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Example of models, metaphors and analogies in the sciences

Discussion in 'Science and Technology' started by Jim, Dec 9, 2019.

  1. Jim

    Jim Nets of Wonder

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    NOTE: I edited the thread title from “physical sciences” to “sciences.”

    I’m looking for examples of models, metaphors and analogies in the physical sciences. I’ll list a few to begin with.
    - Direction of conventional current flow in electric circuits.
    - Norton and Thevenin equivalent circuits.
    - Flat map projections of the earth’s surface.
    - Wave and particle models of the transmission of light.
    - Lines of force.
    - Planetary model of the atom.
    - Schrödinger's cat.
    - Colors and spins of elementary particles.
    - The Big Bang.
    - Tree, web and ring models of the history of life on earth.
    - The Last Universal Common Ancestor
     
    #1 Jim, Dec 9, 2019
    Last edited: Dec 9, 2019
  2. Heyo

    Heyo Well-Known Member

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    - Laplace' Deamon
    - Mitrochondrial "Eve" and Y-chromosome "Adam"
    - The "god" particle
    - The "Oh my god" particle
    - The diverse models of the future of the universe, i.e. Big Rip, Big Crunch, Heat Death
    - The "hysteresis" curve in electromagnetism
    - The grandfather paradox
    - The bed sheet model of warped spacetime
    - The elevator analogy
    - The butterfly effect

    Edit: I noticed that Adam and Eve are from biology not physics or a related field.
     
    #2 Heyo, Dec 9, 2019
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  3. exchemist

    exchemist Well-Known Member

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    You need to exclude models. ALL scientific theories are models. So you can't make a list like this on the basis of models unless you include absolutely all the theories of science, in which case it becomes a meaningless exercise.

    The things on this list involve analogies or metaphors, apart from the last one, which you seem to have slipped in as part of your strange apparent crusade to attack or degrade the concept of common descent, by a sort of passive aggressive technique. (As you can perhaps tell, I am beginning to find this slightly annoying. ;))

    Firstly, the last universal common ancestor is not part of the theories of physical science but the life sciences.

    Secondly, it is a feature of the evolutionary model but is neither an analogy nor a metaphor. It is meant literally. If the model is right, all life today is actually, literally, descended from this original population of micro-organisms: Last universal common ancestor - Wikipedia Try again? :D

    But to give you more examples from physical science (if that is what you are genuinely interested in), I can offer, from chemistry:

    - the "arrow pushing" model of organic reaction mechanisms. No one can really say the electrons in bonds move in the way shown by the arrows during the reaction, but the effect is as if they do.

    - the concept of oxidation state or oxidation number. This is based on what the charge on each atom would be if all its bonding were 100% ionic, but is nevertheless applied to all compounds, regardless of what type of bonding is involved. It is found to be very useful, even though the situation it describes does not literally exist.
     
    #3 exchemist, Dec 9, 2019
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  4. Jim

    Jim Nets of Wonder

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    Thanks. I’ve corrected the thread title.
     
  5. exchemist

    exchemist Well-Known Member

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    But not the list, I notice. You need to take last universal common ancestor off it.

    But I think you won't because, I suspect, this thread is really not about models or the use of analogy and metaphor in science, but about trying to weaken the concept of common descent by misleading people about it. ;)
     
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  6. Polymath257

    Polymath257 Think & Care
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    ALL scientific theories are ultimately models, so I'm going to ignore that aspect entirely.

    Yeah, that's an amusing one historically. Early in the development of our understanding of electricity, there was no way of knowing which direction the particles involved moved. Everything known at the time was consistent with either particles of one charge moving one direction *or* particles of the opposite charge moving the opposite direction.

    So, *for convenience* it was taken as a standard that positive charge moves a particular direction in a certain reaction.

    Well, later it was found that the actual particles involved were electrons and they had a negative charge. None of the equations changed. We just have negatively charged particles moving one direction, meaning the current is in the opposite direction. If you have a current made of protons, the current and the particle flow are in the same direction.

    This brings out that metaphors and analogies are often used as ways to simplify computations. We find something 'equivalent' and simpler to allow the calculations to go. The justification is that the math actually does work out.
    Or any map whatsoever.

    Yes, those are models for the transmission of light. Both are subsumed in the QED model, by the way.

