Why The Speed Of Light* Can't Be Measured

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Mánuði síðan

Physics students learn the speed of light, c, is the same for all inertial observers but no one has ever actually measured it in one direction. Thanks to Kiwico for sponsoring this video. For 50% off your first month of any crate, go to kiwico.com/veritasium50
Huge thanks to Destin from Smarter Every Day for always being open and willing to engage in new ideas. If you haven't subscribed already, what are you waiting for: ve42.co/SED
For an overview of the one-way speed of light check out the wiki page: ve42.co/wiki1way
The script was written in consultation with subject matter experts:
Prof. Geraint Lewis, University of Sydney ve42.co/gfl
Prof. Emeritus Allen Janis, University of Pittsburgh
Prof. Clifford M. Will, University of Florida ve42.co/cmw
The stuff that's correct is theirs. Any errors are mine.
Einstein, A. (1905). On the electrodynamics of moving bodies. Annalen der physik, 17(10), 891-921.
(English) ve42.co/E1905 (German) ve42.co/G1905
Greaves, E. D., Rodríguez, A. M., & Ruiz-Camacho, J. (2009). A one-way speed of light experiment. American Journal of Physics, 77(10), 894-896. ve42.co/Greaves09
Response to Greaves et al. paper - arxiv.org/abs/0911.3616
Finkelstein, J. (2009). One-way speed of light?. arXiv, arXiv-0911.
The Philosophy of Space and Time - Reichenbach, H. (2012). Courier Corporation.
Anderson, R., Vetharaniam, I., & Stedman, G. E. (1998). Conventionality of synchronisation, gauge dependence and test theories of relativity. Physics reports, 295(3-4), 93-180. ve42.co/Anderson98
A review article about simultaneity - Janis, Allen, "Conventionality of Simultaneity", The Stanford Encyclopedia of Philosophy (Fall 2018 Edition), Edward N. Zalta (ed.) ve42.co/janis
Will, C. M. (1992). Clock synchronization and isotropy of the one-way speed of light. Physical Review D, 45(2), 403. ve42.co/Will92
Zhang, Y. Z. (1995). Test theories of special relativity. General Relativity and Gravitation, 27(5), 475-493. ve42.co/Zhang95
Mansouri, R., & Sexl, R. U. (1977). A test theory of special relativity: I. Simultaneity and clock synchronization. General relativity and Gravitation, 8(7), 497-513. ve42.co/Sexl
Research and writing by Derek Muller and Petr Lebedev
Animations by Ivàn Tello
VFX, music, and space animations by Jonny Hyman
Filmed by Raquel Nuno
Special thanks for reviewing earlier drafts of this video to:
Dominic Walliman, Domain of Science: ve42.co/DoS
Henry Reich, Minutephysics: ve42.co/MP
My Patreon supporters
Additional music from epidemicsound.com "Observations 2"

James Goudreau
James Goudreau 2 mínútum síðan
Wouldn't this make navigation different in different directions because when we launched vehicles to planets the calculations would be off if we used the convention to assume where the planet was/is and will be?
Ellie Parkinson
Ellie Parkinson 3 mínútum síðan
Could you not measure this in the photon sphere or near the event horizon of a black hole? Fire a beam of light and knowing the distance wait for it to come back around and meet you. The light is travelling through space in a single direction. However space time is curved resulting in it arriving at the same location. This would test if light can travel at different speeds for different directions so long as it doesn't take curvature into account for this data xD. It would be one half of the problem solved at least.
Xerox Prime
Xerox Prime 3 mínútum síðan
Hey I have an IDEA to synchronise clocks and verify if its correct or not. So one guy is 200km away from a car. Car start is running at 40km per/h. So at certain time difference after car will be in a specific distance away for from a first position. So the guy can synchronise his time by throughing a bomb at the car. If the car hits than he can figure out the speed of light by time dilation equation. He would first try with default speed of light to get a time delay and throw a bomb on the car based on the pre knowledge how fast the car is moving. So how much time its light to reach him and how far the car is moving at that time and how much time it will take for the bomb to drop and where the car will at that time, with this information he can verify wether or not the speed of light is too far away from reality. If bomb hit the car with 5 sigma significant then it will be proved. If not then speed of light will be revealed. We can easily limit speed of to be off not more than 1-100 seconds, because we demonstrate if speed of slower by 10 second then our speech and hand movements would have been unsynchronized.
