This is based on the presumption that light travels the same speed in all directions!!!! Here is why this is NOT provable: Why The Speed Of Light Is Unmeasurable ua-cam.com/video/pTn6Ewhb27k/v-deo.html
This is a great video, very educational. I loved the 3d render!!! You are very good at this. Please continue making content! I'd love to see you as one of the main educational channels on yt.
Great visual animation and modern way to determine the speed of C. Interesting side note, it was in 1676 Danish astronomer Ole Roemer determined that light has speed and was not too far off by observing the difference in time of the appearance of Io coming out from behind Jupiter as being either 8 minutes early or 8 minutes late, depending on where earth was in relationship to Jupiter. When earth was farther away on the opposite side of the sun it was late, when it was on the same side of the sun as Jupiter (much closer) it was early. He was off by approximately 1/4 in his speed calculations based on an incorrect assumption of the distance earth was from the sun. It still amazes be that it could be determined with that close of accuracy nearly 350 years ago!
You changed my perspective about physics. I used to love physics in my high school and when I entered the university, I found it sooooo hard that I started hating it, but now, a spark of love has produced after watching the video. Thanksssss.
Nice! I’ve heard about this experiment many times in the histories of science but they hardly ever or never go into the details of how it was done. Great video!
I dont think its practical in the example because even if you used a laser pointer with very low beam divergence (say 0.5milliradian), the spot size becomes 8m in radius after travelling the 16km mentioned here (16km*0.5mrad=8m). You'd need to decrease the distance, make it rotate a lot faster and make the teeth sufficiently large that it blocks the spot after the beam is diverged. But he did do it somehow, so I think I'm wrong in what I said above
I searched for a video like this from so many days .I finally got a good video.keep it up.Try to make more videos.Urs way of explanation and animations are perfect.My suggestion is whatever ur situation work a little hard.May u'll get better responses ....
This is based on the presumption that light travels the same speed in all directions!!!! Here is why this is NOT provable: Why The Speed Of Light Is Unmeasurable ua-cam.com/video/pTn6Ewhb27k/v-deo.html
This is a cool animation and explanation but if the regular mirror was actually positioned like this the light would reflect off it and way over the rest of the apparatus. It needs to be tilting downward to reflect the light back to the cog. Angle of incidence = angel of reflection.
This is based on the presumption that light travels the same speed in all directions!!!! Here is why this is NOT provable: Why The Speed Of Light Is Unmeasurable ua-cam.com/video/pTn6Ewhb27k/v-deo.html
In 1849..... Where was this 800 meter experiment set up...? What was a strong enough source of light...? How was the cog rotated at precise and constant speed....? What instrument was used to record time in 10,000ths of a second..?
I have heard descriptions of this experiment but it was never made clear that the 1:59 total length of the light path was 16 km. I had always thought it was done in the lab which woul require the wheel to be rotating at several thousand rpm.
Now that the speed of light is fundamental constant used to define the metre, the output from this experiment is actually an accurate measure of the distance to the mirror.
Your eyes is camera that captures in limit frame per second . So the limitation is from the Eyes not from the light I mean when you see the light stop blinking that mean your Eyes stop distinguish . Example if you see helicopter in the movie you will see the fan is always turning or slower turning and that related to the camera used limited frame per second not to other parameter. I am not convinced with such experiment. But thanks you have the best explain
I was hoping you would explain how the light source worked. The beam has to be bright enough and collimated enough to still be visible at a distance of over 16 km. I assume this was the main barrier to performing an experiment like this before Fizeau. After all, the precision-made gear and adjustable rate of rotation were figured out by clockmakers centuries earlier. And semi-glazed glass had existed for quite a while (though I don't know how well they worked as beam splitters).
the lamp was a regular gas lamp. his apparatus was a very clever tabletop device -- a telescope with the eye piece separated from the body of the telescope, with the cogged wheel and a beam-splitter in between. the telescope is BOTH acting as a collimated light projector and receiver. light is projected out from the telescope, to the mirror, back to the telescope [eg you are looking at your own reflection on a distant mirror, through a telescope which itself is projecting light outward]. the beamsplitter/light src arrangement is kinda similar to a modern front-projecting microscope or optometrist's ophthalmoscope. the margin for error would be small but aligning the mirror would not be very hard because you basically have to just roughly set the mirror, then 'find the spot where you see your own reflection through the telescope' then put the device there.
