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Why The Speed Of Light* Can't Be Measured

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  • Why No One Has Measured The Speed Of Light

    19:05

    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

    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:

    For an overview of the one-way speed of light check out the wiki page:

    The script was written in consultation with subject matter experts:
    Prof. Geraint Lewis, University of Sydney
    Prof. Emeritus Allen Janis, University of Pittsburgh
    Prof. Clifford M. Will, University of Florida
    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) (German)

    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.

    Response to Greaves et al. paper —
    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.

    A review article about simultaneity — Janis, Allen, Conventionality of Simultaneity, The Stanford Encyclopedia of Philosophy (Fall 2018 Edition), Edward N. Zalta (ed.)

    Will, C. M. (1992). Clock synchronization and isotropy of the one-way speed of light. Physical Review D, 45(2), 403.

    Zhang, Y. Z. (1995). Test theories of special relativity. General Relativity and Gravitation, 27(5), 475-493.

    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.

    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:
    Henry Reich, Minutephysics:
    My Patreon supporters

    Additional music from Observations 2

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  • The Speed of Light is NOT About Light

    12:46

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    Help translate our videos!

    The speed of light is often cited as the fastest anything can travel in our universe. While this might be true, the speed of light is the EFFECT and not the CAUSE of this phenomenon. So what's the cause? On this week's episode of Space Time, Matt helps explain what the speed of light REALLY is and why it’s the cosmic speed limit of our universe!

    The Real Meaning of E=mc²:


    Are Space And Time An Illusion?:


    ----------------------------------------­­---------

    SOURCES:

    Einstein's derivation or the Lorentz transformation from the invariant speed of light:
    Einstein, Albert (1916) Relativity: The Special and General Theory


    Lorentz Transformation without invariant speed of light, from relativity, isotropy, and consistency of frame transitions (closure group postulate):
    von Ignatowsky, “Das Relativitatsprinzip,” Archiv der Mathematik und Physik 17, 1–24 (1911)

    Berzi1 & Gorini, J. Math. Phys. 10, 1518 (1969)


    Pelissetto & Testa, American Journal of Physics, 83, 338, (2015) Getting the Lorentz transformations without requiring an invariant speed




    ----------------------------------------­­---------

    COMMENTS:

    Denny Hiu


    . (RadimaxRadimaX)


    Epsilon Lazerface


    LassieDog999


    Tenebrae


    ----------------------------------------­­---------

    REFERENCES:

    Krauss & Scherrer 2007

    Vardanyan, Trotta & Silk, 2011

    ----------------------------------------­­---------

    Let us know what topics you want to learn more about:

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  • Light Speed Doesnt Really Exist, Heres Why

    8:58

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    How fast does light travel? The official speed of light has changed several times throughout history. After centuries of debate and experiments with different results, the scientific community finally settled the matter in 1983…maybe. To measure the speed of anything, you’ll need to know 2 things: the distance between point A and B, and the time it takes for an object to travel between those points. With distance divided by time, you’ll have yourself the speed of light.

    But with every experiment done to measure light speed, there’s always been an extra cog in the wheel that everyone overlooked. Or rather brushed aside. And this is what we're going to talk about. But the truth is that the speed of light is the ultimate question among scientists, and so far, there’s just no way of truly measuring it. Unlike the speed of sound which is more conceivable, the speed of light might just be light-years ahead of us!

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  • The Speed Of Light Is Wrong! Ft. Sean Carroll | Think Inc.

    7:37

    You didn't misread the title - The Speed of Light should really be called The Speed of Causality!

    Subscribe to Think Inc. →

    Professor Sean Carroll dives into why The Speed of Light has stuck around for so long when it should really be called The Speed of Causality, why we use meters and seconds when measuring the speed of light, and much more!

    This clip is a recording from our Outside The Box series - an event where Sean dove head-first into the biggest mysteries of of our universe, unraveling the preposterous nature of the very fabric that makes up our world.

    The event was hosted by Alan Duffy, Research Fellow and Professor at Swinburne University and Lead Scientist at The Royal Institution of Australia.

    ABOUT THINK INC.
    Think Inc. is a community of individuals on a mission to expose the true face of modern society. Armed with ideas, we defy the stale conventions of learning by shifting the world’s attention to global ideas, while opening minds.

    We’re not on the fringe. We are trendsetters with the power to shift perceptions and reshape the face of the mainstream.

    In 2014, Think Inc. launched with the mandate of creating a community where ideas can be shared, challenged, voiced and became a champion of democratising ideas. On this foundation, Think Inc. has grown into a powerful collective.

    CONNECT WITH US
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    #seancarroll #space #universe

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  • Why cant you go faster than light?

