
What If The Speed of Light is NOT CONSTANT?
Arvin Ash
Why isn't the speed of light infinite? What if it were?
HISTORY
The Universe: Breaking Barriers to Reach Light Speed (S3, E3) | Full Episode | History
TED-Ed
Light seconds, light years, light centuries: How to measure extreme distances - Yuan-Sen Ting
FloatHeadPhysics
Why is speed of light the same (c) in all frames? (An intuitive explanation)
Summary
00:00
"Measuring the One-Way Speed of Light"
- The speed of light is precisely 299,792,458 meters per second, defined since 1983 to determine the length of a meter.
- Measuring the speed of light differs from measuring other speeds, requiring knowledge of distance and time, calculated by dividing distance by time.
- Hippolyte Fizeau in 1849 first experimentally measured the speed of light to be 313,000 kilometers per second, close to the current accepted value.
- The round trip speed of light has been measured, but the one-way speed remains unmeasured, leading to the possibility of directional variations.
- Einstein's 1905 paper established the convention that the speed of light in opposite directions is the same, emphasizing it as a stipulation rather than a verified fact.
- The two-way speed of light is the only constant for all observers, with attempts to measure the one-way speed proving challenging.
- Various methods proposed to measure the one-way speed of light, such as using fiber optic cables or synchronized clocks, face obstacles due to the nature of light.
- Synchronizing clocks for measuring the one-way speed of light presents a paradox, as knowing the speed of light is necessary for synchronization.
- The implications of differing speeds of light in different directions are illustrated through a scenario on Mars, showcasing the complexities that arise from such variations.
- The challenge of measuring the one-way speed of light highlights the fundamental role of the speed of light in defining our understanding of time and space.
13:11
"Time delays and light speed debates"
- Two communicators experience the same messages with local time delays, but their clocks are out of sync by 10 minutes, leading to a discrepancy in perceived moments.
- Due to the time difference, a message from Earth to Mars would take 20 minutes but arrive at 12:30 Mars time, causing confusion in communication.
- Einstein's convention states the one-way speed of light is constant, but other interpretations exist, including one where light is instantaneous one way and at 'C' over two the other.
- Physicists debate the significance of measuring the one-way speed of light, with some accepting the convention while others question its empirical verification and impact on concepts like simultaneity and the nature of the universe.
