Measuring the speed of light the old fashioned way: Replicating the Fizeau Apparatus
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- čas přidán 24. 05. 2018
- In 1849, the first terrestrial measurement of the seed of light was made by Hippolyte Fizeau using a bright focused lamp, a spinning slotted wheel, and a reflector a few kilometers away. This famous experiment is one that I've spent the better part of the last year thinking about and very slowly replicating! Using a 5mW green-dot laser sight, a "slotted disk" laser-cut from black posterboard, a speed-controlled dremel, a digital camera, and a full spool of retroreflective tape, I succeeded in measuring and calculating the speed of light! In this video I introduce and explain the theory behind the experiment, and actually perform the experiment to calculate a result. (You'll have to watch to see how close I got!)
An English translation of Fizeau's original (very short) paper: skullsinthestars.com/2008/03/...
Future videos in this series:
-Repeat experiment with 10-mile round trip for the light
-Mechanics of the Fizeau Apparatus (incl. wheel speed control and measurement)
-Optics of the Fizeau Apparatus (incl. retroreflectors)
Music in this video:
I Dunno by grapes is licensed under a Creative Commons Attribution license (creativecommons.org/licenses/)
ccmixter.org/files/grapes/16626
[Original Score] by Wyatt W., used with permission - Věda a technologie
this guy is critically underrated
well he now gained >50k subs in 3 days
@@3nt3_ that was crazy to watch
@@3nt3_ Guess for some reason his videos were on lot of peoples recommended these days...
The algorithm did something good. Jumped on the train too 2 days ago
Who does he remind me of..
@@deadsi Smarter Every Day.
So, if he was 5% high, and you 1% low, the logical conclusion is that the speed of light slowed down by 6% over those 175 years ;P
So by 4763, man will be able to walk faster than the speed of light.
Well, the universe _is_ expanding ...
😂😂
the light in this experiment is moving through air and not through a vacuum. there are other factors but of course, the speed of light should remain constant
@@ambershah5741 The index of refraction of light in air is about 1.0003, which means the speed of light in air is about 99.97% of c.
When you consider the true speed-of-light (actually speed of propagation) at 10M above sea-level (about where you are) and also at about 75% humidity (standard RH near salt water) the refractive index increases due to greater atmospheric density and humidity increasing the propagation time of light (slowing the speed-of-light). So your results may actually be "spot on". Quite amazing.
Seriously? All that and you didn't calculate it? I am disappointed. Apparently you are as lazy as I am. Another engineer, perhaps? :-)
Man I thought the same thing, looked up the speed of light through air (~99,97%) and concluded that it didn't matter, but this humidity thing might change everything. Too bad I am too lazy to figure it out...
@@traywor1615 Aren't we all. :-)
@@MrJdsenior I am wondering how lazyness accelerates man kind, as those celeb engineers trying to tell us.
I mean I actually figured it out and just posted the comment as a meme, but really, how does lazyness benefit us? I mean particulary in this case.
@@traywor1615 The joke is that engineers are lazy which means they design stuff with the least effort and in the shortest time possible. It doesn't benefit anyone, it's just silliness. And in my case I used to keep tweaking until they said, "enough already", so there's that.
You took almost a whole month to put this whole thing together. You are amazing, man. Thank you.
lol this was like a year from buying the first parts to publishing the video
Hol up Mathis, weird to see you here 2 years later bro. Lol
@@AlphaPhoenixChannel how many times did you drive these 1.93 miles back and forth in that year? LOL
I also remembering Alpha Phoenix making the original parts and the Santa Barbara Hackerspace!
I’ve got some great footage of testing the big jumbo flywheel on the hackerspace shop floor that should see the light of day if I ever bother to edit up the pt. 2 video
“Gravity is 10 and Pi is close enough to 3 that nobody cares.” *Engineers wince*
Reminds me of xkcd 2205
Yep, much cringe from this math nerd who wants to be an engineer.
