Why No One Has Measured The Speed Of Light

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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"



30 Eki 2020




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Just Some Guy without a Mustache
I swear this channel is a gold mine for educational and entertaining content
peter gibbs
peter gibbs 5 gün önce
Please dont tell me you understand it, as i dont. I watched one about gravity but i was just totally confused.
Rishom Evans
Rishom Evans 8 gün önce
And I swear you're in the comment section of at least 80% of all videos I have watched.
Pigzrulesp 19 gün önce
@Automatiic the real question is why are you watching this on the same day he is
Michael Bariso
Michael Bariso Aylar önce
If the light waves from the sun were 8 minutes and 20 seconds in a past dimension of Einstein's space-time then people on Earth are just imagining the infrared warmth of the sun coming up on the horizon. The communications delay between Earth and Mars is approximately 20 minutes. We're either viewing the light from Mars in the future, Einstein's past dimensions of space-time or in real time, which do you think is more logical? Einstein's relativity is wrong light has no limitation of speed; it cannot be slowed down because it isn't moving. From every vantage point in the universe light is omnidirectional-instantaneously traveling in both directions. Light and electromagnetic waves are independent of each other. According to Einstein's relativity-time dilation's, photos taken of the Earth from the Discovery Space station traveled from the past to the future violating the laws of physics, conservation of energy and common sense. According to Einstein's projectile light particle proton light has a (constant speed) of 186,000 miles per second moving through spacetime, but if light has a (constant speed) then moving clocks cannot run slow through spacetime! :-) If a Big Bang alien astronomer just discovered our Milky Way galaxy and claimed it was 13.8 billion years in a past dimension of Einstein space-time then people on earth won't exist for another 13.8 billion years. The speed of light according to Einstein's relativity is 186,000 miles per second, but according to physics if two mechanical watches were synchronized on earth and one traveled across the universe and back, there would be no difference in time between the mechanical watches proving the speed of light is instantaneous as the only way a mechanical watch will run slow is if you tighten the main spring. Big Bang, Einstein's relativity-time dilation and nearly all of science debunked. Using optical clocks, lasers and GPS to prove Einstein's time dilation-space-time curvature is like using a metal detector to find gold at Fort Knox. The closer you are to the electromagnetic fields, mass and gravity of the earth the more light bends aka gravitational lensing. If the speed of light is constant then past and future dimensions of spacetime and an expanding universe would not be possible, obviously destroying the twins paradox as each twin cannot move faster or slower than the other. A mirror is a wave reflector that flips images from left to right, but according to Einstein the images you see are the result of projectile light particle photons being transported into past and future dimensions of space-time. Explain how particle light photons can re-converge their molecular structures in mirrors and how this is done without violating the law of conservation of energy. From every vantage point in the universe light is omnidirectional-instantaneously traveling in all directions (forwards and backwards through Einstein's space-time) while violating the law of conservation of energy. Explain how Einstein's projectile light particle proton can travel all directions having a (constant speed) of 186,000 miles per second. Einstein would have made a great used car salesman :-). Light waves can stretch, bend-curve and occupy a state of superposition, whereas the hypothetical Einstein projectile light particle (photon), a particle that has never been observed cannot. Unlike a TV or computer monitor the images we are viewing in the universe are in real time, not a series of frames that create the appearance of a moving image. There are no DCU digital convergence circuits in space yet Einstein's disciples believe the light and moving images they see in the universe aren't really there, they're just video recorded images of the past 13.8 billion years. You could lead a cult to water, but you can't make them think. Neither time, energy nor mass can create itself into nothing, reside in nothing or expand into nothing simply because nothing has no properties. Time and space are independent of each other, not material bodies or fantasy unions that magically stretch Time, energy, and matter like a rubber band into space-time dimensions. Einstein's projectile light particle proton has a (constant speed) of 186,000 miles per second moving through spacetime and because so wavelengths of light cannot stretch through spacetime! Red-shifts are simply the result of decelerating electrons, as moving electrons of charged electromagnetic waves-light travel through the plasma of the universe each lump (or "quanta") of energy in the electromagnetic waves are charged then discharged to the next lump, eventually the energy dissipates causing the delay in radio communications giving the appearance of time dilation - longer wavelengths in red shift. Will the James Webb Telescope view the birth of the first galaxies? Nope, the universe goes on to infinity. Neither time, the atom, energy nor mass can create itself into nothing, reside in nothing or expand into nothing simply because nothing has no properties. The James Webb Space Telescope is not a time machine, you can’t travel back in time to view the beginning of the universe with telescopes that were made in the future :-). Light and electromagnetic waves are independent of each other. If science uses Einstein's wrongly theorized speed of light like an odometer to calculate past dimensions of distance and time, then using that same method to calculate forward dimensions of distance and time would mean the Big Bang was created and expanded in the future before time existed. Unlike a television or computer monitor the images we are viewing in the universe are in real time, not a series of still image frames that hypothetical Einstein projectile light particles photons create to give us the appearance of a moving image :-). The speed of electromagnetic wave is 186,282 miles per second vs Einstein's projectile light particle proton at 186,000 miles per second. Is this a coincidence or did Einstein plagiarize yet another phenomenon to fit the math of relativity? Electromagnetic waves in space can neither slow down or speed up, this is consistent with the law of conservation of energy. If light slowed down, its energy would decrease, thereby violating the law of conservation of energy so the speed of light is instantaneous and cannot travel slower than it does. If Einstein's projectile light (particle photon) had mass it's light could not travel across the universe, high speed particles traveling at 186,000 miles per second would break the Hubble and James Webb telescope mirrors, debunking the speed of light, Big Bang, Einstein's relativity and any science that uses relativity in their theories. Everyone knows cell phone electromagnetic radio waves travel both ways, yet Einstein's disciples believe time energy, mass and light can only travel one way back in time. If you simply run the Big Bang theory in reverse you reveal the insanity of Einstein's relativity and Big Bang theory. If the expansion of the Big Bang were true, time, energy, mass and light would be in the future from the vantage point of an expanding singularity-Big Bang and planet Earth would now reside in a past dimension of Einstein's time dilation (moving clocks run slow) space-time 13.8 billion years ago :-). From every vantage point in the universe light is omnidirectional-instantaneously traveling in both directions (forwards and backwards through Einstein's space-time) while violating the law of conservation of energy. Explain how Einstein's projectile light particle proton can travel in both directions having a (constant speed) of 186,000 miles per second :-) It's truly amazing how the science and politics of the left are able to keep people denying reality, there are no DCU digital convergence circuits in space, yet Einstein's disciples believe the light and moving images they see in the universe aren't really there, they're just recorded images of the past 13.8 billion years. Pretending not to notice the gross contradictions-pseudoscience in Relativity is typical of Einstein's disciples, devaluing the source of any information that's in contradiction with their beliefs-theories. You could lead a cult to water, but you can't make them think. If the light from the universe travels to past dimensions of time then it's light is also traveling into future dimensions of time (instantaneously). “And God said, Let there be light: and there was light.” a state of superposition where time and gravity run inwardly, outwardly, in all directions in the same time frame, similar to the electromagnetic field having no beginning and no end. "I am the Alpha and the Omega, the First and the Last, the Beginning and the End" Revelation 22:13. Disciples, remember thy 1st commandment, thou shalt not question thy lawgiver of relativity for blasphemers are the devil's pawn. Let thee not dwell in dissension of our Lord Albert, shun them, drive them back to their jungle lair amen. Albert Einstein, an autistic violinist patent clerk that had access to more papers than Suzanne Somers litter box yet creates theories with more bugs than Terminix- Magnetron
anavan7 Aylar önce
@Automatiic I just got your message at the same time! Wait can we measure this?
apok578 18 gün önce
Wait if the speed of light was different in different directions, wouldn't the universe look to have a different composition when we look at one part of the night sky compared to the other? Since on one side of earth we would see light from long extinct galaxies and on the other side everything we see would be light from galaxies that currently exist?
apok578 18 gün önce
Thought about it for a sec, even if that were the case, since space is expanding, we would literally "run into" the light going in the opposite direction (since it would be moving slower) and like the video states, we wouldn't be able to tell the difference between a constant speed for light or one dependent on direction
RoboNator 5 gün önce
two digital clocks start in the centre both on rails, start the clocks, have them automatically stop when they hit the end of their respective rails, start moving them on the rails driven by the same motor, let them hit the ends and stop, bring them back to the centre, compare values. If what was said in this video is right and the distortion from relativity should match any difference in the speed of light traveling in different directions, then the clocks recording their measured time at the end of their travel which is a constant should accurately measure any temporal distortion.
