How Special Relativity Makes Magnets Work

  • Опубликовано: 23 сен 2013
  • MinutePhysics on permanent magnets:
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    Magnetism seems like a pretty magical phenomenon. Rocks that attract or repel each other at a distance - that's really cool - and electric current in a wire interacts in the same way. What's even more amazing is how it works. We normally think of special relativity as having little bearing on our lives because everything happens at such low speeds that relativistic effects are negligible. But when you consider the large number of charges in a wire and the strength of the electric interaction, you can see that electromagnets function thanks to the special relativistic effect of length contraction. In a frame of reference moving with the charges, there is an electric field that creates a force on the charges. But in the lab frame, there is no electric field so it must be a magnetic field creating the force. Hence we see that a magnetic field is what an electric field becomes when an electrically charged object starts moving.
    I was inspired to make this video by Prof. Eric Mazur
    Huge thank you to Ralph at the School of Physics, University of Sydney for helping us out with all this magnetic gear. Thanks also to geology for loaning the rocks.
    This video was filmed in the studio at the University of New South Wales - thanks to all the staff there for their time and support.
    Music: Firefly in a Fairytale, Nathaniel Schroeder, and Love Lost (Instrumental) by Temper Trap licensed from
  • Длительность: 4:19
  • veritasium  science  physics  magnet  magnets  magnetic  how do electromagnets work?  how do magnets work?  special relativity  length contraction  attract  repel  minutephysics  charged cat  

Комментарии: 4 077

  • ruka suirenji
    ruka suirenji 8 часов назад

    Does magnetic field only generate when the magnet is moving together with the electrons then?

  • Black Jack 21
    Black Jack 21 10 часов назад

    Omg thank you mannnn

  • polyb 1123
    polyb 1123 2 дня назад

    Since LIGO is basically the Michelsen-Morley experiment on steroids, couldn't we say those recent observations were a negation of the null result observed by Michelson-Morley? If so then what are the implications regarding special and general relativity? I have no particular attachments to any particular model, except in the regards that it works. Therefore I have no problem running with the 'ether' model, what gives besides grants?

  • Shifu Careaga
    Shifu Careaga 2 дня назад

    Bass Ackwards title. Relativity is not the answer. EMF is the answer, Relativity is the model used to understand it.
    God i used to subscribe to you. What happened to you? Next you'll be shilling for Dark Matter despite its massive failures.

  • Peter Morris
    Peter Morris 2 дня назад

    If the cat is in the same inertial reference frame as the presenter then wouldn't the electrons be closer together and therefore attract the cat rather than it not moving at all?

  • Jibril Channel
    Jibril Channel 3 дня назад

    This is completely wrong. Even there is no conductor and only electron moving in space magnetic field still exist

  • Harikrishna K
    Harikrishna K 4 дня назад

    Got a dbt.From our frame of reference we see that the electrons are moving ND protons stationary. so it would appear as if negative charges are more concentrated/dense.even If a "stationary" +ve charge is kept near wire...won't it get attracted due to this?? Can you explain this pls...

  • bm830810
    bm830810 5 дней назад

    well how does changing the direction of the current change the direction of force then?!

  • Mattia Moroder
    Mattia Moroder 6 дней назад

    As you explain it, the magnetic field seems to be only an emergent phenomenon due to relativistic effects of the electric field, which it is not. The magnetic field is as fundamental as the electric one.

  • Kevin Player
    Kevin Player 6 дней назад

    I saw this in my dad's physics book many years ago. It is beautiful. Thank you for the video.
    Maybe try the Aharanov Bohm effect next so we can all grok gauge theory.

  • Aiden Smith
    Aiden Smith 9 дней назад

    3:06 Arrows are pointing in the wrong direction.

  • Davis Jensen
    Davis Jensen 9 дней назад

    I'm now very curious as to what someone could manipulate if they had an absolute control of magnetism.

  • Adya820
    Adya820 10 дней назад

    This is completely wrong. This implies that the electric field converts into a magnetic field just by changing the reference frame , and this is wrong. Both fields exist simultaneously in both frames, only one is stronger than the other depending on the reference frame. One field can have an intensity of 0 in some of the reference frames, but it still exists. It is not that when you look at a electric field in another reference frame it looks like magnetic field!

