Тем временем — квантовой механике исполнился век
https://home.cern/news/news/physics/century-quantum-mechanics
https://home.cern/news/news/physics/century-quantum-mechanics
Начал следить за 3I/ATLAS после этого фанфика https://avi-loeb.medium.com/is-the-interstellar-object-3i-atlas-alien-technology-b59ccc17b2e3
И более взвешенная статья: https://skyandtelescope.org/astronomy-news/interstellar-comet-3i-atlas-what-we-know-now/
И более взвешенная статья: https://skyandtelescope.org/astronomy-news/interstellar-comet-3i-atlas-what-we-know-now/
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deranged physics
Photo
я даже не буду изображать что понял этот мем без пояснительной:
The joke is that, although Δ looks like the “square” of ∇ (since Δ = ∇·∇), Δ is usually easier and better-behaved, while ∇ is slippery and easy to misuse.
Why ∇ feels scarier:
• It’s not a true vector; it’s a differential operator. Whether it means gradient, divergence, or curl depends on what you put next to it (scalar vs. vector, dot vs. cross), and it only “acts to the right,” obeying product rules—fertile ground for mistakes.
• Algebra with ∇ is treacherous. Treating it like an ordinary vector leads to sign errors and bogus identities, especially in curvilinear coordinates or on manifolds (where you really need covariant derivatives).
Why Δ feels friendly:
• It’s unambiguous: \Delta f = \partial_{xx} f + \partial_{yy} f + \partial_{zz} f (in \mathbb{R}^3).
• Nice properties: rotationally invariant, self-adjoint (with common boundary conditions), nonnegative, and smoothing (think heat/diffusion). There’s a rich toolkit—Fourier methods, Green’s functions, maximum principle—for solving with it.
So the meme says: the “complicated” operator (Δ) is a good dog, while the seemingly simpler symbol (∇) hides a whole zoo of behaviors and rules—hence the werewolf.
Why ∇ feels scarier:
• It’s not a true vector; it’s a differential operator. Whether it means gradient, divergence, or curl depends on what you put next to it (scalar vs. vector, dot vs. cross), and it only “acts to the right,” obeying product rules—fertile ground for mistakes.
• Algebra with ∇ is treacherous. Treating it like an ordinary vector leads to sign errors and bogus identities, especially in curvilinear coordinates or on manifolds (where you really need covariant derivatives).
Why Δ feels friendly:
• It’s unambiguous: \Delta f = \partial_{xx} f + \partial_{yy} f + \partial_{zz} f (in \mathbb{R}^3).
• Nice properties: rotationally invariant, self-adjoint (with common boundary conditions), nonnegative, and smoothing (think heat/diffusion). There’s a rich toolkit—Fourier methods, Green’s functions, maximum principle—for solving with it.
So the meme says: the “complicated” operator (Δ) is a good dog, while the seemingly simpler symbol (∇) hides a whole zoo of behaviors and rules—hence the werewolf.