Noether's Theorem and The Symmetries of Reality
Why Hacker News recommends it
HN commenters point to it as an approachable explanation of how symmetries give rise to conservation laws, including the story of Emmy Noether.
What it is
PBS Space Time explains Noether's theorem: conservation laws such as energy and momentum are consequences of deeper symmetries. It also covers why those laws hold only under certain conditions.
Recommended by 5 HN commenters across 5 different months, 2018 to 2026.
What Hacker News said
Recommends ben509 · 2020-01 · on “Evidence that the key assumption made in discovery of dark energy is in error”
Things are conserved when there's a corresponding symmetry; this is Noether's Theorem.[1] I won't pretend to understand half that article, but here's a video[2] on it. [1]: [LINK] [2]: [this video]
Recommends tzs · 2021-05 · on “Physicists identify the engine powering black hole energy beams”
I'd recommend the two episodes released right before the one about the black hole information paradox too. They set up for what is covered in the information paradox episode. "Why Quantum Information is Never Destroyed" - [LINK] "What Survives Inside A Black Hole?" - [LINK] Maybe the episode before those two also. I vaguely recall that something from the information paradox episode used something from that (and if I'm misremembering, it was still a neat episode): "Noether's Theorem and The Symmetries of Reality" - [this video] I have a question about the episodes you cited. They cover how beyond the event horizon space becomes time and time becomes space. They go over how that means that inside y
Recommends michelpp · 2022-08 · on “Noether's Theorem in a Nutshell (2020)”
PBS Space Time has done a couple of episodes on Stationary Action and Noether's Theorem that are approachable by those not yet already exposed to Langrangians: [LINK] [this video] Sabine Hossenfelder also has a good episode on it: [LINK]
Recommends psychphysic · 2023-03 · on “The little-known story behind the 2022 Nobel Prize in physics”
If you like reading about Wu from a woman in physics hidden in plain sight aspect you might like the story of Emmy Noether[0]. A mathematician who worked a few doors down from Einstein and produced era defining result in physics. The connection between symmetry and conservation. Noether's theorem to this day is one of the most profound holy shit moments in many physicists education. Her life was been cut tragically short. [0] [this video]
Recommends twiceaday · 2025-02 · on “Noether's Theorem Revolutionized Physics”
TLDR: Do an experiment, then move 10 meters to the left (or rotate 90 degrees, or wait a few days) and do it again. The results don’t change, because the laws of physics don’t change. This realization alone is enough to produce conservation laws. Translational and rotational symmetries produce conservation of linear and angular momentum, and the time symmetry produces conservation of energy. Each symmetry you find leads to new physics. It's such an aha moment. PBS Space Time: [this video]
Cites geon · 2018-05 · on “The SpaceDrive Project – First Results on EMDrive and Mach-Effect Thrusters”
> if you're saying conservation of momentum can be violated, or conservation of energy can be violated, then basically all of modern physics would have to be wrong. Conservation is not a fundamental law, but an emergent property of a deeper principle called Noether's Theorem: [LINK] [this video] And it is constantly violated.
Cites igravious · 2018-05 · on “The SpaceDrive Project – First Results on EMDrive and Mach-Effect Thrusters”
The section of the video dealing with Noether's Theorem and The Symmetries of Reality actually ends at t=594s :/ so just the main link is needed: [this video] If one or another of these so-called fundamental laws is being apparently broken by the EmDrive then that would make it a very very unusual object. Consequently there would need to be repeatable verifiable evidence that it does so and at least the beginnings of a theory as to how in fact this breakage is occurring–Noether's theorem notwithstanding.
Cites stcredzero · 2018-05 · on “'Impossible' EmDrive Space Thruster May Really Be Impossible”
Yes the actual laws of physics can't be broken Conservation laws should be considered more as powerful analysis tools than as foundations of reality. So more Newtonian gravity than Relativity. In fact, you can regard Newtonian orbital mechanics as elaborations on conservation of energy and momentum. Conservation laws themselves have an underlying principle: [this video] Another analogy: Conservation laws are like Euclidian geometry. On the scale of building a cabinet or an office building, Euclidian geometry rules! On intergalactic scales, it simply fails. So too, with the conservation of energy. If someone tries to sell you a perpetual motion or over unity machine, it is pretty rock solid. But i