Finbar S
Finbar S 2 gün önce
Matthew Hill
Matthew Hill Gün önce
To measure the speed of light in different directions. Setup a central device with a photoreceptor and have it record the patterns of light it receives. Have multiple light sources around the central device spaced equidistantly. Have each light source in turn fire an identical pattern of light at the central device's photoreceptor. The patterns recorded centrally will differ if light travels differently.
David Wheeler
David Wheeler 3 gün önce
This is weird! If we imagine two points, A and B, being left and right of each other, and if we postulate that the speed of light is 2C in one direction and instantaneous on return, then what happens if we imagine two points, C and D, in the vertical plane?
Markus Ström
Markus Ström 10 aylar önce
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.
larry zepol
larry zepol Gün önce
🤣🤣🤣 the best comparison to something totally irrelevant to the point I have ever seen. BRAVO!
•potato• Gün önce
Origin 6 gün önce
@Tomasz Gniew yeah. the comment was really funny
Origin 6 gün önce
lmao. you the funniest guy on the internet ty ❤
Wesley Williams
Wesley Williams 9 gün önce
2 BB -2
2 BB -2 3 gün önce
I feel like "A stipulation that I can make of my own free will to arrive at a definition" can be used to explain anything. As long as you come up with the correct answer, or an answer that agrees with whatever the correct way your supposed to solve the problem, it's correct. Even though it's a stipulation that I can make on my own. Basically people can make up their own system of measurement so long as it meets certain criteria and arrives at the same conclusion as a hypothesis or supposition that ended up being correct.
hans kok
hans kok 7 gün önce
I have a question: C figures in many physics formulas, E=MC2 comes to mind, but I have seen more. If C is depending on direction, what would that mean for these formulas? Or, the other way around, if formulas like E=MC2 yield a constant result, wouldn't that indicate that there is only one valid value for C? What would it mean for the yield of an atomic bomb, if C is infinite in one way and half of what we assume in the other direction? It is hard to imagine that something like the yield of an atom bomb depends on the direction of the observer.
Gregory Rovira
Gregory Rovira 7 gün önce
Loved this video! it really makes it clear that certain theories and laws are just assumptions... agreed upon assumptions. Here is another one I'd like to hear about: Nothing can travel faster than the speed of light and speed of light is a constant
ø 5 gün önce
right! idk what to rly trust. we rly don't know everything like they say we do and if im being honest idk how i'm alive on a rock replying to another human on a electronic device. life mane, it's uncomprehndable
Matt Tolea
Matt Tolea 17 gün önce
If the speed is different, then wouldn’t the event horizon of black holes be larger on the side where it is slower?
CGP Grey
CGP Grey Yıl önce
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.
ProTip SkipToEndOfVideoAndReplayForNoAds
@Joseph Burchanowski we shouldn't be worried about anything but finding a way to make the laws of the universe work together. Til then we can't answer anything.
Σά ββας
Σά ββας 18 gün önce
You have a physics degree for years but yet you never questioned the pseudo science evolunist came up with nice
Daigan Bledsoe
Daigan Bledsoe 23 gün önce
Cool to see you here!
C D Aylar önce
The reason you never thought of it, is because it is nonsense click bait. If you were “intrigued” by it, then I feel very sorry for your physics students..
peachierose 2 aylar önce
evrardmusic 3 gün önce
Your theory makes perfect sense. I have been thinking about how light travels to us from stars that are in motion but reaches us as a defined object.
aneesh dubey
aneesh dubey Gün önce
David Osolkowski
David Osolkowski 14 gün önce
Would we have noticed this in astronomy? We can look out from the Earth in all directions and see stars, including very far away stars from earlier times in the universe (because the light has taken so long to reach us). If the speed of light wasn't consistent in all directions, we might see an uneven distribution of red-shifting or star ages--at least enough to tell if an effect is there.
Matthew Reddick
Matthew Reddick 4 gün önce
We’re not in the center of the universe to begin with.
alon shusterman
alon shusterman 6 gün önce
Pavel 9 gün önce
You wouldn't be able to tell the difference. The distance ladder in astronomy is complex and depends on the speed of light. If you don't know c, you won't be able to tell the correct distance. I am wondering if it would rule out the infinity speed. It must mess up the astronomical observations in one direction, b/c we would not be able to see galaxies forming unless they are growing right now. How would such light be affected by the expansion of spacetime? If the difference was small, b/c some hypothetical attractor, for instance 0.98c one way and 1.02c the other way, there is no way it would be noticeable.
Mirosław Kołodziej
Mirosław Kołodziej 13 gün önce
@David Osolkowski No. You just never can tell how old the star is, if you do not know how much is the speed of light in given direction. Becosue it makes impossible then to guess the distance for a given star. Especialy, if let's say speed of light in given direction would depend on how fast is the space expantion in given direction. You would just not be able to make a difference, between stars that are close, but their's light travel slowly, and stars that are very far away, but their light is traveling very fast.
David Osolkowski
David Osolkowski 13 gün önce
@Mirosław Kołodziej if the speed of light is faster in a given direction, when we look back along that direction, on average, we would be seeing older stars, because we're not looking back in time as far (it hasn't taken as long for their light to reach us). Looking at any one given star, you're right that we probably wouldn't be able to tell. But, if we catalog *lots* of stars, we might be able to tell that if we look in one direction, we see stars that are on average older than when we look in another direction.
skelybrinegaming 7 gün önce
I think an interesting thought is that if the speed of light is instantaneous in one direction, then how can we see a limited distance when we look into space? Shouldn’t we see a lot more in one direction than the other?
Santiago Almeida
Santiago Almeida Gün önce
This could be an interesting option 🤔🤔 I saw that lots of people here on the comments end on this exact idea, and it seems no one has proveen it false so...maybe you're right. In any case, I'll think of light like going at the same speed in every direction because it's far more easy
skelybrinegaming 2 gün önce
@Mr_Syncc this comment is kind of a jumbled mess. Although one thing I can point out is that the universe is not expanding faster than light. If it were, we would have stopped existing thousands of years before that due to our molecules not being able to stick together.
Mr_Syncc 3 gün önce
it might be instant but the universe would also be expanding instant in that direction which would cancel the light out so instant needs a new definition now. if light is coming in instant the only way light could be negated would be at a certain point the universe is expanding instant so light would never come in. thats the only way instant light would never been seen. also the universe is expanding faster than light so ig it would have to be faster than instant 2.
skelybrinegaming 3 gün önce
@wtoggled that is a good observation :)
wtoggled 4 gün önce
I've been thinking about this for a few minutes and I thought to myself, "instead of trying to find the speed of light in one direction, why don't we try to find out if the speed of light is the same in all directions or not?" In the video, Derek said that you couldn't measure the speed of light using a high-speed camera. If we were to use a high-speed camera, we would see the light LATER but the delay would be the same throughout the whole journey. If the camera were to be rotated in different directions and light beams were to be observed from those different directions, we could tell whether or not the speed of light is the same in those different directions. For example, if the light is observed 1 second later than the time the light is actually at the "starting point", the light would be observed at the "ending point" 1 second later. Instead of trying to find what the delay would be, we could just see if the light travels faster in different directions since the light would instantaneously be seen at the "ending point"
henningsplace 2 gün önce
I thought this was the whole point of relativity. Imagine an outside observer watching our galaxy fly by. He would see differences in the time that light takes to travel between Earth and Mars, if I'm correct, but we wouldn't be able to notice it. However, the observer wouldn't be able to tell whether we are flying by or he is. Thus, no-one will ever be able to prove or disprove the existence of any kind of absolute coordinate system. As I'm a lay person, please tell me if I'm wrong. In any case, this was probably the best, simple demonstration of it I've seen so far.
SmarterEveryDay Yıl önce
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.
godzilla47111 Aylar önce
@Cédrick Greenoak how do you verify that it's the same time on both devices?
Dan Kaufman
Dan Kaufman 3 aylar önce
@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.
RerikR 4 aylar önce
quantum entanglement it can be use?
Bill A
Bill A 6 aylar önce
Dustin finally broke through the ice with his submarine. ;)
Chas Setterfield
Chas Setterfield 6 gün önce
What about Michelson-Morley, who set out to 'prove' the existence of 'Lumeniferous Aether', by measuring the speed of light [ albeit using interferometers] in the direction of the Earth's travel, & the reverse direction, & transverse to the Earth's direction of motion? They got the same answer in every case. It was one of the elements that lead Einstein to postulate that light speed was independent of the motion of the source, & from there that it was constant.
Chas Setterfield
Chas Setterfield 4 gün önce
The implicit paradox of the Mars communication scenario is the metaphysical notion that light, or E-m radiation, somehow 'knows' where it is going when it leaves the source, & hence at what speed it should travel. If the concept is that there is an underlying 'up' & 'down, 'left & 'right' to space, then the interplanetary communication speeds must vary at differing points around the orbit. It might work out mathematically that the 'there & back' time, & hence average speed would still be constant.
