How Special Relativity Fixed Electromagnetism
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- Опубліковано 25 лип 2024
- 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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Maxwell's Equations Visualized:
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The Ultimate Guide to Relativity:
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*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.
Thanks
Thank you
Thanks!!:D
Hi Nick. Is it really true that the electrons length contract in the lab frame? For example, suppose two people (A and B) are running a race and both are traveling a significant fraction of the speed of light (somehow, lol) . A is ahead by about 20m. A and B will surely be length contracted as seen by someone observing them, but the space between them will surely not length contract, or am I mistaken? In other words, they should both appear contracted, but they should not then move closer to each other because the space between them and the floor, etc, are not in motion. Similarly, the individual electrons shouldn't move closer to each other in the lab frame because the space between the electrons is not moving too. In the clone frame it makes sense for the wire with the positive charges to length contract because all the charges and the entire wire are moving as one thing. Sorry for the long story. Please tell me if I am on to something here or just over thinking. Lol
How come the wire is electrically neutral in the lab frame before and after you hookup the battery, then? The electrons should contract when they start moving, compared to their stationary state in the lab frame.
The way you present complex science like a kids show simultaneously makes me feel very smart and very dumb... I love it
Clair Patterson said good scientists have the mind of children.
Therefore there isn't any contradiction.
@@localverse I don't know where I've heard this, but I've always thought that "absurdity is the plaything of an intelligent mind."
Smart, dumb...it’s all relative.
Whenever I feel dumb, I remind myself that this feeling is simply how learning begins.
@@ScienceAsylum Whenever you feel dumb you can just say it's relative because you made everybody else smarter.
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
I know, right?!
The Science Asylum I remember the moment that I realized that the charge density of a straight wire would be affected by the motion and was elated
And that is how electric motors work.
The gamma factor is not small if the squirrel 🐿 is moving at the same speed as the electrons.
@@TheHzh82 electrons move around circuits incredibly slowly. It's often measured in mm/s or m/h.
The idea that electrons are whizzing around the circuit either hundreds or thousands of times per second is simply wrong.
Of course this is only net movement of the electrons (called mean drift velocity), they are actually travelling rather fast as they get pushed around by the atomic nuclei, but still nowhere near the speed of light (so the gamma factor is still very small) and in this situation the average speed of them is all that matters, and that's *incredibly* slow.
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.
He goes into this in the pinned comment and theres a discussion on it. Maybe you'd like to join in :)
The wire stays neutral in a lab frame when electrons start moving. While they become more spaced out in a moving frame, they remain at the same distance in a lab frame.
Btw he never actually showed the moment of acceleration, so no mistakes here.
How would you explain that? What other relativistic effects are you talking about?
Once the current starts flowing, there is no contraction, because the very repulsion between the electrons cancels-out any relativistic contraction (in the lab, where all the electrons are moving at the same speed everywhere inside closed loop). The electrons will simply spread out over the whole loop keeping the wire neutral.
However, the contraction explains the difference in electron density from the squirrel's perspective, because the electrons are no longer moving at the same speed everywhere, they are more densly packed where the speed is higher (most packed at the lower part, somehow packed in the vertical parts). I would explain that by visualising the _sphere of influence_ of the charge of individual electrons, which contracts as well as the electron itself in the axis along which the electron is moving, therefore allowing denser packing proportional to the speed. And that explains the charge (positive in upper half, negative in lower part, neutral in vertical parts).
First, hey Eugene! Second, I've been getting this comment a lot so I started a thread in a pinned comment to handle it. Yes, I'm aware of the problem, but it wasn't worth over-complicating the model of the wire to explain. As with a lot of these explanations, there's a lot more going on than is shown.
@@ScienceAsylum Could you link the full explanation? Maybe just edit pinned com. Thx
2:15 That metal music is a bit on the Heaviside.
😂😂😂😂🤣🤣🤣🤣🤣🤣🤣🤣
I see what you did there 🤣
What song is it?
Dad joke for the win. Or is it a physics joke?
Cringy af
It's videos like this from people like you who make the world a better place to live in
Adityachk2002 yep , makes my day with all the other stuff that is going on
I didn't know it until I searched about how magnet was made then I found these ：０
It is utterly amazing that anybody could figure this out. That the speed of waves in Maxwell equations are based on two constants immediately suggests that the speed of light cannot be relative to the frame of reference.. totally bedevils ordinary perception
It's pretty wild.
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.
Thanks for letting me know! 🤓
Fantastic video! However, this illustration depends on the fixed positive charge background. How is this question resolved if the electrons are moving in free space with neutral background?
Maybe small series about tensors in whole physics? And what dou You think about Susskinds Theoretical Minimum series? I found it very interesting.
Yes, tensors please.
He should do linear algebra first because it’s a prerequisite to understanding tensors
Oh 3 great ideas
Oh yeah tensors plz! was about to comment the same.
This is a Tensor Series for Beginners:
ua-cam.com/video/8ptMTLzV4-I/v-deo.html
Your vids are usually top notch but this one is epic in all frame of reference I can think of...
This is possibly the physicsest physics video ever. I’m greatly impressed. You got to the heart of it. Thank you!
That was a very unexpected explanation for me, liked it much!
Awesome simple explanation. Amazing as usual. If I had seen this content as a kid, I would be a physicist today.
When does this channel grow??? It's criminally underrated
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.
The EM force is strong, but the main contributor here is the amount of charge. There is _a lot_ more charge in that wire than my animation implies. Also, "at speeds much lower than c" is a statement that depends on context. For example, 8700 mph = 0.0013% of "c" ...so it seems like that would be sufficiently slow to ignore relativistic effects ...and it is most of the time, but not for GPS satellites. Relativistic effects are _always_ there. It's just a matter of whether or not those effects are outside whatever error we're happy with. That's a wicked cool thought 🤓
Science is cool.
Well you are subtracting 2 large numbers the size of Avogadros number…so it doesn’t take much. One goes up by gamma, and one goes down by gamma. And the electric field is c times stronger than the magnetic field.
The best, easiest and intuitive video on this topic; finally after all the years I understand
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.
The videos are getting better and better! Keep up the good work
Under the humor and presumed ease of explanation is a very very well thought out plan to get us to think differently and want to know more at a deeper level. Your analysis of your earlier presentations is refreshing. The way you link thinking about Maxwells' equations is brilliant. A sincere thank you. raphael santore
4 years in engineering college and still have my mind blown by a youtube video.
Cornell Benefield Thats how higher education works
Wow .. Finally a home gamer like me can glue together parts of half-knowledge about EM. Thank you!
Lazy INTPs unite!
The craziest part about special relativity is that length contraction and time dilation are physical. They are not an appearance, they are actually what happens in the world. That part just blows my mind.
I think it's easy enough to wrap my brain around time being contracted, but actual physical objects still just don't make sense to me! 🤪🤯🤯
You can't lose energy while still having to preserve laws of physics in all reference frames.
So spacetime must acquit.
He left out that time is slanted too across the direction of motion. I wonder if that magnifies or lessens the charge difference.
I just found this channel, so I don't know if it's addressed in another video, but a big component of special relativity is disagreement over simultaneity. For example, if you fly past someone in your rocketship (it's always a rocketship), and they measure your length as contracted, you say it's because they first measured where the front of your ship was and later (after you've moved) where the back was, so of course they think you've contacted. Spacetime Physics by Taylor and Wheeler is a great resource.
Same, I don't understand how it's not talked about with forces like internal compression. I am such a contraction skeptic and I hate it because I am trying so much to just accept the established theory as it's taught 😭 but if something really got physically shorter, wouldn't it feel increased pressure/density? This video is cool because it's the first mention of density alongside contraction I've ever heard
Some of the best content out there in the entirety of UA-cam. Please keep it up Nick!
great video! one full length explanation better than trying to understand this topic from 10 short incomplete videos
Glad it was helpful!
Believe it or not. I learnt today electricity for the 1st time as a high school student. Yet I understood the concept and main points in the video(Although not everything which I couldn't have) . Your quality in teaching is that you don't complicate things. Great Nick!