    More of a mathematical consequence of seeing force fields as vector fields. You can always find 'lines' that have the force vectors tangent to the line at every point. Convenient to visualize.

    Groan. One we should dispense with. Leads to too many problems later.

    Not so much a model, metaphor, or even analogy, as a paradox of thinking classically in a quantum system.

    The words are 'colorful', but the properties themselves exist and are modeled by our theories. Spin does correspond to angular momentum, but an intrinsic one, not one caused by actual spinning.

    This is actually a (several) model(s) deriving from our models for gravity (general relativity). Again, ALL of science is ultimately about models.

    Not examples of any of the above.

    And some to add to your list:

    --Electron dot diagrams (the electrons don't actually behave like that)

    -- resonance diagrams (the actual molecule does not alternate like that)

    --the concept of an ideal gas (no such ideal gas exists)

    --the analogy between electrical circuits and certain mechanical constructs (the governing math is the same)

    --any treatment of quantum mechanics using classical particles or waves.

    --seeing gravity as higher dimensional fluid flow (the governing equations are the same)

    --certain types of resistance in electrical circuits described as the electron having a different mass (the math is the same)

    --the movement of holes in semiconductors

    --if you're going to include force lines, you should also include 'potential', which is another mathematical consequence for some forces

    --liquid drop model of a nucleus (actually a model, but acknowledged as an analogy)

    --analogy between nuclear energy states and atomic energy states

    --any number of systems that have the same underlying mathematical description (usually leading to Laplace's equation, the heat equation, or the wave equation).

    Anyway, this is off the top of my head. I'll come back with more later.
     
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  7. exchemist

    exchemist Well-Known Member

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    Good list. And thanks for including "resonance" in chemical bonding - I should have thought of that.

    But how about this: the concept of the "particle"? We use this almost entirely fictitious and ridiculously impossible entity to simplify all sort of phenomena in classical mechanics. An object with mass but no spatial extent, i.e. of infinite density! Preposterous. But we are brought up with it and no one bats an eyelid.
     
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  8. Jim

    Jim Nets of Wonder

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    I started this discussion for educational purposes. I’ll be glad for anyone to post more examples of models, metaphors and analogies from the sciences, but now I have another question: What are some beneficial uses of models? One that I see is stimulating, guiding and facilitating research. Another is facilitating communication about results of research. Another is helping us to guess what might happen in some circumstances.
     
  9. exchemist

    exchemist Well-Known Member

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    I've already told you that all theories of science are models.

    If you need help to understand the benefit of scientific theories, then I suggest you look around you at the modern world.
     
  10. Jim

    Jim Nets of Wonder

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    (edited for typos)
    Different kinds of maps of the earth’s surface are used for different purposes. None of them are true in any way that excludes all the others from being true. “True” and “false” are not useful labels for map projections, for any beneficial purpose. They can be more or less useful, depending on what they’re used for and how they’re used. There is no single kind of map that is the best kind for all purposes. The kind that most closely resembles the earth’s surface is a globe, and that is used far less than some of the others for most purposes. The best kind of map for some purposes, a Mercator projection, can’t be used to compare areas, distances or shapes. No matter how far it’s extended, there’s no place on it for the North and South poles.

    I think of models, including the ones used in the sciences, in the same way. None of them are true in any way that excludes all the others from being true. “True” and “false” are not useful labels, for any beneficial purpose, for any models, including the ones used in the sciences. They can be more or less useful, depending on what they’re used for and how they’re used. No single model is the best one for all purposes, and the best ones for most purposes might not be the ones that most closely resemble whatever it is that they represent.
     
    #10 Jim, Dec 11, 2019
    Last edited: Dec 12, 2019
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  11. exchemist

    exchemist Well-Known Member

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    Up to a point, I agree with this. But one needs to bear in mind the models of science are not fixed: they are continually adapted to fit new observations. This implies that the model before adaptation is a poorer fit to apparent reality than the version after adaptation. So, while I am with you 100% in saying that the black-and-white labels "true" and "false" are often not helpful in science, this by no means implies that any given model is just as good as any other. This kind of relativism, which I have occasionally come across, is a serious misunderstanding.

    The history of science is littered with failed models, discarded because they were shown to be so wrong that there was no further use for them once the replacement had been developed. One of the most famous examples in chemistry is this: Phlogiston theory - Wikipedia
     
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  12. Polymath257

    Polymath257 Think & Care
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    It's a good analogy, and with a lot of truth in it. But there is a significant difference when it comes to the sciences.