Marc Colten
Marc Colten 4 gün önce
Thank you. Scientists have spent my entire life telling us one thing (light is always going the same speed no matter what) and now we just toss it out and change everything. It's very frustrating.
Jack Brent
Jack Brent 23 gün önce
Question: what if a signal is sent from earth to mars at one orientation, and then scientists wait until mars is oriented the opposite direction to send a return message? That way at the very least the signal is traveling in the same direction?
hemish madala
hemish madala 22 gün önce
@Combustible_lemons i dont get it how could the direction be unknown? his question makes it so that they travel the same direction
Combustible_lemons 22 gün önce
With this theory how is one to tell if light is moving forward and not backwards
Zach Schultz
Zach Schultz Gün önce
What if you use quantum entanglement to trigger the second clock? Since entangled particles react instantaneously, we will have no time delay or any other time dilation issues
rland93's research page
A couple of thought experiments: In your Mars example: could the time taken to pass in one direction be a positive very "slow" value, so it takes say 30s for the signal to travel from Earth to Mars, and then -10s for the signal to travel from Mars to Earth? This would have the same result: the observer on earth sends the signal, the receiver sends it back and reports 12:10 under the Einstein assumption ( even though it's "really" 12:30!) and since it takes -10s for the signal to get back, the observer sees it come back at 12:20? Basically, the question is, is some other part of the GR math somehow constrained to positive values? Another thought experiment: What if the "actual" speed of light changes with respect to space also. Let's say, near earth, the signal travels to mars instantaneously. So the observer sends out his signal, and it gets to some point between the two planets immediately; at which point, some property of space causes the light to instantly "slow down." Then, from the leg from that point to mars, it takes say 10 minutes for the signal to get to Mars. The receiver marks the timestamp, 12:10, and sends a signal back to earth. Now I haven't thought about this too hard, but it's conceivable to me that in the direction pointing at earth, and near Mars, the speed of light could be instantaneous (in this region, but in the opposite direction, it's "slow") and then near earth, it slows down again, and takes 10s to get to the observer. She marks 12:20 and the invariance remains preserved. My intuition is that if there were some vector field like thi for the "slowness," it would need to be conservative, but I haven't really thought it through. Just some things to ponder. Anyway, thanks for the fun video.
Ernst Borse
Ernst Borse 23 gün önce
Hi there, you made me think… Knowing that light is bent by gravity… so photons are attracted by gravity. A ray of light from a distant star takes longer when it goes around the edge of our sun (as observed with eclipses.) Therefor the light of a laser aimed at Mars (or moon), might take longer when it would move against the gravity of the sun. The photons in the return beam might go faster when facing the sun and reach the Earth. The average would still be c. With kind regards of Earnest
deva kumar
deva kumar 25 gün önce
Intresting one
Tejas 26 gün önce
Rigel Yıl önce
Light: "My speed is immeasurable, and my time is ruined"
kevin Kurt talento Tablizo
No! why light speed have no exact measure cuz its instant. instant teleportation speed but its longer version.thats why even camera could not slow it down humans naked eye could not see it down cuz eye will get blind and need some time to procesed it.
ayka ayka
ayka ayka 2 aylar önce
You got me
Thiago Curtis
Thiago Curtis 3 aylar önce
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.
monirhtc 3 aylar önce
Neotrazim YT
Neotrazim YT 3 aylar önce
We dont know your time tho
Yousef Imran
Yousef Imran 19 gün önce
I think the suggestion that the round trip light might have different speeds in each direction is not crazy comprehend. However, (and excuse my ignorance) I don't think it can ever be c/2 in one direction and infinite in the other. Simply because "instant" (As "infinite light speed" was described) means that: 1. Light changes speed based on the distance it needs to reach back (Which seems impossible for my simple mind to comprehend) 2. It also means, that if light can be instant at any distance, that light can be at different locations at the same exact time, which again, seems an impossible suggestion. (Considering what I little know about light) Based on the above, It seems that light speed cannot be c/2 in one direction, and infinite in the other. Respectfully, The none-physicist physicist enthusiast.
Muhammad Nasir
Muhammad Nasir 21 gün önce
Thank you very much for the video. As you said at the beginning of the video, distance is relative to the speed of light and time depending on atomic transition, which means we don't have an absolute value of distance and time. As you said conventional we assume the speed of light to be constant but didn't consider the space-time curvature. Therefore, if we don't assume the speed of light to be constant then we don't know the distance and also the time.
Daniel C
Daniel C 21 gün önce
We actually do, same way as we can calculate absolute zero for temperature, it's not just for "light" but for all electromagnetic waves in a vacuum.
km_1911 19 saatler önce
Unless I missed it, the one thing that was never explained was why the direction would have any effect on light at all. All I heard was that it just could have one. On top of that, space is directionless. Still, great thought-provoking video!
Paul B
Paul B 24 gün önce
I’m 50 and I feel like I have been cheeted, a profound question I didn’t even know excised until I stumbled on your video, I have often thought about the stars at night and the light they produce definitely could be instant, truly mind bending
Atlas Yıl önce
I love when Destin is presented with something he genuinely didn't know/understand before. His face lights up with extreme excitement and intrigue.
boycycy Yıl önce
That moment led me to evaluate my whole existence on whether I could share something interesting enough to impress Destin that much.
Scoobius Maximus
Scoobius Maximus 22 gün önce
So I have an idea, although I assume that there is some physics reason it wouldn't work because it is a relatively simple idea that someone would have already thought of. Set up a laser and a mirror that moves relative to the laser with a known velocity. Shine a laser in a pulse so that the light would intercept the mirror if and only if it is moving at about the speed we expect light to move. If the light is too fast it arrives too early and passes in front of the mirror's location causing it to miss. If the light is too slow it passes behind the mirror and misses. The light intercepting the mirror to be reflected back is dependent on it moving at the predicted speed.
James Jubber
James Jubber 24 gün önce
Could you measure the difference in the directional speed of light by having the trigger in the exact middle of two timers. Send out a start signal, and then a stop signal and then note the difference in time it took for the signal to reach each timer in the respective directions?
Megad 22 gün önce
@Smart gamer 123 but wouldn't we, in that example, know the difference of the speed of light in oposite directions if we just look at the clocks? (in the animation, the difference is 2 seconds for example)
Smart gamer 123
Smart gamer 123 23 gün önce
He mentioned this at 9:47 …
Jeffery Haney
Jeffery Haney 7 gün önce
Something is bothering me about the measurements of the one-way speed of light using the round-trip speed of light. If it's true that the speed of light is a constant regardless of direction, wouldn't you expect the one-way speed of light to change (relative to the observer) depending on the direction of travel? Considering that our observations are not made from stationary object(s)?
CrewRanger Gaming
CrewRanger Gaming 18 gün önce
You could measure the speed of light in one direction with the two clock method, of course relativity affects the speed of the moving clock, but if you can very carefully move the clock at a fixed velocity and calculate the time delay caused by moving the second clock you know exactly how much time you have to add.
Leo Vincii
Leo Vincii 17 gün önce
I think u missed most of the video....if we're unaware of the speed of light in one direction then we cannot use the conventional formula for time dilation because it already assumes that speed of light in any direction is the same....
Karthik Garimella
This was brilliant. Thank you for this. Never stop giving us such videos and theories,etc.
Vivek Balamurugan
Vivek Balamurugan 15 gün önce
New to this page and love all the ideas here.! About this video, can't we calculate relatively? Like thunder and lightning we can start two inputs (one light and other sound) from same start and measure the time taken for both to be received at the other end?
Ngọc Duy Nguyễn
Ngọc Duy Nguyễn 14 gün önce
did you not watch the video? It's impossible to actually synchronize 2 inputs if we assume that light travels at different speed in different directions
sonicx1324 21 gün önce
What if you took advantage of quantum entanglement as the clock to measure the speed of light? Shoot a laser through one of the entangled atoms, then the other atom theoretically changes instantaneously giving you an accurate measurement one way
MrWingedSpirit 17 gün önce
You cannot use quantum entanglement to transfer information. Don't ask me why, but I looked into it once as I thought it would be a way to do faster than light communication in science fiction. Anyway, I would presume the same principle prevents your solution.
Shparky2197 7 gün önce
Ok, I had a really weird thought. You might think that you could determine the one way speed of light by examining what you can see in the CMB. But that's the brain breaking thing. We determine our distance from objects by using the defined one way speed of light, so we could be seeing things at half the distance in one direction, and at infinite distance in the other. Maybe.