I was thinking the same thing, but context is everything. 5% error makes your building collapse, but it's fine for things like prototyping. Prototypes never work the way you think they will anyway, so you do some back of the napkin calculations, build it, test it, and tweak it. And that's if you're an old man like me. I suppose the kids model it these days - when they're not sniffing glue anyway. :)
@@charlesenfield2192 5% error makes your building collapse, not if you overengineer by 50% as you should
@@monad_tcp Safety factors are used to compensate for things like material and construction defects, material deterioration that comes with age, overloading, misuse, etc.. Safety factors are not meant to compensate for careless design.
Really makes me appreciate just how much effort it took to 'science' 2000, 500, even 100 years ago. Even today, with all the modern tech toys that exist, this was still (at least) a month long job just to recreate an experiment that you already *know* works..pretty impressive. Just imagining the practical undertaking that this must have been 150 years ago hurts.
And imagine all the effort that went in experiments with uninteresting result... A dozen of the world's brightest mind, working for years with the peak of 1700's technology just to get, sell, nothing interesting...
@@Orlandofurioso95 Almost as if valuing truth for its own sake actually mattered.
How did he know it worked already if he hasn't done it? The key thing of science is repeatability, not trusting that "it works."
@@Orlandofurioso95 Null results are some of the most important results in physics, you ignorant oaf
Adjusting for the refractive index of air (1.000293) you are are actually at 99.4% of the speed of light. I wonder if it is even closer considering that the air is (probably) humid and further slowing down the light. Amazing video 👏👏 I love how you made the speed of light so much more accessible and "real". This is one of the best videos on CZcams
This is a criminally underrated channel. These videos combine the knowledge and practice required for these experiments and demonstrations incredibly well. This channel needs more subscribers.
The problem is that majority of people doesnt care shit for anything remotely like this they just want their brain dead entertainment that tricks their dopamine but if they did something like this they would get to feel even better and learn stuff but that takes effort.
Great video easily worth a sub, thanks.
This was awesome, I've never seen this experiment replicated and the speed of light is such a cornerstone of physics. You put so much time and effort in to this and it's really appreciated. Good job.
Thanks! It was a pain at times, but it was a lot of fun!
I did a similar experiment (science fair project) back in the early 90s, but was slightly different and based on Albert Michelson's experiment from 1870s ? Mine was based on angular rotation of a flat mirror (rather than a shutter) and light didnt need to travel nearly so far (about 100m) to establish a delta time. This alpha pheonix guy did get a more accurate answer though
I did this experiment at university- it was the highlight of my 4 years there. We did it over 30 meters in the lab and not 4 miles. We had a tiny mirror that could spin 1000 times per second, and we looked at the dot through a microscope and measured the angle of deviation.
It was magical to get 3X10^8 as the answer and to get the error calculation bounding the true value.
I left the lab elated that I had physically “caught” light in a trap - we were “faster” than the light - light speed became so real and finite.
Bloody hell. Such a simple method produces such an accurate result. Talk about standing on the shoulders of giants!
Lets talk about standing on the shoulders of giants
@@botyaltotertutal468 you'd be able to see a really long way.. unless there's another person standing on a taller giant in front of you.
I should take off my shoes, he probably has sensitive shoulders
Wow, just wow.
Hooe you get big here in CZcams someday.
328k subs, I would say our boy is on his way 🎆
I'm glad you've stuck with this channel despite it not getting the traction it deserved all this time. Lots of great content in your library and still making more!
Wow, great! Original, explained well, and I love how you show all the troubleshooting you had to do.
But most of all, I now have an EXTREME level of respect for Fizeau, who did this more than 150 years ago without lasers, cameras and digital tachometers, and most importantly, without knowing in advance what the result should be (at 13:11 you explain that you got a value of 93% c, but then found the result could be improved by correcting for camera movements. An advantage Fizeau did not have).
Agreed, Fizeau's work was amazing
"π is close enough to 3 that nobody cares" :D
contrary to popular belief, e and pi are the same number
All the engineers, myself included, are shaking rn
@@nstvntt7410 true. As an engineer, 2=e=3=π=4
I'm just offended that he outed himself as a former physics major who did those approximations. It makes him sound like just an icky engineer.