  • KapustaCuber
    KapustaCuber 10 дней назад

    Holy crap... I am in a relativity + quantum intro course right now and this makes so much sense. Hated E+M because we were basically taught "these are things that happen," which never gets the job done for me. I know this is an old video, but thanks for illuminating this topic so many people claim to know but don't understand!

  • Daniel Lopez
    Daniel Lopez 10 дней назад

    This videos are truly great! I will show this to my students today. :-)

    • Adya820
      Adya820 8 дней назад

      Do not show this video to students it is nice video but it is wrong.

  • Nerd Knowledge
    Nerd Knowledge 11 дней назад

    This is well explained!

  • Akash Stephen
    Akash Stephen 11 дней назад

    Thankyou <3

  • Shivanshu Siyanwal
    Shivanshu Siyanwal 11 дней назад

    But wait a second, the cations i.e, kernels remain fix in the metals, they just oscillate about their mean positions.
    Also, their is no stream of electrons which tend to move uniformly in one direction. Electrons drift towards a direction. So w.r.t to which electron is the cation in rest?

  • Paul-Sebastian Manole
    Paul-Sebastian Manole 12 дней назад

    Btw, if there is a moving electric charge in a wire, it is creating an attractive force with the stationary positive charges due to SR length contraction. Now why is that? Is it to keep the charges from flying away?

  • Paul-Sebastian Manole
    Paul-Sebastian Manole 12 дней назад

    @2:44 Wow there, you better slow down!

  • Vaibhav Rajput
    Vaibhav Rajput 12 дней назад

    However in real life ,there is only magnet and no cat ,,that too stationary so how you explain no force is applies because of net charge being same

  • Sod Almighty
    Sod Almighty 13 дней назад

    Allow me to summarise 90% of the comments thusly:
    Quantum mechanics is utter horseshit.
    Science tells us in one breath that motion is relative, that object A moving and object B remaining stationary is no different to the opposite situation. Science then tells us in the next breath that a moving object experiences time at a slower rate, and also becomes physically compressed in the direction of motion. While the latter could depend entirely on your frame of reference, the former is an objective statement - and one which directly contradicts science's first assertion. If the moving object experiences time slower than the stationary object, then clearly there is an intrinsic difference between moving and not moving.
    The entirety of quantum physics - starting at wave-particle duality and continuing onward from there - is valid ONLY as a metaphor, an APPROXIMATION, and is most definitely NOT a truthful representation of reality. It serves a purpose in the same manner as the square root of minus one. It's useful in equations, but nevertheless it is a purely IMAGINARY construct.
    This can be clearly demonstrated by the fact that a PARTICLE is a physical object, while a WAVE is an action performed by physical objects. Saying that something is both a wave (an action) and a particle (an actual object) is no different to saying that something is both a banana AND a musical symphony.

  • Frydays
    Frydays 13 дней назад

    im stuck in an infinite loop. help

  • s A
    s A 14 дней назад

    After studying on relativity class, I found that this video is incorect, so please delete it ok?

  • Robert Elliott
    Robert Elliott 15 дней назад

    Now Einstein is responsible for magnetism...These communists have no shame.

  • HG Madsen
    HG Madsen 15 дней назад

    So a magnetic field is an electric field watch from another POV. Why then dont we see sparks between magnetic fields an alectric fields?

    • Adya820
      Adya820 8 дней назад

      No this is completely wrong. This video implies that the electric field converts into a magnetic field just by changing the reference frame , and this is wrong. Both fields exist simultaneously in both frames, only one is stronger than the other depending on the reference frame. One field can have an intensity of 0 in some of the reference frames, but it still exists. It is not that when you look at a electric field in another reference frame it looks like magnetic field!

  • Stephen Blackwell
    Stephen Blackwell 16 дней назад

    I love the knowledge I learn from watching your post so much so I am a subscriber
    Plus this channel does a great job of explaining tough subjects in a way I can understand
    But the goofiness is not apart if what I like
    It's use to be attract a younger audience
    It's just me giving feed back I love the channel
    Stephen D Blackwell

    KRIPA SHANKAR SHUKLA 17 дней назад

    But the positive charges are moving in the cat's frame of reference so how will their length be contracted. But actually they are stationary so how will the wire acquire a positive charge? Electrons are moving really so their length must be contracted and so the wire should be negatively charged. Why he said so????