Jonsse 10 mínútum síðan
No-one's measured the speed of light outside of a gravity well either. We assume light moves at a set pace, but we've only ever experienced and measured light inside our own little gravity well. What if light moves faster in a smaller well and slower in a larger well? What if time moves in the same relative speed to light?
Dario G
Dario G 18 mínútum síðan
Just turn on two clocks at the same time. You can turn them on at the exact same time if they are triggered via the change of spin of two entangeled particles, because their spin changes at the exact same time (quantum entanglement). 👍
John O.
John O. 19 mínútum síðan
Darek is like Elon Musk if Elon Musk was anywhere near as smart as he pretends to be.
carl gangl
carl gangl 20 mínútum síðan
So the speed changes on the bounce? And is influenced by the direction of gravity.
Sofonias Fikadu
Sofonias Fikadu 37 mínútum síðan
The light speed may be opposite(unequal) b/c the nature surface may absorb some light. They have the same vf(final velocity)and vi(initial velocity) but may have effect on the time by physical state like solid,liquid,gas.(in my taught)!!
3d Chris
3d Chris 40 mínútum síðan
Place a theoretical pulley on the moon, and run a theoretical rope from the earth to the pulley and back. On earth, pull one side of the rope, it will take 3.6 seconds before the other side of the rope moves. Half the rope didn’t move instantaneously.
Sports94freak Humaro
Sports94freak Humaro 41 mínútu síðan
@Veritasium Curious of your thoughts on this concept: instantaneous/infinite speed, in relation to: time travel, gravity, bending of space, or at least the optical illusion of bent space, and possible the age of the universe itself into question. The concept of instantaneous travel almost breaks the concept of physics though, because of it has mass, it must be accelerated. And if light is a photon, and can be affected by gravity, meaning it has mass, and can be slowed by changing the medium it’s traveling through, then infinity is impossible. However, if it were possible to exceed the speed of light in any one direction, then things light time travel could actually be possible. The issue comes when gravity affects light, how doesn’t it respond? Does it slow, bend, refract, disappear, or blink? If black holes are so dense that the gravity keeps the light from escaping, then that suggests that light has mass and can be manipulated by gravity. The only way that I could imagine light being a different speed of travel in different directions is it along the way, in either direction or both directions, if it is influenced by gravity. Meaning, that if space can bend, or if space is bent, or if light is bent because of the various density pockets of space due to celestial bodies, then things that appear to be billions of light years away may be a lot closer, or even a lot further away than we thought. If gravity bends light so much that it slows down, and in fact must travel a further distance to get to us u stead of a theoretical straight line with the shortest possible distance between the two objects, (similar to the phrase “as the crow flies, and how it means the true distance may be 30 miles away, but to drive there, you may have to travel 42 miles, because you are not able to travel in a tree straight line in the shortest possible route connecting those objects in that mode of transportation at this time. However, what if instead of being slowed down, if gravity were to maybe “slingshot” in a way, or using centrifugal force to accelerate the light even faster around very dense celestial bodies. We don’t know yet.
Orkun Uslu
Orkun Uslu 52 mínútum síðan
In order to do that experiment, we need to find a way to transfer information much more over the speed of light. I think it would be possible to do that by using the 'Quantum Entanglement'. I presume, who reads that knows about the quantum entanglement and simultaneous superposition states of particles whatever the distance between them. This is how we can do that: We superpose two particles in one location and put one of them on earth, just by the beam source and put the other on the moon for example. When we shoot the beam from the light from the Earth, the entangled particle triggers the one at the other end and it makes the clock start. When the light reaches to the clock, than it stops. Now we know how fast is the light moving through the direction from earth to moon. Than we do the experiment at the reverse direction. This will help us to find the speed of light through the direction from moon to earth. In the end, we will have 2 data illustrating speed of light at both directions. We are capable of doing this experiment. The problem in here is, finding the money to establish this test set-up.
Alex Wilke
Alex Wilke 58 mínútum síðan
This "One-way" speed of light theory, has me wondering if this answers the riddle of "Entanglement"
jlhawa Klukkustund síðan
Very interesting video! I'm inclined to think that the speed is the same in any directions.
Stefan Sjöberg
Stefan Sjöberg Klukkustund síðan
Why not send a photon to a goal, and at the same time trigger 2 entangeled particiles where one is placed at the start and the other at the goal. Then meassure the time difference at the goal??
