How Special Relativity Makes Magnets Work

  • Опубликовано: 23 сен 2013
  • MinutePhysics on permanent magnets:видео.html
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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

Комментарии • 4 195

  • Haridinee Vikhe
    Haridinee Vikhe 6 часов назад

    Amazing job. The realization of magnetism is really worthy

  • Mk Km
    Mk Km 7 часов назад

    Finally I understand the tape recording.
    Well, not completely. You need time to think about it.

  • Electromorphous
    Electromorphous 9 часов назад

    So we should be able to use this for making the theory of everything that is supposed to connect relativity and quantum mechanics.

  • T. Baggins
    T. Baggins День назад

    Are you high dude?! ....I don't care to argue right or wrong, me just thinks you'd like a pipe and a crepe.

  • Prajwal Kumar K
    Prajwal Kumar K 2 дня назад

    what does the cat represent

  • vanscoyoc
    vanscoyoc 2 дня назад +1

    This video has made me catatonic!

  • Onkar Patil
    Onkar Patil 2 дня назад

    U are awesom

  • Husni Jabir
    Husni Jabir 2 дня назад

    Excellent. Love this.

  • Pankaj Jain
    Pankaj Jain 3 дня назад

    As in ur frame of reference cat is stoped n so is +ve charge in wire but electron are moving so in your frame of reference linear density of electron must increase n that of +ve must decrease. This will make wire begave like negative charge n thus attract +ve cat. Plz help to solve me this puzzel ...

  • apple embedded
    apple embedded 4 дня назад

    but what about the speed of a moving electron, i read in an article before that says the speed is so small than a moving snail.
    then how it will work.
    can you clarify my doubt?

  • OHTYCH 100
    OHTYCH 100 4 дня назад

    Is there an object that when you have a compass, and a battery the needle gets weird but is there something you can put between them and nothing will happen to the needle

    MANIKANTT M 4 дня назад +1

    But the electrons keep on colliding which means they are accelerating or decelerating which makes it a system with non constant velocity and unfit for the usage of special relativity right , but why are we using it then.

  • Yoyo Tsui
    Yoyo Tsui 5 дней назад

    Wow! thanks for this

  • Tanay Mehta
    Tanay Mehta 5 дней назад

    What about a single electron. When it moves it creates a magnetic field. But how can you apply special relativity apply here?

  • mumblernumber
    mumblernumber 5 дней назад

    yo science wtf

  • Kane Sweet
    Kane Sweet 5 дней назад

    Hell yeah dude good video

  • Noah Mikov
    Noah Mikov 5 дней назад

    good song. Also, I recommend going to dr physicsA to understand all the math.

  • sammbo250
    sammbo250 6 дней назад

    ARRGH, my head hurts now. I've never understood Relativity even as a physics nerd.

  • André A
    André A 9 дней назад

    0.0000000001% of the speed of light is about 0.03 m/s for those interested.

  • Jonty K.
    Jonty K. 11 дней назад

    If this all is based on the fact that nothing can travel faster than light than....... What about neutrinos?...... Does it mean that special relatively is all a hoax!

  • Dhaval Deshmukh
    Dhaval Deshmukh 12 дней назад

    god bless you

  • Gonzalo Diaz
    Gonzalo Diaz 13 дней назад

    so this is the quantum explanation of Faraday law?

  • Mike kirock
    Mike kirock 14 дней назад

    This is all fine, but how do you explain that the force is a right angles, i.e come out of screen?

  • Simon sez
    Simon sez 14 дней назад

    So, if two wires are connected in parallel to the same power source and have the same total Resistance and have the same amount of current passing through (in phase in case of AC), does it mean there will be no magnetic effect between the two wires?

  • Tanay Kohale
    Tanay Kohale 16 дней назад

    Thanks for solving my old dought but second question is what is relativity (both special or general) or to be specific why speed of light is constant???
    I tried Search it many times but no one tell me any equation or any phenomenon, or principle
    They just move around topic n finally give statement speed of light is constant.

    • Tanay Kohale
      Tanay Kohale 16 дней назад

      In other comments I found people r saying its fundamental
      If it is then how humans come to know it's constant in all frame

  • Martin Schober
    Martin Schober 18 дней назад

    great work! thanx for this insight - and i mean it! WOW!!!

  • Leo Yohansen
    Leo Yohansen 19 дней назад +1

    Amazing how length contraction can be acknowledged for electromagnetism in special relativity but totally ignored for gravitation in general relativity exposing the fact that black holes cannot exist due to the impossibility of the total length contraction of the mass that would have to occur at the so-called event horizon.

