Veritasium - 2020-10-31
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 https://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: https://ve42.co/SED For an overview of the one-way speed of light check out the wiki page: https://ve42.co/wiki1way The script was written in consultation with subject matter experts: Prof. Geraint Lewis, University of Sydney https://ve42.co/gfl Prof. Emeritus Allen Janis, University of Pittsburgh Prof. Clifford M. Will, University of Florida https://ve42.co/cmw The stuff that's correct is theirs. Any errors are mine. References: Einstein, A. (1905). On the electrodynamics of moving bodies. Annalen der physik, 17(10), 891-921. (English) https://ve42.co/E1905 (German) https://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. https://ve42.co/Greaves09 Response to Greaves et al. paper — https://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. https://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.) https://ve42.co/janis Will, C. M. (1992). Clock synchronization and isotropy of the one-way speed of light. Physical Review D, 45(2), 403. https://ve42.co/Will92 Zhang, Y. Z. (1995). Test theories of special relativity. General Relativity and Gravitation, 27(5), 475-493. https://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. https://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: https://ve42.co/DoS Henry Reich, Minutephysics: https://ve42.co/MP My Patreon supporters Additional music from https://epidemicsound.com "Observations 2"
If the speed of light was different in different directions, wouldn't we notice odd effects like unexpected variability in Dopler shift measurements on the rotation of extra-solar planets? Or the relative brightness of the same object depending on which leg of the orbit of the earth we happened to be on?
Light moves at 1,080,000,000kmh. The Earth moves around the sun at 107,000kmh. This means that the difference in velocity of the Earth will be in the order of 1% of 1% of c. You're probably right, but the difference will be so small that you'd never be able to tell without sensitive instruments.
If the speed of light is ever proven to be variable, that would have pretty massive implications for astrophysics. Also, what about the speed at which anything in the universe interacts through other forces? I seem to remember we assume all interactions and information travel up to or at the speed of light.
@DraakBlue "Everyone accepts C is a constant" is a more accurate statement than saying everyone "knows". It seems reasonable to me that, since we use C to define every other standard of measurement, and given the importance of C throughout the field of physics, we should devote at least some effort into investigating and verifying its accuracy, and whether or not it changes over time. Avoiding the issue entirely simply because it seems unlikely (and, I have to say, it does seem unlikely) or because it would make things harder for us seems a touch unscientific to me. Leave no stone unturned...
@Dan Kaufman nope if u see someone waving their hand at 1 million light years away their probably dead cause for light to travel that far it will take 1 mil light years so basically ur seeing the past
@Dan Kaufman I didn't see your comment until today, and funnily enough I was thinking along these lines myself and came here to write up some comment about it :)
Maybe C can't be directly measured because it doesn't "exist", so to speak? Through quantum mechanics/relativity we've discovered that there are no discrete objects or locations that have properties or even exist independently, and instead of matter our universe is comprised of phenomena and events, in which everything quite literally only exists and has properties in relation to something else. So perhaps a better way to conceptualize the one-way speed of light is, (currently) "undefinable"..!
The speed of light 100% is variable. Depending on the medium it is going through and if there is mass around. Light moves at different speed through the vacuum of outer space, the atmosphere, and water for example.
@Dan Kaufman if you take the made up measurement of "time" from the equation everything is happening everywhere all at once in one eternal moment.
Would it be possible to sync the clocks using Entangled particles since we know that the information transfer between those particles is faster than light?
Imagine that the speed of light is c/2 in one direction and infinite in the opposite direction. Wouldn't this conflict with observations of extremely far away objects in space? If I can look at the sky in one direction and see it as it is right now and in the other direction very far in the past, I imagine that one half of the night sky would be noticeably different than the other half of the night sky.
Smart
@THT Eneag not future but present
@Aloof Watcher he talks about seeing in the future or in the past
@Name Redacted That would only work if you could get the exact same position for both sensor and mirror for the measurement in the opposite direction.
Given that the earth is spinning, moving around the sun and the solar system moving through the universe, you can never get the exact same point as before unless you measure both at the exact same time...which means using 2 different sensors....which then takes account of the issue raised in the video of how you activate the firing at the exact same time without having an element of time dilation between the sensors.
2 sensors creates the same issues as a 2 way measurement, unfortunately.