  • Robert Ruta
    Robert Ruta 19 дней назад

    He got the right hand grip rule wrong

  • josy26
    josy26 21 день назад

    So it only has to move veryyy slowly as stated in 3:31 to feel the repel force?

    BARZ TEDx 22 дня назад

    Electric universe

  • ViciosVeloceraptor
    ViciosVeloceraptor 22 дня назад

    oh so the cat's charge is PAWS-itive

  • sedative chunk
    sedative chunk 23 дня назад

    "If you can't explain it simply, you don't understand it well enough." - Richard Feynman

  • Toshi Purohit
    Toshi Purohit 23 дня назад

    I have a question. If you are stationary and the negative charge is moving a positively charged stationary cat should get attracted as from its frame of reference the density of negative charge is more than that of positive charge.

  • Хабиб Юсупов
    Хабиб Юсупов 24 дня назад


  • Matteo Matteo
    Matteo Matteo 24 дня назад


  • ali alimetlak
    ali alimetlak 26 дней назад

    for science and physics to proceed all scientists must dump special and general relativity.

  • kk chandrakar
    kk chandrakar 27 дней назад

    What does north and south pole mean in realtivistic version of magnetism? ?how can changing magnetic flux induce current according to this theory? ?.?

  • yoppindia
    yoppindia 27 дней назад

    i am not convinced with explanation!

  • felix winchester
    felix winchester 28 дней назад

    0:11 he didn't move the metal. but it still attracted? how?

  • sefa demir
    sefa demir Месяц назад

    Hey Veritasium,
    Can we apply this to general relativity or Newton's gravity theory?
    For example if a planet or black hole goes at near-light speed what would be happend?

  • Abanoub Halem
    Abanoub Halem Месяц назад

    I really want to go deep in understanding the AC current. I know how to solve all kind of problems, but I really want to understand how the magnetic field push the electrons inside the wire and after the magnetic field push them how the electrical field play its rule and does the electron jump from atom to atom or they just move. And when the electrons move inside the wire the leave lots of holes( positively charged atom) and these should generate electrical field to get the electrons back. I am really confused. And the last thing I have known that we get zero electrons to our house from the powerplanet station, and we only get electrical field that push the electrons inside the wire how this theory really work. I feel I want to be an electron to understand what is going on

  • Tushar Pal
    Tushar Pal Месяц назад

    Let us suppose that in the stationary frame of reference the cat and the electrons in the wires are moving in the same direction and same speed, and the positive charges are stationary. Then according to Theory of Relativity, the moving column of electrons will be contracted and there will be a net negative electric field due to the wire and the cat should be attracted. Why doesn't this happen?

  • Robin
    Robin Месяц назад

    Alright. Can you expand this explanation to deduce the maxwell equations - i.e. dB/dt=-rotE, which work without having acutal charges involved?

  • H.m Sekender
    H.m Sekender Месяц назад

    How does electromagnetic induction in special theory of relativity. Please make video about this.Thank you

  • Λlok
    Λlok Месяц назад

    I doubt him

  • Andrii Kukhar
    Andrii Kukhar Месяц назад

    While electrons are drifting, according to special relativity their separation will be ever-so-slightly contracted. Why still positively charged cat is not attracted to the wire?

  • Pranav Jain
    Pranav Jain Месяц назад +1

    Hi Guys,
    Looking at the comments, it seems that a lot of people are confused about why a stationary proton is not attracted to the wire. I tried to answer this question in a video I made
    I think my video clears this misconception up, but if I made any mistakes please let me know.

  • Rogelio Alcala
    Rogelio Alcala Месяц назад

    Cool !

  • John Ortiz
    John Ortiz Месяц назад

    God this is beautiful explain, on all my physics class i just assumed the magnetic force as a fact, and you just proved it with relativity

  • James Tan
    James Tan Месяц назад

    If a force doesn't exist in all reference frames, isn't it fictitious?

