history of the speed of light and how its speed was determined
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- Опубликовано: 18 апр 2019
- What is the history behind determining the speed of light? How did past scientists determine it'salue value
This video covers Rømer, Bradley, Fizeau and Foucault and how they determined the speed of light.
CORRECTION: As some have noted I have made an error in the discussion on Rømer. I acknowledge this , and here is my correction as well as animation: • Ole Rømer correction
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Just a note to say thank you! This was a great video. Have subscribed. Keep up the excellent work!.
Thanks for not disturbing your interesting story with background music.
Just letting you know I am currently working on a follow up to this video with more recent experiments on determining the speed of the light. Stay tuned
Timestamps for each speed of light experiment
Worth mentioning : XVIIth century judge Fermat (of famous math conjecture fame) had the intuition that light takes the shortest route in TIME between A and B. This implies a finite speed. From this principle, Descartes and Snell independantly derived the law of refraction, fundamental to lens design.
My high school physics teacher explained Foucault's method to me in 1983, and it was my first experience of finding out that something that seemed unknowable to mere mortals like me was actually a simple matter to explain and understand. I had that same experience again as an undergrad when I asked my biology prof how we knew about transmembrane cell proteins. (The amount we seemed to know about molecular cell structure baffled me.) In about one minute he explained freeze-fracturing to me. It was so simple! So I went into research.
Hi Paul, thanks for another fantastic video! I think there is a slight error in your explanation of Romer's data... the apparent period should depend on the relative velocity of Jupiter/Io and Earth, not upon their distances (as suggested at
Wow. At age 65, I am suddenly a high school student studying a subject that teenaged-me dismissed as boring. Thanks for that!
Excellent presentation! Easily one of the best I've seen on the subject. I'm just a hack layman on physics, but I do relish videos like this. Thanks a million!
A fabulously clear explanation of how Roemer calculated the speed of light! Worth it for that alone! Ty
This is amazing! This video definitely deserves more views! Thank you.
This video deserves more attention. You guys really helped me with my uni report on thr measurment of light speed
Thank you for great video. We learned about the early scientists at school, and I was amazed, and still am, at the intellect and the determination of Rømer, Bradley and Fizeau, and many others, using basic astronomical equipment etc. I mean, if I'm correct, Fizeau's mirror was five and a half miles away, and he was using something like an oil lamp or a candle. I know there was not a lot of light pollution in thise days, but still!
My first thought was about the attempt to measure the “aether” by Michaelson and Morley. I also thought of the slit experiment which shows that light behaves like both a wave and a particle. That always fascinates me.
It's appreciated that this is a history/basic concept video , yet an introduction to the measurement being relative to Earth normal space with time dilation would be appropriate.
This video is such a good explanation that you appreciate the genius of the scientists who study nature and become more aware of our universe. Now if we could have an explanation of quantum entanglement and quantum measurement like this, that would be brilliant. But the finest minds are still pondering what quantum mechanics means.
In an episode of the television series Bonanza ("Look to the Stars", broadcast March 18, 1962), Ben Cartwright (Lorne Greene) helps the 16-year-old Michelson (portrayed by 25-year-old Douglas Lambert (1936-1986)) obtain an appointment to the U.S. Naval Academy, despite the opposition of the bigoted town schoolteacher (played by William Schallert). Bonanza was set in and around Virginia City, Nevada, where Michelson lived with his parents prior to leaving for the Naval Academy. In a voice-over at the end of the episode, Greene mentions Michelson's 1907 Nobel Prize.
The real reason is as fallows. As the Earth and Jupiter move in their orbits there are periods when the distance between them becomes smaller, they are closing to each other, and there are periods where the distance becomes larger and larger. In both situations you see Io starts an eclipse and measures the time when it is visible again. In the first situation the light had to travel a shorter distance that in the second situation, so the eclipse is "shorter" than when the planets are moving away from each other. So the important factor is the relative movement between Earth and Jupiter.
Found a small mistake: