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.

References:
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., \u0026 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., \u0026 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., \u0026 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"

Kommentarer
  • Can we physically synchronize the clocks? Imagine a 1 km long metal plate that hovered over two clocks on each end. If we push the plate down in the center, it would hit both clocks at somewhat the same time. Even if, in a precisely controlled environment, the plate still doesn't hit them at exactly the same time, you would have an accurate "enough" sync to at least prove that one way light travel is not instantaneous. It wouldn't prove subtle differences in C based on direction if the clocks were offset a bit, but still a win!

  • yeetus boi
    yeetus boi

    what if you just moved the clocks closer together

  • coookie man
    coookie man

    i thought could earth at 3am say that both mars and earth will say what Jupiter looked like at 12 pm both would see Jupiter instantly according to 14:43 so earth would say at 12 pm Jupiter looks like A but mars which is 10 mints behind at 12:10 earth time would say at 12 pm that Jupiter looks like b which what Jupiter looked like at 12:10. i think i am wrong please some one correct me

  • blazed lizurd
    blazed lizurd

    saying that light doesn't travel the same both ways is possible just because we can't prove its not is silly. what actual reason would be for light to not travel in all directions equally OTHER than just "we don't know, it just might!"?

  • TrapJawGaming
    TrapJawGaming

    Okay so, I'm sure someone must have thought of this, but; use one clock. at the end of the 1km vacuum, sync the firing system & the recipient sensor and clock together to the same time, set the experiment to run at set intervals from that unified time?

  • amr siddiq
    amr siddiq

    It's a fun theory but it's flawed, who controls which direction is instant and which is not, and why is it not both ways, if it's true this means that we might be seeing everything around us in the observable universe as it is which is not true

  • ꧁Sp00n꧂
    ꧁Sp00n꧂

    Alright so I'm not done viewing this video yet, but here's my idea: have 2 clocks in the same spot and move both of them in opposite directions by 500m (Or much less if you have a more precise clock). Problem solved? Assuming (I'd love to put this in italic) that the clocks are both moving slower when moved apart in opposite directions, that should solve the problem. You could measure one-way and two-way speed of light in the same experiment and compare them. 🤔

    • ꧁Sp00n꧂
      ꧁Sp00n꧂

      Yup, alright, it's a flawed solution 😂

  • C
    C

    This host is too hot to take seriously.

  • C
    C

    There’s no such thing as instantaneous bc infinity isn’t a number it’s a concept.

  • Bonded castaway
    Bonded castaway

    We measured light by the change it causes in the electric field and magnetic field. Which is by definition what light is. A disturbance in the field. This is why anything with energy creates light. Because everything that moves, moves through these two fields. The rate it is disturbed is “speed” of light

  • Tim Rice
    Tim Rice

    How does this impact the tracking of planetary orbits? Watching Mars orbit the sun, or the moon orbit the Earth. At what point does the light change speed?

  • Truth Seeker
    Truth Seeker

    Direction is irrelevant in space ... this is just fun talking video.. Period. 😉

  • Kc B.
    Kc B.

    @veritasium This might be a weird thought but couldn't we use quantum entanglement to measure the speed of light? afaik changes with quantum mechanic entanglement is instant and afaik not bound to the laws as physics, so literally instant regardless of distance. Wouldn't that allow smarter people to set up an experiment to measure one way?

  • BS Caller
    BS Caller

    It’s cool that Sergey Brin takes time out to do these kind of videos.

  • John Shalamskas
    John Shalamskas

    If c was not invariant in all directions, I think that GPS would fail since you are measuring the time delay from multiple satellites to get multiple overlapping spheres around each satellite, and your position is at the point where all the spheres intersect. If light moved at varying velocites depending on direction, then the sphere would look like a cardioid instead.

  • Tomor Inferno
    Tomor Inferno

    now the question is, why would it matter? If clocks change anyways over the delay then what is the problem

  • SuperGorli
    SuperGorli

    wait, isnt it also plausible that the speed of light is more than infinite and less than c/2? So basically earth is sending at 2c and the response is -c, so basically the mars response is reaching earth half of the time before it was sent?

  • Breno Barros
    Breno Barros

    Hey, how about, instead of 1km we use 10cm then the clocks could be in sync and problem solved. :)

  • randall mckinney
    randall mckinney

    Relativity has always BENT my brain ,and trying to imagine the concept of Quantum Entanglement (spooky action at a distance) BREAKS my brain. This video gives me at least a mental framework with which to ponder all these concepts in new ways. BRAVO {{ C=(C1+C2)/2 is an ASSUMPTION }} Never knew that…mind blown

  • midan94
    midan94

    It is absolutely important to know that physics, and science aren’t always necessarily based on verifiable fact.

  • Dick Tracey
    Dick Tracey

    Don't measure time by clocks, measure time by a very distant pulsar. You don't have to be concerned with time dilation. Though the time between pulses changes for the moving measuring device, just count the pulses.

  • Razvan
    Razvan

    What if we build the clocks at the intended place?

  • Matt Wilson
    Matt Wilson

    If you look in every direction as far as you can, don’t you see the cosmic microwave background - the beginning of the universe? Doesn’t that mean that the speed of light is the same in all directions because if it wasn’t you wouldn’t see the beginning of the universe if c was instantaneous?

  • John Adama
    John Adama

    we live in a sphere - in the center of the sphere the speed of light is zero 0. the higher you get - the slower you get. wake up! everything is warped in circles - proof: from very large distance everything is supersmall, but if you minify distance to a minimum, everything is maxed out. mandelbaum knew that.

  • Mauro Tamm
    Mauro Tamm

    We can measure it - the only question is how accurately. We can pre-sync clocks on earth, send other to mars. It may be off some ns or even seconds. We can agree that earth sends 12:00 and mars will measure the time until the message is received and we can do the same experiment in reverse. Then compare the results. If it took 5 minutes one way and 15 the other - it is measurable even if we had synced pocket watches that are off by a minute. It's a different story if the difference is in milli or nanoseconds and is measurable at galactic distances.

  • The Average Guy
    The Average Guy

    What makes this better is the fact that its basically just two homies having fun discussing about the speed of light.

  • Homing Lam
    Homing Lam

    I stopped the video as soon as he pulled out the Einstein paper to avoid having a brain damage

  • Jonny Marshall
    Jonny Marshall

    this is so simple; keep both clocks syncronized, and running from before the experiment starts. log the start time on clock A when laser beam is projected from point A, and then log the time on clock B after the beam travels 1km to reach point B. since both clocks are synchronized, the subtract the start time of clock A from the finish time of clock B and get total travel time.

    • Jonny Marshall
      Jonny Marshall

      move both clocks simultaneously in opposite directions to counter the desyncronization effect

  • Sergey Kolesnik
    Sergey Kolesnik

    I guess you could use a wormhole and measure the speed with just one timer.

  • Theeduckie
    Theeduckie

    17:02 “…and we’ll wonder why we didn’t ‘C’ it before”

  • David J
    David J

    Our study of the cosmos should suggest that the one-way speed of light is roughly c in all directions. If it were c/2 in one direction and instantaneous in the opposite, we'd observe one direction in which distant galaxies appear "older" (equally as old as earth) and in the other, they'd appear "younger" (because less time has passed before the light started its journey towards our telescopes). But observation suggests that in all directions, as we look at things that are further away, they appear to be from an earlier time in the universe's development. You could concoct all sorts of other theories to explain why the universe appears this way, but I think you'd have to abandon or bend our understanding of the universe's development (I'm not Stephen Hawking, I could be totally wrong on that). You could also argue there's a directional bias that isn't as extreme so it's harder to tease out by an approach like this, which is totally fair since this approach only provides evidence against a strong bias where the speed of light is skewed orders of magnitude faster in one direction.

  • Sava Silviu
    Sava Silviu

    It would be so amazing that this video would survive until someone finds the answer to this problem.

  • iPsychlops
    iPsychlops

    So I'm 8 minutes into the video and I'm wondering if you did the same experiment at the same time in both directions, meaning have both a laser and a mirror at both A and B, then measure the two way speed at the same time. You could record when the light hits the mirror on both sides and when it reaches the origin.

  • Michael Borkowski
    Michael Borkowski

    I am sticking with red shift and blue shifts from really fast objects is proof enough for me, But I don't know much at all really.

  • Hades Obsidian
    Hades Obsidian

    Why would a different direction make any difference. There's not even direction in space, its relative to you. Traveling though water, or vapor or a nebula, maybe. This seems like smart people making up a problem with weird stipulations as to how it's solved, like when you were a kid and tied a huge knot in your shoe laces and couldn't figure out how to untie it.

  • Ujjawal Pal
    Ujjawal Pal

    Or might be two way in its one way reflecting from every very tiny things every moment

  • Dilip Sharma
    Dilip Sharma

    How do you know for sure that vacuum is a vacuum if even 0 has some value; when put on a denominator! Just a question! '? '

  • 3DManShadowland
    3DManShadowland

    Round trip vs one way at the speed of light. Conversely is equivalent to the relative energy conserved during that trip, if in fact energy from the start differs from that at the end then you know the values have changed. That may be measurable. Knowing that you can make calculations with in the variant of probability until it can be defined. Thus, the calculation of the speed of light can be deduced within a defined curve if not absolute across time.

    • 3DManShadowland
      3DManShadowland

      There is an effect that causes an increase on its way back. That is with the use of explosives as the blast wave hits a barrier and is then replicated on its way back with more force.

  • Keno Redeker
    Keno Redeker

    if we know the speed of sound can we not try to see the speed of light relative to this.

  • Cthary
    Cthary

    Quantum Mechanics ? Use that spooky action of quantum entanglement to synch the clocks ?

  • Pancake
    Pancake

    Why not just take a really long stick and shake it as a signal to synchronize the clocks? The stick would shake at the same time since you’re not sending anything from one way to the other, you’re only shaking something that is already there

  • powerfactor powerfactor
    powerfactor powerfactor

    Can it really not be detected? I'm sure that this has been thought about by people with much more expertise than I have, but here's my proposed experiment, using the "astronaut on mars" example: Create 4 identical stopwatches - 2 on earth (E1 and E2) and 2 on mars (M1 and M2). They all read 0:00. The astronaut sends a signal to earth to start their watches at exactly the same moment he starts the pair that are with him on mars. If the signal travels instantaneously, then the stopwatches will all perfectly agree, and if not, then E1 and E2 will be delayed compared to M1 and M2 by some measurable amount. Now, have the astronaut bring M1 back to earth, and have a new astronaut bring E2 to mars. So on earth we can compare E1 to M1, and on mars we can compare E2 to M2. Now repeat the same experiment, but send the starting signal from earth. Wouldn't a directionally-dependent speed of light show up here? I'm not silly enough to think that I've cracked this as a layperson thinking about it over my lunch break, when a hundred years of physicists haven't been able to. But I'd be interested to learn why this idea doesn't work.

  • rickity randy
    rickity randy

    Ok I have a theory so if you measure the speed of light Both ways then turn the measurement taker around and each way if the time is the same all ways that is the speed of light divided by two

  • RedwoodTheElf
    RedwoodTheElf

    Well the speed of light varied depending on where it is. the speed of light IN A VACUUM is different than the speed of light in Earth's atmosphere.

  • Sunset
    Sunset

    Not sure if this works, but dont all electromagnetic waves go at the speed of light? So if you found the frequency and the wave length of one of them, surely you can use the wave equation velocity = frequency*wavelength to prove the speed of light?

    • John Shalamskas
      John Shalamskas

      Ah yes, for radio waves v = f * wavelength, so if v is infinite in one direction, then wavelength in that direction is also infinite, and if v is c/2 in the opposite direction then the wavelength is 1/2 what it would be with an unchanging v. HOWEVER... on the return half of the wave cycle you get the reverse... so the average speed is still c. I wonder how the radiation pattern for a dipole would model out! The thing about EM radiation is that it moves at the same speed whether you have a single photon or trillions. It moves at the speed of causality. If causality is instantaneous then time would cease to exist.

  • Clockwise
    Clockwise

    Wait but doesn’t the fact that laser cooling using 3 lasers and mirrors works prove that light moves the same speed in both directions? In order to be able to cause the atom or molecule to stop moving, the light would have to impart the same momentum in both directions towards and from the mirror meaning that light would have to move at the same speed in both directions

  • Aayush Garg (Ayshy)
    Aayush Garg (Ayshy)

    At 12:56, the signal took 20 minutes to reach mark, and since the time on earth was 1200, shouldn't he set his clock to 1220? Here's what I am trying to say: signal sent from earth to mars definitely must have had some sort of header or appended information, like a simple stopwatch. The stopwatch will go on for about 20 minutes (± time dilations) and would let Mark know it's 12:20. He'll sent back the signal and the stopwatch (inbuilt in signal headers) would tell NASA that it reached instantaneously. Am I wrong somewhere? Also... Calculating speed of light is meaningless, as it is just a constant which is used to be canceled out in time equations (don't forget time is manmade and we have to omit it in complex astronomical studies)

  • Akshat Srivastava
    Akshat Srivastava

    I love this channel more. Thanks Derek!

  • Banana Eater
    Banana Eater

    why dont they make one really big clock

  • Hassan Rehman
    Hassan Rehman

    16:14, that might be the most emotional/motivational words i might have heard...

  • Jr. Lureca
    Jr. Lureca

    so what if you ignore the lazer so signals also as fast as the speed of light so you need to measure the speed of the SIGNAL not the light itself by making clocks connected to the device that will send out pulses and measure the time diffirence in all 6 clocks goin in all directions see if there is any time difference so idk if that would work but i think it wont im dumb

    • Jr. Lureca
      Jr. Lureca

      and if dose work maybe we are measuring the speed of the signals the speed of light is diffirent

  • Fender Ignacio
    Fender Ignacio

    I’m having an extreme existential crisis after watching this

  • Walter Linares
    Walter Linares

    Maybe my idea is crazy but around a black hole were we can make the light go around and found at orbit we can set a clock taht the start is the end is crazy but maybe

  • Walter Linares
    Walter Linares

    Usd the same clock sen a light around rhe eart gravity will keep it around till get to the clock again or something like thta take my idea send a light from the same point that will end

    • Walter Linares
      Walter Linares

      Is like a race we start at the same point that we finish

  • Debot_Vox
    Debot_Vox

    Why watch the video when the answer is in the thumbnail

  • AviVijayEdits
    AviVijayEdits

    So basically the measurement of a meter actually came from a guy putting a mirror on the ground then walking some random distance and keeping a torch in one of his hand & a clock in the other & then flashing the torch to the mirror and thus obtaining the return trip time to be 2/c secs so he thinks okay now that I have randomly placed mirror and myself and light took 2/c secs time to cover double this distance it means it takes 1/c secs time for this random distance.... Let me just call it a meter and move on with my life....And while Im on it lets just call 'c' the speed of light??? It just keeps getting more & more confusing... Please do reply and point out if anyone finds out any mistakes in this comment coz I'd like to clear my confusion by having a discussion... Thanks in advance!!

  • JumpingJames
    JumpingJames

    I'm sure there's an obvious answer here, but why can't you measure the one way speed of light by comparing it to the speed of an object having the same speed in all directions? For example, you have two positions (position a and position b) one mile apart, you simultaneously fire a laser and a gun from position a to position b. The observer at b measures the time difference between the detection of light and the arrival of the bullet. You know the speed of the bullet (or rather how long it should take to cover a mile), so you can record the difference in time between the detection of light and the arrival of the bullet. You then repeat the same experiment in the other direction (b to a). If there is any difference in time between the arrival of the bullet and the detection of light for the a to b case and the b to a case, then I guess there is evidence for a difference in the one way speed of light.

  • Oleg Celić
    Oleg Celić

    Hmm.. two satelite in space that recive a single signal from the ground (laser) , we use the signal light as main to rederect by mirror to the other satelite. They both measure the time from one satelit to the other.. same distance but two oposite direction.. after all we mearure the distance from moon with laser and mirror, so we have a laser already 😅 Distance is not important as equal time Then again, why dont we measure it in a bose-eistan condesat or some other medium?

  • Adrian Saenz
    Adrian Saenz

    On the Mars example, why not do to trials? One with the assumption that it takes 10 min to reach and the other setting the clock at 12:20 and then compare the two times the message is received back at mission control?

  • Erik M
    Erik M

    There wouldnt be an observable universe as you could see the entire universe if you look one way

    • Erik M
      Erik M

      Also if the light hadnt infinite speed one way then the observable universe wouldn't be a sphere

  • Burgo361
    Burgo361

    This could really matter if we ever got close to FTL

  • eskil walle
    eskil walle

    We mesure the speed off ligt in all 360• . And se if it gose faster in -x to -z and x to z

  • sya chan2
    sya chan2

    I think we can measure the speed if we smaller than the light particle.

  • iKinda “ogc ender's alt” likeRockets
    iKinda “ogc ender's alt” likeRockets

    I am the smartest person ever , why? Because if you put the laser at one end opposite of you you get one way

  • Kristie Sullivan
    Kristie Sullivan

    The swift square alarmingly launch because smash lately replace save a flowery cloakroom. cheerful, colorful hamburger

  • Steeve Talus
    Steeve Talus

    Just go watch slow mo guys. They filmed it

  • yensteel
    yensteel

    idea: Quantum Mechanics to the rescue? Would entangled particles be helpful in any way?

  • Felix Ungureanu
    Felix Ungureanu

    ...so we should try to rethink our own speed limits: we might be able to be faster when going in one direction and slower in other direction. We might even exceed the speed of light when going towards Mars (as in your example) and only be limited on the way back.. cool..

  • Anh Nguyen
    Anh Nguyen

    What about entanglement? First we make two particles entangled let's say A and B. We separate them at a certain distance d. From A position we shoot B, when B state is changed, A is immediately changed. We can measure the duration of A state change and calculate the speed. Am I too naive?

  • Maria Ana
    Maria Ana

    Thank you you’re explanations🙏🏻🙏🏻🙏🏻...I hope you study also about that,the earth is not a globe ,such as you have behind you 😉...just because the children needs to know the true!!

    • Dick Tracey
      Dick Tracey

      children need to know how to form a correct sentence. Way more important.

  • Mithica
    Mithica

    In case you see this comment for some ungodly reason, here is how you can use two clocks to measure travel time in one direction. You hook up two clocks to a metal wire. You start the first clock as you send an electric signal to the second clock. Second clock starts as it receives the signal. You have synced clocks with a measurable traveltime for the electricity through the wire, just subtract it from the second clock.

  • 3 .5
    3 .5

    I’m way too high for this. I’m still not sure why you couldn’t just have the 2 clocks and the laser all 3 simultaneously remotely activated.

  • Rahul Singh
    Rahul Singh

    ye bakwaas video hai

  • Skwańczyk
    Skwańczyk

    And what about quantum teleportation? Can we use quantum teleportation to launch laser pointed at us and measure time required by light to travel from laser to us.

  • Michal Nemecek
    Michal Nemecek

    I was going to suggest starting a huge clock on the moon so you can see how fast it's ticking and then go there and see how much it's delayed, but then I realized that by going there you are moving and relativity strikes again

  • 3 .5
    3 .5

    Would it not be possible to have the 2 clocks just both start when the laser is triggered? Like all 3 start the same time. I feel like technology should be able to remotely trigger them all 3 simultaneously. But what do I know

  • Riley Braden
    Riley Braden

    Ok, so set up a laser on each side of this 1km span. Laser 1 starts on. As soon as laser 2 sees Laser 1 turn off, Laser 2 turns on. Set up your clock at laser 1 and measure the time between Laser 1 turning off to receiving light from Laser 2, and vice versa.

  • John Lakatos
    John Lakatos

    Wouldn't the speed be slower on the return do to absorbtion?

  • Luis Avila
    Luis Avila

    What if you have a 4 clocks and 4 sensors one meter apart fashioned into a square and shooting the beam of light??

  • Hypothesis Tester
    Hypothesis Tester

    So glad I found this channel!!

  • Shoggo
    Shoggo

    Why not just get a central machine, send a synchronous pulse of light to both clocks to start. Then wait a predefined amount of time for both clocks and have the clocks stop themselves after this time has elapsed. If there is any discrepancy in the time the clocks show, then we know light travels at different speeds. Repeat the experiment in various directions of space. If there is no discrepancy, then we can safely assume Two-way time is just twice one-way time. I think the issue is we’re trying to measure two variables with proposed experiments. One, measuring whether or not light travels at the same speed everywhere, and two, the speed of light. Break it down to parts and both become very solveable.

