How Special Relativity Fixed Electromagnetism

Electrodynamics (electricity and magnetism) is governed by Maxwell's equations and the Lorentz force law, but that left it a little broken. It would take Albert Einstein inventing special relativity to fix it. If magnets are based on motion and motion is relative, how does that work?
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VIDEO ANNOTATIONS/CARDS

Maxwell's Equations Visualized:

The Ultimate Guide to Relativity:

Galilean Relativity:

Older Version of this Video:
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Veritasium on Relativistic Electrodynamics:

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Einstein 1905:

[ScienceAsylum]

*Clarification:* We know from _observation_ that the wire is neutral in the lab frame. You can't argue against that. _That's just reality._ Yes, the electrons are moving in the Lab Frame and would be length contracted. They're _already_ contracted in the picture. They're contracted in such a way to make sure the wire stays neutral. That's why they expand when we switch to the Clone Frame and give the wire a charge density in that frame. The wire can only be (uniformly) neutral in one frame and we _observe_ that to be the Lab Frame.

[outside]

The way you present complex science like a kids show simultaneously makes me feel very smart and very dumb... I love it

[EugeneKhutoryansky]

When you switched from Lab frame to the clone frame at 6:26, you correctly "uncontracted" the distance between the electrons (which are now stationary), but when you originally showed the relativistic effects of the lab frame at 5:45, you never showed the length contraction being added to the distance between the electrons in the first place. If we assume that the wire is electrically neutral when no current is flowing, then once the current does start flowing, the length contraction of the distance between the electrons (in the lab frame) would cause the wire to become electrically negative, thereby creating an extra electric repulsive force which was not taken into account in the video. To properly solve this paradox, we need to take other relativistic effects into account (besides just length contraction). You are probably already aware of everything I just said and you just wanted to keep things simple for the explanation in the video, but I thought I would mention this. Thanks.

[Chris]

2:15 That metal music is a bit on the Heaviside.

[Lucky]

Hey Nick! Just wanna let you that I shared this video with my classmates in my electromagnetics course, since none of the material in the prereq course covered the relationship between E&M and SR, and the professor endorsed the post, so I he must think it's a valuable educational video too. Even after all these years, I think this is still my favorite one of your videos, because it just make the connection between electricity and magnetism make _so much sense, _ instead of just being a postulate. Plus, as a bonus, using a squirrel as the positive charge is amusing.

[marloc]

Your vids are usually top notch but this one is epic in all frame of reference I can think of...

[adityachk]

It's videos like this from people like you who make the world a better place to live in

[tawe]

Maybe small series about tensors in whole physics? And what dou You think about Susskinds Theoretical Minimum series? I found it very interesting.

[Nebuch]

That was a very unexpected explanation for me, liked it much!

[kushlanaluwihare]

great video! one full length explanation better than trying to understand this topic from 10 short incomplete videos

[chonchjohnch]

I actually just learned about this last week in physics! It’s amazing that even a small gamma factor can cause the effects we see

[globaldigitaldirectsubsidi]

Awesome simple explanation. Amazing as usual. If I had seen this content as a kid, I would be a physicist today.

[petermuller]

GREAT VIDEO!!!

I got my physics master 25 years ago (didn't work in that field since) and your videos reveal new and forgotten depths of the science.

Also i'm amazed of the perfect combination of being accurate AND easy to comprehend AND fun (both watching the video and inspiring science) at the same time!



Thank you very much!!

[Lucky]

I'm just amazed that SR applies at such a small scale at speeds so much less than C. The EM force has got to be _really_ strong for such miniscule length contraction to make a significant difference. Or is it just because because the EM field propagates at lightspeed? Either way, it's really cool. Electromagnetism became infinitely cooler when I saw SR is involved.

[BLADESTER]

This, this right here. Direct and to the point and explained exceptionally well, this is how it should always be done

[LacenWolk]

The videos are getting better and better! Keep up the good work

[sivamynthannadesamoorthy]

I just viewed all your videos and its crazily awesome

[nbonasoro]

This is such a great channel. I used to watch PBS spacetime but they made everything so complicated and hard to understand, you explain everything so well. Thanks for these interesting videos.

[pedrom.]

Just found this channel. New subscriber for combining visual and material interpretation with physical rigor.

[chrisdeep]

Definitely one of the better science channels. It seems to cover a level of detail missed out on most other "science" channels.