  • fritzz2
    fritzz2 23 дня назад +1

    einstein = wrong e=mc2 = Poincaré Relativity = Lorentz einstein = fraud

    • An artist theory on the physics of 'Time' as a physical process. Quantum Atom Theory
      An artist theory on the physics of 'Time' as a physical process. Quantum Atom Theory 19 дней назад

      Or we can reformulate it: (E=ˠM˳C²)∞. With energy ∆E equals mass ∆M linked to the Lorentz contraction ˠ of space and time. The Lorentz contraction ˠ represents the time dilation of Einstein’s Theory of Relativity. We have energy ∆E slowing the rate that time ∆t flows as a universal process of energy exchange or continuous creation. Mass will increase relative to this process with gravity being a secondary force to the electromagnetic force. The c² represents the speed of light c radiating out in a sphere 4π of EMR from its radius forming a square c² of probability. We have to square the probability of the wave-function Ψ because the area of the sphere is equal to the square of the radius of the sphere multiplied by 4π. This simple geometrical process forms the probability and uncertainty of everyday life and at the smallest scale of the process is represented mathematically by Heisenberg’s Uncertainty Principle ∆×∆pᵪ≥h/4π. In such a theory the future is unfolding photon by photon with the movement of charge and flow of EM fields. This gives us a geometrical reason for positive and negative charge with a concaved inner surface for negative charge and a convexed outer surface for positive charge. The brackets in the equation (E=ˠM˳C²)∞ represent a dynamic boundary condition of an individual reference frame with an Arrow of Time or time line for each frame of reference. The infinity ∞ symbol represents an infinite number of dynamic interactive reference frames that are continuously coming in and out of existence.

  • Deepak K
    Deepak K 24 дня назад +1

    So, this means that if either a positive charge or a negative charge is brought near the conductive wire, it will repel? But that is not the principle of electromagnet. And also how do you assume that the outside positive charge is moving with same velocity as that of electrons inside the wire? In an electromagnet, the electrons move in the conducting wire creating magnetic field around them, not electric field. This video is quite misleading.

  • Saleh Algadeer
    Saleh Algadeer 24 дня назад +1

    I think that the video doesn't exactly explain the magnetism, but rather the electromagnetic force (applied on an electric charge).

  • yayJohn P
    yayJohn P 24 дня назад +1

    0:38, Derek, are you sure you shaved?

  • syed hussain
    syed hussain 25 дней назад +1

    Brilliant way of clearing concept....

  • Surneel Sehgal
    Surneel Sehgal 25 дней назад +1

    Why there is not any electron contraction ? In the stationary frame of reference of cat.

  • Coco Deng
    Coco Deng 25 дней назад +1

    One of the question in my magnetic field unit test (G12) asked, which direction would a ball move if a wire that has a current moving out of the page and a ball moving into the page. According to right hand rule, the ball is going into the page (v= the thumb) and the magnetic field created by the wire is acting on the ball is from left to right (field=fingers). Therefore, the force of magnetic field should be down. However, according to relativity, obj. compress in the direction of motion, so, in the frame of reference of the ball, the density of e- should be increased. Thus, force of magnetic field is up? I know that I must’ve messed something up but, I really don’t know how...

  • Yes I entered My Name Correctly
    Yes I entered My Name Correctly 26 дней назад +1

    I think anyone who watches this video will be dumber for having watched it.

  • e w
    e w 26 дней назад +1

    Didn't appreciate the bait and switch of the title . "Now, come take a look at my business partner's work and get the information my title lured you with in the first place." I still gained new information, but you Veritasium, I would think, would be above naked selling and cheap diversion. Money corrupts all. I would like to have a chance to personally experience it someday.

  • gaurav goyal
    gaurav goyal 27 дней назад +1

    this video has given a wrong explanation.

  • vj lockett
    vj lockett 27 дней назад +1

    How Special Relativity describes magnetism would be a better title. Special relativity does not make magnets or anything else work it's simply a tool used to understand how they work.

  • Alex M
    Alex M 28 дней назад +1

    This is the most amazing explanation I've ever seen about eletomagnetism.

  • Bishamonten
    Bishamonten 29 дней назад +1

    Why doesn't the cat in her frame of reference perceiving a new net positive charge violate the conservation of charge?

  • Eric jones
    Eric jones Месяц назад +1

    This title is misleading. This is explaining ELECTROMAGNETISM. Magnetif force is NOT explained here with virtual photons.

  • An artist theory on the physics of 'Time' as a physical process. Quantum Atom Theory

    This is one of the best videos on this subject!!!
    Well done!!!