HELIFY NOE 22 gün önce
Idea # 2. The Sagnac effect. If light moves at different speeds in different directions, and a a Sagnac interferometer was spinning, would not the interference pattern be inconsistent ? Due to the spinning, the light will have to travel in one direction longer than in the other, thus the differences will cause the interference pattern to be inconstant during the rotations.
zaxmaxlax 11 gün önce
This video was dumb, he never ever mentioned interferometers or the michelson-morley experiment, let alone the sagnac effect.
Shadex Yıl önce
This channel always makes me feel smarter when I actually have basically learned nothing.
Dhruv Maheshwari
Dhruv Maheshwari 3 aylar önce
@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).
Jake Zee
Jake Zee 6 aylar önce
go to school. this video is very misinformed
taxmanXD 7 aylar önce
Finding out that something is not known IS itself learning, or hopefully at least gaining curiosity for further learning. :)
Franklin Dsouza
Franklin Dsouza 10 aylar önce
without synchronizing the clocks, I think I found out a way of calculating the speed in one way. Please check my comment today.
Krish 11 aylar önce
Nothing in the universe can travel at the speed of light, they say, forgetful of the shadow's speed. Howard Nemerov (American poet)
Zboy! 15 gün önce
Probably a bad idea: a giant turntable, with a button, a laser, and a clock that create an equilateral triangle. The button is pressed and tells both the clock to start and the laser to fire using an equal amount of cable. The laser fires down a vacuum tube to the clock, and the time should say the speed of light of the speed of light is equal in all 3 directions. Then turn the turn table 1 degree and repeat until you have measured at all 360 degrees. Would this work?
Adrien McIntire
Adrien McIntire 12 gün önce
This makes me think that the one-way speed of light might be instantaneous!
j s
j s 14 gün önce
could you take a wave mechanical approach ? via c= frequency × wavelength or does that build on that c is known
Angry bull
Angry bull 14 gün önce
Also the Earth is constantly spinning so the direction is changing.
Zboy! 15 gün önce
@-_- thanks, knew it wouldn’t be that easy.
-_- 15 gün önce
This won't because if the speed of light is different then it would take slightly different speeds to reach the clock and the Lazer so the difference would be c
Michael McDermott
Michael McDermott 26 gün önce
If you had a long solid rod extending from the start line to the finish, wouldn't the movement of the ends of that stick be instantaneous? My theory is you could push the rod at one end (at the start line) the moment you release the light, the other end of the rod (at the finish line) would instantaneously start the timer. The moment the light then reaches the finish line the clock (also located at the finish line) would stop. You could then repeat this linear speed test in different directions to see if it varies. Feel free to let me know where this idea falls down theoretically.
Anders Jenbo
Anders Jenbo 10 gün önce
@Tomasz Gniew I don't think you understand how quantum entanglement works, they don't change and you can't see when the wave function collapsed.
Tomasz Gniew
Tomasz Gniew 10 gün önce
It is possible!!! You need to put two split electrons within distance of 299,792,458 meters away from each other. They change straight away if you change one. You change one at the very same time you switch laser on and check on the other side where other electon is placed what is the time from electron change to receiving laser light. So deam simple. Sorry my english is crap, can i get nobel prize now?
Michael McDermott
Michael McDermott 22 gün önce
Appreciate the replies, it seems no known material is up to the task. The speed of sound compression is very interesting, and that it simply comes down to atoms moving atoms at the end of the day. Speed of light limitation seems to win every time - except against the 'spooky action at a distance', which appears to deliberately refuse to work with us in any practical manner.
YY Li 23 gün önce
Einstein use rigid body in introduction of Special relativity, but forget how he do this :(
Anders Jenbo
Anders Jenbo 25 gün önce
It reacts at the speed of sound for the medium. For an iron that would be about 5km/s. So if you had a 5km rod of solid iron it would take 1 second from you push it until the other end moves.
Mike Newbon
Mike Newbon 25 gün önce
Could you use something that has both a visual output (light) and another force that isn't effected by light such as gravity that moves at a predictable speed and then measure the time each take to get to the sensor in multiple directions to see if there is a discrepancy? I get that we probably can't because the events arrive at very different times, or do gravity waves not move at a constant speed? Or do they move at the speed of light 🤔 if we could generate small gravity waves on earth could this allow us to test this?
Jesus Adfasd
Jesus Adfasd 22 gün önce
When this video talk about the speed of light it doesn’t have to do with light. It is more the speed of causality. Gravitational waves travel at the speed of light.
Vaghul Srivallaban
Vaghul Srivallaban 15 gün önce
But wait, I don't know if he already addressed the video, but what if someone looking from Mars is seeing Earth at its present time. while we see Mars with a 20 minute delay? This could change our view of how old other stars, galaxies, etc really are. They could be an infinite amount of years old, depending on where the light travels to instantaneously, and where it takes 2 times the normal time.
John Cookie
John Cookie 13 gün önce
@Nick Barton "both directions" I think that's the logical fallacy here.
Nick Barton
Nick Barton 13 gün önce
@John Cookie Quite but that's the point. We cannot disprove either way by experiment, nor rationalise why it might be constant in both directions or not. Such things are outside our human experience.
John Cookie
John Cookie 13 gün önce
Why should it be like that? What is the difference between the light traveling from Earth to Mars, and the light traveling from Mars to Earth? Why should there be an asymmetry to begin with?
Nick Barton
Nick Barton 14 gün önce
Exactly my comment above.
Varasalvi2 Yıl önce
Your last 3 videos have been absolutely mind blowing. Relativity is such a mind bending subject and you've done such a good job explaining the basic.
Bing H
Bing H 24 gün önce
I'm curious why you can't have the two clock mechanism with 4 parts: 1. a switch 2. the laser 3&4. the clocks Why can't the switch stand in the middle of the clocks and travel the same distance away from both while activating the laser as it starts the clocks? I'm not really well versed in this, so if someone could explain why not, that would be great.
Sir Kain
Sir Kain 18 saatler önce
Can't this be measured with pulsars? They are a one way source of light that can be measured from different locations (6 months apart on an orbit) to sees if there is a difference in timing.
Jimmy Huang
Jimmy Huang 21 gün önce
Let's assume that there is a difference in the speed of light depending on the direction. IMO you can quickly conclude that this difference would be quite small. Reason is if it was large enough, GPS satellites would come crashing to the ground due to misnavigation of said satellites.
Michele C
Michele C 24 gün önce
If we assume that the light has a preferred direction where its speed is infinite and in the opposite direction has speed c/2, wouldn't the cosmic radiation be absent in the preferred direction of the light? Since in that direction we are not looking in the past and the cosmic radiation is light from the past
Lone Hawk
Lone Hawk 21 gün önce
If it were c/2 and infinite in the other direction, then time dilation would only exist in one direction, meaning half of that cosmic radiation is happening right now. Which then implies that half of the universe is in the past relative to us, but the other half is in sync with us. Which raises questions about what “past” and “present” even mean over long distances.
Ben T.
Ben T. Yıl önce
"So someone has measured the speed of light...or have they?" Huge Vsauce moment right there
Dhruv Maheshwari
Dhruv Maheshwari 3 aylar önce
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).
Franklin Dsouza
Franklin Dsouza 10 aylar önce
without synchronizing the clocks, I think I found out a way of calculating the speed in one way. Please check my comment today.
805atnora Fertsera
805atnora Fertsera 10 aylar önce
jamie marsden
jamie marsden 11 aylar önce
no we have only tried to gain a poiint of reference ie the >> 299*
Prince Desirion
Prince Desirion Yıl önce
@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.
RoHei 22 gün önce
Since 2004 I've been thinking much about relativity theory. I'm also convinced our universe is the inside of a black hole. But something else: of course I've also been thinking about the "speed of light" (which is only so in the vacuum!). Couldn't it be it is rather the speed in which an event impacts the surroundings. Since two colliding black holes are too complicated to catch the thought, let's imagine, on object suddenly appears in space. The impact of this object to its surroundings spreads with the "speed of light". When you're a light year away, it takes one year for you to *realize* there is something new. Is it so, that you not just don't know it, or is it so, reality itself arrives there only after one year, *i.e. it does not exist at all until then?* This also sheds a different light on the "edge of the observable universe". Beyond that, the stars are moving away from us faster than the speed of light. According to the Lorenz transformation the solution is "imaginary" when v>c. Are these objects not only not visible, but no longer in our reality?
Nina & Joe Pierce
Nina & Joe Pierce 3 gün önce
what if we sent 2 clocks to mars, then sent one of those clock back to earth, following a very strict path with a very strict speed. We could find the time dilation for the pair of clocks on their way to mars, and we could find the time dilation of the one we sent back to earth. So, if the time dilation is the same number both ways then wouldn't that confirm the one way speed of light or that the speed of light is in fact c in all directions?