I don’t understand all of what you’re saying, but your videos are so enjoyable so I watch it nonetheless, thanx!
this was one video that I didn't quite get
Excellent video once again Nick.
The interchangeability of electricity and magnetism or the fact that these seemingly independent forces or fields are really just perspectives of the one field is a mind bending concept.
I've seen other videos on this topic but never seen it so well explain! Another great video!
I just viewed all your videos and its crazily awesome
This, this right here. Direct and to the point and explained exceptionally well, this is how it should always be done
Masterpiece of the understanding of electromagnetism.
Your work is amazing! I've never seen this concept explained in such a ludic and didactic way.
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!!
You're welcome 😊
Watch Eric dollards origin of energy synthesis he has a completely different way of shedding light on these concepts along with accompanying math to back it up.
I remember you responded to a question of mine about the same thing! Love your work :)
I’ve been looking into this and so far this is the simplest yet technically detailed enough explanation.
Not just clear explanation but complete as well. This is what I like about this channel. Well done The Science Asylum 👍
I have learned more from this channel than my whole life, Thank you very much Nick Lucid
Yay! A new video! Thanks so much, you are really amazing!!
I've watched most of your videos, and they keep getting better. Thanks for going a bit deeper and ignoring the false assumption that UA-cam viewers can't handle equations.
Looks like you put quite a bit of effort into this video. Paid off for sure on several levels.
I did. Glad to know it paid off.
This Lucid guy is way too smart to be making UA-cam videos, but I’m glad he does anyway. 😁
The explanations gives me lucid dreams.
Nick is our Einstein of teachers. He's so good at explaining or breaking things up even for your average Joe like myself.
But the most beautiful thing about this is that once you have special relativity and coulumbs law, you can derive the entirity of maxwells eqns. I was mind blown when I first learned this and saw magnetism just arising out of the equations.
pukkandan interesting, do you have references?
I think you also need Gauss's Laws (divergence of E and B). Coulomb's Law can only get you Lorentz's Law. As for a reference, I'm pretty sure Feynman covered it in Lectures on Physics.
@Dr Deuteron I'm thinking of Coulomb's Law as F = qE, which tells you nothing of how E is generated. I see now that, using F = q q' / 4 pi eps_0 r^2, you can infer the existence of a field E generated by one of the charges.
Amazing video! I was confused by this topic when I read about it in Purcell and Morins electricity and magnetism book. This is so much clearer. Also thanks for including the links to the Feynman lecture reference in the description.
your best video so far! glad you to see you improving yourself. thank you!
Best science channel on UA-cam. Thank you Nick for these.😀
You ain't "a little crazy." You is "a whole lotta crazy" but I guess that why we love you.
Brilliant exposition of this topic - and in only ten minutes! A truly great intro IMHO 😃. Much happier about tackling the underlying maths now 👍. Many thanks buddy!
Thanks for clarifying that bit about how the total _amount_ of charged is conserved but the charge _density_ changes.
I HIGHLY appreciate Chauffeur clone's music taste
"I'm thinking Einstein's field equations"
Big YES!
Hey man. I didn't know you had a UA-cam account. Cool :)
Surprise Surprise :)
@@GottfriedLeibnizYT teach me the math behind brachistochrone curve
Fantastic!!! Thank you SO MUCH for making these videos! Please keep it up!
If I keep watching enough of these videos, I'll finally understand it!
This might be your best video. It's hard to describe this issue in a textbook, even to experienced physics students. You continue to impress!
It's not a problem with form i.e. textbook, it's a problem with curriculum and the system of teaching per se.
Most of our knowledge, physics very much included, is taught in order of historic discoveries and with a bent toward engineering application.
The true "understanding" part comes late in the process of teaching, only when the student is *finally* presented with the current up-to-date knowledge on the subject. It should be the other way around.
Present what we know currently about how the thing works, be it in a general manner, and only THEN dive deeper into specific aspects knowing the student has at least and overview grasp of the field he's studying and won't get lost in the endless stream of engineering equations.