Unless we have more data on the real measurement , there is no way we could tell.
This was a very fun present to unwrap. When you called me and told me to turn the camera on I knew something weird was going to happen and you certainly delivered. As long as I’ve known you Derek you’ve been destroying assumptions. Thank you for this friendship. It’s certainly enjoyable from my perspective.
Both you and Derek are my favorite science channels. You both have a way to make it entertaining and even somewhat understandable for a big dunce like myself. I have so much respect for your ways of explaining the worlds mysteries. I've been following you both for the better part of a decade and even though I haven't had the chance to see every video my mind keeps getting challenged and blown away every time. Thank you both for your contributions to my mind and life! <3
Dustin finally broke through the ice with his submarine. ;)
quantum entanglement it can be use?
@Lindorosso if we could send information with these entangled electrons, I wonder if we could ever "know" that entanglement happens at the same moment since al the observations or confirmations would be round trip to transfer the information. All the proofs and experiments about entanglement probably make the same assumption about C being the same in all directions.
I love all of these people. It's sad that they don't introduce more scientists!
What about redshift of far away galaxies? Wouldn't galaxies at one side not have any redshift if the speed was instant? Or at least reduced if it was faster that way?
I like how some random people on the internet sound like, or COULD be smarter than most physicists
I don’t think that’s how it works. That’s just the wavelength of the light, which I don’t believe has anything to do with the speed at which it travels. I could be wrong though.
No, redshifting has to do with the wavelength of light being stretched out as it follows a geodesic trajectory through space/time, rather than a straight line. It changes the visible optical characteristics of the visible light rays, but its not a function of speed. Due to relativity this does not slow the light down, even if the return path is not effected by redshifting.
Doesn't this also raises the option that MAYBE light can reduce and increase its speed while moving in space but in different parts of it due to forces we don't know yet? Or even worse that possibly light may indeed decrease speed after some distance?
Holy cow, that could implement a whole new understanding of our entire universe! It's insane! I'm so glad I watched this video!
Great video. Despite getting a physics degree and teaching physics for years, I never came across this or thought about it. I was treating the video mostly as a 'fun to think about' sort of video, but your point at the end is really intriguing.
true
See my series crushing atheist myths. I proved the big bang wrong, racist macro-evolution wrong, and quandumb wrong. Also: ice ages never existed, dinosaurs never existed.... but you guys don't question what you're taught, almost invariably. I get it... THe truth is not welcome.... to most of you. But maybe one of you cares.
Are you a shill? This puzzle has been circulating for years and it is just as stupid as it was originally. Either c can be affected by external conditions or it can't, but if it can, it certainly can not be altered to the degree indicated in these stupid puzzles.
⚠️ God has said in the Quran:
🔵 { O mankind, worship your Lord, who created you and those before you, that you may become righteous - ( 2:21 )
🔴 [He] who made for you the earth a bed [spread out] and the sky a ceiling and sent down from the sky, rain and brought forth thereby fruits as provision for you. So do not attribute to Allah equals while you know [that there is nothing similar to Him]. ( 2:22 )
🔵 And if you are in doubt about what We have sent down upon Our Servant [Muhammad], then produce a surah the like thereof and call upon your witnesses other than Allah, if you should be truthful. ( 2:23 )
🔴 But if you do not - and you will never be able to - then fear the Fire, whose fuel is men and stones, prepared for the disbelievers.( 2:24 )
🔵 And give good tidings to those who believe and do righteous deeds that they will have gardens [in Paradise] beneath which rivers flow. Whenever they are provided with a provision of fruit therefrom, they will say, "This is what we were provided with before." And it is given to them in likeness. And they will have therein purified spouses, and they will abide therein eternally. ( 2:25 )
⚠️ Quran
damn.
But if the Speed of light would be Infinite in one direction, wouldnt we be able to see the whole universe in that direction and not only the observable universe?
Infinite return speed is only the upper bound (for lack of better terms) of this theory. In fact, it could be argued that away speed is larger (as the whole universe expands faster than the speed of light) and the return speed is lower. If the previous statement is true, then this theory still holds water
Yeah and i guess there would be no speed barrier or time dilation in that direction where the speed is infinite because time slows so that you don't cross the speed of light and if it's infinite, time shouldn't essentially even slow down and we could theoretically go as fast as we want am i right??