Guy That
Guy That Klukkustund síðan
Wouldn't comparing the two clocks from mars and earth show the Difference if you were to bring them next to each other?
Jester Klukkustund síðan
If it's possible to create wormholes in the future it'll be possible to find out
Gary Klukkustund síðan
Not a physicist, instead I'm a computer scientist. Here's my thought. Set up a "course" for the light to travel, set your clocks to run at the same speed, the time isn't important as long as they are running at the same speed. Within your course have a series of gates, say 1/4, 1/2, 3/4, turn around point, 1/4, 1/2, 3/4, end. At each check point you measure when the photon crosses the gate. Since we are only looking at deltas we should be able to calculate the speed as it crosses each gate during its round trip. We would know if the speed of light is faster in one direction than the other.
TRothrock Klukkustund síðan
Perhaps E is better thought of as how we experience time at the local level. And perhaps the light travel is more like a long “rigid” stick that can “poke” something as far away as it wants to, and do it instantaneously. After all, it seems almost absurd that a photon can leave its source at E and arrive hundreds or thousands of miles away still traveling at the same speed. It seems more rational to think that a photon leaves its source then “bumps into the next photon” and that one bumps into the next photon, and so on until the light reaches its destination in an effect that is essentially (or literally) instantaneous. Like pushing the fabric of space, but without any compression whatsoever.
TheMrPapst Klukkustund síðan
What if you take two stopwatches. One at point A where the light source is and the other at point B where the light arrives. when the light is switched on you start stopwatch A and stop it when you switch it off. When the light arrives at point B start clock B and stop it when the light is off at point B . If you now place the light source at point B and repeat the experiment you can compare all times. This way you can prove that light is equally fast in both directions.
Kuya Kogz
Kuya Kogz Klukkustund síðan
Why i lose reading when there is a bend in my fiber optic cable?
Andrew Phifer
Andrew Phifer Klukkustund síðan
I have a solution! change the definition of what a straight line is by doing this experiment near a black hole, so that firing a laser pulse forwards will simply hit you in the back of the head, this location is known as the photosphere of a black hole. that way you can have your source and sensor in the same location. More accurately this would need to be conducted just above the surface of the photosphere that way you can still get information out of the system to the wider universe. That means that you might not hit the back of your laser pointer, but rather, just above it. good luck filtering out the effects of such an extreme local source of gravity on your math, but I'm betting someone can do it. Another potential solution requires the universe to be in the shape of a torrid. Assuming that light moves instantaneously in one direction, you should see your laser pulse behind you instantly if it moves instantly to its destination. The major issue is that you would need to find a path traversing the whole of the universe that has negligible distortions to space time, to make the process of finding the right angle to point in to get the laser light to appear behind you as simple as possible. Again, we have to change the definition of what a straight line is, but this should avoid the issue of light moving at different speeds depending on what direction you are facing, and half of the cases for how light may move on reflections.
Animesh Joshi
Animesh Joshi Klukkustund síðan
Use quantum entangled stopwatches so when you start the timer it will be simultaneously started at the other stopwatch
Rogelio Gaona
Rogelio Gaona Klukkustund síðan
What about compare the 2 way speed with the 3 way speed?
Maximilian Sutanto
Maximilian Sutanto 2 klukkustundum síðan
What about utilizing black hole? What if lets say we shine light at a cone shape, at an angle. A portion will get absorbed, a portion will orbit the black hole, a portion will manage to escape black hole. We repeat the experiment by moving the light source. If speed of light differs on different direction, the portion of light absorbed will be different because more of the "slower" light will not be able to escape black hole. Will this work?
Nikioko 2 klukkustundum síðan
The Michelson-Morley Experiment proved that there is no light ether and that the speed of light is the same in all directions. And there is no reason to assume something different. So, even if you do a two way measurement, you can simply divide the time by 2.
Josh Fitzpatrick
Josh Fitzpatrick 2 klukkustundum síðan
Wouldn’t this therefore mean that looking at galaxies far away in one direction would show early galaxies from billions of years ago, as normal, and looking the opposite direction would show galaxies of the same age as our own, and not the early years of the universe?