Wow! I’m was trained as a Mechanical Engineer and was never explained this. Perhaps, it wouldn’t have changed things since my practical “pre-relativistic” working knowledge was adequate. But this has blown my mind!!! Keep it coming Nick !! Can you please make more working examples of your ideas..almost like Problem based explanations applying your “Theoretical Physics made actionable” perspective..
You are Brilliant my friend!
Fantastic and enlightening use of diagrams as usual. Two thumbs up. Thank you.
This is the first of your videos I've watched and I love it when a principal is being explained to me in such a way that it actually clicks in my mind and I have that "ah ha" moment. For now I'm chalking that up to Dr. Feynman's elegant example ;) Seriously though, kudos to you and your clones you've earned yourself a new subscriber. I'm looking forward to many more such videos.
I am from India and I am learning this concepts now in 12th standard. It's really helpful with your video
Me too
I learned the same in 12th but from Veritasium channel.
Me too
@@ravitej8396 could you link that?
@@ravitej8396 that is also a good channel I have watched some of the videos
Einstein's field equations! Please!
(ok, make a poll about the next visualization. But this will win!)
Thanks! I was looking for this. I love your videos :D
Nick, great explanations, thanks! I like the animation you use making everything visual.
Hi Nick nice video
Because of you I learner physics and mathematics in the real way and now I love both
Einstein said with you can’t explain to a seven year old you don’t know well enough. You explain things so well that my young brother understands. Thanks Nick For Making a Such Amazing Channel For All Of Us Crazies. Love you bro 😎 Big Fam From Brazil 🇧🇷!!!!!!!!!!!
Awesome as always Nick.
YAY!! I have been waiting for a while to get a detailed explanation about this, glad you made the video and keep up the great content...(i should try get my physics teacher to show these vids)
This video literally made my day
But in the lab frame, the electrons are moving and thus are contracted. So, the rod should have a net negative charge, and therefore should exert an electric force on the squirrel in the downward direction opposite to the magnetic force on it. But you seemed to neglect this force. Why?
They're _already_ contracted. That's why the expand when we switch to the clone view. However, we know from _observation_ that the wire is neutral in the lab frame. You can't argue against that.
@@ScienceAsylum you mean to say that the wire became neutral when the electrons had contracted?
@@Someone-ex5ed I think what is going on is that the electrons are contracted differently than the (positive) atoms. That's all that matters. In the lab frame, I think the width of the electrons themselves will be contracted, but not the space between them (because that space isn't moving relative to our (lab) frame of reference).
I'm getting this question a lot, so I pinned a comment about it.
@@MidnighterClub Electrons don't have a width. They're point particles. It is the _space between them_ that changes.
Thank you for another AMAZING video! Really helps me to visualize the behavior of electric and magnetic fields! Well done!
one of your MOST IMPORTANT videos! well done
"Sometimes, Electricity is just Magnetism - in a different Frame of Reference." Mind blown.
Oh dear this was an awesome episode - I bet even people without any idea of anything would get the concept - gotta show it to some noobs! O_O
This is an amazing video and I actually understood it. Your videos are so amazing. You explain things the best, most of the time :) Thank you for existing
You could take the principles in this video and explain how induction works in a transformer. This was a great explanation!
Finally, i freakin' understand what the frick a tensor is. I know that wasn't even the focus of the video, but it finally clicked on this one!
*celebratory rocking out with chauffeur clone 🤘
That’s great!!
Woah... I enjoyed learning electromagnetism in my Geology major, watching MIT courses and all... But this is a whole other level of teaching! Many thanks!
Amazing Nick, this gave me a complete new perspective on EM.
This was amazing! For me it still added a lot of value even after I had seen minute physics video on the topic!!
Thank you! =D
Great work!
Oh Boy! That helps a lot! Thx!
One question though: What mediates the force propagated? Photons? How? Where do they come from?
Force-carrying particles are from quantum field theory. That's a much deeper conversation.