I thought the same thing… If the speed of light does travel at different speeds and different directions wouldn't we be able to look at very edge of space and be able to tell a difference in the age of space from one direction to the other? for instance in the direction where light travels instantaneously we would expect the universe to look more developed/old and if we look in the direction of the universe that travels at C/2 would be younger/less developed. Obviously I'm not an astronomer so I don't know what this would look like exactly but would think it would be a big difference.
Ah yes, but what if the difference was relative to you, out from you, back to you? Not in any specific cardinal direction, it's the theory of relativity after all.
the light probably gets more dimm over distance no matter how fast it went. It's even very likely because most sources of light shine in a radial way rather than being focused like a laser.
Some things that come to mind here (not fully thought through):
1. IIRC conservation of angular momentum is a consequence of the isotropy of space. Maybe we could see violations of the conversation law. But I guess, since Einstein pointed out the problem with speed of light, he would have handled this in GRT.
2. Cosmic microwave background. If the speed of light from, say, the left was greater than from the right, woundn't we measure a higher temperature from the left?
3. Objects would seem to be nearer in the direction of higher speed and, intuitively, i'd guess there is some linear dependency in this distortion. OTOH we observe a redshift, which goes by sqrt(c+v)/sqrt(c-v), which would differ from linearity for distant (=faster) objects. That would make Hubble's constant dependent on direction.
4. The avg distance between distant objects (e.g. quasars) would depend on direction.
This was a very interesting concept. A fantastic job done explaining how based off time and relativity there is no way to conclusively tell if the speed of light is a constant. However I think there is a way to definitively prove that the speed of light is or isn't constant. In theory if light were to travel at different speeds it's color would shift. By shooting a specific wavelength and measuring the wavelength returned you can definitively measure the difference (if any) in the speed of light going in both directions.
The ONLY way this would not be true is if time flows at different speeds in different directions. And there is absolutely no way to actually measure that because we and any instruments we can currently use exist within time. There is no way to be an outside observer of time. Yet....
Great thought experiment!
i think that as the light slows down it loses energy by the slowing down itself instead than changing colour maybe? So it could still be asymmetric. Great thought tho!
Some thoughts: A continuous 2- way light interaction carried on from immediate contact to Earth-Mars, both parties carrying clocks synchronized at the starting contact. Fluctuations in speed from Earth gravity/Solar gravity/velocity of Earth around sun/velocity of Mars around Sun/velocity of Solar system around Milky Way/velocity of Milky Way around the Big Bang expansion point ,would be expected ,by me, to be expressed in variations of light speed and clock time. Also, since the one-way speed is not considered to be known since Einstein, why did Einstein incorporate Hubble's one-way frequency change due to the presumed relative velocity differences of distant stars with respect to Earth, into the General Relativity equation, as a reasonable factual conclusion?
Because hubble's preposition was based on doppler effect which can be experimentally conducted in a lab. The core difference here is the frequency of light in itself is a spatial phenomena contrast to the nature of light used for it which infact is the point of debate.
i feel like a caveman here
Light: "My speed is immeasurable, and my time is ruined"
What if the light speed is decreased while travelling, traveling, traveling
@Mailcs06 there have been approximations of the “life expectancy” of a photon. If it does in fact degrade at all, after 100 trillion years, it would have experienced the passage of time. Just on a scale that’s experientially incomprehensible. Second possibility is that if 100 beings are moving at the speed of light they might experience a level of subtly in time that we aren’t aware of it. How much of a difference would it be moving 1/10 of a m/s slower and 1/5 m/s slower. They would likely experience a relative difference. Relative to us, it’s still functionally the speed of light. To them, not so much. Everything we know that is factual, is only approximately and currently so.
We dont know your time tho
corret
I think I did it: If we build a system of communicating vessels of the same size and both within the same distance of a source that pours a fluid in the system at a constant flow the two vessels would fill at the same speed, right? Even if the distance from the source is 1/2 Km. So if we put a reader at each vessel they would read the same level between them at any given time. We program the readers to start a clock when the level reach X and that would happen at the same time in each vessel. Also when the level reaches X one of the readers would activate a lazer, that would stop the other clock when it reached it.