Anti alluvion
Anti alluvion 19 gün önce
would quantum entanglement (which is instantaneous) have an answer in these considerations? With highspeed cameras that appear to follow a photon, could they not setup an experiment where a photon is recorded traveling a very short distance to a mirror and back? a third party view. How does this also affect the dual slit experiment? If you're "measuring" anything moving at light speed and measuring those results, would that impact the interpretation of the dual slit experiment? Many of those experiments would have the same issue of measuring the one way signal versus reflected signals. To a degree, suggesting that nothing involving light speed can provide observable results.
Masks 8 gün önce
@GOOGLY but it dosent need to we just need to mesure the time in between the signals the signals could phistical objects like rockets so if A sends the signal and B reseves it 1 second later the "signals" will arive at C with 1 second between them (it could take the signal a day or more to reach C) but it dose not mater beacose we just need to mesure the time between the signals
GOOGLY 8 gün önce
@Masks it cannot be possible that signal would reach past the reflection as according to the Special Theory of Relativity no one can exceed the speed of light.
GOOGLY 8 gün önce
@Anti alluvion yes thats a possibility as q entanglement itself is very fast and cant exceed c how can we measure entanglement speed😅
Tomasz Gniew
Tomasz Gniew 8 gün önce
@Yantan4 lol I will try translator tomorrow. Imagine trying to understand quantum mechanics not knowing English well 😂 thank you very much for the answer, I will try to digest it 2morrow 👍
Yantan4 8 gün önce
Quantum entanglement also occurred to me as a possible solution. Unfortunately, I think working on a sub-atomic level wouldn't work, as due to Heisenberg's uncertainty principle, when it comes to sub-atomic things, due to the wave-particle duality of any potential particles to be used, we couldn't measure both the location, at the same time as the speed, as measuring the location means treating it as a particle, which is static in space, while measuring the speed means measuring the wave properties, which means it is not in a fixed spot. This means we wouldn't be able to measure the speed.
Nathan Dudash
Nathan Dudash 16 saatler önce
What if you use the exact same “Mars with Mark” experiment, but after synchronizing the clocks in a way both parties agree to be correct, Mark returns to Earth with his clock and they compare. Sure the trip would take a long time, but am I missing anything? It seems like it would be measurable at that point, at least the radio wave speed would be.
Spencer Wiltse
Spencer Wiltse Yıl önce
I absolutely love when people can take something ordinary and make us step back and see how much we don't actually know! Even if you can't confirm or prove the knew idea. The greatest discoveries are made when people are willing to challenge the status quo. Thanks for another amazing video
TheSkystrider Yıl önce
Measuring the speed of light doesn't seem ordinary to me even if it's the same in all directions.
barlowike 98
barlowike 98 13 gün önce
How did I not find this channel sooner? You've planted so many new thoughts in my head that my brain will be forced to expand! Thanks!
ewallt 23 gün önce
What comes to my mind is having a third observer in many different locations. That is, instead of synching the clocks with each other, you sync both of them with a third party. There can be a million different locations for the third party. It’s theoretically possible that all million of them have different speeds in different directions, so it’s not a rigorous proof, but you can make the idea that they have different speeds seem absurd.
Sid1138 15 gün önce
@Scott ShadowR. three (or more) would not make sense unless light speed is different in different directions. Then, multiple sources would give you the directional variance, which would allow the sites to synch
Scott ShadowR.
Scott ShadowR. 16 gün önce
@Sid1138 wait fr? dayum okay
Sid1138 22 gün önce
@ewalt - excellent proof, and this is exactly what GPS does - uses millions of third-party systems spread around the world.
Scott ShadowR.
Scott ShadowR. 22 gün önce
if the two clocks are in sync with the third party then they are in sync with each other what difference would a third synced party make?
Eonwulf 21 gün önce
What if you bounced light in a triangular pattern to get back to the clock instead of just back and forth? If light moving in 3 different directions still comes back to expected results then I would say that direction doesn't matter and light always moves the same speed.
Tmpqtyu Tmpqty
Tmpqtyu Tmpqty 8 gün önce
There is no "expected result", The result is the same but the conclusion from it can differ.
Eonwulf 19 gün önce
@mdoerkse ok
mdoerkse 19 gün önce
@Eonwulf what difference does it make what shape the spool is? You are not thinking straight. Also, what do you mean if it ended at a different point?? If your starting and ending points are at different places then you would have to synchronize their clocks and that issue was also discussed in the video. I don't think you understood the video and that is why you don't see the problem.
Eonwulf 19 gün önce
@mdoerkse I think a spool would work as well if it ended at a different point than it started. I think the reason they denied it was because he assumed every tangent on the spool had an equal an opposite tangent on the opposite end of the spool. But this assumes the spool is perfectly circular. Honestly I don't think this problem is as deep as he wants us to believe it is, nor is it actually a problem.
MUSA 10 gün önce
I find it difficult to grasp the speed of light being instantaneous in any situation. Anything that goes from point A to B has to take time. Instantaneous travel would be the breakthrough to telepotation
Sublime TV
Sublime TV 9 gün önce
This makes sense. The speed of light is the fastest known thing in human existence. Mars, on average, is 225 billion meters away from Earth. As you stated, the speed of light still needs time to travel, which is known to be 299 million meters per second. This might be the speed for a two-way trip, but let's assume it's one-way. So if you divide those numbers, on average it should take 12 minutes for light to travel from Earth to Mars. I think the video goes a bit deeper than that though, since time and physics don't always move in a straight line or align with what we currently know. Other factors, such as forces (like gravity), the distance of the planets at any given time, and light bouncing through objects can delay or construe the actual time it takes to go from point A to B. So his argument isn't that light doesn't require any time to travel back; when he says "instantaneously" he means that it's so fast that we mortal humans cannot perceive the fractions of milliseconds it could take for the light to return to Earth. So it's still possible that light can travel at different speeds, but we might not be sure how or why that would be caused. Definitely a fascinating topic.
Crowbars2 3 aylar önce
If the speed of light was different in different directions, wouldn't one side of the universe look younger than another side?
Francis Smart
Francis Smart 2 aylar önce
​@Catfish Billy 3.7 There are ways to determine relative amounts of energy by different star types. Stars which are older tend to collapse into white dwarfs or supernova while some smaller stars known as white dwarfs can burn for much longer. I would expect an older "direction" of the universe to have more of these types on being observed. You might also expect that one direction of the universe (that with faster light speeds) would have less constant microwave background due to more CMB being redshifted out of detectable spectrums
Catfish Billy 3.7
Catfish Billy 3.7 2 aylar önce
How exactly do you accurately determine what is a “young” universe compared to an “older” universe?
RGXYZ 123 3 aylar önce
It would, but you wouldnt know if which side is younger or if there's even a difference at all
Zach Ward
Zach Ward 3 aylar önce
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.
Undercoft 3 aylar önce
@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.
Erik Lewis
Erik Lewis Gün önce
Would the speed of light affect the perceived color of the light? And could you expect a Doppler effect from a stationary object when its position is moved to the opposite side of the observer, much like star color is affected by how quickly it is moving either toward or away from us? Like a Doppler effect between relatively stationary objects? Or is wavelength on an entirely different scale and unrelated to the speed of light?
pedro Nonofyourbusiness
Here is a question .... after having watched you video again (and I am one that constantly points out that many theories are questionable due to being built on other theories) But what if we use 4 points .... not in line, but a 'square on point / diamond' .... so that shift might be detectable as logic says differences would have to be created by other influences and creating tangents and by your presented theory signals sent to 3rd base and then to 2nd and signals to first and then to second should show up at second base at ether the same or at different times
Colton Vine
Colton Vine 20 gün önce
Question, if you technically were already on mars and keeping track of the time you could measure that message being sent if he logs the exact time he sent the message out back to mission control versus them just sending it thinking it takes 20 minutes both ways it is or should be definable
Sleep Gün önce
Well moving clocks tick slower, and how did the guy reach mars? Well, rockets.
Xeverous 16 gün önce
Doesn't matter because if at any point one side wanted to reply result to the other, it would involve a roundtrip.
Sean 4 gün önce
Does entanglement help solve this? From what I understand, entangled particles move simultaneously at a distance. Then we can measure light in a single direction by measuring “from particle” and “to partial” sending and receiving light.
Noah Friedman
Noah Friedman Yıl önce
If the speed of light were not the same in every direction, then wouldn't the cosmos look very different in different parts of the sky? For instance we would look in one direction and see early quasars and a warmer cosmic microwave background, and in the other direction see nothing but red dwarfs. Of course, the universe might not be isotropic, but if it isn't then we have bigger theoretical problems.
frootloop edibles
frootloop edibles 3 aylar önce
Exactly what I was thinking; though I think that only rules out extremes in the difference of one way c, right? It could still vary by just a smidge, I guess. Since the CMB we observe is fairly homogeneous, I feel like that would have to mean c is, too.