    8:37

    One of the most counterintuitive facts of our universe is that you can’t go faster than the speed of light. From this single observation arise all of the mind-bending behaviors of special relativity. But why is this so? In this in-depth video, Fermilab’s Dr. Don Lincoln explains the real reason that you can’t go faster than the speed of light. It will blow your mind.

  • Why can’t anything go faster than the speed of light? | The History of the Speed of Light Part II

    11:49

    Figuring out that the speed of light was the ultimate speed limit of the universe is part of the late 19th-century and early 20th-century history of Physics. This is part 2 of my “history of the speed of light” series.

    Part 1 - How did we measure the speed of light?

    Michelson & Morley 1887 -

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    ????????‍???? Dr Becky Smethurst is an astrophysicist researching galaxies and supermassive black holes at Christ Church at the University of Oxford.

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  • Measurement of the Speed of light in 1 direction

    3:23

    Reply to Veritasium video

    So this experiment is discussed in Theory of Double Fizeau toothed wheel by Herbert Ives.
    Below is the best link I could find



    It would be awesome to see a Veritasium Video explaining this!

  • Can You Go the Speed of Light?

    4:13

    Einstein's classic thought experiment involves sitting on a train travelling at the speed of light. If you hold a mirror in front of your face, will you see your reflection in a mirror? How could light from your face reach the mirror if the mirror is travelling away from you? But it would be a pretty spooky train if you couldn't see your reflection so Einstein felt this solution wasn't realistic. On the other hand if you could see your reflection, it would mean light was travelling at the speed of light inside the train. But that meant the same light observed from outside the train would be going twice the speed of light. This again seems inconsistent. So Einstein resolved that you must see your reflection but that light must travel at the same speed inside and outside the train. The only way this is possible is if space and time are perceived differently by observers inside and outside the train.

  • Why you cant go faster than light - Sixty Symbols

    12:46

    Featuring Professor Mike Merrifield from the University of Nottingham.
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  • Why You Can Never Reach the Speed of Light: A Visualization of Special Relativity

    9:36

    This video is an entry for the Breakthrough Junior Challenge 2015 which gives a unique visualization of Special Relativity using hyperbolic geometry.

    This idea was inspired by the famous woodcut by M.C. Escher Circle Limit III.

    I liked the idea of making a video on Special Relativity because I had already explored the use of M.C. Escher’s woodcut Circle Limit III as a teaching tool for explaining the hyperbolic geometry of Minkowski spacetime. The main intuition is that the principle of Relativity asserts that the manifold of frames of reference is homogeneous and isotropic, and there are exactly three geometries associated with this: Sphere (which exists as rotations through space), Plane (which represents Galilean Relativity) and the Hyperbolic Plane (which exists as rotations through spacetime).

    I wanted to find a way to use this intuition without overwhelming the audience with technical terms. When the timelike unit vectors in 2+1 spacetime (which correspond to velocity four-vectors) are projected onto a disk (see Wikipedia: “Hyperboloid model”), the result is the Poincare Disk Model, which is (almost) the geometry portrayed in Circle Limit III. I had never seen anyone to use this as a visualization of Special Relativity, and so I decided to make the video.

    Public Domain Image Sources (in order of appearance):
    Einstein:
    pulse of light:
    stopwatches:
    crowd:
    beakers:
    map:
    wall clock:
    starburst:
    Electric Current:
    mouth:
    water waves:
    cosmic lake:
    Galileo:
    flashlight:
    Poincare:
    Einstein:
    Lorentz: :
    Minkowski: :
    star cluster:
    trash can:
    Einstein and Lorentz:
    car:
    bicycle:
    jet:
    spacetime:
    atomic cloud:
    stopwatch:

    Software used to create this video includes iMovie, Keynote, Pixelmator, MathType, and Quicktime Player.

  • Was Einstein Wrong About The Speed Of Light?

    3:36

    The speed of light is the cosmic speed limit and it can't been changed. Or can it?

    Here's What Parallel Universes Might Look Like (360 Video) -
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    Theory that challenges Einstein's physics could soon be put to the test

    Scientists behind a theory that the speed of light is variable - and not constant as Einstein suggested - have made a prediction that could be tested. Einstein observed that the speed of light remains the same in any situation, and this meant that space and time could be different in different situations.

    Putting the Brakes on Light

    The atoms, now one big atom, act in unison. They are analogous to the photons in a laser, all lined up the same way, producing what physicists call a coherent beam of light. On the quantum mechanical level, atoms have dual personalities, just like photons of light.

    What is the Inflation Theory?

    The Inflation Theory proposes a period of extremely rapid (exponential) expansion of the universe during its first few moments. It was developed around 1980 to explain several puzzles with the standard Big Bang theory, in which the universe expands relatively gradually throughout its history.

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  • Measuring the Speed of Light | Wonders of the Universe w/ Brian Cox | BBC Studios

    3:43

    In the last episode of Professor Brian Cox's epic journey across the universe, he travels from the fossils of the Burgess Shale to the sands of the oldest desert in the world to show how light holds the key to our understanding of the whole universe, including our own deepest origins. To understand how light holds the key to the story of the universe, you first have to understand its peculiar properties. The man who first grasped these properties was Danish astronomer Ole Rømer, who in 1676 made the first quantitative measurements of the speed of light.



    Having explored the wonders of the solar system, Professor Brian Cox steps boldly on to an even bigger stage - the universe. Who are we? Where do we come from? For thousands of years humanity has turned to religion and myth for answers to these enduring questions. But in this series, Brian presents a different set of answers - answers provided by science.


    This is a commercial channel from BBC Studios. Service & Feedback

  • WHY CAN NOTHING TRAVEL FASTER THAN THE SPEED OF LIGHT?

    5:21

    Hi Everyone, today we’re exploring one of the fundamental characteristics of our Universe - that no particle can be made to travel faster than the speed of light in space. Why is that?

    TOPICS COVERED IN THIS VIDEO:
    Why light travels at light speed? - 0:13
    What happens when we try to accelerate a particle to the speed of light? - 0:35
    What is time dilation? - 0:57
    What are Tachyons? - 2:37
    What is the causality principle? - 3:16
    What are wormholes? - 3:34
    How fast does space expand? - 3:56
    Quantum entanglement explained | Spooky action at a distance defined - 4:14

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    #Physics #TimeDilation #SpeedOfLight

  • What Is The Speed of Dark?

    13:32

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    SOURCES BELOW:

    this is the video where I talk about THE SPEED OF PUSH:

    Big thanks to Martin Archer for help with this episode:

    And thanks to Guy Larsen for his shadow magic:

    music by
    and

    shadows faster than light:





    making the moon brighter:

    sunset and earth’s shadow and belt of venus in single pics:




    amounts of evening-types in a city:

    superluminal scissors:




    wave animations:





    phase velocity vs. group velocity:

    faster than light dark patches:




    make a light interference pattern at home:




    the speed of ignorance:






    Dunning-Kruger:




    “animalcules”:

  • We all move at the Speed of Light

    11:57

    Is it possible to go faster than the speed of light? Would this mean going back in time? What is so fundamental about this precise speed? Answers to these questions in 12 minutes!

    For more videos, subscribe to the YouTube channel :
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    Alessandro Roussel,
    For more info:

    _
    To learn more :

  • Visualizing video at the speed of light — one trillion frames per second

    2:47

    MIT Media Lab researchers have created a new imaging system that can acquire visual data at a rate of one trillion frames per second. That's fast enough to produce a slow-motion video of light traveling through objects.

    Video: Melanie Gonick/MIT

    Read more:
    Project website:
    Follow us on Twitter:

  • We are all moving at the speed of light

    6:11

    You've probably heard that nothing moves faster than the speed of light. But did you know nothing moves slower than the speed of light? We are all moving at the speed of light.

    Einstein's special relativity forces us to think of time as a dimension we travel through - just like we travel through the three dimensions of space. The unit of measurement of this space-time is called the 'proper distance' and it supersedes both meters and seconds. Because meters and seconds are unified by the proper distance, speed loses it's meaning. We are only in control of the direction we travel through space-time. Fast moving objects appear to be ageing slowly - they are moving almost entirely through space and very little through time. Slow moving objects age quickly - they are moving almost entirely through time and very little through space.

    Transforming between frames of reference moving at different speeds is very much like a rotation. In fact it IS a rotation - a hyperbolic rotation. In the context of special relativity however, it is called a Lorentz transformation.

    Animation done using manim - a software created by Grant Sanderson of 3blue1brown.

  • If the universe is only 14 billion years old, how can it be 92 billion light years wide?

    9:46

    The size and age of the universe seem to not agree with one another. Astronomers have determined that the universe is nearly 14 billion years old and yet its diameter is 92 billion light years across. How can both of those numbers possibly be true? In this video, Fermilab’s Dr. Don Lincoln tells you how.

    For further information, see

  • How Einstein Abolished the Aether - with John Spence

    1:16

    The fact that light travels at the same speed in all frames of reference is one of the greatest revelations of modern science.
    John's book Lightspeed: The Ghostly Aether and the Race to Measure the Speed of Light is available now:

    How have physicists from the ancient Greeks to Einstein tackled the problem of how light travels and what discoveries did it lead them to along the way? John Spence tells the stories of some of the greatest experimental scientists in history as they searched in vain for the mysterious 'aether' and a frame of absolute rest in the universe.