What if you send the light from a clock into a wormhole, and the light gets out from behind you to the same clock? The light would've only travelled one way then right? Practically impossible but theoretically this could work
I had to go through several scenarios in my head to realize how universal the time dilation effect is on this for the speed of light in a vacuum. Like Destin, it's not something I had thought about before and it's really perplexing.
That said, we SHOULD be able to determine that this isn't true of the speed of light in other materials. For example, Cerenkov radiation should be brighter on one side or another if it had a preferred direction. Or Prof. Hau's sodium experiment slowing light to a crawl. With these, relativity is taken out of the equation because we're working below the speed of light in a vacuum but at or above the speed of light in a material. And it is also still relevant because the wavelength is what's being slowed when light passes through a non-vacuum medium.
While that doesn't answer for the speed of light in a vacuum, it should narrow it down. We can rule out the 1/2 C and infinity, for example, since infinity would mean it wouldn't slow down at all going the opposite direction in Prof. Hau's experiment. The slower one makes light in such an experiment, the more it can be narrowed down. The earth didn't sit still while she was running her experiment, so it seems to me we already have an answer to within a fair degree of accuracy.
Obviously, the degree of accuracy still matters and it means your title isn't false, we can't measure it unidirectionally. But I think we've boxed it in to a much tighter range than you mentioned to Destin.
Thoughts on photography of photons moving through a bottle? Effectively faster than light recording (kind of). If light had an odd behavior of speed in one direction, how could we repeat this? We did obviously.
@peacemaker The bottle is a hypothetical. We can't actually do that and as he mentioned, it's still 2-way.
The sodium cloud isn't measuring the speed of light, but it might be used to make bidirectional comparison to bound the range of directionality.
Any time we can't measure directly, the next things to try are induction and bounding.
Interesting. Since we use c to determine the distance of far objects, wouldn't it mean, that objects seem nearer than they are, if the light moves faster from that direction. Since they are actually father away, the intensity of Cerenkov radition would be lower and the effects could cancel out.
@Scotty1701D Nothing we're using c to determine the distance of is close enough for us to see Cerenkov radiation. The parts in a nuclear reactor have known physical sizes.
@Merennulli Right, I only try to find out, if I overlook something, so that it's possible, that you don't see any difference despite different speeds. Maybe it could work.
The intensity of Cerenkov radiation depends on the rate of particles. The emission angle could be influenced by this effect, though.
Would it (theoreticaly) be possible to measure the one-way speed in a loop in curved space-time? As it seems to be a straight line from the perspective of the light?
We should be able to tell differences in the speed of light by directionality by redshift. While this requires us to have another point of reference for distance to the emitter, as long as red-shift is consistent in every direction than speed of light is consistent in relation to the expansion of space-time.
@Ben Weigt \9
@Ben Weigt Well, redshifting is created because light travels through space. And space expands with time. So if it's travelling for a billion years through expanding space, it redshifts a lot. If it travels instantaneously, well, space doesn't expand much at all in that time and so there's almost no redshifting.
I'm sure there's a good reason we can't use redshifting to measure the one-way speed of light, but I can't think of what that reason is.
@Ethan McDonald One problem is just that we tend to use red-shift to measure distance in the first place and cosmic redshift is too small for things in our solar system. We could just as easily be wrong about how far away some stars and galaxies were when they made the light.
@Unreel Namme The relation between redshift and distance was discovered throught cepheids method in the first place actually, and the cepheids method depends on luminosity and not speed of light
@Unreel Namme that would still mean the density of stars would be greater in one direction (since they all appear closer together) so it would still produce an asymmetry in astronomy
If that's true, then how did the Michelson-Morley experiment prove that light doesn't travel through a medium (ether)? After all, they only concluded that there's no ether because light arrived at the same time on the detector. So, in practical terms, I don't understand the difference between light traveling differently depending on the direction and light traveling through a medium.
@Ronald Van kuyk English please!
Or it does not travel at all; when you push one end of a stick the other end moves instantaneously does it not? you do not talk of the movement moving from one end of the stick to the other, and conversely if you push the other end in the opposite direction both ends move simultaneously, and no more does light move.
@Peter Codner Yes, and earth is flat. :-)
No, a transient change in speed propagates with the speed of sound (speed of sound in that specific material), because acceleration (at the far end) requires force, and force requires compression/elongation, and compression/e. requires time at a speed. The speed of sound in construction materials is typically 1...5 km/s.
