8 ms·

My favourite example of the intractabilities of some theories is that magnetohydronamics apparently can't predict the formation of streamer jets when you put yo

My favourite example of the intractabilities of some theories is that magnetohydronamics apparently can't predict the formation of streamer jets when you put your finger on a kid's plasma ball – i.e. the main point of the toy is beyond the most advanced theory that lies behind NIF, JET, ITER, etc...

Buttons840 4y ago
At this point in the thread, I'm wondering if we do a disservice to physics students by making it appear we have it all figured out.
- treeman79 4y ago
  If it was all figured out why get into the field? Sure some do it just to know. But the hunt is what drives most.
- maegul 4y ago
  So much this! There’s surely a huge argument that all of scientific education is a massive disservice. The point should be to learn and appreciate the method or process of scientific investigation of uncertain and mysterious or hard to understand phenomena. Instead we get dogma as a proxy of measuring intelligence with little regard for what the fundamental tools are of being a scientist. I’ve gone all the way through to Grad School and came out astounded at just how little commitment to or a sense of the essence of scientific investigation and what’s expected of the investigator there is in the system. They don’t prepare you for it because they themselves weren’t prepared. You can try to leverage some meta understanding of the “process” in conversation or debate, but so often the conversation falls flat because few are prepared or accustomed to it. Research is often done, IMO, in philosophical poverty by people eking out a living in the gutters of novelty and paradigmatic safety, averting their gazes from the sky (flourishes aside, you get my point). Putting aside the health of actual research. If the general public is to benefit from education and pass that benefit into their society (that’s the point right), it needs to be more than soon to be forgotten and often useless fallacies.
  - cwalv 4y ago
    > There’s surely a huge argument that all of scientific education is a massive disservice. > If the general public is to benefit from education and pass that benefit into their society (that’s the point right), it needs to be more than soon to be forgotten and often useless fallacies. I realize this is hyperbole, but still I think it's obvious that there is more than soon to be forgotten and often useless fallacies. I do generally agree though that current models/paradigms are usually presented more as "the final word" vs "a useful mental model". Esp. when paradigms are challenged by, or conflict with untestable traditional explanations, ppl tend to get irritated and overstate the confidence of their own understanding
    - maegul 4y ago
      Agree. I’m guilty of descending to hyperbole at times! Nonetheless, while I agree with your pushback, I do wonder how much utility there is in the “dogma” approach. There’s a lot of “facts” being thrown around in education, from what I’ve seen, that are often forgotten or become vague memories. How much better would it be to focus on skills and practice and concepts? Especially in the digital age where a fact is easily discoverable, provided one has the appropriate research skills.
- moloch-hai 4y ago
  It is easy for children to come up with questions for biologists that none can answer, and that none has even tried to answer. Biologists are almost unique among scientists in being happy to say how little they still know about their subject. Up until last year nobody had thought to see whether anything eats viruses! Turns out some do.
  - eru 4y ago
    > Biologists are almost unique among scientists in being happy to say how little they still know [...] Citation needed. > Up until last year nobody had thought to see whether anything eats viruses! Turns out some do. Nah, lots of things eat viruses. It's nothing unusual at all. You eat viruses, I eat viruses. They are everywhere, after all. The novel finding was a critter that lives / can live solely on viruses.
    - abudabi123 4y ago
      > Nah, lots of things eat viruses. It's nothing unusual at all. You > eat viruses, I eat viruses. They are everywhere, after all. When an engineer walks in front of an idling jet engine you don't say the jet eats viruses.
      - eru 4y ago