    One of the constraints with a map is that it be 'flat'. This is what inevitably leads to distortions and inaccuracies. If you want a better model than a map, you go to a globe. And when you do that, you get *one* model that all the flat map models are approximations of *and* gives much better results.

    The flatness of the map is the artificial constraint that forces inaccuracies. But those inaccuracies can be removed once the constraint is removed.

    At the initial stages of any science, you will find a lot of approximate models. They work for certain questions and gives some sorts of insights, but are acknowledged to be maps with in inaccuracies.

    But the *goal* of science is to find the 'ultimate globe' That would be one model that subsumes all the local maps and explains why they give results that are accurate to the extent they are, but also gives *more* accurate results and, for the 'ultimate' has no known counter observations.

    And we can see this progression from local maps to general maps to globes happen in several areas of science. Physics, for example, started in some ways with Aristotle. His was the first recorded attempt to explain how and why things move the way they do. The Aristotelian system was the base of the Ptolemaic model of the solar system, which gave decent approximations to the movements of the sun and planets for a thousand years.

    Then Copernicus, Galileo, and Newton came along and found an *incredibly* accurate map (they thought it a globe) that was easy to use. This map was flexible enough to allow the inclusion of electromagnetism and the beginnings of statistical mechanics.

    But it was found to be incomplete. And incomplete in two ways. It was found that the Newtonian model was wrong for large speeds and high gravitational fields. It was also found to be wrong when it started looking at small items like atoms.

    So, new, broader, more useful maps (even with some curvature built in) were found: relativity and quantum mechanics. Both of these were much, much more accurate than the Newtonian map and explained why the Newtonian map was a good approximation. Even today, these are the most accurate maps we have.

    But we *know* they are not the globe we are looking for. Why not? Because the pieces of the two maps don't quite fit together. This is why there is a goal to find a quantum theory of gravity: a single map that encompasses both the relativity map and the quantum mechanics map.

    And we have even had some success in finding maps that do this: that piece together the best maps we know into one (globe?). But there are several proposed ways to to this merger and, at this point, we don't know which, if any, is the correct way to put the pieces together.
     
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  13. Jim

    Jim Nets of Wonder

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    A globe is not the best or most useful model for most practical purposes.
     
  14. exchemist

    exchemist Well-Known Member

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    It is the best. It is not the most useful.
     
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  15. Polymath257

    Polymath257 Think & Care
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    I said more accurate. Best depends on other constraints.

    But, for example, the 'wrong' model of Newtonian physics is still used, preferentially to relativity and quantum mechanics. The reason? It usually gives accurate enough answers and is greatly simpler to compute with. So, in practice, it tends to be 'best' for most situations that don't require more accuracy.
     
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  16. Jim

    Jim Nets of Wonder

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    However that may be, I don’t think you would say that it’s wrong for people to use flat maps instead of globes, for most purposes. Am I right?
     
  17. Polymath257

    Polymath257 Think & Care
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    Depends on the map. If you are using Isadore of Seville's medieval map (which had Jerusalem as the center of the Earth) to navigate, you will experience some difficulties.

    Some maps have been so poor that they are no longer used and for good reason.
     
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  18. Jim

    Jim Nets of Wonder

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    The point that I’m making is that there isn’t any single model that is the best model for all purposes, and there isn’t any single model that is true or right in any way that makes all other models false or wrong.
     
  19. Jim

    Jim Nets of Wonder

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    I would agree that all the theories in the sciences are models. What I’m thinking is that models are chosen according to how useful they are, or how well they fit some data. In some cases, no single model is the best model for all purposes, and sometimes the model that fits best is not the best model for most purposes. A model is not true or right in any way that makes all other models false or wrong. A model is not true or right in any way that makes it foolish or ignorant for anyone not to believe it. An agreement between researchers to use some model is not an agreement to denounce or ridicule anyone who doesn’t believe it.
     
    #19 Jim, Dec 12, 2019
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  20. Jim

    Jim Nets of Wonder

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    I don’t see how any globe that anyone actually uses could be better or more accurate than a flat map, for any purpose other than visualizing the whole earth, or a part of its surface wider than a few hundred miles. Apart from that, flat maps fit the data snd provide more information, more accurately, than any globe that anyone actually uses.
     
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