It must have been tedious to get the return mirror adjusted. I mean, how did he communicate with his helper 8 km away? A corner cube and a laser would have helped!@@PplsChampion
im guessing, but i think it was semaphores + something like 'lets both look at eachother through 2 telescopes, then once we both see the other, one of us will set a mirror to reflect the image at their eyepiece back up the telescope towards the other'. the second telescope is the aligned retroreflector. @@randydewees7338
@@PplsChampion I was wondering if he used an arc lamp, but it seems you're right, it was just "a lamp," presumably a gas streetlight (since an oil lamp couldn't get bright enough). I'm surprised he could even see it over a 17 km distance.
@@randydewees7338 Easy. They could've used a light source + morse code. Put your hand in front of the light source = no light = 0(.). Remove your hand = light = 1(_).
This raised more questions than it answered. What kind of light did they use in the 19th century to be able to shine it 8km and back? (One thing is power, and yet another is how they kept the narrow beam on that distance) How did they measure the exact rotation speed?
Good questions! This experiment was done on two large hill tops (8 km apart ~ 5 miles) in the middle of the night. Without streetlights and a moonless sky, it would be dark enough to see a focused candle a that distance. It must have taken some precision work and patience with lenses and mirrors to align the whole thing though. And no, it does not need to be a tightly focused beam. They were only concerned with the light that passed through the gear. Measuring the speed of the cog would be no harder than measuring the gears of a spring-wound clock (invented in 14th century). They were pretty accurate for the day. Galileo tried this experiment centuries before with just a handheld lantern. He concluded that light is way too fast to measure, or it COULD be instantaneous as many scientists of the day thought. Also, the 8km ~ 5 mile limit is due to the Earth's curve. Any farther and you would need a taller hill. :)
Also, the speed of light was roughly calculated in the late 1600's by observing delays in Jupiter's moon orbits. This gear experiment was no random guess. They were basing the gears, distances, and rotation speeds off prior knowledge (and a few hunches).
Was wondering the same thing. This experiment may be right theretically, but i would like to see it done for real... How many lights can shrine 8 km x2?
TQ for the effort made in explaining the method sir, was this exp.tried?, After watching this video I have three questions, was the light continues or pulse? And second how eight km maintained? Three does the earth's radius have any effect on your experiment? I'm a common man if find my questions are incorrect, please justify and correct me.... Thanks
From a translation of Fizeau's original paper: "The first glasses were placed in the view-point of a house located at Suresnes, the second on the height of Montmartre, at an approximate distance of 8633 meters.". The location where he made the measurement seems to have been the house of his parents in Suresnes. He also left photographic plates of the community which are being traded in the art market.
Has anyone measured light after two reflections? It's theoretically possible that light is instantaneous in one direction and twice (c) as long in the reverse.
Light has a different speed according to the environment. Light speed is not a constant, Gravity affect the speed of light, Also oxygen particles affect it's speed slowing it down, We've only measured it here on earth affected by Gravity and gas molecules. Out of space, in a perfect vacuum, without gravity, in one way direction, light travels much more faster because it has no barrier. It also means that 14 billions light years away galaxies are been measured wrong, light does not take that long to reach us, we are receiving it's light much more faster, so the age of the universe are also being dated wrong.
I don't believe any of their BS....! In 1849..... Where was this 800 meter experiment set up...? What was a strong enough source of light...? How was the cog rotated at precise and constant speed....? What instrument was used to record time in 10,000ths of a second..?
I believe speed of light is infinitive if not reflected or pass a transparent object. Light comes out from our sun reach earth in no time. Each experiment of light speed always using mirror to reflect light, slow the speed and get the number.