Noah Friedman
Noah Friedman 6 aylar önce
@Ripcord I don't think anyone really believes the speed of light differs in different directions, but Relativity implies there's no way to prove that, unlike in a Newtonian universe where time is absolute everywhere. In a relativistic universe, I think the combination of expansion and isotropism provide good empirical evidence but there's no local experiment you can perform. And if the universe turns out not to be as isotropic as we think it is, that makes the case even weaker.
Jake Zee
Jake Zee 6 aylar önce
@Thomas Horne you miss the major problem with the theory. The universe is expanding in all directions evenly (based on our perception). If light travelled differently in different directions that would mean catastrophic things for the universe, and would make the problem of what the universe really is a lot more complicated than it already is. Because you are basically saying, "no the universe doesn't look like it's expanding because the amount of light reaching us is equal on all sides, it looks like it's expanding because it literally is magically expanding." Just think about how dumb that sounds and try to still believe what this video is saying. Take some advice from a photonics graduate. The guy couldn't be more misinformed. If you are genuinely curious go study photonics too.
Jake Zee
Jake Zee 6 aylar önce
@Siddhant Kanoi no, they can't elaborate because they didn't think before they commented.
Andy Hengst
Andy Hengst 7 aylar önce
We don't know anything first-hand about the distant universe. We also don't know, with certainty, the behaviour of light that is a million years old. Maybe we need to get a distant probe to get closer (or farther) from the gravity-lensed supernova that we expect to see again in a few months? years?... and take measurements. Unless we can't synchronize our clocks. Uh oh.
426simon Gün önce
So what if your timers were quantum entangled, reaching the target changes state of quantum particle which instantly changes the entangled particle at the transmitter, so giving a one way speed. Yes there are measurement issues, but… This lead to this thought, what if observing the light, transmission etc causes an entanglement that means the return journey is instant?
HolyWizard 2 gün önce
What if we measure simultaniously several 3 ways of light and see if they are equal? (using 2 mirrors spaced by 1km each and spaced from the time by 1km and repeating this in several directions)
GenghisN7 11 gün önce
So, I have a thought. Let's start with a pipe in which we know the exact air pressure. On each end is something to send light and a device that detects light, as well as a clock. Light travels from one end to the other and activates the detector. The detector creates an incredibly loud sound (at an exact frequency) that travels from one end to the other and stops the clock. Since we know the exact speed that sound took to travel the distance of the pipe, we know exactly how much time it took (v=d/t, t=d/v). Subtract that time from whatever is shown on the clock, and you have the one-way speed of light. You can repeat this the other way as well. If light truly is instant one way, then when you subtract the time it takes for sound to travel the the pipe, the answer should be zero. This, however, doesn't rule out the possibility that light is instantaneous one way in a vacuum, but its the best I could think of.
Tmpqtyu Tmpqty
Tmpqtyu Tmpqty 8 gün önce
You can't tell the time from when the detector was hit to the time it sent the signal
Arghore 3 gün önce
When talking about Earth to Mars and back, there is reason to suggest the round trip speeds are NOT equal (given Earth and Mars are at a straight line seen from the sun as center). Mainly because on the trip from Earth to Mars, the light has to travel against the gravitation of the Sun and Earth and may be slowed down (and is again somewhat accelerated by the gravity of Mars), the other way around the opposite may happens; light may be slowed down as it leaves mars's gravitational field, and is then may be accelerated by the gravitation of the sun and furthermore by the gravity of the earth once it reaches is field of influence. We know this is the case (even at the molecular level - a few molecules more or less changes the redshift) because we can measure the red and blue shift of the signals. What we can not measure though, is whether besides the red/blue shifting the ACTUAL SPEED of the light also changes... PS. IMO this has no effect on the moment 'NOW' which i postulate is the same all across the universe as a property of the 0th dimension, that of time... Because we have to acknowledge that our perception of time is mainly defined by clocks and our eyes. The speed of light may have nothing to do with the speed of time... aka. our observational bias is NOT equal to the passage of actual time (if it even does).
Andreas Meyer
Andreas Meyer Yıl önce
When we look at the stars, we look back in time (at least if c is isotropically constant as usually assumed). The furthest look we can have is to observe the microwave background, isn't it? And as it changes smoothly the speed of light should change continously depending on the direction. Moreover, if we assume c is infinite for a particular direction, we should therefore be able to see indefinetly far into the universe and thus indefinelty much galaxies. So, if we compare the galaxies visible in different regions of the sky, we should be able to estimate an upper limit for deviations from an isotropically constant speed of light?
hweirdo Yıl önce
@hedare Many people make this mistake. Redshift has nothing to do with how fast light travels; it only depends on distance traveled.
Nocare Yıl önce
@Science Revolution general relativity is wrong for only one reason. It doesn't work in conjunction with quantum mechanics. Everythng else it predicts holds as it produces accurate predictions. Let's see all the math you have to make accurate predictions on your model. You have nothing but supposition and logical fallacies. Give me the math for the relativistic correction factor of gps satellites then. Cause according to your view we don't need one.
bob roberts
bob roberts Yıl önce
Question? Is there such a thing as the speed of dark? In principle, shadows can move faster than the speed of light. ... If the shadow is large enough, it could move across the surface faster than light. This is an illusion that light travels faster than the speed of darkness since darkness is all around the light and it is still agreed that no physical object can travel faster - since light and darkness has no mass. Hey, how do you find a blind man on a nude beach? youu know, it's not hard. The scientists of today think deeply instead of clearly. One must be sane to think clearly, but one can think deeply and be quite insane. If you want to find the secrets of the universe, think in terms of energy, frequency, and vibration. Today’s scientists have substituted mathematics for experiments, and they wander off through equation after equation and eventually build a structure which has no relation to reality. If we only knew the magnificence of the 3, 6, and 9, then we would have the key to the universe and the understanding to view the model were in. But to believe in Space - The Impossible Frontier! That's not a blind man, it is just too hard.love this channel. Space - The Impossible Frontier! trvid.com/video/video-VFEdPCJTwSs.html
blengi Yıl önce
@Nocare Awesome, double shift enter!! Thanks for making me think for the first time in years lol and good luck with your ambitions in global robot domination :)
Arick Reifenstal
Arick Reifenstal Gün önce
light are like particles, the travel it takes varies from its source and vice versa when it comes back. imagine an object traveling with the wind it will go faster, against the wind it will be slower. even in a vacuum of space there will always be variables, even light itself has different spectrum different wavelengths.
Will Ans
Will Ans 23 saatler önce
Triangle. Fire two lightbeams at the same time. One towards the receptor, which starts the timer. The secound beam goes towards a mirror, which reflects the light towards the same receptor, which pauses the timer. This way the light travels in 3 different directions. This does not tell you how fast light moves, but if you do the math, you either see irregularities in the calculated time the second beam SHOULD have took to arrive according to "c" - or you dont.
Marshgray 22 gün önce
If light speed is effected by direction, wouldn't that mean the edge of the universe would be highly skewed in one or more directions compared to others, Giving it an odd shape?
Robert Strawser
Robert Strawser 4 gün önce
I think the point is just that we can’t actually measure the speed of light, one way, in a controlled experiment. The problem with light having varying speeds is that now you need to assign it a preferred direction. Obviously light traveling towards us is not traveling instantaneously because we can still see the CMB. There is obviously a speed limit on the “one-way” trip. I could see an argument that light has a finite speed on the trip out in that it is establishing some sort of wave-function/connection to another object. Once that connection is established the emitting particle and absorbing particle experience a form of quantum entanglement that allows the return trip to be instantaneous. I feel like, at some level, this might somehow break the rules of causality. Any particle physicists out there that can answer this?
Doctor Fate
Doctor Fate 18 gün önce
James McClelland
James McClelland 19 gün önce
Why would it be linked to the direction instead of gravitational density. Really just got to look into Loop Quantum Gravity for this one
Brian Anderson
Brian Anderson 21 gün önce
I agree. I’m not an expert but I know we measure the expansion of the universe using red shift and it relies on c being the same in all directions. The observation is that the universe is expanding at the same rate in all directions. So, seems to me that the only alternative here is that the universe would need to be super duper lopsided in order for these observations to be as they are and light to travel faster in once direction. For my part, I think it’s obvious that c is the same is all directions if you are using distant light sources like stars. But what I’m now convinced you can’t do is design a local experiment to measure the one way speed.
Joshua D
Joshua D 19 gün önce
Wow, great video! My brain is buzzing right now. What if instead of 2 clocks, you just had 1 clock placed directly in the center of 2 censors a meter apart from each other, with a wire leading to each sensor that is exactly the same length (1/2 meter each)? I have a feeling the answer is going to be that you still can’t be certain the signal traveling from each sensor takes the same exact amount of time to reach the clock…
Kodi Howard
Kodi Howard Gün önce
Still wouldn't work.