        To be more precise, viruses are just made up of proteins and DNA / RNA. Your normal digestion that can handle proteins and DNA/RNA from animals, plants etc doesn't have any more problem breaking down virus proteins into amino acids and absorbing them.
        whatshisface 4y ago
        I think the OP was talking about the bacteria that derive non-negligible sustenance from viruses. >Moreover, our foraging trials demonstrated robust growth in the Halteria population with only chloroviruses as food (rint = 0.66 ± 0.26 [SD], black lines, Fig. 1A), with minimal to no growth in the controls (with chloroviruses filtered out; rint = 0.22 ± 0.12 [SD], blue lines, Fig. 1C). The abundance of the larger Paramecium did not increase in treatment or control trials (Fig. 1D), indicating that not all ciliates can grow on chloroviruses in these conditions, even when they consume them. https://www.pnas.org/doi/10.1073/pnas.2215000120 https://www.pnas.org/doi/10.1073/pnas.2215000120
- flockonus 4y ago
  Calling mental models "laws of physics" is the biggest linguistic disservice to science itself, so in a way, yes.
- zinclozenge 4y ago
  I don't think I've ever, out of all my physics classes up to grad seminars, been given the impression we have everything figured out. In fact, it was hammered into us that all we have are "effective" theories, at least when it comes to high energy physics, and that's not even talking about grand unification (electroweak + strong force unification), let alone Theory of Everything (electroweak + strong + gravity).
  - epicureanideal 4y ago
    Maybe not where you studied, or at the level you studied, but in upper division undergrad physics at a top tier California school I definitely was given the impression that I should just crunch the numbers and not think too much about how it might be working.
    - njarboe 4y ago
      Was this a quantum mechanics class? Thinking about how it might be working leads to strange things like the Many-Worlds Theory[1] and other very weird ideas. "Shut up and calculate" is the usual method of dealing with these deeper questions. Beware; deep rabbit hole. [1]https://plato.stanford.edu/entries/qm-manyworlds/#:~:text=The%20Many%2DWorlds%20Interpretation%20(MWI,and%20thus%20from%20all%20physics https://plato.stanford.edu/entries/qm-manyworlds/#:~:text=Th....
- mr_mitm 4y ago
  Who do you think makes it appear we have it all figured out? That is not my impression at all. All the scientists I know are extremely aware of the limitations of their field.
moloch-hai 4y ago
Magnetohydrodynamics is, specifically, the "easy part" carved out of plasma fluid dynamics. It is inadequate to almost all applications, with only rare, precious exceptions, mostly manufactured. Devices that rely on plasma fluid dynamics to work are carefully designed to keep the plasma in the domain where MHD can be used to model them. Astrophysicists, as a rule, hate to be obliged to consider phenomena that involve plasma fluid dynamics, even what can be shoehorned into MHD. Such phenomena are thus orphaned, and you won't find anybody talking about them. The exception is solar physics, where nothing can be done at all without fully general plasma fluid dynamics. Solar physicists have the largest gonads in science, on par with rocket propellant chemists.
- srcreigh 4y ago
  Is plasma fluid dynamics the most important hated obligation of astrophysicists?
  - moloch-hai 4y ago
    I think most consider it "somebody else's problem". I know some don't like to think there is anything to it beyond MHD, so they call anything involving plasma "MHD". Are there other phenomena they see but don't like to talk about? Maybe?
- HPsquared 4y ago
  Is it called "hydrodynamics" because of an assumption of incompressibility (like regular hydrodynamics vs aerodynamics)?
  - moloch-hai 4y ago
    It has several commonly unphysical assumptions, including infinite conductance, "freezing" the magnetic field in a chosen frame, and assumptions about time and length scales. "Effects which are essentially kinetic and not captured by fluid models include double layers, Landau damping, a wide range of instabilities, chemical separation in space plasmas and electron runaway." That electrons are 1836 times less massive than the lightest positive charge carrier is neglected. Accelerated, they strike positive and neutral particles and knock loose more electrons.
brotchie 4y ago
Intractable in the analytic sense, or intractable numerically… or both?
- azalemeth 4y ago
  Both!