    Watch the Q&A:

    Prof John C.H. Spence is a Fellow of the Royal Society and the Richard Snell Professor of Physics and a Regents Professor at Arizona State University. He is also the director of science for the NSF BioXFEL Science and Technology Center on the application of X-Ray Free-electron lasers to structural biology.

    This talk was filmed in the Ri on 11 March 2020.

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  • This is why we cant have nice things

    17:30

    This video is about stuff: light bulbs, printers, phones and why they aren't better. Go to and use code VERITASIUM to get a 2-year plan plus 1 additional month with a huge discount. It’s risk free with Nord’s 30 day money-back guarantee!

    References:
    The Man in the White Suit —

    London, B. (1932). Ending the depression through planned obsolescence. —

    Slade, G. (2009). Made to break: Technology and obsolescence in America. Harvard University Press —

    Krajewski, M. (2014). The great lightbulb conspiracy. IEEE spectrum, 51(10), 56-61. —

    Planet Money, The Phoebus Cartel -

    The Light Bulb Conspiracy -

    Special thanks to Patreon supporters: Mac Malkawi, Oleksii Leonov, Michael Schneider, Jim Osmun, Tyson McDowell, Ludovic Robillard, jim buckmaster, fanime96, Juan Benet, Ruslan Khroma, Robert Blum, Richard Sundvall, Lee Redden, Vincent, Lyvann Ferrusca, Alfred Wallace, Arjun Chakroborty, Joar Wandborg, Clayton Greenwell, Pindex, Michael Krugman, Cy 'kkm' K'Nelson, Sam Lutfi, Ron Neal

    Written by Derek Muller and Petr Lebedev
    Animation by Ivan Tello
    Filmed by Derek Muller and Raquel Nuno
    Edited by Derek Muller
    Video supplied by Getty Images

    Music by Jonny Hyman and from Planet, Rhythm of Dreams, Tread Lightly, Unexpected Visitors, Curved Mirrors Drunken Lullaby Fluorescent Lights

    Thumbnail by Raquel Nuno and Karri Denise

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  • Relativity: how people get time dilation wrong

    11:07

    Einstein’s special theory of relativity is notorious for being easy to misuse, with the result that sometimes result in claims of paradoxes. When one digs more carefully into the theory, you find that no such paradoxes actually exist. In this video, Fermilab’s Dr. Don Lincoln describes a commonly claimed time dilation paradox and shows how to resolve it.

    Related videos:


  • 2015 Herzberg Memorial Public Lecture: Faster than the Speed of Light by Prof. Miguel Alcubierre

    55:37

    Visit us on twitter & facebook (@CAPhys) or on our website (

    2015 Herzberg Memorial Public Lecture, University of Alberta, Monday June 15, 2015, 7:30 P.M., Myer Horowitz Theatre

    Miguel Alcubierre, Nuclear Sciences Institute, National Autonomous University of Mexico
    Faster than the Speed of Light

    ABSTRACT: In this talk I will give a short introduction to some of the basic concepts of Einstein’s special theory of relativity, which is at the basis of all of modern physics. In particular, I will concentrate on the concept of causality, and why causality implies that nothing can travel faster than the speed of light in vacuum. I will later discuss some of the basic ideas behind Einstein’s other great theory, General Relativity, which is the modern theory of gravity and postulates that the geometry space-time is dynamic and the presence of large concentrations of mass and energy produce a “curvature” in space-time. I will then talk about how the curvature of space-time can be used in several ways to travel “faster than the speed of light” by distorting the geometry away from that of flat space. In particular, I will discuss the ideas behind the geometric model for a “warp drive”.

    BIOGRAPHY: Prof. Miguel Alcubierre was born in Mexico City in 1964. He obtained his Physicist degree from the National University in Mexico (UNAM) in 1988, and a PhD in Physics from the University of Wales in 1994. He later worked for several years as an Adjunct Professor at the Max Planck Institute for Gravitational Physics in Potsdam, Germany. Since 2002 he joined the Nuclear Sciences Institute at UNAM where he is now a Full Professor, and since June 2012 the Director. His research is in the area of numerical relativity, which is concerned with the computational simulation of astrophysical systems using Einstein’s theory of general relativity. In this area he has concentrated on the study of sources of gravitational waves, and particularly black hole collisions. He is author of more than 50 publications, as well as a textbook published by Oxford University Press.