I had a physics professor cross out a pi/3 term in sophomore year modern physics. It was a formative moment
Fizeau is an absolute beast, managing to do all this 170 years ago
It really is crazy how old school scientists did all their work with none of the modern tools we take for granted. Also good job recreating this, ive heard about or vaguely seen the diagram of spinny wheel as a kid but never actually learnt how it works or seen it in action. Thanks for making this vid it really does put a smile on my face.
Also "π is close enough to 3 that nobody cares" I dont know how I feel about this statement having played the drawing internal and external polygon game when i was younger to find pi manually
Such a great video!! Experiment, presentation, editing, all of it! You nailed it brus! Have a good day mate.
A little Pythagorean Theorem would've solved this problem fairly quickly. I think the GPS solution is fine for helping explain the real concept of the video though! 😄
From one physics graduate to another, amazing. I wish I had thought to copy experiments when I had the chance. This has a lot of the intrigue and excitement of copying the experiment myself, but with none of the energy investment. I've a few friends who ended up teaching, this type of video seems perfect to build interest in the type of person considering a physics undergraduate.
It's incredible that we can have this level of content and knowledge here in youtube.
Holy crap man.
We learned about this in my optics class during my physics undergrad, but we were like meh, that's waay too much work to replicate. I swear, your projects could turn into several scientific papers. A modern replica of the Fizeau apparatus to measure the speed of light is much more than publishable. I've also commented this under your most recent video, testing Veritassium's problem experimentally. The amount of seriousness and work that goes into this is unheard of on youtube, even in most Colleges (like mine lol). You're so underrated, you deserve si much.
Saw the title and immediately remembered this from physics class ~20 years ago. We only read about it, but for some reason it always stuck with me. Very nice to finally see the experiment in action.
Fizeau will be proud of your work. Well done
Fantastic setup and results as well!
This dude is incredible. His passion is contagious and his excitement as he’s describing things keeps me engaged. I wish I had professors like him in Uni
This level of pedagogical mojo and edge-of-your-seat anticipation is inspirational. Can’t wait to see what happens next! Elite!
I laughed at 18:00, "If you convert that into some more useful units". Miles per hour? Fourlongs per fortnight? Meters per second, please.
Furlongs per fortnight sounds like a fun unit. Typical highway speed limit: 174720 fpf. Average walking speed: 8064 fpf. Average cycling speed: 53760 fpf. Airliner cruising speed: 1344000 fpf.
@@Hyrum_Graff are you aware that furlongs per fortnight is the standard unit of speed in the FFF unit system? (Furlong Fortnight Firkin system, it’s like SI but with older British units; see en.m.wikipedia.org/wiki/FFF_system )
Also, given your name, have you read Card’s “Children of the Fleet”? If not, I won’t give any spoilers other than to recommend that you do so.
@@jpe1 I have. Also, your the first person to say anything about my name’s origin.
And, a hilarious system of units that I was not aware of. I just did the conversions because I wanted to see how silly that speed unit was.
This makes me want to go outside and perform the experiment myself! It's reassuring to know that the value you obtained is so close to the accepted value of c. Doing a proper experiment is a laborious task, and I'm happy you took the time to produce this video and put it on youtube so that we can go on this journey with you. Thank-you!
Also c is less in air....
Being able to do that opening in one shot really shows his working understanding of this stuff, it would be hard to memorize all that information but since he understands how it works he doesn't need to remember anything, just articulate what he knows.
VERY well done!!! You clearly have what it takes to be an actual experimental physicist. Bravo!
This is beautiful. Love how you integrated math in your videos which is something other CZcamsrs shy away from. Keep up the amazing content please !!!!!
This is a freakin’ amazing effort. I have watched this before but again I sat through mesmerised. This deserves way more views. It breaks my heart that it doesn’t
The quality of your content continues to impress.
great channel! I'm into home experiments since being 7 yo. now in my 30's its never boring! sadly in the 90's there wasn't CZcams yet and most kept a lab journal
Congratulations! I've thought of trying to do this for a few years, and also couldn't find record of anyone else that has done it. And now you have, and here in SB! Love it, good work.
Very impressive, this video deserve millions of views
This video is absolutely awesome. Fantastic measurement and data analysis as well. Thanks for going the extra two miles for this video!