Garance A Drosehn
I will say it's pretty impressive that Einstein realized that this was a significant issue before he started to tackle relativity.
Ognyan Gerasimov
Ognyan Gerasimov Yıl önce
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.
Pratik Ray
Pratik Ray Yıl önce
Impressive!! Is there another way to describe that man?
Garance A Drosehn
@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".
Ophir Averbuch
Ophir Averbuch Yıl önce
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
J J Yıl önce
@Michael Frankel Why shouldn't it be?
The Armed DIYer
The Armed DIYer Gün önce
I like the idea to measure the speed of light with fiber optics and I would consider that a 1 way trip HOWEVER 😂 the problem is assuming the fiber doesn't provide some resistance. The (theory) of the speed of light is "measured" in a vacuum...
Enric Ruche
Enric Ruche 23 gün önce
I believe that it is possible to measure the speed of light in one direction, if we use quantum entanglement we would only need a clock to make the measurement in any direction. If you change the spin when the light beam leaves the source, this can trigger the start of the timer at the destination instantly, now you just have to stop the timer when the light beam arrives. In theory this can be done.
Leo 10 gün önce
@Enric Ruche His paper was about an update to bells inequality which does prove(to some degree) that fact that the collapse of an entangled state is instantaneous. However, you are unable to communicate any information faster than the speed of light with entangled particles. The simplest way I can explain why you cannot transmit information is that you cannot know if you collapsed the wave function or if your partner did.
Enric Ruche
Enric Ruche 18 gün önce
@manank patel The existence of two clocks in different locations makes it impossible to measure the speed of light in the same direction. The synchronism should be provided by quantum entanglement in a single clock.
manank patel
manank patel 18 gün önce
maybe If they put 2 synchronized clocks that track current time maybe some sort of atomic clocks, and upon light entering and exiting they note timestamps and then subtract value registered at start point from end point they can find time of light, and same can be measured in round trip to check whether light's speed is different in both directions or not.
Enric Ruche
Enric Ruche 22 gün önce
@Jesus Adfasd In 2015, Professor Ronald Hanson of the Technical University of Delft (Holland) could experimentally verify the spooky action to which Einstein referred. In the different articles that I have read they talk about instantaneous communication or communication superior to the speed of light. A similar experiment was also done from space. I am not a physicist, my knowledge is limited and engineering is not my field. Thanks for answering
Jesus Adfasd
Jesus Adfasd 22 gün önce
That’s not how entanglement works. You can’t alter the spin and modify the other instantaneously doing so will violate relativity. You can only measure one and you know the others participle spin .
asher cabral
asher cabral 25 gün önce
start the clocks in the middle at the same time, have them move apart at the same pace in the same vacuum environment. Have the clocks when they reach a certain distance away. If the clocks have the same time then the speed of light is the same in both of those directions, if they are different, then you know the speed of light is different in those two directions. @veritasium
Finn Kelln
Finn Kelln 2 gün önce
Simple solution to measure the speed of light (though we don’t have the technology for it today) is to look to another of Einstein’s theories: the wormhole. Now try looking into that for some mind-bending science! 😁
feedmyintellect Yıl önce
Thank you for putting a camera on Destin when you had this conversation with him. I wanted to see his pondering/puzzled face so much! 😁😁😁
Just A Man of Culture
We* wanted
Kieran Curtis
Kieran Curtis 4 gün önce
take two timers set to start by a certain time down to the millisecond. have one shoot a laser and one to receive the laser. when the time hits, both timers will start and one will light the laser. when the light is received by the second timer, it stops. that's my theory on how to measure the one way speed of light.
Isak Kilkki
Isak Kilkki 2 gün önce
I was thinking a camera with a huge amount of frames per second and star with a planet blocking it for a bit, if you know how far away it is you can start the clock and the moment light gets picked up you can stop the camera and see how long it took after the planetary body moves out of the way, and do it the other ways too as you can just multiply both numbers up to match the other numbers and see if it’s the same
Owen Keegan
Owen Keegan 5 gün önce
What if the speed from the source and the speed back from the mirror are both instantaneous, but the delay (eg, “speed of light”) is caused by the time it takes for the electrons in the mirror to release the photons?
Nihal Rissane
Nihal Rissane 3 gün önce
10:40 well how about you do that but instead of sending a laser beem right away, you compare the number on both clocks which allows you to get by how much one is faster than the other. With that number in mind you can just readjust the value of c and everything works out, doesn’t it?
Humulator 2 gün önce
heres a idea:put a camera on mars and earth then compare them after, if its different, on both cameras the other camera would see a different thing at the same time, im unsure if you could measure it like this but you would know if its different.
Nihal Rissane
Nihal Rissane 3 gün önce
@Alexandru David wow im officially mind f!ucked🤯. God this is interesting though
Alexandru David
Alexandru David 3 gün önce
There is no way to start the belt moving on the far away side before the light reaches it. Even if you pulled the belt from where the laser starts at the same time, the end part would only start moving after the beam reaches it. This is because movement is propagated at a speed, it's not instantaneous just because we consider the moved item a solid. For example, if you had a straight stick long one light year and you pushed it from one end, the other end would only start moving after one year (or more). If there was a way to move items far away faster than the speed of light, there would be ways to comunicate information faster than light (and we still don't think there is a way).
Nihal Rissane
Nihal Rissane 3 gün önce
@Alexandru David i thought about another contraption. It starts with a laser beam at one end. To that laser beam a mechanical belt is attached with photographic paper. The belt and the laser beam started working exactly at the same time since they are one next to the other. The belt does sort of a long “n” shape to cut the laser beam 1km later. So basically, you start the machine, the laser beam shoots light and the photographic paper at the other end ( tip of the “n”) starts moving. The second the light reaches that 1km, its gonna stain the paper. With, the speed of the photographic paper belt and the distance on the belt between the moment it started moving and the light stain, you can calculate the time it took. The time wont be influenced by distance since the belt goes all the way down next to the laser beam. Now you have the time and the distance = SPEED!! If it’s unclear, let me know, i tried to phrase it the best i could😅
Alexandru David
Alexandru David 3 gün önce
There is no way to compare the number on the clocks without the comparison being influenced by speed of light. For example, if by "compare" you mean watch the display of both clocks, remember that watching things means waiting for the light emitted (or reflected) by the things to reach your eyes. Light that could travel at different speed and reach your eyes with different "delay".
Jack Hagerty
Jack Hagerty Yıl önce
Dude! Your cinematography is killer! The shots of you on top of that hill with the Belt of Venus visible in the sky was positively cinematic!
Strange Man
Strange Man 8 aylar önce
If using not 2 timers, but 3 timers. Possible to get real speed)))
Adarsh Venkateswaran
@Yolo 2.0 This should be fun.
The Sceptic
The Sceptic 13 gün önce
THANK YOU! I learned something that I had had never thought about!
MysteryMatt 7 gün önce
can something be done with.... synchronization of metronomes? its interesting how if two metronomes or something of that matter are put on the same beam or object, the metronomes eventually become synchronized.
Nikolay Myastkovskiy
Can you measure the one way speed of light by using some kind of clock that used engagement particle mechanism. This mechanism would hit a particle at the end of the light path and stop the clock on the other end.
Munch KING
Munch KING 23 gün önce
5:12 You're also assuming an astronaut that can instantly process your message and craft a reply with no down time. :D 5:50 Well the "faster one way through space-time" seems like it would be easy enough to test. Just rotate your laser-apparatus after each test and notice any discrepancies. I know it's more difficult to adjust for stuff on a cosmic scale, but if light flew faster relative to planetary north for example, that testing East-west would be slower than North-South. I would assume that the very fact that light seems to have a consistent speed relative to all our testing instruments despite the fact that we are on a rapidly spinning ball that is itself rapidly flying through space indicates that any greater cosmic variance would be either negligible or big enough to cover our range of testing, I.E our entire solar system.
Munch KING
Munch KING 22 gün önce
And in case anyone thinks that first bit is me just picking apart the metaphor, it's actually an interesting aspect of the thought experiment. If mirror added some imperceptible to the human eyes amount of delay to the equation, we might not know that, because we only measure the speed of light two-way, we can't actually measure the speed of light as it goes to the mirror.
Vitor143 Yıl önce
I love that all these guys are friends and all they care about is figuring stuff out, learning and showing us.
jayspeidell 3 aylar önce
He should have called a quantum physics TRvidr like Matt O'Doud.