    HISTORY OF THE HERZBERG MEMORIAL PUBLIC LECTURE: In 2000, the CAP Council made a decision in to change the Sunday lecture given at its Annual Congress from a keynote lecture to a public lecture. The lecture would be named the “Herzberg Memorial Public Lecture” in honour of Nobel Laureate Dr. Gerhard Herzberg, longstanding member of the CAP, in recognition of Dr. Herzberg’s known desire to increase the awareness and appreciation of science amongst the public, particularly youth. Support for the Herzberg lecturer is provided, in part, through a bequest from Dr. Herzberg.

  • Laser diode self-mixing: Range-finding and sub-micron vibration measurement

    27:46

    A plain laser diode can easily measure sub-micron vibrations from centimeters away by self-mixing interferometry! I also show how this technique can be used for range-finding.







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  • The Richness of Time

    1:29:38

    Join a physicist, a neuroscientist, and a linguist as they explore the deep enigmas of time. Time feels like it flows, but does it? Time seems to have a built-in direction, from past to future, but is that real or merely a quality imposed by the human brain? Time on earth elapses at a uniform rate, so why does the human experience of time seem so varied? How do various neurological afflictions change the perception of time? And underneath it all, how does human language impact our ability to think about time and fully experience its rich and mysterious contours?

    PARTICIPANTS: Lera Boroditsky, Dean Buonomano

    MODERATOR: Brian Greene

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  • Length contraction: the real explanation

    11:23

    Relativity has many mind-bending consequences, but one of the weirdest is the idea that objects in motion get shorter. Bizarre or not, Fermilab’s Dr. Don Lincoln explains just how it works. You’ll be a believer.

  • One Way Speed of Light Veritasium Response

    7:24

    You may view this subsequent parts to this response in the playlist here:

    Question 1: Since I have hade this video, many people have posted essentially the same question. What if we did this... What if we did that? Couldn't we determine that the one-way speed of light is the same in all directions Below, I offer four equivalent explanations. The first is the best nontechnical explanation. The second is equivalent to the first, but gives much more mathematical specifics. For a video response:

    Question 2: If it makes no experimental difference, why make the argument? (See Explanation 5, below)

    Explanation 1: Essentially, YES. Unless two fairly strange and unlikely suppositions are accepted and both by some strange coincidence happen to cancel one another exactly. The first is that the speed of light is different in the two directions, and the second is that the times on the clocks are desynchronized to exactly cancel out the observation of that difference in the speed of light. These two suppositions in combination cancel out any possible observation of either effect, under any circumstance, no matter how simple, or complex.

    Explanation 2: Each of your emissions, detections, and reflections represent an event. You can calculate the coordinates of those events, as positions (x,y,t) in space and time.

    If you believe, as I do, that the one-way speed of light is constant, you KEEP THOSE NUMBERS. There is no reason that you should use any other numbers, unless you want to analyze them from some different point-of-view.

    However, if you believe, for some reason, that the speed of light is 1/(k+1) in one direction and 1/(1-k) on the way back, you can ALSO find the true coordinates of those same events by applying a transformation

    x'=x

    t'= -k x+ t

    Now, the transformation does absolutely nothing to the existence of the events or their properties. All it has done is slid all of the events forward or backward in time. Events at x=1 slid forward in time by k.

    The combined effect of these TWO assumptions make it impossible to measure the value of k.
    If k is nonzero, that means, the speed of light is asymmetrical, BUT the desynchronization of clocks completely hides the fact from you so that you can never determine what the value of k actually is.

    Explanation 3: If you're still trying to experiment your way out of this problem, you're still not getting it. A position-preserving-temporal-skew changes no observable phenomena. No reading of rulers or clocks or digital devices are changed. However, it does change the slope of the speed of light in the space-time-diagram, as well as the slope of synchronized comoving clocks. But whatever non-light information-carrying method you find; your bullet velocity, sound wave, compression wave, tension wave--all would have essentially the same undetectable velocity asymmetry as light, and therefore, could not be used to detect the presence or absence of that asymmetry.

    Explanation 4: It has been noted that some people think this question about the asymmetry of the speed of light is academic. This is a more polite way of saying that this question is literally useless. In no way should anything in this video or the others be seen to endorse the idea that the speed of light is different in different directions. I firmly endorse the Principle of Relativity, which says that physics is independent of reference frame. The idea that this Principle is wrong--that the speed of light is actually different in different directions, but that that difference is literally undetectable by any physical experiment? It's a useless idea, and let me go ahead here, and go so far as to say, I also think it is a STUPID idea. If you have any interest in Special Relativity, this topic is a red herring. In NO WAY will this question lead you to a greater understanding of Special Relativity.

    Explanation 5: ​Alder's Razor “That which cannot be settled by experiment is not worth debating — Mike Alder. This is not a razor in the spirit of making a decision between two theories, but rather, a razor to tell you that a decision should not be made.