They didn't have lasers in the 19th century, let alone ones that could shoot 16km within a cm accuracy, so no, you couldn't use this to actually measure the speed of light.
He didn't need a laser. Just a light source bright enough to be visible after 10 miles. The nature of this source has been mentioned several times here.
You’re not moving the wheel at the speed of light. You’re rotating it fast enough for the light to be blocked, and using the speed of the wheel’s rotation to compute the speed of light.
There's a question, the speed of light reduces according to the medium it travels through... so after light travels through the glass, it's speed decreases... so we do not get the exact speed of light
2:30 However, if the wheel speed is not 100% synced, the light, that passed through the 1st gap, on return will pass through the 2nd gap (i.e. during the travel of light, the wheel rotates a bit more than one tooth/gap angle). What are the chances the wheel's rotation speed can be set so precisely? In the end, light may become invisible by other reasons, that have no connection to light's alleged speed.
Super animation! (Although the angle of the mirror seems wrong, it's not in 90 deg with the incoming laser beam.) The interesting is, at least according to my concept after seeing this experiment, that we don't actually need the partially glazed glass. We just have to watch the other side of the wheel. If its back side is illuminated by the laser beam then we already know the light is blocked, without the partially glazed glass.
You mean if we watch to see if the light disappears when watching from the point of the partially glazed window? How would you do that for a ray of light without blocking it?
@@merion297 The important part of this simplified schematic representation of the experiment is that the laser is modelled as a light ray. Therefore we can only observe the light at a point of termination outside of the experiment. If not, we will block its traversal through the necessary parts of the set-up. We therefore use the reflection off the partially glazed window so that the termination of the light ray is outside of the actual experimental apparatus. I hope you understand what I mean. It would be so much easier to show you.
This is a great explanation, but how does one manage a perfect return on a beam of light on an 8km range? I understand the theory (now at least), but the execution and engineering side of things is a mystery to me. A parabolic mirror maybe? Then you'd just have to make sure your mirror was extremely high quality and adjust the direction it was pointing very carefully.
It is a small telescope + tabletop device. Fizeau aimed a telescope at the distant mirror, at its own reflection in the mirror, then shine a flashlight [gas lamp] through the same telescope; looks at the returning lamp reflection via a beamsplitter. the spinning cog is between the eye piece of the telescope and the telescope body. apparently his biggest challenge was actually measuring the speed of the gear.
This experiment measures the average speed over the 2 distance (wheel to mirror and then mirror back to the wheel) therefore there is no way of know the actual speed as the speed in either direction may be different. From the observation point everything is stationary, but from any other point in space ie the moon the setup is moving and the speed at which experiment setup is moving through space is likely to affect the results.
Nice explanation, but to be strict, it shows only how the average speed of the light is when traveled back and forth to the mirror. It is in principle impossible to measure the speed of the light without assuming that the speed is the same in both directions.
Something that I've noticed about speed of light measurements is that it seems like it can't account for 2 things. 1 is relativity. Even though these are stupidly small distances and relativistic effects are going to be mad small, it still exists especially for things moving at the speed of light (aka light itself) also like you said we have no way of verifying the 2 way speed of light. It could be effected by things like refection. Also going back to the relativistic stuff. Something I never quite understood was how they apparently got around that problem by using a mirror. The idea is that you can't 2 seperate emitter. And reciever. Because relativity is going to skew your results due to the distance between the two objects. So to not have this happen you have the emitter and reciever be on the same device abd just bounce the light back from a mirror. The issue I find myself contemplating is.. how is that any different? Like yeah the light technically starts I'm the same place it ends up but the measurement is taking place between the mirror, and the reciever. How does that not functionally operate as if the emitter was just were the mirror was, because if it does then any problem youed have from having seperate emitters amd recievers is going to also be present when using a mirror set up.
13 RPS = 780 RPM How was Fizeau able to measure this rotational speed in 1849? What were the dimensions of the toothed wheel and the gaps between the teeth? What light source did Fizeau use?
My question involves the speed of light vs the speed of sound. Physics tells us the speed of sound increases/decreases relative to the density of the medium through which it passes. To that end, how dense would the medium have to be to allow the speed of sound to reach the speed of light?