Jonis 3rd time's a charm yt
Jonis 3rd time's a charm yt 2 klukkustundum síðan
And why would the speed of light be different in different directions? Why would we think that? Has it been tested
John Wallace
John Wallace 2 klukkustundum síðan
One simple thought. If light travels at different speeds in different directions then looking at anything would mean that your perception of any one object you are looking at would change as you viewed it from different directions correct? Seems to me we would have known this since astronomers are looking at so many stars in so many different directions. And even me looking at stuff here on earth would change as viewed from different positions on the compass. This was way over thought
Sophie 2 klukkustundum síðan
Wait. The man on the moon is no mirror. He sends an own, original signal, which would again take its "forward" time back to earth. Not the however reduced "backwards" time. Or how do you define "forward" or "backward" in that context?
Jonis 3rd time's a charm yt
Jonis 3rd time's a charm yt 2 klukkustundum síðan
How can an analog clock tick differently to another clock nearby? I mean, how much different would it be
Rommel Corpuz
Rommel Corpuz 2 klukkustundum síðan
The six beginner hepatosplenomegaly influence because clef nutritionally excite onto a wiry swan. psychedelic, hard heaven
Silly2smart 2 klukkustundum síðan
Was it Stanford that has a sub-pico second camera that can record light as it travels through a milky bottle of water? Its a must see as it travels a bit strange. Oops you have it!
Leibel 3 klukkustundum síðan
Veritasium Good point, however why stop there, why not take this idea to the next level, are you ready for this: suppose in one direction light travels super slow and in the other direction it not only travels instantaneously but it actual arrives a year before it left, what does that mean you ask, it’s simple, every mile you travel in one direction you are traveling a year into the future, and in the other direction your traveling into the past, here is a simple example, imagen that California is 3000 years ahead (in the future) of New York but you can’t feel it because for every mile you travel west it’s a year later and if you go east every mile is a year earlier, so even light takes a year to travel one mile westward but if it travels eastward it will arrive a year before it left, mind blowing isn’t it.
Tophat 3 klukkustundum síðan
As I recall from studying physics the distance to the background radiation is the same in all directions based on redshift, which at the close end fits in with geometric measurements of distance, so wouldn't that conflict with the idea of c not being equal in different directions, since in the case of light being instantaneous in one direction, in that direction we wouldn't be looking "back in time" and so we wouldn't see the background, or in the case of light being faster one way, we would see the background further away in that direction? The feeling that I got from studying relativity was that the whole idea of "simultaenous" events was not really applicable, once enough distance was between events. Instead we had to use different metrics that combined space and time, essentially calculated quantities that would always be the same no matter the observer. I believe one of them was something like x^2+y^2+z^2 - c t^2 or something like that.
Varad Deshpande
Varad Deshpande 3 klukkustundum síðan
11:03 You Talk about Time Dilation in clocks, which is based on Einstein’s theory, which in turn is based on the definition that c is same in all directions. How could one consider Einstein’s theory to Quantitatively affect( influence) the very definition the theory was built on?
Kozak 3 klukkustundum síðan
Assuming that light travels the same speed in both directions is a safer assumption than believing the speed changes rapidly when changing direction. Why? There is no evidence to suggest there would be a drop in speed. If you could find evidence or some experiment that could slow the speed of light then perhaps your idea would be worth considering. Also, wouldn't GPS be all messed up since we make the assumption light travels the same speed in both directions? Seems to me you need a device that requires perfect precision and assumes light travels equally in both directions - then if it isn't accurate you might have evidence to suggest that light is travelling a different speed in opposite directions. Until then it seems more like a philosophical question.
mistirion 3 klukkustundum síðan
Everything he says makes more or less sense but i still refuse to accept "we don't know for sure if light just goes slower in one direction because we cannot proof it"
Frisco o
Frisco o 3 klukkustundum síðan
Instead of using 1 Wagon Wheel with mirrors you could use 2 that way you would have an odd number of bounces and you could verify that c is correct by dividing by 3
003-Mohnish 3 klukkustundum síðan
Does this really matter ?
003-Mohnish 3 klukkustundum síðan
Why does this matter ?
Micah Ritter
Micah Ritter 3 klukkustundum síðan
Could you use an entagled particle and observe the second particle at the same position the first one is at so that the entangled particles react instantaneously and the speed of light from the detector can be measured by the amount of time it takes to get the signal back?