  • yu zhen
    yu zhen Месяц назад

    But why the positive charge cat is nt attracted to the copper wire when the negative charge is moving and the cat is stationary .since from the examples mentioned before you said that the driver look slimmer at the view of the observer when the car is moving but the observer is stationary . So I supposed the positive charge cat will be attracted to the copper wire when the negative charge is moving as in the cat view the space between the negative charge is contracted. Am I confusing ? Pls tell me if I'm wrong. 😃

    • yu zhen
      yu zhen Месяц назад

      Found ans from others comment.☺ this video is awesome

  • pranav singhal
    pranav singhal Месяц назад

    This guy is a whole new kind of an idiot

  • TheRecycledToys
    TheRecycledToys Месяц назад

    I love your 999999...thing .That was funny.
    laughed my head off!

  • Infinitus
    Infinitus Месяц назад

    mind blown

  • wildan nugroho
    wildan nugroho Месяц назад

    this explanation is beautiful.
    finally it can explain why the electromagnetic wave has not only electrical field but also magnetic field as well which is mutually and perfectly perpendicular on each other.
    thank you for giving the piece of missing puzzle

  • steve istheman
    steve istheman Месяц назад

    it's funny how everyone rips on icp for asking how magnets work. it's actually a good question.

  • Nicolas Duguay
    Nicolas Duguay Месяц назад

    Am I the only one who's seeing a cat with his anus in place of his face?

  • Bio Hacker TV
    Bio Hacker TV Месяц назад

    Love your show bro

  • Rick Flare
    Rick Flare Месяц назад

    Faraday wondered why, when the distance between two objects is doubled their mutual attraction (voidance) for one another falls
    off to one-fourth the former. Faraday was highly dubious regarding Newtons conclusions about force. The fact is that the “missing three-fourths of the force” is not lost whatsoever, the loss of mutual acceleration is in counterspace and mediated between both dielectricity and magnetism, both impelled by and ‘lost’ therein; this is a natural attribute to dielectricity, either as found in the so-
    called “magnet” or in its aggregated form as found in mass/matter. Newton’s equation is not about force, or as argued by others, tension, rather dielectric voidance. In which case we have the equation of Newton corrected: D.V. = M1 x M2/ Distance^2. All acceleration of bodies via gravity or “magnets” are undergoing dielectric voidance, or magnetic (so-called) induction and resultant acceleration is the simplex process of dielectric voidance. The presumed increasing or decreasing ‘force’ is merely a field attribute necessitated by which spatial voidance is enacted to mediate the dielectric field voidances which eliminate space in their accelerations towards pressure voidances created by magnetism. Absolute acceleration is zero empirical movement, or perfect Ether inertia. F=ma is correctly pertaining to “magnetism” and gravity: Voidance = dielectricity as measured in mass x acceleration. As stated, magnetism cannot, has never attracted or accelerated anything, rather only causes dielectric coherency and resultant acceleration by means of dielectricity in voidance. Both gravity and so-called “magnetic attraction” operate off the principle of shrinking spheres of dielectric voidance in which, as found in the case of both, the decreasing spherical area is proportional to the voidance and resulting acceleration. Faradays “missing three-fourths of the force” is not missing, it is and always has been a
    translational exchange between increasing or decreasing space in which both magnetism and dielectricity mediate field pressures.

  • DanyDM
    DanyDM Месяц назад

    My life is a lie

  • Hexor1211
    Hexor1211 Месяц назад

    Great application of relativistic thinking, but it would be very nice to mention a few things. isn't that Theory of relativity combines some older electromagnetic theories with other theories.
    Aren't just Maxwell's Equation enough to explain the phenomenon?
    Maxwell was before the Einstein. Isn't Einstein knew the Maxwell's equation and used this findings in his research?
    Also, Einstein had to know about Lorentz's factor.
    May be we tend to credit the Einstein and relativity for findings of others?