James Barnett
James Barnett 11 aylar önce
Maybe the real speed of light is the friends we meet along the way
Sonja Schellevis
Sonja Schellevis Yıl önce
@nik sullivan hahahaha lol
nik sullivan
nik sullivan Yıl önce
@Sonja Schellevis yeaaaa delete your comment and then play victim, ok
The Fiscally Logical Social Humanist
What if you had like 8 synchronized clocks go off in 8 different directions for one 3 seconds but all at different speeds then come back. So you have 4 pairs going in 4 different directions all at different speeds for the same amount of time from the center so they all have traveled 8 different distances. Compare all the clocks?
Pedro Romero
Pedro Romero 3 gün önce
My question would be, which is the preferred direction? (Where light travels faster) if such direction is defined with respect to one observer, which direction would be the corresponding one for the other observer? In other words, if life goes faster from earth to mars than vice versa, what happens when the two planets are in the opposite direction respect to one another? There can’t be a preferred direction for light in the universe, for it will be a different direction for each observer, and it would change all the time, as we are all moving in one direction or another. Also, what about light traveling in a direction orthogonal to the “preferred” direction? It doesn’t make sense to me.
Dman1791 16 gün önce
If it were instant in one direction and c/2 in the other, would we not be able to tell based on astronomical observations? Given how much the universe has evolved over time, I imagine that we would be seeing very different things in one hemisphere of the sky versus the other, since we would see one side as being vastly older than the other.
Pavel 9 gün önce
You wouldn't be able to tell the difference, I think. The distance ladder in astronomy is complex and depends on the speed of light. If you don't know c, how would you be able to tell the correct distance? I am wondering if it rules out the infinity speed? This must mess up the astronomical observations in one direction, b/c we would not be able to see galaxies forming unless they are growing right now. If the difference was small, for instance 0.98c and 1.02c, there is no way it would be noticeable.
Biach Piach
Biach Piach 14 gün önce
or the light wraps so you see same thing from different times
Tobias Toader
Tobias Toader 15 gün önce
I was thinking of something similar. If it were instant in one direction and c/2 in the other, the universe being 13.8 billion years old shouldn’t we see just 6.9 billion light years in one direction and infinitely in the other?
birdsinacage 26 gün önce
In quantum physics the concept of entanglement when two particles that were together are separated by an infinite distance a change on one particle instantly affects the same change on the other. How do they know that?
Giovanni Mazzolo
Giovanni Mazzolo Yıl önce
Couldn't we be able to tell by observing the universe? This is what I thought about but I can't get my head around an answer: Just like Derek mentioned in the video, if light traveled at c/2 in one direction and instantaneous in the other when sending the signal to Mars, then wouldn't we be able to see mayor discrepancies on the age of the universe and how the universe looks? Astrophysicists have been able to observe very far into space, being able to observe very young celestial formations. Like seeing what the universe looked like at younger stages. If light traveled at c, then we would be able to see similar formations and celestial bodies all around at similar distances. But if light does really does travel at speeds depending on the orientation (instantaneous on a specific direction), then wouldn't we be able to observe that certain parts of the universe look significantly older that others? Meaning that there are close to no signs of early celestial formation on one general direction and many on the opposite general direction?
Hyrum Hammon
Hyrum Hammon Yıl önce
@Vincent Stigling Yeah, the main things I've been considering though are how black holes would be affected.. would they change shape into more of an ellipse or function differently? Also, how is red/blueshifting affected? It's crazy to think there isn't some way to verify a uniform speed of light.
Jude Waide
Jude Waide Yıl önce
@Josh Mellon every point is the centre
TheThomasites Yıl önce
@Vincent Stigling thats why i would choose the distant object. 1km apart is _negligible_ in comparison. Unless we have an extreme local fluctuation in c speed around our observer. Then you could do the experiment again but reverse the source target. This removes the need to "synchronize" and move apart through this different speeds of c. Your sync is done by the object at the exact distance away, and a negligible angle.
Vincent Stigling
Vincent Stigling Yıl önce
The biggest problem with this is that gravity has a affect on photons (light) so with enough distance gravity can slingshot light. So light could travel instantaneous from left to right but as it gets curved thru gravity and change direction the speed would also change meaning that what you see in front of you could be a object +- 45 degrees to your left / right or up / down
TheThomasites Yıl önce
I have to put this here as my other comment will get lost. Could you use a known trigger, like a pulsar near perpendicular to both source and target. Time from expected trigger to impact is your time of flight. Am I wrong?
fuzzyhair321 18 gün önce
One thing I find it's impossible to count is that everything how we observe stuff is in speed of light. So how do you measure something when you can only observe it when it enters your eyes
strollas 2 gün önce
why dont you measure a partial distance, instead of a whole distance, on the light's return trip to see if the speed of light is faster in one direction? you measure both directions of course, but if right 100% reflected to left 75% has a quicker time than left 100% reflected to right 75%, then it means light is different directionally. i think the issue is the clocks being too far but in this case, you can make the clocks closer if you need to.
maL oun
maL oun 10 saatler önce
What if we make space between mirror and light source shorter as maximum as we can? The middle speed will more accuracy? And if we measure such accuracy speed on different spaces, can we know what experiment shows different results for different spaces?
Mr_Syncc 3 gün önce
So think of a triangle. A on the bottom left, B on the top middle, and C on the bottom right with all sides equal in length(just easier to visualize). B starts clock and sends light to A and C. Each of them receive light start clock and send light back to B and each other. B should receive both light at the exact same time if not the clocks are offset so its like a way to check itself. A and C should both receive light from each other and stop their clocks at the exact same time. Sending light back to B verified the clocks where synced then the test of if they stop at the same time shows that light does or doesn't travel at the same speed going both ways. Also rotating the starting point from B to C then A should verify that the light is traveling at or not at the same speed in all 6 directions. OFC gravity could have effect on light speed so idk if this could even be tested bc gravity is literally everywhere (might be small but still there). this is just my first though process on this topic so please reply to this comment if you have any opposition. B gets mirrored back to itself from C and A but isn't the light being timed. its just to start the clocks at the same time and verify they started at the same time. then the light should be received at C and A from each other at exactly the same time and should stopped the clock at exactly the same time if the light travels the same speed both ways. this is my solution to the problem but I'm sure I did something wrong so please correct me and I will try again.
v10011011 Yıl önce
I love how he called it right off the bat, “oh you’re talking relativity, you’re gonna something weird aren’t you?”
Simon Waters
Simon Waters Yıl önce
@trumpetbot Pratchett held that dark must move faster than light as it always manages to get out of the way when light arrives. Privatives for the win.
Kristian Yıl önce
@TheMelbournelad Think about it in two ways. 1. If you shine a torch at your hand in a dark room and form a shadow on the wall behind you, it will mimic your movement perfectly, moving at the exact same time regardless of how far your hand is from the wall. However, the shadow would be nowhere near the speed of light. 2. In the second scenario, if you could cast a shadow of your index finger onto the moon (which would be very difficult to do), and you moved your finger so that the shadow moved from one side of the moon to the other, the shadow would move faster than the speed of light. The problem however, is that your thinking of a shadow as a physical thing. Shadows are a lack of physical things (Photons). They don't technically 'move'. The shadow 'moves' only when the object obstructing the light moves and so the light is obstructed in a different area. In summary, the speed at which a shadow 'moves', is not constant because it depends on the object (the object location in relation to where the shadow is formed and the speed at which the object is moving. I hope that was helpful.
TheMelbournelad Yıl önce
@Kristian but why is it not that speed. That is the question
Kristian Yıl önce
@trumpetbot No
Salman Musaew
Salman Musaew 16 gün önce
One thing I can say for sure. The speed of light, that traveling between earth and mars in two directions, can't be the same. The one that traveling from earth to the mars, will be slower. And from the mars will be faster than its precise speed. The sun's gravity will play bigger role, then the planets etc. Imo, the precise speed can't be detect. Too many involvements.
Royce Crowe
Royce Crowe 23 gün önce
Now, with the earth being about 93 mm from the sun you might think you can measure light using this math. However you must take in effect that the earth has an elliptical orbit around the sun . So the distance is never the same. Thus the light takes longer to get to earth at throughout the earth's rotation around the sun. So You must know the E.R.S. plus the E.O.S. plus the S.R.S. then you need to know the distance at any one moment of the EARTH to the SUN. So perhaps once per year on a particular day at a particular hour or even minute you can repeat the math and come up with an near exact speed. Near, because even then the SUN is pulsating in and out thus changing the distance from earth at every second.
Zerlan Victoria
Zerlan Victoria 17 gün önce
What if you do it like this: use 2 timers, set both timers for atleast 3 hours, then start both at the same time, use the 3 hours to get to point B, then wait for the timer to finish then start the experiment at the moment the timer hits zero?
Alan Tomczak
Alan Tomczak 4 gün önce
Ok, but in example with two clocks in the middle: we sync them and move them away, then stop at exactly same moment. We compare times - if they are the same, then Einstein was right.
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