Joshua Bissell
Joshua Bissell 3 klukkustundum síðan
There is a way around this... Indirectly. Looking at stellar evolution in various directions from earth would indicated if there was a directional difference in the one way speed of light, at least over interstellar distances.. In one direction we would see more Population III stars, in the other more Population I stars. It could also tell us the extent of the difference, if not the exact quantitative value. Heck, you may even see different "edges" of the observable universe depending on the direction you looked if there was a directional difference in the speed of light.
Cat 3 klukkustundum síðan
I don't understand anything, but wow
Van Sams,III
Van Sams,III 3 klukkustundum síðan
if you put a mirror at half a meter then you can measure
Amijeet Kumar
Amijeet Kumar 3 klukkustundum síðan
Just loved your approach. I, myself, have always wondered if the speed of light is always the same in all directions.
Vegeta 3 klukkustundum síðan
U miss something but I can't explain it in English
Jay Lim
Jay Lim 3 klukkustundum síðan
Its easy to synchronize if your light is a coded pulse with time. You can then measure the speed of light in one direction.
Internet Disorder
Internet Disorder 3 klukkustundum síðan
Unsubscribing you. I can not handle this much of pressure
Bert Pasquale
Bert Pasquale 3 klukkustundum síðan
Is the fact that the universe appears just as old in all directions not empirical evidence for C being direction-agnostic? If light came faster in one axis vs. the other, the universe would appear younger in one axis. But this is not observed. Wait, relativity would be different in that axis, so time delay would be longer, so it all washes out again. So... we'll never know or be able to tell if it's the case or not -- So it doesn't matter if it's true or not!
Ryan Singer
Ryan Singer 4 klukkustundum síðan
Simultaneity isn't simultaneous.
Tomasz Stanek
Tomasz Stanek 4 klukkustundum síðan
What if shuttling laser in one direction with one second pauses and measured it on the end? Don’t compare clocks only measure pauses,
SudPAD 32
SudPAD 32 4 klukkustundum síðan
what if the end timer and start timer are the same?
mmm 4 klukkustundum síðan
I will say the answer of it : Measure the Speed of Light With a Bar of Chocolate and Microwave , check this out. You can measure with this technique.
Gabie Dubin
Gabie Dubin 4 klukkustundum síðan
thumbnail doesn't match the laws of physics
jelmer prins
jelmer prins 4 klukkustundum síðan
if you measure 2way lightspeed in 360x360 degrees. wouldn't you need to see differences if the speed of light is different?
Jay Lim
Jay Lim 4 klukkustundum síðan
We can measure the speed of light if the distance is not moving. Light has no mass so they have the same speed forever and everywhere. Put pulse codes in the light to measure light.
Walker Silha
Walker Silha 4 klukkustundum síðan
Wouldn't the Mars experiment tell you if the speed of light is different in different directions? If their clocks do not end up in sync at 12:20 you would know that the speed of light is not constant in all directions.
TelaKalle oy
TelaKalle oy 4 klukkustundum síðan
maybe the problem is the "time" Our perception is wrong for fast moving "objects"
Corey Seymour
Corey Seymour 4 klukkustundum síðan
Couldn't you have 2 lasers on either side with 4 clocks? then if the timing is off in one direction it travels quicker? or vice versa?
Gerd Reidesack
Gerd Reidesack 5 klukkustundum síðan
Can't we use the angle of the sun as indication for a synchronized signal?
Luis Martinez
Luis Martinez 5 klukkustundum síðan
Could it be then that by some sort of relativity principle, C is always instant for an observer, and half for everything else outside said observer, but, and, by the same way, instant for those other observers relatively to me, and half from me to them but from their "point of view"? The experiment of earth-mars clock will comply if C is instant for each observer, and half relatively to each other. :V
OFFiCiaL FLaVoR 5 klukkustundum síðan
I thought I heard that scientists caught a black hole sucking up light, shouldn't gravity have a big affect on light travel just like it has on everything else?
Creepmobile 5 klukkustundum síðan
Do the "equally moving apart synchronized clocks" experiment, but in many different directions to see if there's a difference. Do it with a third reflection point at varying unequal points to see if there's a difference. Have each clock tell the other what time they should be receiving the message. There, science. That'll be $2m please.