  • xkguy
    xkguy Месяц назад

    Proving again that the internet was built for cat videos (and i guess pron)

  • Electro-Cute
    Electro-Cute Месяц назад

    That is not how magnetism works. If that was the case then the cat would be attracted when not moving because the electrons should contract from the perspective of the cat. Another problem would be if the current was made out of cats moving to the left and the electrons where stationary. Then the cat should experience a repulsive force when it is stationary, even if the current isn't the same.
    None of these examples happen in real life, it is only when the cat ion starts to move trough a magnetic field that it starts to experience a force, but that is based on how it moves relative to the field and not relative to the movement of charged particles. This is why magnetic fields tend to induce torque or angular velocity and not simple forces.

  • Sumner Stuart
    Sumner Stuart Месяц назад

    Hahaha hahaha hahaha special relativity is an explanation. And a poor one.

  • Bill Aynes
    Bill Aynes Месяц назад

    Why you people continue throwing BS?

  • Obnyr
    Obnyr Месяц назад

    From your frame of reference, the electrons are moving, so they should be slightly closer together, creating a net negative charge that would attract the cat. So the cat is attracted in your frame of reference but repelled in its own. Paradox.

  • CLeeP1983
    CLeeP1983 Месяц назад

    More likely, all the electrons being pumped into the wire are pushing out protons.

  • CLeeP1983
    CLeeP1983 Месяц назад

    Ok, so protons can bunch up when the cat moves but electrons cant bunch up under current flow?

  • IronMongoose1
    IronMongoose1 Месяц назад

    Thanks for making this video. I didn't want to ask a scientist.

  • NAANsoft
    NAANsoft Месяц назад

    Awesome! A great, fun explanation that is easy to understand. I am catalyzed... :-)

  • Serock
    Serock Месяц назад

    This is so cool, how can i never have heard about this before?

  • A Newt
    A Newt Месяц назад

    electric motors make much more sense to me now

  • Arturas Karbocius
    Arturas Karbocius Месяц назад

    Ant super strong magnetic force is Midi-chlorian? or 0,000000001% of earth gravity ?

  • Arturas Karbocius
    Arturas Karbocius Месяц назад

    Ant super strong magnetic force is Midi-chlorian? or 0,000000001% of earth gravity ?

  • GraemeMarkNI
    GraemeMarkNI 2 месяца назад


  • Don
    Don 2 месяца назад

    Ignorant nonsense. Take more physics courses before you pretend.

  • Alex Layton
    Alex Layton 2 месяца назад

    Somebody call ICP

  • Shaun Janoschka
    Shaun Janoschka 2 месяца назад

    complete utter nonsense.... and I'm being polite.

  • 55rebels
    55rebels 2 месяца назад

    Guess they haven't figured out yet, that relativity is DEAD. Quantum physics and relativity do not play nice together. This should, give them some kind of clue, that they are indeed... clueless.
    ....What a joke.

  • Albert Person
    Albert Person 2 месяца назад

    This is the biggest crock of pooh that I have ever heard.... Better start looking for a new gig Veritasium dude...

  • Daemon Nice
    Daemon Nice 2 месяца назад

    Nonsense. His explanation is absurd. How can you describe how magnetism works if you do not even know what a charge is? What is a positive or a negative charge and more importantly; what makes them different? And as far as an electric field is just a magnetic field viewed at different angles is even more nonsense. Within electromagnetism you have two fields at right angles to each other and at right angles to the flow; one is the electric field and the other is the magnetic field. Electric fields can have monopole moments but not magnetic fields, they are always dipolar. This is just another church of Einstein propaganda moment and as brilliant as he was, he was not always correct and even he seriously doubted the longevity of his work.
    What is a charge? It seems rather obvious and Maxwell even referred to it as well it is a quality that is similar to what is used to describe the motion of electrons and protons and even quarks and is seen in both the micro and the macro world(spiral galaxies)., and that is spin, though, just because they use the word spin does not mean that they mean spin. OOOO those quantum physicists and their confuscating language.
    Spin is an oversimplification for it is more like a vortex and vortexes are an established quality of fluid dynamics and therefore magnetohydrodynamics. I will offer two hypothesis that does not involve Einsteinian equations.
    #1~Draw a clockwise spiral on a piece of paper and right beside it draw a counterclockwise spiral of exactly the same dimensions. This is a visual representation of the charge as spin(spiral/vortex). Note clockwise and counterclockwise appear to move in opposite direction and therefore have opposite charge. Fold the paper midway between the two image and see how they now appear to move in the same direction causing attraction. Draw two clockwise circles side by side and fold the paper and they do not align up therefore repelling.
    #2~This is my personal favorite and is based on the observations of Viktor Schauberger, aka, the water wizard. His motto was, comprehend and copy nature. Again it is all about vortici, but rather than just being clockwise or counterclockwise, they are convergent and divergent, aka, centrifugal and centripetal. Positive charge = Q+ is centrifugal and divergent (moving from the center to the outer) and negative charge = Q- is centripetal and convergent(moving from outer edges towards the center). The north pole is Q+ moving outward and the south pole is Q- moving inward thus attracting.

