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.
ALL scientific theories are ultimately models, so I'm going to ignore that aspect entirely.
- Direction of conventional current flow in electric circuits.
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.
- Norton and Thevenin equivalent circuits.
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.
- Flat map projections of the earth’s surface.
Or any map whatsoever.
- Wave and particle models of the transmission of light.
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.
- Planetary model of the atom.
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.
- Colors and spins of elementary particles.
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.
- Tree, web and ring models of the history of life on earth.
- The Last Universal Common Ancestor
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.