Fizeau's 1850 Experimental Measurement of the Speed of Light | Doc Physics
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- Опубликовано: 11 фев 2013
- I love ancient experiments! So CLEVER! Armand Hippolyte Louis Fizeau - yep, he was French. His name is also engraved in the Eiffel Tower. But not like he was a punk kid - they actually honored him that way! I've got to ask my Francophone readers - is Fizeau french for carbonated water?
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If I had you as a teacher when I went to school, I would have never dropped out in the 11th grade! I'm 71 now and a couple of years ago wrote, Infinity, Time, Death and Thought, which explains the anomalies of Young's double slit, quantum eraser and delayed choice conundrums. I had to teach myself whatever physics I could get my hands on by reading, reading and reading.
Fizeau's light source was the Sun
Has that experiment been doe facing up or down instead of horizontal? I know for certain it will change the speed.
Ha! I LOVE how they used laser telemetry to measure the distance in their experiment, then used that distance to "measure" the speed of light. Thanks for the reference. I presume that you would want a wheel of big-as-possible mass to increase its angular momentum to smooth out frequency concerns. Also, with their 360 slices, you'll be well within your motor's capabilities. I suggest verifying frequency with a high-quality strobe. Good luck!
Fantastic explanation, keep going man.
Thanks a lot!
I had so much fun and learned the subject in 4:30 minutes, you are a great teacher !!!
Thank you!
@@DocSchuster nice!!!
Subscribed within a minute! You have an awesome of explaining stuff :)
Thanks so much for this!
Excellent. The backscattering of, e.g., a green laser at night seems to be hugely humidity-dependent. Is that effect also dominated by aerosol?
thanks this helped me understand alot better than textbook explanation.
I'm glad I "found" your channel :)
What a great enthusiam doc
Thanks. Simple, easy which works for me!
Dude you're amazing!
1:29 is my favourite part
Again, great explanation.
Brilliant. I will be far better prepared to teach this this year! Thank you.
So, what'd you get?!? Sounds perfect. Does the LED turn off quickly enough?
wonderful video
Nice explanation, but I think your chronology is wrong. Fizeau's experiments were before Maxwell, so he wasn't backing Maxwell up. In 1850 Maxwell was in his late teens and on his way from Scotland to Cambridge University. In addition, Fizeau's experiment wasn't very accurate. In 1728, over 70 years earlier, English physicist, James Bradley estimated the speed of light in vacuum to be around 301,000 km/s. using stellar aberration, much closer to our current measurements (299,792) than Fizeau's effort at 313,000. For the best effort using a mechanical device, you do need a Frenchman, Leon Foucault, who three years before Maxwell published his equations (1862), used a rotating mirror to measure a speed of 299,796 km/s. Astounding accuracy for a earthly mechanical device.
FazerWiz - Correct. Maxwell published in 1865.
Astounding accuracy for a Frenchman too. Did Fizeau not know about the art of the 'Gaelic Shrug'? With a Gaelic shrug you can be wildly inaccurate, and then somehow justify your statement with a simple twitch of the shoulders.
OMG ! , i've been watching videos about this subject and i didnt get the point , finnallyyyy i saw ur video 😍
A few years ago, to celebrate the 50th anniversary of the invention of the laser, a French university tried to re-create his experiment using a powerful laser, and a modern high speed electric motor to drive the optical chopper. They were not able to do it and had to adopt an alternative approach. It made me wonder how he was able in 1850 to drive the toothed wheel round fast enough, and what sort of light source he used that could be shone so far and then reflected.
Great video, question, at that time, how did he have a disc spinning at the same speed, without any acceleration ?
Thanks for all the tips. I think I'll add a lab next year!
This is such a good video.
Amazing video, love it. (y)
It’s with a heavy heart that we announce the unexpected passing of Doctor Schuster last evening at approximately 7:30 PM after falling from a ladder at his residence in suburban St. Louis, MO. He’ll be missed by fellow students and his family. Fly high!
Who even are you
bro had me scared there for a moment
Amazing, este video es perfecto
Thanks a lot! I´ll have a physics test tomorrow and you helped me more than my teacher though he speaks german &you speak english :) thanks
Interesting, great idea in that era. BTW, what's the speed in Maxwell's measurement?
Pretty cool experiment he did. My question now becomes is there a variance with other light sources. And how do we know if all light is the same ?
What was the distance between the apparatus?
I have not consulted any primary sources for this presentation, and it seems like my ignorance is showing. I should revisit this topic after some deeper research. Thanks for the push!
Very clever!
i have a exam next week and its apretty ggod way to start the first chapter with this cool epreiment
Veryy Nice Video
Thanks!
I'm not a historian, but according to Wikipedia, Maxwell first calculated the speed of light in 1862 - well after Fizeau (Wiki James Clerk Maxwell, Electromagnetism). Which actually makes it even more amazing, because he didn't know what speed he was looking for. Also, at 3:50 you have it backwards - if you go too slow, you hit the first, paddle, too fast you hit other paddles. But anyway, great video and explanation of the experiment.
