Insights Blog
-- Browse All Articles --
Physics Articles
Physics Tutorials
Physics Guides
Physics FAQ
Math Articles
Math Tutorials
Math Guides
Math FAQ
Education Articles
Education Guides
Bio/Chem Articles
Technology Guides
Computer Science Tutorials
Forums
Classical Physics
Quantum Physics
Quantum Interpretations
Special and General Relativity
Atomic and Condensed Matter
Nuclear and Particle Physics
Beyond the Standard Model
Cosmology
Astronomy and Astrophysics
Other Physics Topics
Trending
Featured Threads
Log in
Register
What's new
Search
Search
Search titles only
By:
Classical Physics
Quantum Physics
Quantum Interpretations
Special and General Relativity
Atomic and Condensed Matter
Nuclear and Particle Physics
Beyond the Standard Model
Cosmology
Astronomy and Astrophysics
Other Physics Topics
Menu
Log in
Register
Navigation
More options
Contact us
Close Menu
JavaScript is disabled. For a better experience, please enable JavaScript in your browser before proceeding.
You are using an out of date browser. It may not display this or other websites correctly.
You should upgrade or use an
alternative browser
.
Forums
Physics
Special and General Relativity
How to rule out that the speed of light was different in the past?
Reply to thread
Message
[QUOTE="Dale, post: 6847934, member: 43978"] To measure the speed of light you need to measure a distance and then time how long it takes for light to travel that distance. So suppose you have a distance where it takes ##t=10\mathrm{\ ns}## for light to go. Now, to determine the length in meters then by the SI definition of the meter the distance is ##d=c \ t=2.99792458 \mathrm{\ m}##. So then you get exactly ##d/t=(c\ t)/t=c## for the speed. There is no way to get a different number for ##c## because the time and ##c## together determine the distance in meters. [/QUOTE]
Insert quotes…
Post reply
Forums
Physics
Special and General Relativity
How to rule out that the speed of light was different in the past?
Back
Top