@Jake Zee , who says I'm taking Derek's word for it? I have studied physics very much in depth, I have a Master's in Mathematics, I have studied GR. I don't watch these videos just because I want to specifically learn new things from them (although I often do, as in the case of this video; that the one-way speed of light is not known was not something I had thought about before), but because good, accessible educational material is hard to find, and I try to seek it out to share with others.
Having said that, it would be nice if you specifically cited even one experiment which provably demonstrates that the one-way speed of light is c, and not merely that the round-trip speed is c. You mention modern technology, but none of that's ability to function is predicated on the one-way speed of light being c. Feel free to cite specific counterexamples if you think what I'm saying is not true; I will be happy to rebut them unless you happen to have found a true counterexample/demonstration, something worthy of a Nobel Prize in Physics.
Wouldn't the observation that far-away galaxies at the edge of the observable universe are similar (as in they are less developed and less spiral-elliptical-shaped) hint towards an equal vacuum speed of light in all directions? Or at least roughly equal speed of light, since galaxies close to us appear more recently developed than far away galaxies, regardless of direction.
The difference in the speed of light in different directions is exactly what the Michaelson-Moreley interferometer experiment measured wasn't it? To the great surprise of the experimenters (who believed that light was a wave in an invisible fluid that the Earth was moving through in one direction) it was the same in all directions. I have personally conducted the experiment and verified the result myself. It makes some assumptions, which are not valid in relativistic physics, which is why the definition is necessary in Einstein's paper, but it does rule out the speed of light being different in different directions in a meaningful way, i.e. any situation where this would be observable to a single observer or a set of observers communicating who are constrained by the laws of physics (i.e with no superluminal communication).
Doesn't M-M (like any other such experiment) measure that the average of the two-way speed of light is constant?
Never thought about light that way before, very intriguing! I have a question though, what if we were to measure the speed of light in a "kind of" round trip that isn't really? Namely, we could use gravity. Since gravity is a straight path on a curved surface, then if that surface is curved just enough, the straight path will loop back on itself, even though it's going in the same direction. Black holes already somewhat do this, but that's a bit dangerous, so if we can theoretically find a way to make light orbit something due to gravity, could we measure its speed in one direction using Einsiten's relativity and non-euclidian geometry?
First of all I don't know.
Theoretically light will orbit a black hole without our help.
Whatever the light will orbit is already a black hole, doesn't matter what it was before.
Light orbiting a black hole is out of our reach, another video on this channel touched that topic.
Most importantly: in order for the light to return to the clock, it would have to follow a path below the path in which it would orbit, so it would not return because of the nature of the black hole/situation, the orbiting path already does not allow escape without interference, only paths above orbit would allow return, but that requires interference with a mirror to reach the clock, the clock is in the blind spot for a returning orbit.
Let me compress my expression: As I see it the (orbital geometry + nature of black hole) situation would not allow that to happen.
Once it has looped back on itself i.e. turned through 180º relative to us it's direction and therefore speed may well have changed. I love the idea of using gravity to return the light, but it's a 2-way measurement.
In Einstein's special theory of relativity, all observers measure the speed of light, c, to be the same. However, this refers to the round-trip speed, where a clock at the origin times the outward and return trip of light reflecting off a distant mirror. Measuring the one-way speed of light is fraught with issues of clock synchronisation, and, as long as the average speed of light remains c, the speeds on the outward and return legs could be different. One objection to this anisotropic speed of light is that views of the distant universe would be different in different directions, especially with regard to the ages of observed objects and the smoothness of the Cosmic Microwave Background. In this paper, we explore this in the Milne universe, the limiting case of a Friedmann-Robertson-Walker universe containing no matter, radiation, or dark energy. Given that this universe is empty, it can be mapped onto flat Minkowski space-time and so can be explored in terms of the one-way speed of light. The conclusion is that the presence of an anisotropic speed of light leads to anisotropic time dilation effects, and hence observers in the Milne universe would be presented with an isotropic view of the distant cosmos.
If the speed of light was different in different directions, wouldn't one side of the universe look younger than another side?
I realise saying "I have decided to assume them true" dose not represent what i was trying to say, I was trying to say I will take them as true for now, until they change, and do belive their are better truths out their and that these "Truths" arent nessisarily true, but true enough for now and our limited understanding.