    Say, someone hands you a wadded up piece of paper, and says, my theory is written on that paper. But when you attempt to un-wad it, he says, un-wadding the paper will make no experimental difference. Do you leave the paper wadded?

    A more realistic and relevant example in this case is that most textbooks present the twin paradox without converting to the reference frame of the moving twin on either his outbound, or returning journey. (They don't set k=0 from explanation 2) This is essentially the same as leaving the paper wadded.

  • Regarding the One-Way Speed of Light

    13:22

    Responding to some comments I've received about Dr. Liar, Part 4. For more information about this, please see

    My Patreon:
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  • How the Speed of Light Was First Measured

    13:16

    Examines How the Speed of Light Was First Measured and discusses the Applications of these Measurements. What can we use this knowledge for? Great for science students.

  • How did we Measure the Speed of Light

    7:41

    Seems like a difficult task. Also an important one, since c is widely used in Physics.

  • How did we measure the fastest speed there is? | The History of the Speed of Light Part I

    24:26

    The speed of light is 299,792,458 meters per second. That's an incredibly fast speed. But how did we even figure that out in the first place? And how do we even know it that accurately?

    Part 2 - Why can’t anything go faster than the speed of light?

    My phases of the Moon necklace is from Eclectic Eccentricity, who have a great selection of space-themed jewellery:

    -------

    More details on measuring the speed of light (or really, the length of a meter!) with your microwave:

    Here are links to the papers mentioned:

    Rømer (1667) -
    Huygens (1677) -
    Newton (1704) -
    Bradley (1729) -
    Fizeau (1849) -
    Weber & Kohlrausch (1856) -
    Maxwell (1864) -
    Essen (1950) -
    Evenson et al. (1972) -
    ----

    ???? Space: 10 Things You Should Know:

    ???? US & Canada version: Space at the speed of light (same book, different title):

    ???? German translation Das kleine Buch vom großen Knall :

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    ???? Don't forget to subscribe and click the little bell icon to be notified when I post a new video!

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    ????????‍???? Dr Becky Smethurst is an astrophysicist researching galaxies and supermassive black holes at Christ Church at the University of Oxford.

  • Measuring the Speed of Light

    6:27

    Using a microwave oven, egg whites, and a pie plate, measure the speed of light. Not my idea. I was thinking about something similar using neon bulbs, etc. and searching the internet when I ran across this:

  • How to Measure the Speed of Light

    2:14

  • why is the speed of light a precise value?

    11:57

    The speed of light exactly 299792458 m/s. It was set that value. This video looks how it got to this point and also explores some of the more recent attempts at measuring the speed of light, including Michelson and Eveson. I also explore how the meter definition was refined over time and led to its redefinition based on the speed of light.


    Errata: A small typo in my title that appears briefly at 0:47. The last three numbers should be 458, not 568. Sorry - The T shirt is correct!!

    Also see
    History of the Speed of Light -

    Measuring the speed of light using chocolate -

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  • The Speed of Light is NOT Fundamental. But THIS is.

    16:34

    This is my journey to find all of the fundamental constants of nature which took some surprising turns. Check out Brilliant who sponsored part of this video:

    When you learn physics, you very quickly encounter the physical constants of nature, things like the gravitational constant, the speed of light in a vacuum, planck's constant, the elementary charge things like that. These are numbers which we believe are the same everywhere in the universe, for all time. They are baked into our laws of physics and are very special, because if they were even a few percent different, then the Universe wouldn’t exist and neither would we. They are also fundamental because we can’t derive them from any underlying theory, we just have to take them as being true.

    So I wanted to go on a quest to find all of the fundamental physical constants and collect them all together so you can see them all in one place, because that’s the kind of thing I do on this channel. So this video is the story of me doing that. But it took some fascinating twists and turns along the way, and the final set was definitely not what I was expecting, because it doesn’t actually include the ones we are familiar with, the ones I just mentioned: speed of light, gravitational constant, planck’s constant. Watch to find out why.

    --- Links to source material ----
    How many fundamental constants are there? By John Baez

    Note that his final set is a little different to mine which is explained in his article. I chose my set to be the easiest to understand.
    Here are the actual numbers for all these dimensionless constants from David Black


    How fundamental are the fundamental constants?


    Dimensionless constants and cosmological measurements


    How do neutrinos get their mass?


    Helpful wikipedia pages




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  • Why the Speed of Light Cant be Measured | Podcast #3

    11:35

    In this video, I'd be making another podcast (I've been really into podcast recently!) and today, I'd be sharing about why the speed of light can't be measured. Look, I know what you're thinking. The speed of light can't be measured?! That's impossible! What about the countless researches and experiments conducted?!