This is absolutely amazing man! I have never understood the fizeau apparatus until you explained it in this video, A very big thank you to you! Keep this great work up!
This give me even more appreciation for how Fizeau was able to measure the light you have to use lots of modern stuff that he didnt have and its still hard.
Hi YT algorithm, i'm here to promote this channel.
This is awesome. I remember reading about this experiment in high school and being blown away by the fact that they were able to make such a precise measurement using 1800s technology. I always wanted to recreate the experiment myself, but never managed to follow through. Thanks for sharing your work!
Your videos are literally the best out there. Really fascinating! I appreciate all that you are doing. Keep up the good work!!!!
First, I'm so glad I found your channel, you're both entertaining AND educational, especially for a simple software guy like myself :)
Second, have you seen the Veritasium video where he talks about speed of light in a single direction being truly unmeasurable? I'd be curious to know your thoughts on it, perhaps a new video idea?
He's totally right
but what if we set a runway for a light beam with 45 degree half transparent mirrors several miles apart, measuring two consecutive flashes in two different places several miles perpendicular to that runway?
@@jskratnyarlathotep8411 how do you correlate the time of the recorded flashes of light, without making assumptions about the speed of light?
@@jpe1 we know the distance, we know the time therefore we know the speed. The question was that we were measuring speed of light accross a single direction, but in opposite sides. In that way we'll measure combination of speeds accross two directions, but all in a single sides.
@@AlphaPhoenixChannel until you can send a single photon?
From this you can work out the air density based on the reduction in C
The difference is far too small to measure with this apparatus.
You are amazing. Thank you for creating this type of content. Any of your videos makes me very happy!
That´s really great! I remember having learned about this experiment in school like 30 years ago, and it was fascinating.
Thanx for sharing it, it was a lot of fun to watch! "Grabbing" the speed of light in real life is something worth trying to get a feeling of fascination.
As I recall, light travels slower through various materials, including air and water. C is speed of light in a perfect vacuum, possibly including a spherical cow. So your number may not be incorrect, you may have inadvertently measured that attenuation.
It may help to set up a longer shot. And try it at higher altitudes, like between mountain tops. Both tried on days where the atmosphere between the points is fairly stable and equal along the whole path.
Did you allow for the slower speed of light in air to get your 99.3% of C?
The speed of light in air is 99.97% of c in vacuum, pretty insignificant.
Great job! It's very interesting to see people today recreating these older experiments with new tech.
Great video! I was literally thinking about how this was done the other day, and learned about the astronomical method, but this is what I wanted to know. I am forever amazed by what was possible for people who didn’t have electronics, or easy access to information. Humans are incredible!
Goes on a quest to measure the speed of light... by using GPS which relies on the known value of the speed of light XD.
lol I can see this.. however to be fair, the distance could have been measured without GPS, it was just much more convenient to use modern technology than it would have been to measure it in a more traditional way, especially with the water in-between. Maybe a follow up showing the accuracy of GPS distance measurements vs stepping it out vs some other measurement technique (long string, repeated smaller measurements, etc.) My bet is that GPS is pretty accurate.
definitely does not invalidate the experiment, or the video. I think it was great.
@@akunog3665 It actually does invalidate the experiment as it stands because this methodology makes this experiment a tautology. GPS only measures time delay with high accuracy clocks. To get distance data, you have to convert that time in distance using the speed of light (yes it is done internally from the GPS side that only provides distance measurement but still). So the thing is that this way, what ever the numerical value of the speed parameter is used in the GPS is what you will get as the result of this experiment. So obviously, 299792458 smurfs equal 299792458 smurfs.
A precise enough way to measure the distance travelled by light here would have been to measure some parallax effect using sticks and a graded panel or whatever. No need to measure a long string crossing the distance, it would obviously be a bad idea with high inaccuracy (due to the streching of any material over such large distance and bending due to gravity).
@@mirijason while I do agree that the experiment is circular in the way you described, I was merely suggesting a way to rectify the circular-ness of it would be a follow-up experiment showing how accurate the gps distance measurement is. Could be interesting to see what method he would come up with to measure distance and compare to GPS results. I was not trying to argue that measuring with a string was the best option, I was just spewing flippant methods, like anyone would feel confident in a distance paced out, or measured 10 feet at a time lol, your parallax method sounds interesting, but I would need to see a diagram or something to build it in my mind.
