6 ms·

Why is it still taught as a tree, then? That seems like a pretty big discrepancy to just be a matter of "simplifying". Would also be more inspiring to student

by yters 8y ago

Why is it still taught as a tree, then? That seems like a pretty big discrepancy to just be a matter of "simplifying". Would also be more inspiring to students to know there is so much more to discover, as you point out.

klodolph 8y ago
Well, chunks of it are tree-like and chunks of it have less well-defined structure. The tree still works very well. We still teach the Bohr model of the atom, too.
- gbrown 8y ago
  I never understood why we were taught the Bohr model. If it was a history of science class then maybe it would make sense, but IMHO it just lets students develop incorrect intuitions.
  - klodolph 8y ago
    Science is not an accumulation of knowledge, science is a set of techniques for discovering new knowledge and testing it. So if a chemistry class just taught you the most accurate world view that teachers had at their disposal, it would be a failure. Understanding the history of science—experiments are done, new models are proposed, old models are overturned—is critical to understanding how to do science in a way that is perhaps less critical in some other fields. Besides, every other model lets students develop incorrect intuitions. Incorrect intuitions are still useful, and by letting students develop intuitions based on more obviously incorrect models like the Bohr model, you are teaching them the same skills they will need to use when they discared Lewis dot diagrams for molecular orbitals, or any other point in the future when established models are replaced. If you can't do that, you’re not doing science, and if you can’t teach people how to discard theories, you’re not doing a good job at teaching science. There is a tendency among the older generation (any older generation, at any given time) to complain about how their children are being taught wrong. Parents will pass onto their children a bunch of facts and skills, only to find out that schools teach something completely different. This is natural, of course. You can’t freeze a curriculum in time and still make it useful, you have to throw some parts of it out. But if you take students through the process of throwing something out, like the Bohr model, they’ll be more prepared for a changing future.
    - burning_hamster 8y ago
      This assumes a tabula rasa state of mind, where children have not formed any intuitions about the parts of the world they have not formally been taught about. However, when we learn about the sciences, we always discard incorrect intuitions (although probably often only nebulously defined). IMO, there is no need to explicitly teach something incorrect only to be able to un-teach the very same thing later. At best you alienate students because they feel either confused, lied to, or patronized. At worst, you do form incorrect intuitions that are even harder to get rid off than normally because they were taught as scientific gospel earlier.
      - klodolph 8y ago
        It's clear that you have a very different idea of what I am talking about than I do. The comment about "tabula rasa state of mind" makes no sense to me. First of all, I want to focus on this part of your comment: > IMO, there is no need to explicitly teach something incorrect only to be able to un-teach the very same thing later. At best you alienate students because they feel either confused, lied to, or patronized. This is an impossible demand for science education, because every model of the atom we could possibly teach is "incorrect". You could teach students only the most recent, most accurate theories of the world, but at this point in time that means starting with something like relativistic field theory and that approach is obviously wrong. If there is a scientific gospel, the gospel is "test your theories", and you can accomplish that by teaching students about the Bohr model. "Here is a theory about how atoms work, the theory is useful because it opened the door to quantum mechanics, it explained phenomena like the hydrogen spectra given by Rydberg, but it was known to have certain shortcomings." This gives students a case study for the scientific method. We can put an electric current through hydrogen gas and look at the spectrum with a prism or diffraction grating. We can calculate a formula for the spacing of the spectral lines. Then, we can come up with a model for how the atom works which explains those lines. Finally, this leads to more observations