    Well, it's because all of the experiments and research about the speeds of light are only measuring the 2 way speed of light, the time it takes for light to go from one point into another, and back to the first point. However, all of those researched are based on a hypothesis, which is that light takes the same time to travel in opposite directions. However, it's only a convention - something that everyone agreed upon, without actually being scientifically verified. So, in today's podcast, I'm going to explain about one way speed of light, what its consequences are, and how it can impact the scientific world.

    I hope you like this video, and make sure to subscribe, like, and share the video! Enjoy!

    References:
    Another article about how the one way speed of light can’t be measured:


    The Conventionality of Simultaneity and Einstein’s Conventionality of Geometry:


    Albert Einstein's 1905 paper On The Electrodynamics Of Moving Bodies (English)


    Also, check out another video about this topic, too!


    Picture:
    Thumbnail and Video:


    Music:
    'Small Guitar' from Royalty Free Music from Bensound

  • A mind-blowing explanation of the speed of light | Michelle Thaller | Big Think

    3:57

    A mind-blowing explanation of the speed of light
    New videos DAILY:
    Join Big Think Edge for exclusive video lessons from top thinkers and doers:
    ----------------------------------------------------------------------------------
    The only things that travel at the speed of light are photons. Nothing with any mass at all can travel at the speed of light because as it gets closer and closer to the speed of light, its mass increases. And if it were actually traveling at the speed of light, it would have an infinite mass.

    Light does not experience space or time. It's not just a speed going through something.

    All of the universe shifts around this constant, the speed of light. Time and space itself stop when you go that speed.
    ----------------------------------------------------------------------------------
    MICHELLE THALLER:

    Dr. Michelle Thaller is an astronomer who studies binary stars and the life cycles of stars. She is Assistant Director of Science Communication at NASA. She went to college at Harvard University, completed a post-doctoral research fellowship at the California Institute of Technology (Caltech) in Pasadena, Calif. then started working for the Jet Propulsion Laboratory's (JPL) Spitzer Space Telescope. After a hugely successful mission, she moved on to NASA's Goddard Space Flight Center (GSFC), in the Washington D.C. area. In her off-hours often puts on about 30lbs of Elizabethan garb and performs intricate Renaissance dances. For more information, visit
    NASA.
    ----------------------------------------------------------------------------------
    TRANSCRIPT:

    MICHELLE THALLER: So, Tom, you asked the question, How does mass increase as you go faster? And this is really a wonderful part of Einstein's theories. It actually is also relatively slippery and kind of complicated because to even answer this question at all, we have to ask the rather strange question: What do you mean by mass? What is your definition of mass? You may have heard that nothing with mass can possibly go at the speed of light. The only things that travel at the speed of light are photons pure energy, light, the speed of light. Nothing with any mass at all can travel at the speed of light because as it gets closer and closer to the speed of light, its mass increases. And if it were actually traveling at the speed of light, it would have an infinite mass.

    So think about that. Even if you had a tiny little particle that was, say, billions of times less massive than an electron just a tiny, tiny little piece of mass if for some reason, that tiny thing accelerated to the speed of light, it would have an infinite mass. And that's a bit of a problem. So let's talk about this. One of the things that you really have to realize is the speed of light is very, very special. It's not just simply a speed of something moving through space. As you go faster and faster and closer to the speed of light, time itself begins to slow down. And space begins to contract. As you go close to the speed of light, the entire universe becomes smaller and smaller until it basically just becomes a single point when you're going at the speed of light. And time, as you go closer to the speed of light, gets slower and slower until basically time is a single point at the speed of light.

    Light does not experience space or time. It's not just a speed going through something. All of the universe shifts around this constant, the speed of light. Time and space itself stop when you go that speed. So the reason you can't accelerate to the speed of light, and the reason we say you have an infinite mass is a little complicated because the idea that mass actually is a measurement of energy. You may remember Einstein's famous equation, E equals MC squared. Energy equals mass times the speed of light squared. Energy and mass are equivalent. Mass is basically a measurement of how much energy there is in an object. When you're moving, you have the energy of your motion, too. That's called kinetic energy, energy of motion. So E equals MC squared, now your mass has not just the stuff that's in you but also the energy of your motion.

    And that's why mass seems to increase as you go faster, and faster, and closer to the speed of light. It's not that you are actually getting any heavier. The increase in mass is something that's only observed by people that are watching you go by. If you were on a spaceship going very fast at the speed of light, you don't notice anything getting heavier. You are on your spaceship. You could jump up and down. You can skip rope. You can do whatever you want. You don't notice any change at all. But if people try to measure your mass as you go by, they not only are measuring your rest mass — your mass when you were still — but this added energy of this h...