@Planet Earth After reading my comment again I have added a footnote as i think it was not getting the point across correctly.
I assume them "true" for now... they most likely arent but they are the best we have.
As explained in the video it would still all even out because physics and mathematics do a great job of explaining stuff but also not explaining anything at all at the very same time.
It would, but you wouldnt know if which side is younger or if there's even a difference at all
How exactly do you accurately determine what is a “young” universe compared to an “older” universe?
Hey. I watched this video sometime last year and I was thinking about it. I love the things we can't explain, because they contain a mystery that people try to explain. I am no physicist, but this video got me thinking, too. First of all, I think proving that the Speed of light differs from A to B compared to B to A should not necessarily involve the exact amount it differs. I have two thoughts.
1. Clocks cannot be synchronized, I got that. But the process of synchronization can be exactly repeated. If we set up an experiment to measure the speed of light One way, with "synchronized" clocks, and then in the same set up (with the same synchronization process repeated) the other way. This would not measure the speed of light, but it might show that it travels at different speeds, wouldn't it?
2. Is the latency of other materials (lets say copper cabel) constant from A to B and from B to A? If yes, you could connect the two clocks with that kind of cable. We could measure the latency that comes from copper cable. That latency would be constant from A to B and from B to A? If yes, couldn't we just use that to set up an experiment that measures the speed of light from A to B. As soon the Light hits B an electrical signal travels to A. We see the time and can reduce the time by that "known" latency. Next shoot the light from B to A and measure again with the same set up. Of course this only works, if electrons travel in a constant speed in all directions between the measuring points.
I would love to know your thoughts on this.
How about if you use quantum entanglement to sync the clock since it works instantaneously? Could you then measure it?
@carpballet No. Gravity waves don't travel faster than light.
There's a well-known thought experiment that considers if the sun suddenly dissappear from its location, earth would continue in its orbit for 8 minutes before the gravitational loss would take effect.
@ptviwatcher I am not certain I fully understand, but if I do, then I think this falls apart because the assumption of ~1000.000004293 seconds used to do the calculation is using the two way time to calculate it. So, we don't actually "know" that. That is the point. it comes out in the wash after we try to calculate using our observations.
@Dan Kaufman actually we do! That's the only thing we know: the 2way speed of light. We just don't know the 1 way speed of light.
@Nux Boxen but how would we know of the entanglement is simultaneously, the whole point is that we can't know if two things are happening at the same time.
@marcel helder intuition
If the speed of light is different in different directions then the intensity of the same light source will differ at the 2 different ends. This would be caused since man made light sources are subject to pulses. If the light pulses are faster then the wavelengths would be longer and appear weaker. If they are slower than the frequency will be greater and therefore appear brighter.
Is it possible to know one's own velocity relatively to their starting point without knowing the speed of light? Supposing it is, could we use something like Breakthrough
Starshot to discover whether an object can travel away from Earth at a velocity greater than roundtrip!c?
"So someone has measured the speed of light...or have they?"
Huge Vsauce moment right there
@Shomex Shome You 're remarks are easy and good. But, light travels bringing informations, and as far we know once you break that limit information won't be carried away. From you're perspective classical physic is ok, but quantun physic would have you to be on a superposition to be right or wrong. So unless you can keep your superposition argument collapses.
no we have only tried to gain a poiint of reference ie the >> 299* << just a singular point not a whole
Ha!
without synchronizing the clocks, I think I found out a way of calculating the speed in one way. Please check my comment today.
What's more funny is how people are unaware that speed of light was discovered about 40000 years ago (earliest available writing is 8000 years old). It's in Rig Veda, one of the 4 vedas of sanatan dharm (Hinduism).
Another great video 👍 would it be possible to have a pulse of light reflect off many reflective surfaces at constant distance apart, have a single time clock at one end measuring the frequency of the light relative to the distance between the reflective surfaces and the light sensor, then have another time clock sensor at the reflective surface end of the test that activates when the beam of light has already done a round trip between the measured distance of the original time clock and the known distance of say the 2nd or 3rd reflective surface? It wouldn’t dis prove the infinity light reflection theory’s but could prove the one way speed of light theory or eliminate any light speed loss when bouncing off a surface to the observer.
Would it be possible to use quantum entangled particles to create what would essentially be a single clock (if I'm understanding that principle correctly) that displays the same time at both locations that those particles exist?