which contradict the model, and the process repeats. This is the scientific process, and if you are not teaching the scientific process, you are not teaching science. The reason you might use the Bohr model specifically is because many of the related experiments can be replicated in a school laboratory by students of relatively modest mathematical ability... just algebra is enough. And to be clear here, we are not teaching the Bohr model as fact. It's not going to be "un-taught" or "un-learned". Other theories you would often teach in a chemistry class include phlogiston theory, again, because the experiments disproving it are easy enough to run in a typical high school chemistry class, not because phlogiston theory is particularly useful.
  - Retra 8y ago
    I was never "taught" the Bohr model... there was a passing mention of it and a statement that it is obsolete, followed by an "electron cloud" model with an explanation that quantum theory is needed to explain it. (I'm remembering my high school classes from early 2000's.) But all my peers remember the Bohr model regardless. Because it is simpler, it is easier to remember. People will develop the wrong intuition regardless of what you do. If you start with the complicated ideas, they just give up on learning instead, substituting superstition. In any case, you can't really do anything with a model of the atom unless you're using equations, and you only get the quantum versions because those are the only ones that work. Everyone else doesn't have any need for a true model of the atom, and thus no incentive to learn it. (Most of the time, you'd rather need a model of molecules.)
  - empath75 8y ago
    It still more or less works as a model for certain systems, just like Newtonian gravity works just fine at certain scales.
  - adrianratnapala 8y ago
    Because it captures important truths about the physics and gets the right answer; all using just high-school mathematics and very little quantum mechanics. The electron really is a wave-like thing confined a by coulomb potential and thus has a discrete set of solutions. Moreover the discrete indexes of that solution map onto mechanical properties like angular momentum and energy. The Bohr model captures all of that, and even gets the right equations for the energy (at least in simple cases). Of course the real wave equation that needs solving is much more complicated than the 1-d cartoon in the Bohr model, but that cartoon works because it captures many essential properties of the real system.
    - gbrown 8y ago
      I apparently did not appreciate this when I was in high school.
  - xelxebar 8y ago
    For the same reason we teach and use Newtownian mechanics, even though it's "wrong".
matt4077 8y ago
Because it is a tree. Each branching point represents the last common ancestor between two species. The only confounding factor is that among bacteria, there is a process called “horizontal gene transfer”, where one bacterium inadvertently (?) aquires some genetic information from another when they’re really just out for a quick snack. Plus viruses, which sometimes just get inserted into a host’s genome and becomes part of it, sometimes even functional. The way animals acquired mitochondria is also a fascinating divergence from the standard “tree” model, although it’s somewhat derivative of how plants acquired photosynthesis. (That’s how everything in biology works. It’s the worst case of spaghetti coding, ever, full of self-modifying compilers, state saved in the JIT’s buffer, and programs only working by exploiting CPU flaws depending on the Hall effect, but only on workdays (according to the Julian calendar), fan speed, and your database server’s support of OpenGL). But it’s really just a tree. What’s far less of a “real” concept, is that of species. That makes essentially no sense in non-sexually reproducing organisms.
- BurningFrog 8y ago
  It's definitely a tree for species with sexual procreation. Each individual has a mother and a father, and species are pretty well defined. For life forms that procreate by individuals splitting themselves into two copies, while also getting DNA from each other in various random or intentional ways, it gets a lot messier. We still talk about "species", but it's a quite different thing.
  - toolslive 8y ago
    No it's not a tree. It's more like a graph. Some branches split and merge again later. Species are not well defined neither (or, if you prefer, there are plenty of competing definitions)
    - BurningFrog 8y ago
      What's an example of species merging?
      - 8y ago