  • Aakash Sharma
    Aakash Sharma Месяц назад +1

    this ia wrong on so many levels

  • PhantoM
    PhantoM Месяц назад +1

    a convertible peugeot? lolk

  • asdf211
    asdf211 Месяц назад +1

    Please do Lorentz symmetry and cpt symmetry

  • Scotch Egg the Guy Guy
    Scotch Egg the Guy Guy Месяц назад +1

    Derek being multiple characters at once is the most surreal thing every time I see it

  • Beemer
    Beemer Месяц назад +1

    Can something exist that is big enough that the electrons are far enough apart from each other that it repels the cat?

  • listerreg
    listerreg Месяц назад +1

    What about shape of magnetic field around a wire? Why it's circling around it? How does it explain current generation in varying magnetic field?

  • Mac Was
    Mac Was Месяц назад +1

    3:20 WHYYYYY does it sound annoying? Did he MAKE himself sound higher pitches so it's more annoying? Why does it sound different? Oh jesus.

  • Billy Bob Joe, The Anonymous Stoner
    Billy Bob Joe, The Anonymous Stoner Месяц назад

    Someone answer me this:
    What if the cat moves the other way?
    I saw someone explain that the electrons move from atom to atom, and that the absence of an electron from an atom creates a positive charge. So if you run a current through the wire, the negative charges move at the same speed as the positive charges (which is really just an absence of a negative one). So you have one stream of moving charges, not two like in the video illustration, and they move in opposite direction at the same speed. So when you move the cat against the flow of electrons, the space between them (which is what we call a positive charge) contracts, making it negatively charged. But when you move the cat with the flow of electrons, the electrons stop moving from its frame of reference (when they were moving at the speed of light before), spreading the charges out from each other. Because that space is the actual positive charge, it becomes positively charged and the cat is repelled. So am I right? Cat is attracted moving one way and repelled the other? How was my explanation? Also, is the cat just a lack of negativity? That’s how I feel about my cats, anyway

  • tomaz kopat
    tomaz kopat Месяц назад +1

    Whene were magnets discovered and by whom?

  • Dave Mateo
    Dave Mateo Месяц назад +1

    This was amazing. Took a whole bunch of stuff I thought I knew and showed how it actually worked. Mind = Blown

  • Prithyish Mandal
    Prithyish Mandal Месяц назад +1

    What would have happened if it was an anion??

  • Rajit Shrivastava
    Rajit Shrivastava Месяц назад +1

    Not clear . Not happy. With explanation.

  • ghost82 chivas
    ghost82 chivas Месяц назад +1

    You suck, there is NO special relativity. Everything is magnetism... yeah, you suck.

  • Jonstegr
    Jonstegr Месяц назад +1

    so if the "cat-ion" is immobile next to the wire while the electrons are moving does that mean the electrons will be compacted by the same affect and the cat will be attracted instead of repelled?

  • Anthony Leggio
    Anthony Leggio Месяц назад +1

    But iron is magnetic and conductive so it can produce both relative and constant magnetism?

  • Dylan Fiore
    Dylan Fiore Месяц назад +1

    Wow, now we're pulling on the girls pussy! Man, now I wish Dick were in this gravitational push!

  • Dylan Fiore
    Dylan Fiore Месяц назад

    how about a L- ion (that is also a cat)!!!!

  • Arjekay
    Arjekay Месяц назад +1

    Ohmg, thank you so much for this video!

  • Shashank Sengar
    Shashank Sengar Месяц назад +1

    "Frame of Reference" Jokes omg😂😂😂

  • panos retsinas
    panos retsinas Месяц назад +1

    Ok so I got the hole thing with electrons move to the right and holes move to the left since if you take an electron then there’s the need to feel that space, that’s why the wire is neutral from the outside but why do then electromagnets work in the first place??? Like I remember in school that the electromagnet was pulling stuff

  • Simon Shugar
    Simon Shugar Месяц назад +1

    1:21 If a current is going from right to left and the cat is positively charged (and moving from left to right), the right hand rule says that the cat should be repelled from the wire. That's what's shown in the video. So is this a way to use physics to understand cross products of vectors in math?

  • kk chandrakar
    kk chandrakar Месяц назад

    What if the cat is not charged??

  • Leif Denti
    Leif Denti Месяц назад

    Magnets.. Fuckin' magnets, how do they work?

  • Renard Leblanc
    Renard Leblanc Месяц назад +1

    Wait, wait... wait wait wait... I just realized, watching this video, since the speed of light is constant, if we increase in velocity, the only way for lights speed to remain constant is if... time slows down? I think? And, since light moves so quickly, our velocity relative to lightspeed is usually pretty negligible. But if we start getting up to relativistic velocities, time has to slow down more significantly... I think? Holy balls, I think I now understand time dilation because of a video on magnetism... you're good. X3

  • swampwiz
    swampwiz Месяц назад

    I am impressed.

  • parimal chhetri
    parimal chhetri Месяц назад

    So moving Negative charge alone cannot produce magnetic field...