Maxwell knew exactly what speed he was looking for. Maxwell's velocity of light calculation is not scientifically sound.
Keep doing what you are doing. Do not listen to the haters. Your video's are extraordinary.
I might have included some equations with the radius, angular velocity, and the like but the basic idea was shared well. You encapsulated the amazing way that someone could have figured out the speed of light before modern technology and I appreciate it!
CHistrue - It isn’t “hate” to insist on accuracy in a scientific presentation.
did you also make michelson experiment I could not find though
Not yet. Good idea!
I dimly remember doing this experiment in a physics lab in the eighties. I don't remember slit, I remember a spinning many faceted cylindrical mirror.
pschroeter1 Ooh! That would be an excellent method, too. Like a cylindrical disco ball!
pschroeter1 That is Michelson method. :) Very similar to Fizeau experiment. :)
Michelson first did it with six-sided cylindrical mirror, and then 8-sided, 12-sided, 16-sided mirror, to achive the most precise result. :)
Thankyou...
could you explain how effective his method was with regards to the accuracy
jugman1 Remarkably, the French were unable to repeat the experiment on a recent anniversary of it. So...beats me how it ever even happened. You should research it more - it's really interesting!
... i came here for the way he calculated the speed of light ._.
DEUS VULT
hi
I have a research paper that shows that speed of light vary with frame of reference for a observer
if you are interested then you have to contact me at pooraramphy@gmail.com
I was really thinking that we all the available modern technology, there should be an easy way of measuring the speed of light accurately. In the end I built a very simple circuit that uses an avalanche transistor to pulse an IR LED, a 300 dollar oscilloscope, and just bounced the light 18 meters round the lab. I still want to try the Fizeau experiment.
Are you sure you have your history right? I don't think Fizeau was looking to test some prediction by Maxwell that the speed of light (c) was 3 x 10^8 m/s. I think Maxwell's work came well after that (circa 1862). Also, Maxwell couldn't have had the constants from electricity and magnetism to calculate c prior to 1850, because this connection was made by Weber and Kohlrausch in 1856. Am I wrong? Perhaps you have different sources than mine you can share?
Dude that was awesome! Thanks for the simple explanation. People don't understand that if a person wants to know how they figured the speed of light, then they obviously are not an advanced student of these things, and so a detailed explanation only obscures the answer. It would be like explaining complex Grammer rules to a toddler.....just sing the ABC's and smile😄
The speed of light is the one way trip delay. This is reflected light.
The LED's I had were not very fast, but you could get a fairly clean measurement based on the on rise. The best result I got was from
Thanku sir❣️
There is no time like the present. And sometimes that's all we have. Carpe planning period.
Apparatus to deduct lights velocity, instead of measuring it, because direct incoming signals can not be measured of velocity, as i suspect is the case when using mirrors to determine lights velocity. mirrors give a direct vision of the source, coming straight at the observer or camera. once the light is seen, the connection is already made.i wonder why mirrors are used for determining lights velocity, and what recorded the signal. if i look at direct incoming light, like a train coming straight at me (same as in space, we see a sphere and big could be big but could also close, and tiny could be tiny, but also far away, size and distance without a background is impossible to tell), i only see a dot traveling towards me, not able to tell where it is exactly. if something like a dot of light travels to me or a camera, and the dot is visible, this means the distance is already bridged to be able to "see" or record this dot. a cop has to stand besides the road to laser a car passing him by to be able to take multiple readings over a period of time. maybe a always on laser (shining against the shutter until both open) attached to the end of a vacuum tube, with two simultaneous shutters allowing for a "time" or duration for light to pass this distance during a certain time, would or would not show a laser dot on a back plate in the back being filmed by the camera. this method uses deduction, if the dot was visible on the back plate, the known, fixed distance was traveled within both the shutters opening time. the reason the camera must be under an 90 degree angle and be always on is to eliminate timing problems. the signal for both shutters must both have the exact same cable lengths delivering the signals at the exact same time to insure both open and close at exactly the same moment. when looking directly into or at a laser dot, like when a mirror is used, will show a connection, after the distance has already been traveled to show us or the camera a red dot. a mirror is like looking back visually to the local light's source and into the source directly.
A modeRn Fizeau experiment for education and outreach purposes". It should come up. I have the PDF but I think you should be able to see where to download it pretty easily. I think that the optical chopper they tried to use might have been a bit heavy. I was trying to set up the experiment myself because it looked like a method that midde school or even some younger students could understand. I was messing with some brushless dc motors that can do 1000 revs per second.
Wow! Can you point me to their paper? Unrepeatable experiments (particularly with improved technology) aren't very nice.
I was looking at how to make a decent optical chopper, but I didn't have acess to any machine tools then. One can buy them of course.