Buttons840 4y ago

At this point in the thread, I'm wondering if we do a disservice to physics students by making it appear we have it all figured out.

treeman79 4y ago
If it was all figured out why get into the field? Sure some do it just to know. But the hunt is what drives most.
maegul 4y ago
So much this! There’s surely a huge argument that all of scientific education is a massive disservice. The point should be to learn and appreciate the method or process of scientific investigation of uncertain and mysterious or hard to understand phenomena. Instead we get dogma as a proxy of measuring intelligence with little regard for what the fundamental tools are of being a scientist. I’ve gone all the way through to Grad School and came out astounded at just how little commitment to or a sense of the essence of scientific investigation and what’s expected of the investigator there is in the system. They don’t prepare you for it because they themselves weren’t prepared. You can try to leverage some meta understanding of the “process” in conversation or debate, but so often the conversation falls flat because few are prepared or accustomed to it. Research is often done, IMO, in philosophical poverty by people eking out a living in the gutters of novelty and paradigmatic safety, averting their gazes from the sky (flourishes aside, you get my point). Putting aside the health of actual research. If the general public is to benefit from education and pass that benefit into their society (that’s the point right), it needs to be more than soon to be forgotten and often useless fallacies.
- cwalv 4y ago
  > There’s surely a huge argument that all of scientific education is a massive disservice. > If the general public is to benefit from education and pass that benefit into their society (that’s the point right), it needs to be more than soon to be forgotten and often useless fallacies. I realize this is hyperbole, but still I think it's obvious that there is more than soon to be forgotten and often useless fallacies. I do generally agree though that current models/paradigms are usually presented more as "the final word" vs "a useful mental model". Esp. when paradigms are challenged by, or conflict with untestable traditional explanations, ppl tend to get irritated and overstate the confidence of their own understanding
  - maegul 4y ago
    Agree. I’m guilty of descending to hyperbole at times! Nonetheless, while I agree with your pushback, I do wonder how much utility there is in the “dogma” approach. There’s a lot of “facts” being thrown around in education, from what I’ve seen, that are often forgotten or become vague memories. How much better would it be to focus on skills and practice and concepts? Especially in the digital age where a fact is easily discoverable, provided one has the appropriate research skills.
moloch-hai 4y ago
It is easy for children to come up with questions for biologists that none can answer, and that none has even tried to answer. Biologists are almost unique among scientists in being happy to say how little they still know about their subject. Up until last year nobody had thought to see whether anything eats viruses! Turns out some do.
- eru 4y ago
  > Biologists are almost unique among scientists in being happy to say how little they still know [...] Citation needed. > Up until last year nobody had thought to see whether anything eats viruses! Turns out some do. Nah, lots of things eat viruses. It's nothing unusual at all. You eat viruses, I eat viruses. They are everywhere, after all. The novel finding was a critter that lives / can live solely on viruses.
  - abudabi123 4y ago
    > Nah, lots of things eat viruses. It's nothing unusual at all. You > eat viruses, I eat viruses. They are everywhere, after all. When an engineer walks in front of an idling jet engine you don't say the jet eats viruses.
    - eru 4y ago
      To be more precise, viruses are just made up of proteins and DNA / RNA. Your normal digestion that can handle proteins and DNA/RNA from animals, plants etc doesn't have any more problem breaking down virus proteins into amino acids and absorbing them.
      - whatshisface 4y ago
        I think the OP was talking about the bacteria that derive non-negligible sustenance from viruses. >Moreover, our foraging trials demonstrated robust growth in the Halteria population with only chloroviruses as food (rint = 0.66 ± 0.26 [SD], black lines, Fig. 1A), with minimal to no growth in the controls (with chloroviruses filtered out; rint = 0.22 ± 0.12 [SD], blue lines, Fig. 1C). The abundance of the larger Paramecium did not increase in treatment or control trials (Fig. 1D), indicating that not all ciliates can grow on chloroviruses in these conditions, even when they consume them. https://www.pnas.org/doi/10.1073/pnas.2215000120 https://www.pnas.org/doi/10.1073/pnas.2215000120
flockonus 4y ago
Calling mental models "laws of physics" is the biggest linguistic disservice to science itself, so in a way, yes.
zinclozenge 4y ago
I don't think I've ever, out of all my physics classes up to grad seminars, been given the impression we have everything figured out. In fact, it was hammered into us that all we have are "effective" theories, at least when it comes to high energy physics, and that's not even talking about grand unification (electroweak + strong force unification), let alone Theory of Everything (electroweak + strong + gravity).
- epicureanideal 4y ago
  Maybe not where you studied, or at the level you studied, but in upper division undergrad physics at a top tier California school I definitely was given the impression that I should just crunch the numbers and not think too much about how it might be working.
  - njarboe 4y ago
    Was this a quantum mechanics class? Thinking about how it might be working leads to strange things like the Many-Worlds Theory[1] and other very weird ideas. "Shut up and calculate" is the usual method of dealing with these deeper questions. Beware; deep rabbit hole. [1]https://plato.stanford.edu/entries/qm-manyworlds/#:~:text=The%20Many%2DWorlds%20Interpretation%20(MWI,and%20thus%20from%20all%20physics https://plato.stanford.edu/entries/qm-manyworlds/#:~:text=Th....
mr_mitm 4y ago
Who do you think makes it appear we have it all figured out? That is not my impression at all. All the scientists I know are extremely aware of the limitations of their field.

moloch-hai 4y ago

Magnetohydrodynamics is, specifically, the "easy part" carved out of plasma fluid dynamics. It is inadequate to almost all applications, with only rare, precious exceptions, mostly manufactured. Devices that rely on plasma fluid dynamics to work are carefully designed to keep the plasma in the domain where MHD can be used to model them. Astrophysicists, as a rule, hate to be obliged to consider phenomena that involve plasma fluid dynamics, even what can be shoehorned into MHD. Such phenomena are thus orphaned, and you won't find anybody talking about them. The exception is solar physics, where nothing can be done at all without fully general plasma fluid dynamics. Solar physicists have the largest gonads in science, on par with rocket propellant chemists.

srcreigh 4y ago
Is plasma fluid dynamics the most important hated obligation of astrophysicists?
- moloch-hai 4y ago
  I think most consider it "somebody else's problem". I know some don't like to think there is anything to it beyond MHD, so they call anything involving plasma "MHD". Are there other phenomena they see but don't like to talk about? Maybe?
HPsquared 4y ago
Is it called "hydrodynamics" because of an assumption of incompressibility (like regular hydrodynamics vs aerodynamics)?
- moloch-hai 4y ago
  It has several commonly unphysical assumptions, including infinite conductance, "freezing" the magnetic field in a chosen frame, and assumptions about time and length scales. "Effects which are essentially kinetic and not captured by fluid models include double layers, Landau damping, a wide range of instabilities, chemical separation in space plasmas and electron runaway." That electrons are 1836 times less massive than the lightest positive charge carrier is neglected. Accelerated, they strike positive and neutral particles and knock loose more electrons.

brotchie 4y ago

Intractable in the analytic sense, or intractable numerically… or both?

azalemeth 4y ago
Both!