Alex Moyer
Alex Moyer 5 klukkustundum síðan
@Veritasium Tesla knew this and is why he disliked Einsteins methods and conclusions. Conventions used for convience, when not recognized explicitly and the true unknown aknowledged throughout continued observation, can falsely color not only the experimental design and direction of inquiries but also the ultimate conclusions made from those experiments. The expulsion of aether from the scientific physics community is one such great tragedy resulting from this; it is another convention which has just as valid explanation for the hard experimental data, but since it colors the conclusions differently it can often lead to pictures of the observations that result in more practical engineering solutions based off it's assumption than otherwise. Science is often a tug of war between egos for fame and wealth when it should be an awe filled investigation into the world around by humble minds and eager hearts fully aware of the limitations of their imperfections.
Alex Moyer
Alex Moyer 4 klukkustundum síðan
Also, btw, awesome video! I would love to see you dig into some of the intricacies of Maxwell's work and how his theoretical assumptions colored and lead to the invaluable formulas that he graced the world with. Particularly the difference between his original formulations and the Heavyside reduction of them.
Himaloy 5 klukkustundum síðan
1:44 Veritasium: Could you measure the speed of light like this? Destin: *Chuckles*
Safety Pete
Safety Pete 5 klukkustundum síðan
Instead of 2 fixed clocks, could we not have 2 phase measuring devices, and then shine a light from each direction located next to a device) into the opposite device. If the phases measured was different then the speed was different in each direction, if the phases measured were the same, then the speed is the same. If they were the same you can measure using a standard clock and mirror with the knowledge that the light travels at the same speed in both directions?
Chris Gonzalez
Chris Gonzalez 5 klukkustundum síðan
What if we had quantum-entanglement synchronized clocks?
Pop Lyle
Pop Lyle 5 klukkustundum síðan
There's a ISpost video where they film the movement of light at, like, a trillion frames/second or something. In one such instance, you can see the light particle moving around like a ping-pong ball. Why can't we use this to measure the speed of light?
Pop Lyle
Pop Lyle 5 klukkustundum síðan
It's actually 10 trillion fps- Here is the video: ispost.info/flow/mr2rw69-e4Grs7Y/v-deo.html The ping pong part starts at 5:40
Cody Osborne
Cody Osborne 5 klukkustundum síðan
Wouldn't the orbits of the planets appear irregular if light was different speeds in different directions? One way the light hits the planet instantaneously and you see it 20 min later where it was 20 min ago. Now you look at it half way through it's orbit on the other side and you see it in 20 min where it is right now. There's a difference there. The planet would appear to accelerate would it not? One way you see it behind itself the other way it's appeared to have caught back up with itself. Then fall back behind again as we see it delayed. So if we cut it into quarters and it had an hour orbit and 15 light min away. First quarter you see it where it is, right in front of you as light travels instantaneously in that direction. Second quarter you see it 7min 30 sec past a quarter of the way around because it takes half of the round trip to get there, presumably. Third quarter it would appear 15 min ahead of where is supposed to be then forth quarter it will fall back to 7.5 min ahead and start over again in an oddly accelerating orbit. Please correct be if I'm missing something.
chris KD2TFJ Luckett
chris KD2TFJ Luckett 5 klukkustundum síðan
Frkm what I learned I think it is no possible way to really know how fast light is just as much as it is no possible to know the distance around a circle we just can't
ChibiNyan 6 klukkustundum síðan
Wouldn't the one-way speed of light be measurable by using a different signal ? Put a clock at the beginning and start it when your beam of light is shot. The beam hits a receiver (anything) who just has to send a different signal back to the first clock, and the first clock stops when it receives the signal. In order to prevent that 2 different speeds for 2 different directions thingy, the signal going back just has to go at a known speed : like a sound signal (we know the speed of sound), or a bullet shot with a gun (we know the speed of a bullet), etc. We can substract the time for the return signal since we can mesure it, and what we have left allows us to get the speed of light. Do it in both direction, and we can verify if the speed of light is constant or not.
salmarwow 6 klukkustundum síðan
That is a clickbait. Title says one thing, which is incorrect. Then in description it corrects itself.
Beardiegames 6 klukkustundum síðan
Is it possible to measure the heat dissapation speed of a laserbeam on a block of metal instead of using clocks?
Just stop its gettin fuckin redundant
Just stop its gettin fuckin redundant 6 klukkustundum síðan
I learn everything and nothing at the same time
DjoG 6 klukkustundum síðan
Do sound waves depend on the speed of light? And if not could we use sound waves to synchronise clocks and measure the one way speed of light?