But that is the two way speed of light, you assumed that the time taken by light to travel in one direction (8000m) and back is same what if the time taken for it cover 8000m is normal but it gets reflected immediately. I got this thought from veritasium and want to know what other people think about it.
So as far as I know, there is no devised physical way to measure the speed of light that doesn’t involve measuring the ‘two way’ speed of light So that ‘problem’ will come up in ANY experimental measure of the speed of light I’m not opposing your point, it is correct, but I am saying it’s not a design flaw specifically of this experiment, there simply doesn’t appear to be any physical way to measure the ‘one way’ speed of light I will say however, that the Maxwell’s equations for light do not indicate that the ‘one way’ versus the ‘two way’ speed of light should be any different 🤷🏼♂️
But light does not have a speed as photons do not travel from the sun to the earth or from a laser to the metal. it is a wave that amplitude and frequency. It is a wave just like a wave in the ocean. No particles move any further than one wave at a time at its best. Just se how fast a boat moves when a wave goes past, all it does is move up and down, a little forward and a little back, but efectively did not go anywhere. So called quantum particle physics does not work and never did. This is all about energy in the aether.
Good job! It's cool that you're focusing on the experiment, not on the history like other videos.
This is based on the presumption that light travels the same speed in all directions!!!! Here is why this is NOT provable:
Why The Speed Of Light Is Unmeasurable
ua-cam.com/video/pTn6Ewhb27k/v-deo.html
Yes
@SzymonMajewski history is just for inspiration and motivation if you have both then comes experiment
Really 🤔🤔
bot
Great finally someone who focuses on the details of the experiments and develops the calculations and not only on the history of the experiment.
This is a great video, very educational. I loved the 3d render!!! You are very good at this. Please continue making content! I'd love to see you as one of the main educational channels on yt.
Great visual animation and modern way to determine the speed of C. Interesting side note, it was in 1676 Danish astronomer Ole Roemer determined that light has speed and was not too far off by observing the difference in time of the appearance of Io coming out from behind Jupiter as being either 8 minutes early or 8 minutes late, depending on where earth was in relationship to Jupiter. When earth was farther away on the opposite side of the sun it was late, when it was on the same side of the sun as Jupiter (much closer) it was early. He was off by approximately 1/4 in his speed calculations based on an incorrect assumption of the distance earth was from the sun. It still amazes be that it could be determined with that close of accuracy nearly 350 years ago!
That was a very clever experiment.
You changed my perspective about physics. I used to love physics in my high school and when I entered the university, I found it sooooo hard that I started hating it, but now, a spark of love has produced after watching the video. Thanksssss.
Nice! I’ve heard about this experiment many times in the histories of science but they hardly ever or never go into the details of how it was done. Great video!
I dont think its practical in the example because even if you used a laser pointer with very low beam divergence (say 0.5milliradian), the spot size becomes 8m in radius after travelling the 16km mentioned here (16km*0.5mrad=8m). You'd need to decrease the distance, make it rotate a lot faster and make the teeth sufficiently large that it blocks the spot after the beam is diverged.
But he did do it somehow, so I think I'm wrong in what I said above
@@miron__ in original experiment i dont think they had lasers and they were 8.6km apart
This is a great depiction of the experiment! I had heard about this, but it was nicely spelled out here. Thanks!!
Wow, excellent video. This is one of the best visualizations of Fizeau I’ve ever seen. Thank you!
I searched for a video like this from so many days .I finally got a good video.keep it up.Try to make more videos.Urs way of explanation and animations are perfect.My suggestion is whatever ur situation work a little hard.May u'll get better responses ....
This is based on the presumption that light travels the same speed in all directions!!!! Here is why this is NOT provable:
Why The Speed Of Light Is Unmeasurable
ua-cam.com/video/pTn6Ewhb27k/v-deo.html
This is a cool animation and explanation but if the regular mirror was actually positioned like this the light would reflect off it and way over the rest of the apparatus. It needs to be tilting downward to reflect the light back to the cog. Angle of incidence = angel of reflection.