I think I can calculate the one way speed of light:
If we build a system of communicating vessels of the same size and both within the same distance of a source that pours a fluid in the system at a constant flow the two vessels would fill at the same speed, right? Even if the distance from the source is 1/2 Km. So if we put a reader at each vessel they would read the same level between them at any given time. We program the readers to start a clock when the level reach X and that would happen at the same time in each vessel. Also when the level reaches X one of the readers would activate a lazer, that would stop the other clock when it reached it.
There is no way to know if both are filling at the same rate, the earth is spherical so the gravity will affect the filling rate, and water needs to push out the air in order to fill the tubes and vessels, the air pressure varies depending on various things and the tubes should not be straigth but follow the earth curvature, but must be at the same distance and affected equally by gravity (I think it would require a perfect shaped and homogeneous surface both on the top and inside the earth, because other things around can affect as they have their own gravity).
Those are so much variables to account for that are not controllable.
The problem is, you cannot use anything other than light to measure the light in a single direction (at least for now I think), but you don't even know if your measurement of speed of light is correct.
Communicating with light. Check mate. Just have them watch each other's clock. USING LIGHT.
10:43 you can do this two times but first one from east to west and second one from south to north. If the two result is same we can find the one way speed of light (If not, we can do this with many directions to see which way light is traveling faster )
well, no, because in order to compare them you would still need to move them together or detect the light coming from them which would mean that you would just get c as a result
My bank uses the same theory, but vice versa. When the money leaves my debit card, it goes really fast. When something is to be repaid, it takes much longer.
They also like to time travel for profit. They'll batch process all of your transactions without a predictable time fence, and make sure the largest deductions are processed first, to get your balance down to zero as quickly as possible, assuming you'll overdraft and they can tack on overdraft fees for each and every smaller transaction thereafter - no matter the order they arrived in the batch. In turn, those in the most dire situations, always suffer the most and in the worst way the bank can possibly make it happen.
I have the greatest idea of all time you know the video said where when earth got mail from mars saying its 12:00 they know it takes 20 minutes so it will be 12:20 but on earth its 12:40 cant we just say it these was send at you in 12:00 so in 20 mins it goes to you and it will be 12:40 for us so put that time. then it will same time in earth as the time said on the clock on mars.
One way measurement, light leaves a galaxy, far, far, away. We measure the frequency and calculate the distance by redshift. We are also measuring the one way speed of light 💡 💡
Bruh 🤣🤣🤣.. u made my day
It goes exactly 301,456,789 m per second
You could set two clocks at the same place in the center of a rotating bar. Then spin the bar sending both clocks at the same speed in the opposite directions until the are a kilometer apart. Then send light from one clock to the next in all 360 degrees of the circle to determine if the one way speed changes based on which direction the light is traveling.
I’ve never taken physics so idk what I’m talking about but could curved spaced time effect how light is measured? Also what if you created a system that measures a beam of light reflecting in essentially a room of mirrors. If you successfully determine the rate/proportion of luminosity lost per transaction, (I assume this wouldn’t be linear) and how long it takes for the light to disappear, couldn’t you determine how many reflections it makes and determine it’s speed from that? You could also modify the values within the system to test if it changes it’s measurement of light speed
1 small problem with the assertion that the round trip time can be variable… There are absolutely no instance in any experimentation where the speed of interactions occur at a different rate. If, in fact, C was variable dependent upon direction, we would be well aware of it after viewing scattering patterns at CERN.
That isn't true though, the results would be identical either way.
What if you had two beams of light that intersect eachother, a clock at the point they'll intersect and two clocks past the point of intersection, then repat this process at a different angle. If light travels the same speed at all angles then both beams of light should take a predictable amount of time between the point of intersection and the end clock.
But how do you measure the time it takes between any pair of clocks, you need to synchronize those clocks first like the video said but that is impossible.
If we try the experiment above, then the time dilation errors between the clocks will cancel out the differences in time when we measure between angles and finally we get the same result as if light speed is the same in every direction.
This channel always makes me feel smarter when I actually have basically learned nothing.
without synchronizing the clocks, I think I found out a way of calculating the speed in one way. Please check my comment today.