  • cory muldoon
    cory muldoon Месяц назад

    I thought if there is a current then even a stationary cat would feel a force

  • Anthony Vanover
    Anthony Vanover Месяц назад

    So how is it that self-propogating light waves have both an electric field and an orthogonal electric field in a different frame of reference?

  • JacqueLaMerde
    JacqueLaMerde Месяц назад

    special relativity is math, really its the other way around first you have the phenomena then math is used to describe it. to make a mathematical structure then bend reality to it is not science.

  • JacqueLaMerde
    JacqueLaMerde Месяц назад

    can they explain gravity first, not just describe it.

  • Usham Ronjan
    Usham Ronjan Месяц назад

    Would it be possible to show that coulombic force is equal to the magnetic force?

  • Usham Ronjan
    Usham Ronjan Месяц назад

    Why did the authors hide this fundamental way to understanding magnetic fields, from us in their textbooks? And why would you tell me now only? Anyway this is mind-blowing

  • Kshitiz Rai
    Kshitiz Rai Месяц назад

    If magnetic field is nothing just a electric field viewed from a different reference than how do we explain the direction. As electric field act along the line joining two particles whereas magnetic field is perpendicular to the direction of current and the line joining current element to the point at which particle is present.

  • Vishrut Verma
    Vishrut Verma Месяц назад

    I am stunned

  • Vikrant Dhapa
    Vikrant Dhapa Месяц назад

    Great work

  • Vikrant Dhapa
    Vikrant Dhapa Месяц назад

    This was awesome

  • kaye swanson
    kaye swanson Месяц назад +1

    i might understand this someday.

  • Sirus Das
    Sirus Das Месяц назад +1

    Went through few comments... seems like we got lots of enthusiastic and talented scientists here. I do appreciate your theory and that you just related the Special Relativity to attraction, just like time warping in space due to gravity make it move slower than one with low or no gravity i would be amazed if that is what is just happening with Magnets on a quantum scale and that to sometimes it wraps something inwards i.e it attracts and sometimes it repels i.e it wraps outwards. If that is what you tried to say then its pretty amazing!

  • cipiripper
    cipiripper Месяц назад +1

    No need for such dumb acting...

  • Voxel79
    Voxel79 Месяц назад

    if I didn't f**k up maths the number of electrons due relativity on a 2.5mm² copper wire with 16Amps increases to x amount of percent and the x is:
    100.000 000 000 000 000 000 000 124 323 820 657 146 277 207 303 311 048 298 651 329 866 600 319 389 486 465 840 576 633 800 577 576 307 815 939 468 578 427 697 988 220 633 869 061 832 980 706 170 158 450 232 805 383 109 941 422 814 318 932 219 922 269 534 001 417 624 689 391 716 127 026 884 470 067 650 848 172 472 004 505 193 017 010 327 610 980 237 122 718 085 064 639 571 381 639 354 058 739 253 010 115 372 725 809 139 437 219 148 886 339 357 261 567 417 076 751 571 767 846 783 160 746 060 843 609 080 637 739 688 010 417 100 320 031 161 730 599 891 056 997 649 737 714 904 549 993 470 900 997 466 026 890 864 957 894 474 364 155 204 239 666 492 235 313 670 807 783 272 730 356 222 278 533

  • Chris Lee
    Chris Lee Месяц назад

    299 792 458 x .000000000001 = 0.0001084581 m/s
    Am I doing it wrong???

  • Arnon Tillmann
    Arnon Tillmann 2 месяца назад +1

    Mind blown!

  • Dylan Fiore
    Dylan Fiore 2 месяца назад +1

    ha, pawstively cation!

  • Dylan Fiore
    Dylan Fiore 2 месяца назад +1

    is that minute physics in your vid

  • Altillo DeLaPradera
    Altillo DeLaPradera 2 месяца назад +1

    this video makes no sense

  • eu4eagle
    eu4eagle 2 месяца назад +1

    If you don't move only the electrons get lenght contracted not the space between them! -> No magnetic force
    If you move -> EVERYTHING is moving backwards relative to you so the space between the protons and the protons get contracted! -> magnetic force

  • ruka suirenji
    ruka suirenji 2 месяца назад

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

  • Black Jack 21
    Black Jack 21 2 месяца назад

    Omg thank you mannnn

  • polyb 1123
    polyb 1123 2 месяца 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 месяца 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 месяца 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 2 месяца назад

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

  • Harikrishna K
    Harikrishna K 2 месяца 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 2 месяца назад

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

  • Mattia Moroder
    Mattia Moroder 2 месяца 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 2 месяца 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 2 месяца назад

    3:06 Arrows are pointing in the wrong direction.

  • Davis Jensen
    Davis Jensen 2 месяца назад

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