Awesome , thank you for that clear explanation.
This is based on the presumption that light travels the same speed in all directions!!!! Here is why this is NOT provable:
Why The Speed Of Light Is Unmeasurable
ua-cam.com/video/pTn6Ewhb27k/v-deo.html
Only 2.4k view ....you deserves millions
In 1849..... Where was this 800 meter experiment set up...?
What was a strong enough source of light...?
How was the cog rotated at precise and constant speed....?
What instrument was used to record time in 10,000ths of a second..?
No light congestion like today.
In complete dark source of light shines a lot.
Strong light source? Sime heated metal or alloy.
@@dtikvxcdgjbv7975 I don't think so... lol
i hope you make more. this kind of videos has so much potential!
I have heard descriptions of this experiment but it was never made clear that the 1:59 total length of the light path was 16 km. I had always thought it was done in the lab which woul require the wheel to be rotating at several thousand rpm.
Now that the speed of light is fundamental constant used to define the metre, the output from this experiment is actually an accurate measure of the distance to the mirror.
Your eyes is camera that captures in limit frame per second . So the limitation is from the Eyes not from the light I mean when you see the light stop blinking that mean your Eyes stop distinguish . Example if you see helicopter in the movie you will see the fan is always turning or slower turning and that related to the camera used limited frame per second not to other parameter. I am not convinced with such experiment. But thanks you have the best explain
Excellent demonstration. To the point and exact.
I was hoping you would explain how the light source worked. The beam has to be bright enough and collimated enough to still be visible at a distance of over 16 km. I assume this was the main barrier to performing an experiment like this before Fizeau. After all, the precision-made gear and adjustable rate of rotation were figured out by clockmakers centuries earlier. And semi-glazed glass had existed for quite a while (though I don't know how well they worked as beam splitters).
the lamp was a regular gas lamp. his apparatus was a very clever tabletop device -- a telescope with the eye piece separated from the body of the telescope, with the cogged wheel and a beam-splitter in between. the telescope is BOTH acting as a collimated light projector and receiver. light is projected out from the telescope, to the mirror, back to the telescope [eg you are looking at your own reflection on a distant mirror, through a telescope which itself is projecting light outward]. the beamsplitter/light src arrangement is kinda similar to a modern front-projecting microscope or optometrist's ophthalmoscope. the margin for error would be small but aligning the mirror would not be very hard because you basically have to just roughly set the mirror, then 'find the spot where you see your own reflection through the telescope' then put the device there.
It must have been tedious to get the return mirror adjusted. I mean, how did he communicate with his helper 8 km away? A corner cube and a laser would have helped!@@PplsChampion
im guessing, but i think it was semaphores + something like 'lets both look at eachother through 2 telescopes, then once we both see the other, one of us will set a mirror to reflect the image at their eyepiece back up the telescope towards the other'. the second telescope is the aligned retroreflector. @@randydewees7338
@@PplsChampion I was wondering if he used an arc lamp, but it seems you're right, it was just "a lamp," presumably a gas streetlight (since an oil lamp couldn't get bright enough). I'm surprised he could even see it over a 17 km distance.
@@randydewees7338 Easy. They could've used a light source + morse code. Put your hand in front of the light source = no light = 0(.). Remove your hand = light = 1(_).
Thank you for this awesome video.I hope you will keep doing interesting videos like this one.
hands down the best explanation of this experiment i've ever seen
awesome video, great explanation and diagram. I really enjoy the way you pronounce tooth
very good animation and a fullcomplete explanation with the calculation
This channel is underrated
Beautiful explanation!
Thank you so much,
Please upload more scientific videos like this..
*For information*
Speed of light is a *constant*
Beautiful explanation, and immaculate derivation. I now fully understand this experiment, as a former math minor.
First time I completely understand an experiment about speed of light. I should have born in the 19th century but having this UA-cam channel at home.
That experiment is pure genius and elegant!