Finding out that something is not known IS itself learning, or hopefully at least gaining curiosity for further learning. :)
go to school. this video is very misinformed
@Ujjawal Yadav What's more funny is how people are unaware that speed of light was discovered about 40000 years ago (earliest available writing is 8000 years old). It's in Rig Veda, one of the 4 vedas of sanatan dharm (Hinduism).
@Dhruv Maheshwari that's interesting brother can you provide some proof to back your claim, I'm too lazy to search on my own sorry
Knowing exact speed of light in one direction is important to calculate how distant the object from earth
What prevents you from measuring time from A to B, then from B to A? Synchronize the clocks at point A, spread them, then synchronize them at point B, spread them. Repeat for the second experiment, you should get 4 time results.
If the speed of light in one direction was instantaneous, then wouldn't we not see the CMB in that direction? It's the light scattering from recombination after all, which happened quite a long time ago. In fact, even if it was a significant amount over c without being infinite, we'd probably be able to tell then. When we look at the CMB it is affected by gravitational lensing and is red-shifted by dark energy based on the amount of space it passes through. If it was coming from significantly farther away in one direction, because of a difference in c, we'd also see different lensing and red-shifting from it passing by more mass and through more space.
What if we measure the 3 way speed of light and divide it by 3 to see if the 3 way speed of light is same as the 2 way? If it is the same, it will probably be the same with the one way speed of light.
Its the same problem as 1 way
I will say it's pretty impressive that Einstein realized that this was a significant issue before he started to tackle relativity.
@Michael Frankel Why shouldn't it be?
The paper Derek quotes from is the one where Einstein laid down special relativity for the first time, so it wasn't before he started tackle relativity
@Ophir Averbuch — So that means it was not AFTER he tackled relativity, right? It was part of what he thought about on the way to writing the theory. Thus, "before".
Impressive!! Is there another way to describe that man?
I would like to add that Mr Muller is not right for measurement of speed of light moving in one direction. The speed of light was measured at first, by two astronomers Ole Roemer in 1676 and James Bradley. Both astronomical observations measures the speed of light moving in only one direction. Roemer observes the eclipses of Jupier moon Io, and the observed orbital period of Io is getting slower if the Earth is moving away from Jupiter or getting faster if the Earth is moving closer to Jupiter. Stellar aberration of light observed by James Bradley in 1728, all stars makes a small ellipses during the year in the same direction as Earth orbital movement, clockwise if you look at the North pole. So astronomical observations are available long time ago and the same speed of light in all direction from everywhere is an astronomical observation fact, not a convention.
Love your videos, thanks for the amazingly great work on all of them
Wouldn't this be impossible given you can split light like a wave, To go in whichever direction you'd like? The same sensor will pick up both directions and the round trip would be identical. And if the roundtrip is identical in all directions, it stands to theory of relativity that light has no directional dependent velocity.
What if you captured a 2-way on that high speed camera?
I know the speed itself wouldn't be calculated because of the light having to reach the camera as well, but wouldn't it be a noticeable change in the light on its way back if the speed changed? Certainly if it's faster going back then it would have a pretty drastic visual difference compared to the first light wave with how much light goes back into the camera?
Suppose you have a sufficiently large sphere with sufficiently strong gravity to keep light tied to its surface (slinging around the sphere similar to an accretion disk). Set a clock at some arbitrary point on the sphere, then start it as soon as the light passes through. The clock will stop when the light passes through it, on the same side. Would this not be a plausible way to measure the one way speed of light? Impossible in practice (atleast at our current state), but theoretically possible. Seems too easy, so maybe I'm wrong. Any explanation for why I would be wrong?
Just Some Guy without a Mustache - 2021-04-16
I swear this channel is a gold mine for educational and entertaining content
Mason Dudley / Click Yes Please!! - 2022-05-14
You would say that if one of these videos weren't clickbait, but there is one, pi has broken multiple prisibles in mathmatics such as the eqatoin that makes the number go 4 2 1 infintly, but pi has broken that, using mathmatics, pi has gone over 4 2 and 1 no matter how many times it gets divied, it will break the recurstion.
Droptuned 83 - 2022-05-14
yes
Droptuned 83 - 2022-05-14
yes!
Maximillion - 2022-05-15
why did this so much likes
Adham Hisham - 2022-05-16
ok. i'm seriously asking, how are you everywhere?!