by yters 8y ago

klodolph 8y ago

Well, chunks of it are tree-like and chunks of it have less well-defined structure. The tree still works very well. We still teach the Bohr model of the atom, too.

gbrown 8y ago
I never understood why we were taught the Bohr model. If it was a history of science class then maybe it would make sense, but IMHO it just lets students develop incorrect intuitions.
- klodolph 8y ago
  Science is not an accumulation of knowledge, science is a set of techniques for discovering new knowledge and testing it. So if a chemistry class just taught you the most accurate world view that teachers had at their disposal, it would be a failure. Understanding the history of science—experiments are done, new models are proposed, old models are overturned—is critical to understanding how to do science in a way that is perhaps less critical in some other fields. Besides, every other model lets students develop incorrect intuitions. Incorrect intuitions are still useful, and by letting students develop intuitions based on more obviously incorrect models like the Bohr model, you are teaching them the same skills they will need to use when they discared Lewis dot diagrams for molecular orbitals, or any other point in the future when established models are replaced. If you can't do that, you’re not doing science, and if you can’t teach people how to discard theories, you’re not doing a good job at teaching science. There is a tendency among the older generation (any older generation, at any given time) to complain about how their children are being taught wrong. Parents will pass onto their children a bunch of facts and skills, only to find out that schools teach something completely different. This is natural, of course. You can’t freeze a curriculum in time and still make it useful, you have to throw some parts of it out. But if you take students through the process of throwing something out, like the Bohr model, they’ll be more prepared for a changing future.
  - burning_hamster 8y ago
    This assumes a tabula rasa state of mind, where children have not formed any intuitions about the parts of the world they have not formally been taught about. However, when we learn about the sciences, we always discard incorrect intuitions (although probably often only nebulously defined). IMO, there is no need to explicitly teach something incorrect only to be able to un-teach the very same thing later. At best you alienate students because they feel either confused, lied to, or patronized. At worst, you do form incorrect intuitions that are even harder to get rid off than normally because they were taught as scientific gospel earlier.
    - klodolph 8y ago
      It's clear that you have a very different idea of what I am talking about than I do. The comment about "tabula rasa state of mind" makes no sense to me. First of all, I want to focus on this part of your comment: > IMO, there is no need to explicitly teach something incorrect only to be able to un-teach the very same thing later. At best you alienate students because they feel either confused, lied to, or patronized. This is an impossible demand for science education, because every model of the atom we could possibly teach is "incorrect". You could teach students only the most recent, most accurate theories of the world, but at this point in time that means starting with something like relativistic field theory and that approach is obviously wrong. If there is a scientific gospel, the gospel is "test your theories", and you can accomplish that by teaching students about the Bohr model. "Here is a theory about how atoms work, the theory is useful because it opened the door to quantum mechanics, it explained phenomena like the hydrogen spectra given by Rydberg, but it was known to have certain shortcomings." This gives students a case study for the scientific method. We can put an electric current through hydrogen gas and look at the spectrum with a prism or diffraction grating. We can calculate a formula for the spacing of the spectral lines. Then, we can come up with a model for how the atom works which explains those lines. Finally, this leads to more observations which contradict the model, and the process repeats. This is the scientific process, and if you are not teaching the scientific process, you are not teaching science. The reason you might use the Bohr model specifically is because many of the related experiments can be replicated in a school laboratory by students of relatively modest mathematical ability... just algebra is enough. And to be clear here, we are not teaching the Bohr model as fact. It's not going to be "un-taught" or "un-learned". Other theories you would often teach in a chemistry class include phlogiston theory, again, because the experiments disproving it are easy enough to run in a typical high school chemistry class, not because phlogiston theory is particularly useful.
- Retra 8y ago
  I was never "taught" the Bohr model... there was a passing mention of it and a statement that it is obsolete, followed by an "electron cloud" model with an explanation that quantum theory is needed to explain it. (I'm remembering my high school classes from early 2000's.) But all my peers remember the Bohr model regardless. Because it is simpler, it is easier to remember. People will develop the wrong intuition regardless of what you do. If you start with the complicated ideas, they just give up on learning instead, substituting superstition. In any case, you can't really do anything with a model of the atom unless you're using equations, and you only get the quantum versions because those are the only ones that work. Everyone else doesn't have any need for a true model of the atom, and thus no incentive to learn it. (Most of the time, you'd rather need a model of molecules.)
- empath75 8y ago
  It still more or less works as a model for certain systems, just like Newtonian gravity works just fine at certain scales.
- adrianratnapala 8y ago
  Because it captures important truths about the physics and gets the right answer; all using just high-school mathematics and very little quantum mechanics. The electron really is a wave-like thing confined a by coulomb potential and thus has a discrete set of solutions. Moreover the discrete indexes of that solution map onto mechanical properties like angular momentum and energy. The Bohr model captures all of that, and even gets the right equations for the energy (at least in simple cases). Of course the real wave equation that needs solving is much more complicated than the 1-d cartoon in the Bohr model, but that cartoon works because it captures many essential properties of the real system.
  - gbrown 8y ago
    I apparently did not appreciate this when I was in high school.
- xelxebar 8y ago
  For the same reason we teach and use Newtownian mechanics, even though it's "wrong".

matt4077 8y ago

Because it is a tree. Each branching point represents the last common ancestor between two species. The only confounding factor is that among bacteria, there is a process called “horizontal gene transfer”, where one bacterium inadvertently (?) aquires some genetic information from another when they’re really just out for a quick snack. Plus viruses, which sometimes just get inserted into a host’s genome and becomes part of it, sometimes even functional. The way animals acquired mitochondria is also a fascinating divergence from the standard “tree” model, although it’s somewhat derivative of how plants acquired photosynthesis. (That’s how everything in biology works. It’s the worst case of spaghetti coding, ever, full of self-modifying compilers, state saved in the JIT’s buffer, and programs only working by exploiting CPU flaws depending on the Hall effect, but only on workdays (according to the Julian calendar), fan speed, and your database server’s support of OpenGL). But it’s really just a tree. What’s far less of a “real” concept, is that of species. That makes essentially no sense in non-sexually reproducing organisms.

BurningFrog 8y ago
It's definitely a tree for species with sexual procreation. Each individual has a mother and a father, and species are pretty well defined. For life forms that procreate by individuals splitting themselves into two copies, while also getting DNA from each other in various random or intentional ways, it gets a lot messier. We still talk about "species", but it's a quite different thing.
- toolslive 8y ago
  No it's not a tree. It's more like a graph. Some branches split and merge again later. Species are not well defined neither (or, if you prefer, there are plenty of competing definitions)
  - BurningFrog 8y ago
    What's an example of species merging?
    - 8y ago