Perfectly explained! great work 😍
Sweet! Can’t wait to test this on my 4 mile laser setup from Christmas
Excellent video, very precise to illustrate the calculation of the speed of light.
This raised more questions than it answered.
What kind of light did they use in the 19th century to be able to shine it 8km and back? (One thing is power, and yet another is how they kept the narrow beam on that distance)
How did they measure the exact rotation speed?
Good questions! This experiment was done on two large hill tops (8 km apart ~ 5 miles) in the middle of the night. Without streetlights and a moonless sky, it would be dark enough to see a focused candle a that distance. It must have taken some precision work and patience with lenses and mirrors to align the whole thing though. And no, it does not need to be a tightly focused beam. They were only concerned with the light that passed through the gear.
Measuring the speed of the cog would be no harder than measuring the gears of a spring-wound clock (invented in 14th century). They were pretty accurate for the day.
Galileo tried this experiment centuries before with just a handheld lantern. He concluded that light is way too fast to measure, or it COULD be instantaneous as many scientists of the day thought.
Also, the 8km ~ 5 mile limit is due to the Earth's curve. Any farther and you would need a taller hill. :)
Also, the speed of light was roughly calculated in the late 1600's by observing delays in Jupiter's moon orbits. This gear experiment was no random guess. They were basing the gears, distances, and rotation speeds off prior knowledge (and a few hunches).
Was wondering the same thing. This experiment may be right theretically, but i would like to see it done for real... How many lights can shrine 8 km x2?
TQ for the effort made in explaining the method sir, was this exp.tried?, After watching this video I have three questions, was the light continues or pulse? And second how eight km maintained? Three does the earth's radius have any effect on your experiment? I'm a common man if find my questions are incorrect, please justify and correct me.... Thanks
I think the light source must be constant and not pulsating
From a translation of Fizeau's original paper: "The first glasses were placed in the view-point of a house located at Suresnes, the second on the height of Montmartre, at an approximate distance of 8633 meters.". The location where he made the measurement seems to have been the house of his parents in Suresnes. He also left photographic plates of the community which are being traded in the art market.
Thank you! That was greatly answered 💕
And here i was thinking Chuck Norris punches were used to measure the speed of light....
Excellent explanation! I 've finally understood the function of the toothed wheel. Brilliant vid! Thanks 😃
Great video! Would you also consider animating Foucault’s experiment?
Very nice channel! Instant subscriber. Keep going, it will grow fast soon.
Has anyone measured light after two reflections? It's theoretically possible that light is instantaneous in one direction and twice (c) as long in the reverse.
This assumes light travels at the same speed in both directions.
It is not assumption it is for abovious because it is seen from laws of reflection that angle of incidence is equal to angle of reflection
Yes, we all saw the veritasium video 😄😄
A simple solution to a very complex question , mathematics is fun to work with.
Fantastic illustration
Please do more video like thia
Wonderful, wonderful video
We have to assume the speed of light from source and speed of reflected light from the mirror is same
Thanks ayuta team it really helped me a lot :)
Just make more videos, you are explaining very well. Thank you!
Woooow! It's a brilliant explanation with simple Math.
Light has a different speed according to the environment.
Light speed is not a constant,
Gravity affect the speed of light,
Also oxygen particles affect it's speed
slowing it down,
We've only measured it here on earth affected by Gravity and gas molecules.
Out of space, in a perfect vacuum, without gravity, in one way direction, light travels much more faster because it has no barrier.
It also means that 14 billions light years away galaxies are been measured wrong, light does not take that long to reach us, we are receiving it's light much more faster, so the age of the universe are also being dated wrong.
I don't believe any of their BS....!
In 1849..... Where was this 800 meter experiment set up...?
What was a strong enough source of light...?
How was the cog rotated at precise and constant speed....?
What instrument was used to record time in 10,000ths of a second..?
I believe speed of light is infinitive if not reflected or pass a transparent object. Light comes out from our sun reach earth in no time. Each experiment of light speed always using mirror to reflect light, slow the speed and get the number.
wow that's extremely clever
good video, the animation really helped!