  • JAIME TAN
    JAIME TAN

    Whoah!! You’re saying that there could be a differential in directions?? That there is no isotropy with respect to the speed of light?? But what would caste the difference?? We see the light coming from distant stars and galaxies the same coming from all around the round earth, that comes from every direction and we detect no difference!! Right??

  • Julien Johnson
    Julien Johnson

    We may never know, untill we find a way to measure the smallest unit of time, then start multiple pairs at different locations, and moving one of the pairs in a agreed distance, and move tham at the "exact" same speeds, then stop time. But this is just a potential experiment, that i would like to try.

  • Vance G
    Vance G

    It would seem to me that what you need is the ability for synchronization of the clocks to be orders of magnitude better than the time it takes the light to travel. Light traveling through a Bose-Einstein condensate has been slowed to 17m/s. You could synchronize the clocks at something close to the speed of light in a vacuum, and then measure the speed in each direction of the light through the B-E condensate. Of course, I am assuming that, if the light goes the same speed in either direction in the B-E condensate, it will go the same speed in each direction in a vacuum. This might not be true, but it seems this experiment could get us a step or two closer to understanding how light behaves. You could use other materials, through which light moves faster than in a B-E condensate, but still slow enough for the synchronization time to be a rounding error, and see if the results are different.

  • Archie & Will
    Archie & Will

    Teacher: the test isn’t that hard The test:

  • Levi Cox
    Levi Cox

    I love getting this confused you never get brain teasing problems like this in middle school

  • Levi Cox
    Levi Cox

    ??? what if you sync the clock in the middle of the area and then go at a set pace in opposite directions and then when you have traveled the distance you stop them when you get to the destination. then you can bring them back together and note the time difference. i am unsure if this makes sense but if it does would it work

  • Adler Fagerström
    Adler Fagerström

    It's an interesting thought but I can't see why light would have different speed on different directions. That sounds so arbitrary. It's like if the universe has a front and a backside. Weird!

  • Zepherlah
    Zepherlah

    Doesn't that mean one side of the universe would be lit up light a candle if light was instant going one way to another. I thought they measured the age of the universe on how fast it is expanding etc. With giant telescopes only receiving light now from starts lightyears away?

    • Dick Tracey
      Dick Tracey

      If light was instant, it has to be instant to every position in the universe at once. If it's not instant in every place at once, then it has to have a speed.

  • raezor82
    raezor82

    Makes me wonder if physics is complete, consistent and decidable.

  • Magic Toaster
    Magic Toaster

    Would the background radiation not be able to be seen on whatever side that light is instantaneous

  • Vanti
    Vanti

    Use a light sensor

  • Tac GAMING
    Tac GAMING

    Why don’t you just put both clocks on a clock that starts both clocks at let’s say 5:00

  • John nixter Perez
    John nixter Perez

    Uhmm. Gravity? Because the speed of light was computed on a vacuum. Also the other one was computed using a rotating gear here on earth. Can we consider the time dilation due to relevance of distance but we also need to consider the pull of gravity. It affects time, mass and distance.

  • justynskates
    justynskates

    Here's my thoughts on how to test it: With the earth on the right side of the sun and Mars on the right side of the earth, the earth send a message to Mars saying its 12 (light traveling to the right). If it takes 20 minutes and we don't know, we assume 10 minutes, Mars writes 12:10 and sends a message saying it's 12:10 (Light traveling to the left is instant). The message gets to earth instantaneous. Wait 1/2 year when we are on the other side of the sun. Now Mars is on the left of the earth and the earth on the left side of the sun. Have Mars send a message to earth saying its 12:10 (light traveling to the right again, a 20 minute trip). If it takes light 20 minutes to travel to the right, we will get a message saying it's 12:10 and 12:30 instead of receiving the message at 12:20

  • Dustin Zimmerly
    Dustin Zimmerly

    My idea may be stupid but imma say it anyways Set up a single clock by the light or lazer with fog in the middle have a short distance of readings like 20 ft for instance...

  • Titus Boudreaux
    Titus Boudreaux

    3:20 Move both clocks away from each other.5k

  • hairold
    hairold

    Couldn't you still use the two clocks, but send a signal to the other with a command to stop since the 2nd clock detects the light and begins counting, and use the speed of the signal to the 2nd clock to determine the speed of light?

  • Will Doum
    Will Doum

    Does Michelson experiment means something to you ?