I'm still glad he showed the experiment, and the methodology behind a classic technique. Was an informative, and interesting video even if he didn't actually prove anything about the speed of light other than google uses a value consistent with known measurements.
So measure the distance on a topographic map. You do remember what those are, right? Or on a photo from google earth. Calibrate the scale using a known measurement or something. This isn't that hard.
@@stargazer7644 obviously, one can measure the distance quite accurately without using the known value for the speed of light. I'm just saying that as it stands, this experiment requires as input the output he's trying to measure because of the GPS inner workings.
Im very happy that someone replicated this experiment. Always wanted to see it.
Really really cool video. We can tell you really know what you're talking about and how passionate your're. Please keep making more videos.
Super awesome video dude. I could learn a lot. Thank you very much!! You really deserve much more fame on internet. Good luck!!!
Been binge watching your videos since they came across my recommendations. They bring to mind the thought experiment of "If you were sent back in time, could you impart enough modern knowledge to mankind to meaningfully change technological advancement?" After seeing you cover such vast topics and your ability to recreate experiments that validate such discoveries, if we ever achieve time travel, I think we know who to send!
u have so much 'school presentation' energy that i cant honestly tell if i love or hate it
WoW, incredible! One hears about how they measured it, but to see it done in video is another level.
If it existed something such as a fair way to measure the success a person deserves, I would have no doubt this guy would be up there.
This guy just sets himself a really interesting and challenging goal, spends maybe a whole year working on it, putting immeasurable amounts of effort.
Then you can literally see in his eyes that he does it because he loves it.
After all he just wraps it all in a spectacular and really well-crafted video so you can witness what he has achieved and learn a lot for free
I really thank you for making all these works of art
YOU ARE THE GOAT, BRIAN
I had looked for a video like this before, but didn’t find it. Now I have!!!
You’re the man! Great stuff on your channel. Your passion and the ease at which you explain everything makes it so digestible for me as a viewer. I just get sucked into your videos and time disappears. And learning some stuff along the way. When I clicked on this I was hoping it was going to be more on the very first calculations with respect to the moons of Jupiter and timing the movements between Earth, Jupiter and it’s moons. A physics teacher explained it, and I’ve always wanted to see the actual math and process of how they figured it out, with that method. That said, I really enjoyed the experiment you did conduct, and how close your results were to the scientific consensus of the speed of light.
Quality content! No clickbait and videos that actually teach you something.
Dude you're so enthusiastic and joyful and it's awesome.
I'm glad that I found your channel. Awesome stuff!
thanks for doing this, this is great i've never really understood the original experiment, you explained it so much better
Stumbled upon you channel by accident. I am hooked. You are trying to dumb i down, but still, you are so smart, that it is still waaay beyond my level of knowledge. You speek with such enthusiasm that, i cant help but listen, and hopefully get smarter 😁
Great work ! 👍🏻
So glad I found this channel. Your content is beyond amazing!
I could imagine going to physics class and you announce “today, lets measure the speed of light… Fizeau way!” So cool!
This was an outstanding project; congratulations on the success! I too would have loved to repeat this experiment and couldn't find any information on the internet that someone actually did. So I congratulate you on that too! I wanted to use a strong light, a mirror, and a toothed wheel with just my line of sight. By spinning the wheel fsater, I'd eventually lose sight of the light, then when it re-appears, I'd check the RPM's.
This is the coolest thing I've seen on CZcams. This guy knows his stuff😃
Wow, outstanding!
About the fifth of your vids I’ve binge-watched now, how is it your channel doesn’t have 500K subscribers? Keep it up, I’m in!
Mate. This Is absolutely fantastic! Well done on a really entertaining video!
This is one of the coolest experiments in CZcams! Loved it.
I wish someone would try to recreate this experiment exactly how Fizeau did it. It seems almost undoable.
I wish there was more information about the original experiment! I couldn’t find much
Excellent video - just shared it with my science class in our optics unit. Well done!