They didn't have lasers in the 19th century, let alone ones that could shoot 16km within a cm accuracy, so no, you couldn't use this to actually measure the speed of light.
He didn't need a laser.
Just a light source bright enough to be visible after 10 miles.
The nature of this source has been mentioned several times here.
Nice job bro, great video!
but how to increase speed of the wheel with the velocity equal velocity of light
You’re not moving the wheel at the speed of light. You’re rotating it fast enough for the light to be blocked, and using the speed of the wheel’s rotation to compute the speed of light.
Too lazy to go 8000 metres to try this
this sounds more theoretical, no? also, the video show the light hitting the mirror at an angle and then returning on the same path ...
Cool animation, but 1:13, that reflection was funny 😂
Very good, friend. Clear and clever. I understand it. 👍👍👍🇪🇦🇪🇦🇪🇦
Albert Michelson's method of measuring the speed of light was featured on a 1962 episode of Bonanza called "Look to the Stars" Episode 92
There's a question, the speed of light reduces according to the medium it travels through... so after light travels through the glass, it's speed decreases... so we do not get the exact speed of light
Oh yeah true i didnt think about that. Maybe this gives us an approximation
@@riyaansheikh7470 yep
How much of a thickness of glass?
Something bothers me about this type of experiment, however. What is the speed of reflection?
What a brilliant experiment.
We need more of this kind of education! Science is super fun when you understand it!
thank you for making this.
Marvelous graphics and explanation.we expect more
Too much underrated channel
I have searching for long to get the clear understanding on measuring speed of light. Thank you for this explaination
doesnt travel the same speed in both directions.your taking an average here
We wanna real experiments, not just theory!
Anyone did this experiment in real life ?!!
2:30 However, if the wheel speed is not 100% synced, the light, that passed through the 1st gap, on return will pass through the 2nd gap (i.e. during the travel of light, the wheel rotates a bit more than one tooth/gap angle). What are the chances the wheel's rotation speed can be set so precisely?
In the end, light may become invisible by other reasons, that have no connection to light's alleged speed.
Super animation! (Although the angle of the mirror seems wrong, it's not in 90 deg with the incoming laser beam.)
The interesting is, at least according to my concept after seeing this experiment, that we don't actually need the partially glazed glass. We just have to watch the other side of the wheel. If its back side is illuminated by the laser beam then we already know the light is blocked, without the partially glazed glass.
You mean if we watch to see if the light disappears when watching from the point of the partially glazed window? How would you do that for a ray of light without blocking it?
@@Bollibompa Okay, in practice, it's really easier to watch if the light is not blocked than watching if it's blocked, good point.
@@merion297
The important part of this simplified schematic representation of the experiment is that the laser is modelled as a light ray. Therefore we can only observe the light at a point of termination outside of the experiment. If not, we will block its traversal through the necessary parts of the set-up. We therefore use the reflection off the partially glazed window so that the termination of the light ray is outside of the actual experimental apparatus.
I hope you understand what I mean. It would be so much easier to show you.
This is a great explanation, but how does one manage a perfect return on a beam of light on an 8km range? I understand the theory (now at least), but the execution and engineering side of things is a mystery to me. A parabolic mirror maybe? Then you'd just have to make sure your mirror was extremely high quality and adjust the direction it was pointing very carefully.
It is a small telescope + tabletop device. Fizeau aimed a telescope at the distant mirror, at its own reflection in the mirror, then shine a flashlight [gas lamp] through the same telescope; looks at the returning lamp reflection via a beamsplitter. the spinning cog is between the eye piece of the telescope and the telescope body. apparently his biggest challenge was actually measuring the speed of the gear.
Thank you for the animation and amazing explanation!
This experiment measures the average speed over the 2 distance (wheel to mirror and then mirror back to the wheel) therefore there is no way of know the actual speed as the speed in either direction may be different.
From the observation point everything is stationary, but from any other point in space ie the moon the setup is moving and the speed at which experiment setup is moving through space is likely to affect the results.