Tomito 6 klukkustundum síðan
Am not so smart but I still wanne say this if light has a mass doesn't that mean that light travels faster to the planet with the most gravitation?
Random Awesome
Random Awesome 6 klukkustundum síðan
Would this not be easily verified by the fact that we'd be able to see a lot more of the universe in one direction if c was instantaneous in one direction?
Hendrik Schokker
Hendrik Schokker 6 klukkustundum síðan
Idea 1: is the speed at which time runs linked to the speed of light? Meaning that if light speed is different than time at speed 0 (through space)would also differ? If that is the case we can have objects moving very very slowly in different directions and we would see a relatively big change in their clocks over a large amount of time. ( lightspeed can be measured without reaching light speed since spacetime is 1 thing and time is linked to lightspeed) idea 2: would quantum entanglement be able to help us here on synchronizing clocks? (Edit: also mentioned by others, probably not possible since communication is not possible with quantum entanglement)
George Jensen
George Jensen 6 klukkustundum síðan
14:34 then a good way to test it is if you see remnants from near the the big bang in one direction and stars that we would expect to see now in the other direction. The 2 directions would look completely different. Since you can heat something up from an em wave, you could place 2 objects and a heat/light source in between them and see which one glows first or gets hot first. If they are different, the speed of light is different in the 2 directions. The light from both of the obiects are travelling towards you from near enought the same postion. Or a mirror that reflects the light towards you.
Christoph L
Christoph L 6 klukkustundum síðan
One Direction sucks, scientifically proven....
eg gamer
eg gamer 6 klukkustundum síðan
I think if u put gravitey u will find something
Hamid Osman
Hamid Osman 6 klukkustundum síðan
Hi, uh a scientist from a time machine here It all relates to dark matter Full information will be revealed by 2058
Ono Kimchi
Ono Kimchi 7 klukkustundum síðan
for some smart boys u seem to be kinda stupid here .... why dont u fuckin ask Mark on Mars how long he waited for the Signal DUUHHHHH!!!! *facepalm* smh give him a sandclock xD hehe but for real good video enjoyed it very much ^^
Ono Kimchi
Ono Kimchi 6 klukkustundum síðan
atom decay clock on Mars& Earth + Satelite in Orbit to the Sun between Mars and Earth ...now at an set Timer the Satelite will laser Mars and Earth ...BOOM DONE !! Give me the next Worldchanging Problem to solve ! xD
Naimul Haq
Naimul Haq 7 klukkustundum síðan
The return path of light from Mars has v=instantaneous is an assumption. If it were true then all GPS data would have been wrong and we would have known it long ago.
Abhishek Kumar
Abhishek Kumar 7 klukkustundum síðan
Just a suggestion, measure the speed of light using two synchronised clock from both directions.
cultusfetus 7 klukkustundum síðan
haha my dumb brain was like "record a slow mo video of turning the lights on in a room. watch how long it takes for the room to filled by the lights." bye. byeeeee my brain is a mush
Paul Williams
Paul Williams 7 klukkustundum síðan
keep going back to direction, have two jets going at the SAME speed of sound just off from head on (same weather) your going to tell me the two jets are going two different speeds relative to someone on the ground now change sound medium to light this is the same
rusamene 7 klukkustundum síðan
So basically light has the same bug as Big Rigs.
Kevon Clarke
Kevon Clarke 7 klukkustundum síðan
You might not be able to measure the speed of light in one direction but you can confirm if the forward speed is the same as the reverse speed. Experiment: 1.separate a light source from a light sensor at a fixed and known distance. 2.Set up a button that controls both the light sensor and the light source. (When it is pressed once the light source fires a short beam of light, at the same time a push turns on the sensor and another push turns the sensor off). 3. The button should be placed at half the distance relaying the instructions by sound to both the light source and the light sensor. 4. The distance from the button to the other 2 devices should be the same and fixed. Also relatively small compared to the distance the light has to travel. 5. Push the button on and off, delaying between states by the expected time light is thought to take, to travel that distance. 6. To confirm the expected speed just verify whether or not the light sensor registered a pulse.(If it did then the speed of light is greater than or equal to what you thought it was. If it didn't it is less that what you thought it was. (A timer can also be placed to measure the duration of the sensor being on to when it received the beam of light.) (This wont measure the speed of light but its like assuming its speed in one direction then confirming if the assumed speed is correct. Similar to mathematical induction.) Please acknowledge my comment!!😅
Ghabriel Galyndeo
Ghabriel Galyndeo 8 klukkustundum síðan
What if, syncronize both clocks using an entangled particle. That is if the theory of quantum entanglement is valid through an experiment. But is it possible??