Really enjoyed watching this, as I was not familiar with the Fizeau experiment. Great effort!
This is so impressive - really appreciate your work!
Modernizing a 150 year old science experiment amazing…..but the joy he has when he spins the wheel…”and now we can….aaand now we can’t !” Priceless. 🤣🤣🤣 Love your passion for Science and Teaching 🙏🏼😄
it makes me happy knowing there are people out there doing cool stuff like this
Awesome! I was searching youtube for someone who recreated this experiment, and this is the only video I could find.
Modern units are defined in terms of physical constants such as the speed of light, so in a way you're not measuring c, just the inaccuracy of your setup :P
Light in air is a little slower than light in a vacuum, so you're even a little closer. Truly inspirational, I instantly subscribed after finding you through one of Steve Mould's videos!
Thanks! I was pretty happy with how all those ice videos turned out in the end - Steve giving me a shoutout before any were even filmed was awesome
I never would have thought it possible to measure c using the stroboscopic effect. Mind blowing.
I have been having trouble fully understanding this experiment, but you explained it well enough that its making sense now.
Thanks - I’m glad it helped!
Very well done. I am looking forward to the future videos how you iterated the apparatus for sure. I like this sort of approach where you evolve an apparatus for a specific experiment. And then later on have building blocks of the things you figured out to be useful for future apparatus. Or even to be repurposed for something entirely different. Like if you were hiking and wanted to precisely measure the distance between two hill tops. We could abuse this same setup in reverse. Knowing the speed of light, measure the time it takes for the round trip of the light and then we have the distance.
Wow, I really like what you have achieved here with your skillful endevour. This kind of experiment is epic, using the same simple idea as Fizeau did, simple but requiring expert performance. One feels so connected with the fundamentals of science. Thank you. If you would like to continue on this path, another experiment you could do, also from a famous scientist from the past, is the Cavendish experiment that gives us the gravitational constant, G.
This man. His videos, amazing. His channel, perfection. His shirts, impeccable.
3 years later and this is this the best implementation of a plastic fly wheel i’ve seen
Worse - it’s actually cardboard
I can't thank you enough. You deserve way more subscribers 😊
You are awesome and reignite the love for science whenever I forgot for a moment
Awesome job, excellent recreation and final analysis. You explained everything so clearly! It would be cool to see you collaborate with Cody’s lab!
Great video demonstration and explanation. As an old guy who has worked around lasers for years, I would urge you to invest in a pair of laser attenuation glasses for any future work for yourself and any of your assistants, particularly when using a green laser at night. I have a couple of friends who suffered laser burns to their retinas from "eye safe" lasers. I realize I am writing this a few years after you posted this video, but please keep it in mind for any future work. It also wouldn't hurt to put suitable laser warnings at the beginning of applicable videos just to avoid liability when you invite other people to duplicate your experiments.
Keep up the good work.
This is an amazing production!
When Hyppolyte did his measurement the Metre was a physical object in a French museum.
The Metre is now defined in terms of the speed of light, so measuring the speed of light in terms of the metre is a circular argument.
It's good that you measured it in miles first! We need people like you to keep checking how far the circular argument has drifted from reality.
Hate to be that person, but the U.S. units have been defined via the SI units for a while now
This experiment is super cool. But it shows just how smart Fizeau and his colleagues truly were.
At university in 1990 I attempted to measure C with a capacitor. I made highly accurate concentric tubes with end rings and ran out of time . Well done , especially on the hardware and software.
That is seriously impressive. Well done.
Super awesome video. I did an experiment like this in high school. I used the osculating laser, a beam splitter and a an oscilloscope with two light sensors.
This made my day!! Keep up great work!
Great video! Fantastic result!
Well done, and yes it boggles the mind how he(Fizeau ) pulled this off.
When I say your km/s number outcome I was so surprised to see how good your outcome was. Very impressive
Well-done! Brilliant!
So, you are closer than Fizeau's initial value.
😊A really unexpected use for a common SLR! Didn't expect you'd use long exposures either. So clever!
I'm trying to remember the video that postulated that the speed of light has never been measured. Only the speed of REFLECTED light has been measured.
A great little factoid for us pedants to enjoy :-)