  • Ratt Butt
    Ratt Butt 2 месяца назад

    Wait, so why does the cat feel a force even when it's not moving? I mean, why does a stationary object next to an electrified wire loop feel a force?

  • B and B
    B and B 2 месяца назад

    if a force is noly noticeable from one view that means that its just a theoreatical force

  • Rubayat Hassan
    Rubayat Hassan 2 месяца назад

    how come no one told me this when they were teaching me about magnets!

  • J Snow
    J Snow 2 месяца назад

    Yeah Science!!

  • Pan Daimonium
    Pan Daimonium 2 месяца назад

    This explanation doesn't make sense. If a cation moving at the same speed as the electrons experiences a repulsion, then a stationary cation should experience an attraction -- it's exactly the same scenario (in the cat's frame of reference) but with the charges in the wire reversed. Also, the theory of electromagnetism predicts that the cat will actually travel in a loop, if at all -- first repelled from the wire and then attracted back toward it.

  • Tim Crinion
    Tim Crinion 2 месяца назад

    Wow, I learnt something today!

  • itsme minime
    itsme minime 2 месяца назад

    i dont understand this but i think i got it !

  • binaryguru
    binaryguru 2 месяца назад

    Electrons don't really 'move' through wire. This explanation makes no sense at all.

  • Zigurath100
    Zigurath100 2 месяца назад

    the holes move too

  • Jim Pifarre
    Jim Pifarre 2 месяца назад

    Do Humans have magnetic fields..?

  • pobembe1958
    pobembe1958 2 месяца назад

    If magnetism is the same as an electric field, then why does it not work on non-metals since an ordinary electric field will polarize and attract non-metals. Aren't you just grasping for an explanation that doesn't really work?

  • AThagoras
    AThagoras 2 месяца назад

    Wow! I didn't know the connection between electric and magnetic forces had anything to do with relativity.
    But a stationary charged cat experiences a force, whereas a charged cat moving at half the velocity of the electrons would feel no force?

  • lerch25
    lerch25 2 месяца назад

    If magnetism doesn't actually exist then all of the physicists searching for a magnetic monopole definitely wasting their time.

    TRASHURE 2 месяца назад

    This does not explain what a field is, no one, and nothing has, they have merely explained many attributes. If you are far away from a train sailing across a plain, it will appear to move slowly, sure. If you are still in your far away vantage point, and use a powerful telescope to expand the resolution, you will see everything moving along just as quickly. Distance has nothing to do with time itself, even if those light waves are reaching you later than the actual event. Be objective, don't gobble down exotic theorums without thinking. You can prove anything with an equation, whether it's correct, incorrect, or correct while being applied incorrectly.

  • Warren NZ
    Warren NZ 2 месяца назад

    Interesting. I've never heard electromagnetism explained like this and I did a degree in physics. Thanks Veritasium!

  • Vadim Ivlev
    Vadim Ivlev 2 месяца назад

    With all my respect to the channel, it seems that is not a correct explanation of magnetic forces. From a frame of reference not moving relative to the wire the same line of reasoning will lead you to the conclusion that the cat will feel the force and move in the opposite direction (to the wire), which is a contradiction of course. The reality should be basically the same for any observer after all.

  • mrchapsnap
    mrchapsnap 2 месяца назад

    pshhhhh.. everyone knows it's miracles make them work duh

  • Robert South
    Robert South 2 месяца назад

    So alternating current can't be used to make an electromagnet?