12 ms·

I, perhaps naively, thought it was a well understood phenomenon. With random references in sci-fi, and a quick appearance in Enemy of The State (movie), I thoug

I, perhaps naively, thought it was a well understood phenomenon. With random references in sci-fi, and a quick appearance in Enemy of The State (movie), I thought it had all been locked down. It's somehow inspiring to learn how much is there for us to learn.

oneloop 10y ago
What does "well understood" mean exactly? Ask the average inhabitant of Hacker News and he will tell you that "Faraday Cage the name of a phenomenon whereby a box of metal prevents electromagnetic fields inside", or something like that. But ask him how the strength of the electromagnetic field depends on the wire radius and mesh size, and he might not know the answer. That said, the answer was known to Maxwell, as the author remarks, although not to the author himself. As is often the case, the problem is in the details. So in a sense, it is a well understood problem to people who know the details well enough. I'm a physics graduate I did not know the answer, and I can assure you that the average physics graduate doesn't know the answer. In the year 2000 a graduate course in physics contains so much "advanced" physics that you end up learning a bit of a lot instead of a lot of a bit. My contemporaries and I know a lot of physics superficially, unfortunately. Time is limited, and in university you learn what you're fed. But yes, I agree with the sentiment of your post, of course :-)
- eternauta3k 10y ago
  A second-year Physics student can work out RF shielding using Kirchhoff's diffraction formula, or just looking at the wave equation in the k domain (spatial frequencies). Electrostatic shielding is the hard bit addressed in the article.
  - lutorm 10y ago
    I'm not sure the diffraction formula has much relevance for computing shielding. I thought that formula was an idealization where you assume that the field strength on the blocking parts is identically zero, but I don't think that's a good approximation if you have a small mesh. Even if there's no propagating wave, there'll still be an evanescent wave going past the mesh, and you don't know how high that field will be.
  - oneloop 10y ago
    You didn't really read the post, did you? Keep on winging it mate.
    - eternauta3k 10y ago
      I did. Where am I mistaken?
smallnamespace 10y ago
It's one thing to be able to know the classical equations of how something works (e.g. Maxwell's equations in this case, or Navier-Stokes is another good example), and quite another to understand the practical dynamics of the system as it evolves through time under boundary conditions that you care about (like the inside of a jet engine).
ChuckMcM 10y ago
Never under estimate the power of asking questions. Even things that are "understood" can be, what I'll call, functionally misunderstood. Basically the understanding allows you to work around the question, but the understanding is wrong. It goes back forever, consider planetary motion, for one. That said, I'm still trying to work out whether doing this analysis in Laplace space is sufficient.
CamperBob2 10y ago
I remember thinking I understood how a Van de Graaff generator worked. Simple enough, you'd think. What I learned when I built one was that there is nothing simple or intuitive about electrostatics.

oneloop 10y ago

What does "well understood" mean exactly? Ask the average inhabitant of Hacker News and he will tell you that "Faraday Cage the name of a phenomenon whereby a box of metal prevents electromagnetic fields inside", or something like that. But ask him how the strength of the electromagnetic field depends on the wire radius and mesh size, and he might not know the answer. That said, the answer was known to Maxwell, as the author remarks, although not to the author himself. As is often the case, the problem is in the details. So in a sense, it is a well understood problem to people who know the details well enough. I'm a physics graduate I did not know the answer, and I can assure you that the average physics graduate doesn't know the answer. In the year 2000 a graduate course in physics contains so much "advanced" physics that you end up learning a bit of a lot instead of a lot of a bit. My contemporaries and I know a lot of physics superficially, unfortunately. Time is limited, and in university you learn what you're fed. But yes, I agree with the sentiment of your post, of course :-)

eternauta3k 10y ago
A second-year Physics student can work out RF shielding using Kirchhoff's diffraction formula, or just looking at the wave equation in the k domain (spatial frequencies). Electrostatic shielding is the hard bit addressed in the article.
- lutorm 10y ago
  I'm not sure the diffraction formula has much relevance for computing shielding. I thought that formula was an idealization where you assume that the field strength on the blocking parts is identically zero, but I don't think that's a good approximation if you have a small mesh. Even if there's no propagating wave, there'll still be an evanescent wave going past the mesh, and you don't know how high that field will be.
- oneloop 10y ago
  You didn't really read the post, did you? Keep on winging it mate.
  - eternauta3k 10y ago
    I did. Where am I mistaken?

smallnamespace 10y ago

It's one thing to be able to know the classical equations of how something works (e.g. Maxwell's equations in this case, or Navier-Stokes is another good example), and quite another to understand the practical dynamics of the system as it evolves through time under boundary conditions that you care about (like the inside of a jet engine).

ChuckMcM 10y ago

Never under estimate the power of asking questions. Even things that are "understood" can be, what I'll call, functionally misunderstood. Basically the understanding allows you to work around the question, but the understanding is wrong. It goes back forever, consider planetary motion, for one. That said, I'm still trying to work out whether doing this analysis in Laplace space is sufficient.

CamperBob2 10y ago

I remember thinking I understood how a Van de Graaff generator worked. Simple enough, you'd think. What I learned when I built one was that there is nothing simple or intuitive about electrostatics.