Mr Doc sholter
I have a research paper that shows that speed of light vary with frame of reference.
then wts ur opinion about this..
Pooraram Jakhar link?
well explained 😁😁😁
Pfft, I did this with cheese and a microwave in my physics class :P Using the wave equation.
I came here cuz I rly couldn’t understand the Wikipedia diagram. Thank you!
Yes; true. Is it aerosol that diffuses the light? Water vapor, too?
Yeah, I'll have to ask a talented student to try constructing this with a green laser perhaps.
Right, so if you look at the old comments, Peter Hunt points out that the French were UNABLE TO DUPLICATE THE EXPERIMENT WITH MODERN TECHNOLOGY. That's kind of suspicious. I don't know what to think, but I want to acknowledge that I'm not the expert here. I'm interested in revisiting this, so thanks for the help!
As I'm a slow learner I wanna suggest you to explain slowly😁😁
tell me. wat formula hi use for Calculate the tight speed ?
BAHODIR BUZRUKOV If υ is speed of the wheel you can write υ*Δt=2*π*R/(2*z) where R is diameter of the wheel and z is number of tooth, and we know that υ=ω*R=2*π*n*R where ω is circular incidence and n number of revolution of the wheel, you can calculate Δt. And if speed of light is c=2*l/Δt, you put t in formula and you get that c=4*n*z*l. :)
BAHODIR BUZRUKOV And, Fizeau came up with result that speed of light is near 315 000 km/s which was pretty good result in his time. :)
+Sanja Košutić Why it is divided by 2*z, not z?
Because you have z - number of tooth, and you have same number of spaces between tooth, so you pratically have 2*z. Do you understand? :)
oh, i see thank you :)
I was drawn to view this info by the indroduction of soda pop at Starbucks. Their trademark is "Fizio".
cool
Good.
Could you see a candle at 40km through a telescope?
the best results I got were from powerful IR LEDs used in CCTV. I think it be possible with some good focussing to use a much larger distance. My set up was really crude and hurried so not much more than 90% accurate.
Q: Lightspeed is constant in water and in glass and in vacuum, so why not also in Earth’s atmosphere?
And: As lightspeed in Earth atmosphere is constant also when the lightsource is at different velocities, that should be different when observers at different velocities would measure the lightspeed.
Or not?
The speed of light actually does vary depending on the medium in which in travels in. It would be slower in water than it would be in space because there would be more stuff it would hit on the way. As for your second question, it would not change depending on the velocities of the observers. Read about Einstein's general relativity.
Kein Problem! Viel Gluck.
Could you do one on leon foucault's experiment? i believe it is similar but i don't know how similar. Thanks for all you do.
Fun idea! Thanks!
You didn’t mention that electricity is a byproduct of magnetism and dielectrics.....light as we now know is a coaxial circuit...resonance =vibrations =friction =heat =illumination.....force and motion. Inertia and acceleration....with magnetism at the core....big question...which travels faster...LIGHT..or..MAGNETISM.?.....
They had lasers in 1850?
If you search on google: "a modern Fizeau
I thought Maxwell published his work much later than 1850...
I know he did this,but still not clear how he or you calculate speed of light ????
I am assuming you make these videos between periods.
U. R. Funny. Also smart. 😁
How does this help me at all? This doesn't explain why it had to pass through a dirty mirror. It doesn't explain all the parts. It doesn't demonstrate how he got any real data. What he watch the light and saw maybe a flicker. So? That means space pass between light which could be explained with a wheel. What real data came from this?
hello I'm French what's up?
instead of explaining the detail just said unnecessary I dont know I dont know comments in the video
I wonder if you have done the experiment or are only reading stuff from a piece of paper. Did you see the experiment done by someone? I in no way that astronomer could calculate the speed of light in 1600's.
is the answer nobody knows cause your the second vid ive watched
There is no way that Fizeau could pick up James Clerk Maxwell's EM papers and read them in 1850! Maxwell published “On Faraday's lines of force.” in 1856; “On physical lines of force.” in 1861, and his complete EM theory “A dynamical theory of the electromagnetic field” in 1865. An otherwise good video spoiled by a bending of the facts.
+Alastair Roxburgh Good call! Thanks!
A candle reflected by a mirror in 8 miles distance? Are you trying to piss down our backs telling us it is raining?
The Kaiser Ew!
He's used the sun
Was that the eiffel tower ? Mxm. This video sucks.
😅 just kidding bro. Nice video 👍👍👍👍. I'm a photographer 📷. So I'm studying light (optics (
too silly
This is not the speed of light.
Sorry again, the speed of light is unlimited, not fixed. "God Based Magnetism" on RUclips already explained and proves this. Do your own investigation and stop repeating other people's lame theories that you or them could never prove.
Are you still married? Sorry im just bored i have to learn this and other things for next week and im not getting anything.
If you read this please HELP...
cool