    For the full transcript, check out

  • Measuring the Speed of Light

    9:09

    Equipment set up and measurements for Speed of light lab

  • How to measure the speed of light - with CHOCOLATE! | Do Try This At Home | We The Curious

    3:47

    All you need to measure the speed of light is a microwave, a ruler & a bar of chocolate! To show you how to do this quantum kitchen experiment, here's Ross & Nerys in this week's portion of tasty science.

    This video was presented by: Ross Exton, Live Science Video Producer, and Nerys Shah, Live Science Team
    Produced by: Ross Exton, and Seamus Foley, Big Screen Producer.


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  • How to Measure the Speed of Light with Marshmallows - Christmas Lectures with Neil Johnson

    6:19

    This may not be something you'd thought of doing but now you know how the speed of light can be measured using only some marshmallows and a microwave oven.
    Watch the full second lecture of the series:

    From the fabric of space-time to the limits of the quantum world, Neil Johnson takes us on a journey through time in his 1999 Christmas Lecture series Arrows of Time.

    In his second lecture, Neil looks at how order emerges from chaos, how complex life can appear against entropy.

    Watch the full series:

    The Ri is on Twitter:
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    Our editorial policy:

  • Can you Measure the Speed of Light using Chocolate?

    15:37

    Can't get enough of Physics? Why not try out Brilliant? =D
    Make sure to check out stemerch.com for all the Merch you have seen in the video! =D
    David's Channel & Outtake: [Make sure to subscribe! =D]
    David's Twitter:

    Can we measure the speed of light c using chocolate and a microwave? Let's find out! =D This video has been sponsored by Brilliant btw =)

    Help me create more free content! =)




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    0:00 Intro
    1:50 Prerequisites
    3:44 Standing Waves
    6:47 Taking Measurements
    9:23 Results

  • Measuring the speed of light

    22:44

    This video is about Measuring the speed of light using household items.

    All you need is a chocolate bar and a microwave oven.

    It's an amazing experiment to do at home.

  • How Jupiters Moons Showed Us the Speed of Light

    5:54

    Light travels through space as fast as anything in the universe possibly can, but before scientists could figure out light’s speed, they had to figure out whether that speed was even finite.

    SciShow has a spinoff podcast! It's called SciShow Tangents. Check it out at

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  • Direct Measurement of the Speed of Light

    26:40

    In this video, I demonstrated the direct measurement of the speed of light using an off-the-shelve red laser diode and a photomultiplier. The principle and circuitry is discussed in detail in the second half of the video.







  • What does it mean for the speed of light to be constant?

    3:17

    Hi Everyone,
    Here's a short clip from a new informal video series I'm doing each week with Albert Einstein -- well, ok, his Facebook page. We'll cover a range of topics at a variety of levels. This video is a basic discussion of what it means for the speed of light to be constant.
    --BG

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  • Measuring the Speed of Light

    2:29

    How did we we learn the speed limit of the universe?

    Want to see more videos like this one? Generally we release a new video every friday, but be sure to keep your eye out for

    some extras. Go ahead and subscribe if you would like to be informed of new videos.

    The links below were used for information found in this video, you can also find more information concerning this topic at

    them.





    Our intro music was created by
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  • Measuring the speed of light

    1:34

    Veritasium video -

    Sorry for my English. It dosent my native language.
    On text: Hi everyone, I'm Alex. I watched the latest Veritasium video about the problem of measuring the speed of light. I have an idea for a mind experiment and I can't understand where the error is. Two high-precision stopwatches with light transmission sensors that measure the time when light passes through them. The distance between them is 1 meter. And I have a device like this that will turn on these stopwatches at the same time, because there is no electrical interaction, but only physical interaction. I'll physically tap both stopwatches at the same time, right? I have one point for turning on both stopwatches at the same time. I didn't move the stopwatch. It's a laser. And now I can measure the speed of light

  • Modern Physics 2-1: Measuring the Speed of Light

    9:42

    These videos are taken from a lecture course on Modern Physics I taught at the Catholic University of Korea in Spring 2016.

    This video describes the first measurement of the speed of light, using observations of Jupiter's moon Io.

    Link to the slides used in this video:

  • 13: Light- Measuring the Speed of Light

    10:58

    From lanterns on mountains to the microwave oven.
    Then some speed of light problems.
    (Do you know how a microwave oven cooks your food, but you don't get hot?)

  • How To Calculate The Speed Of Light With Your Microwave

    3:51

    You may think your microwave is good only for making popcorn or heating up last night's leftovers. But with a big chocolate bar and a little ingenuity, you can use use your microwave to calculate the speed of light.

    Subscribe to HuffPost today:

    Voice Over: Phil Anderson

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  • Measuring the Speed of Sound with an Oscilloscope...and Hearing Test

    25:54

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