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  • 17 Comments
Joined 1 year ago
Cake day: February 1st, 2024
  • qjkxbmwvz@startrek.websitetoScience Memes@mander.xyz•Boss ModeEnglish
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    4 days ago

    No, that’s not really a useful way of modeling it for the case of light traveling through a linear medium.

    The absorption/re-emission model implicitly localizes the photons, which is problematic — think about it in an uncertainty principle (or diffraction limit) picture: it implies that the momentum is highly uncertain, which means that the light would get absorbed but re-emitted in every direction, which doesn’t happen. So instead you can make arguments about it being a delocalized photon and being absorbed and re-emitted coherently across the material, but this isn’t really the same thing as the “ping pong balls stopping and starting again” model.

    Another problem is to ask why the light doesn’t change color in a (linear) medium — because if it’s getting absorbed and re-emitted, and is not hitting a nice absorption line, why wouldn’t it change energy by exchanging with the environment/other degrees of freedom? (The answer is it does do this — it’s called Raman scattering, but that is generally a very weak effect.)

    The absorption/emission picture does work for things like fluorescence. But Maxwell’s equations, the Schrödinger equation, QED — these are wave equations.

  • qjkxbmwvz@startrek.websitetoPolitics@sh.itjust.works•US judge blocks Trump’s order to end birthright citizenshipEnglish
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    6 days ago

    I could be wrong, but I think this could be due to how the states’ suit is worded? As in, I think it’s worded as, “you can’t do that in our state,” and not, “you can’t do that full stop.”

    From another site:

    Attorneys general from 18 other states also sued over the order in federal court in Massachusetts.

    Brown [AG filing the suit] noted his lawsuit is similar, but said he felt Washington should lead a separate case because of “specific and unique harms that are brought here.” He also said that “we have a very good set of judges in our bench here in Washington, so I feel like this is the right place.”

    (My emphasis.)

    So, a good first step, and while this should be struck down in its entirety, my reading is that this was a lawsuit with limited scope, and the injunction matches the limited scope.

  • qjkxbmwvz@startrek.websitetoScience@mander.xyz•China's 'artificial sun' shatters nuclear fusion record by generating steady loop of plasma for 1,000 seconds
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    8 days ago

    While neat, this is not self-sustaining — it’s taking more energy to power it than you’re getting out of it. (You can build a fusion device on your garage if you’re so inclined, though obviously this is much neater than that!)

    One viewpoint is that we’ll never get clean energy from these devices, not because they won’t work, but because you get a lot of neutrons out of these devices. And what do we do with neutrons? We either bash them into lead and heat stuff up (boring and not a lot of energy), or we use them to breed fissile material, which is a lot more energetically favorable. So basically, the economically sound thing to do is to use your fusion reactor to power your relatively conventional fission reactor. Which is still way better than fossil fuels IMHO, so that’s something.

  • qjkxbmwvz@startrek.websitetoAsklemmy@lemmy.ml•To what extent is this accurate?
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    12 days ago

    The amount of money you save (and invest) isn’t accurately depicted with this though. Living expenses don’t necessarily grow with take home, if you keep lifestyle creep to a minimum.

    So what this means is that if you make $100k and save $10k/year, if you start making $200k you can save the same $10k/year, plus the entire additional $100k after taxes (let’s just say that’s $50k+). So you doubled your salary but your savings went up 6x+.