Clay Campbell
Clay Campbell 8 klukkustundum síðan
Detonate nuke on Mars and earth at same time?
pigtailsboy 8 klukkustundum síðan
I've rewritten this other thought several times trying to explain it or to get the arrangement properly figured so it could actually verify C as universal or otherwise. Since such a problem seems so complicated the simplest solutions can be the best ones and increasing the number of receivers/emitters would do that by recording the differences or lack of. There was an example earlier in the video on using a half way clock to synchronize a sender and a receiver. Synchronizing them doesn't matter, the difference in time however does if the experiment is permitted to continue on by ping ponging the signals while recording the the time span between send and receives. If three are set out in a line with equal distances exactly between and the center acts as a relay and starts the processes there should be discrepancies if travel distance in a given time and direction isn't universal. Let the center signal the others to start recording with one set to rebound the signal to the center the instant it receives it, the center relaying that signal to the next one in series as well as the one before. That pattern of receive, emit, relay and receive can continue and with each cycle the record I think would start to express a mismatch. I'm trying to diagram out an appropriate and logical series as well as figure the timing. Wish I could remember how to manage an excel document still.
h k
h k 8 klukkustundum síðan
Isn't light like a stream of water or a waterfall rather than a pulse of heart, so whenever you see it's there, always, other way to put it is if it's a pulse then you missed the light hence you didn't see what it got reflected from, but a stream of light is always there
Manojvradan Balaji
Manojvradan Balaji 8 klukkustundum síðan
what if we place a light source and a reciever and make the light source reflect off a mirror and into the reciever, and note the time taken, then we do the same thing but move the reciever closer to the mirror and the light source further away the same distance and measure the time taken again? if light travels at the same speed at all directions, then the first and second reading will be the same. But if the readings arent the same, that means light doesnt travel at the same speed at all directions, right?
Juha Immonen
Juha Immonen 9 klukkustundum síðan
Because for all wave motion it always is true that frequency times wavelength is the speed.
Juha Immonen
Juha Immonen 9 klukkustundum síðan
Why measure the the speed of light using flight time measurements? The best speed measurement 29979...m/s, which is the current dedined constant, was actually determined by measuring the frequency and wavelength independently and just multiplying them.
MaQ's Edutainment
MaQ's Edutainment 9 klukkustundum síðan
But I think we can measure it in 2 ways: 1. We can use the Sun's light to measure it: We know how long it takes the light from the sun to reach the Earth, and we also know the distance between the Sun and Earth, so we can divide the distance between the Earth and the Sun by the time it takes the light to reach the earth. 2. We can use the curved space-time around celestial bodies to our advantage: For example, we take a big and heavy celestial body and set a clock and a light source. We can start the clock once the photon leaves the source, and measure the time it takes to get around the celestial body and divide the distance it traveled (probably its circumference) by the time it took for the photon to reach us. Now, as space-time is curved around the body, it is almost tricking the photon to believe that it is traveling in one direction, removing the whole different directions different speeds problem. I am really not sure whether this will work, so if I am wrong please give me a reason why this is so? I am 14 and I really love your videos, has actually helped me a lot.
Ben Su
Ben Su 9 klukkustundum síðan
Imagine that you are standing on where light orbits a black hole, shooting a light beam ahead will result in receiving it from the back. In this case, one can perfectly measure the time to calculate the one-way light speed.
Abraham Brandon
Abraham Brandon 9 klukkustundum síðan
it does seem logically true, but its just hard to be grasped, we have known the speed of light is always has been c in all directions but if this is true, then exactly what Dustin said, it’ll break our brains 😂😂 but 👌🏻👌🏻
Nabahaal -
Nabahaal - 9 klukkustundum síðan
If your variable speed theory would be right, can't you test it with a back and forth measuring VS the exact same distance but passing an extra reflector (traveling in a triangle) so it uses different directions? If C is variable, you should get different results between both.
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