Speed of light is same for all observers
Nice explanation, but to be strict, it shows only how the average speed of the light is when traveled back and forth to the mirror. It is in principle impossible to measure the speed of the light without assuming that the speed is the same in both directions.
Something that I've noticed about speed of light measurements is that it seems like it can't account for 2 things.
1 is relativity. Even though these are stupidly small distances and relativistic effects are going to be mad small, it still exists especially for things moving at the speed of light (aka light itself) also like you said we have no way of verifying the 2 way speed of light. It could be effected by things like refection.
Also going back to the relativistic stuff. Something I never quite understood was how they apparently got around that problem by using a mirror. The idea is that you can't 2 seperate emitter. And reciever. Because relativity is going to skew your results due to the distance between the two objects. So to not have this happen you have the emitter and reciever be on the same device abd just bounce the light back from a mirror.
The issue I find myself contemplating is.. how is that any different? Like yeah the light technically starts I'm the same place it ends up but the measurement is taking place between the mirror, and the reciever. How does that not functionally operate as if the emitter was just were the mirror was, because if it does then any problem youed have from having seperate emitters amd recievers is going to also be present when using a mirror set up.
the original experiment didnt require the light to be fully blocked, but partially was enough
13 RPS = 780 RPM How was Fizeau able to measure this rotational speed in 1849?
What were the dimensions of the toothed wheel and the gaps between the teeth?
What light source did Fizeau use?
You can find all the details in the usual places.
@@lawrencedoliveiro9104 I don't know what the usual places are. Please tell me.
@@colt4667 New to the Internet, are you?
I do not know who you are... you worked great... 👌👌best video to know the "how to calculate the speed of light"
But is the speed in one direction similar to the other?
More understanble than the mirror experiment. Its really hard to imagine with that one.
Thank you this was so useful!
Now I'm just curious what the result actually *looked* like. Does the light source just change from blinking rapidly to disappearing altogether?
I saw this idea in one of the talk but this is better explanation, please add the person who invented this first
Wow man! amazing video!
My question involves the speed of light vs the speed of sound. Physics tells us the speed of sound increases/decreases relative to the density of the medium through which it passes. To that end, how dense would the medium have to be to allow the speed of sound to reach the speed of light?
Great video, keep that content
Very good explanation.
Thanks
Very good animation and explanation.
Amazing' idea to determine speed of light.
I must have missed the bit about nineteenth century lasers in history class!🤔
The angle of these light rays very much disobeys the laws of reflection
Please post the Foucault Method and Michelson Method videos.🙏🏻🙏🏻
Why can’t they just measure the direct light but from refracting?
Great work man
But that is the two way speed of light, you assumed that the time taken by light to travel in one direction (8000m) and back is same what if the time taken for it cover 8000m is normal but it gets reflected immediately. I got this thought from veritasium and want to know what other people think about it.
So as far as I know, there is no devised physical way to measure the speed of light that doesn’t involve measuring the ‘two way’ speed of light
So that ‘problem’ will come up in ANY experimental measure of the speed of light
I’m not opposing your point, it is correct, but I am saying it’s not a design flaw specifically of this experiment, there simply doesn’t appear to be any physical way to measure the ‘one way’ speed of light
I will say however, that the Maxwell’s equations for light do not indicate that the ‘one way’ versus the ‘two way’ speed of light should be any different 🤷🏼♂️
Michelson-Morley showed that it made no difference.
Very cleaver.... if we can spin it fast enough.
excellent work, thanks for this.
excellent and an easy explanation
But light does not have a speed as photons do not travel from the sun to the earth or from a laser to the metal. it is a wave that amplitude and frequency. It is a wave just like a wave in the ocean. No particles move any further than one wave at a time at its best. Just se how fast a boat moves when a wave goes past, all it does is move up and down, a little forward and a little back, but efectively did not go anywhere. So called quantum particle physics does not work and never did. This is all about energy in the aether.
What kind of light source was available at the time that could travel 8,000*2 meters ?
1. How they define the distance exactly? 2. Why the frequency of the tooth and gaps only matters? 2*720?
Very nice, pl explain the diameter of wheel will affect or not ??