Great video as always. Sometimes the importance of Special Relativity is overlooked in science content, but it really is special! (Though not special enough for a Nobel?!? Now THAT was crazy.)
Maybe the Theory was too far out for the judging panel. They had to wait to see its effect on physics.
No Nobel for Special Relativity because it puts you in a very SPECIAL place. A place where every clock that is moving relative to you runs slower. Every object that is moving relative to you contracts - regardless of what Nick says - a physical impossiblity. In true Relativity there is no special place
@@michaelstark2832 What? You know time dilation has been tested, right? You know it's used to synchronise satellite clocks with Earth? You know it explains muon decay rates? Who are you to say what's physically impossible?
Satellite clock time dialation has nothing to do with Special Relativity, it is explained by General Relativity.
I said universal Contraction is physically impossible, muon decay rates is Time dialation.
That is just another example of why awards (Nobel, Oscars, Pulitizers etc.) are generally just not that special, I.e., important. Did van Gogh get an award for painting Starry Night? No.
Super explanation , I’ve seen other sites with similar explanation , but yours is better for completeness , clarity , and simplicity , not an easy goal to achieve , thank you !
Loved your video. Thanks for the tensor explanation.
Wow the micro charged squirrel rules the world!
How nick lucid saved my life about umderstanding physics
Fascinating video. Your graphics make it much easier to understand. Very cool.
Definitely one of the better science channels. It seems to cover a level of detail missed out on most other "science" channels.
Even tought I have studied electromagnetism in college, they never touched loretz force law and never made any atempt do connect it to relativity. Those animations on this video helped a lot to visualize and understand a little bit more how frame of refercence impacts on moving "things", as for the video, charged particle. Amazing! Time to get to the books again!
Dang good one.
But I did rewind three times to make sure I caught everything.
You are a breath of fresh air.
I am getting old. I wish you talked a little slower.
But your style is second to none.
You are an asset to millions of people.
UA-cam's speed control is invaluable.
Thank you so so so so so much. You should get some kind of award for your work.
The explanations are clear and simple so the desire for more videos is strong. Among other topics in demand, how about positrons and maybe neutrons and relates fields?
2:11 oooh! metal on your channel! I wish i could resubscribe or double like the video
that's what I say
I hope chauffeur clone comes back someday
@Anzu Shiina I don't remember the track, but it's one of Ethan Mexisell's royalty free tracks you can find on youtube all over the place.
Mind blown… again that pesky Einstein...
I am pretty cool like that indeed!
@@XEinstein we are talking about your old clone
@@averagemilffan It's the same person, but from a different frame of reference.
Your channel deserves much more Subscribers!!
Watching it again Nick...just because it’s such a good one!
I'm in high school and I thought I've read everything about electromagnetism until I saw this video "special relativity with electromagnetism" now I'm thinking to leave my school and start studying by my own coz they aren't providing us full description
Oh but have you heard about quantum electrodynamics? There is a lot to learn still, and when you've learned all that new things will demand to be learned next. The universe full of mystery!
Stay in school. Teachers can’t provide you with a “full description” because it would be too large and complex to understand all at once. This requires them to unpack it and explain it in comprehensible pieces and then to put the pieces back together into a complete whole. Human beings don’t acquire knowledge like an anaconda 🐖🐍 swallowing a pig; we do better eating and digesting food and knowledge in small bite-sized portions. 🧁🍬🍫 🧪🦠🧬 📕📗📘📙 🖍🧮🎛💻
Now i know why the channel is called science asylum
Physics drives everyone crazy 😂
And nick is the best so he is the craziest 😂😂
Great Explanations ! as Always . Thanks
This video is amazing! Thanks for explaining in such a easy way!
Not sure my brain is intact after all of this...
According to the Craziness Relativity, if I stay with THIS video, every OTHER Science Asylum video is not crazy at all! Now, where's my straitjacket! I'm gonna join chauffeur clone \m/ 2:11
This channel needs more people watching!
Far too few science comunicatiors avoid talking about tenors, thank you for doing that
I recently did a whole video! ua-cam.com/video/bpG3gqDM80w/v-deo.html