How Special Relativity Makes Magnets Work
Why Hacker News recommends it
HN commenters recommend it as a short, clear explanation of why moving charges create magnetic fields.
What it is
Veritasium explains magnetism as a consequence of special relativity. Length contraction of moving charges makes a current in a wire attract or repel a nearby moving charge.
Recommended by 7 HN commenters across 7 different months, 2014 to 2024.
What Hacker News said
Recommends kull · 2014-08 · on “How Magnets Produce Electricity (1954) [video]”
Here some modern explanation of the phenomena: (I love the way they explain it) "How Special Relativity Makes Magnets Work" [this video] .
Recommends snarfy · 2020-02 · on “Ultimate Electronics”
That's right. Here is a pretty good video explaining magnetism as a relativistic effect of electrostatics - [this video]
Recommends rovolo · 2020-04 · on “Why is Maxwell's theory so hard to understand? (2007) [pdf]”
Here's a video explainer: [this video] Magnetism affects moving charges, but not stationary charges. A magnetic field in your reference frame is really just an electric field in the moving charge's reference frame.
Recommends HPsquared · 2020-07 · on “Bohr–van Leeuwen theorem – magnetism in solids is a quantum mechanical effect”
Magnetism is a side effect of special relativity: moving charges have length contraction (depending on frame of reference) which makes them appear more/less dense and therefore an attractive/repulsive force. Veritasium on YouTube made a much better explanation: [this video]
Recommends programmer_dude · 2021-09 · on “Why can’t I go faster than the speed of light?”
Wow, this is the first time I have understood why nothing can go faster than the speed of light and why time dilation is a thing. A very easy to read article, give it a try. Also if you are curious why a moving charge creates a magnetic field watch this Veritasium video: [this video]
Recommends lugoues · 2024-06 · on “Why does current flow the opposite way from the electrons?”
Sort of, electricity and magnetism are two sides of the same coin, electromagnetism, so it's waves in the electromagnetic field with the wire acting as a wave guide. (as far as I understand) Veritasium has a video that goes over this. It was pretty controversial at release but it gives a good overview. [LINK] And why magnets work due to relativity [this video]
Recommends amelius · 2024-08 · on “NASA Discovers a Long-Sought Global Electric Field on Earth”
I think what GP meant is that (from one viewpoint) magnetism is an emergent property of the electric field and relativity. Here is a simple explanation: [this video]
Cites snarfy · 2014-11 · on “Is Aluminum Magnetic? (2013)”
Another fun fact: Magnetic fields are a consequence of relativity and length contraction of electric fields. [LINK] This video also talks about it: [this video]