What is Analogy: Definition and 152 Discussions

Analogy (from Greek ἀναλογία, analogia, "proportion", from ana- "upon, according to" [also "against", "anew"] + logos "ratio" [also "word, speech, reckoning"]) is a cognitive process of transferring information or meaning from a particular subject (the analog, or source) to another (the target), or a linguistic expression corresponding to such a process. In a narrower sense, analogy is an inference or an argument from one particular to another particular, as opposed to deduction, induction, and abduction, in which at least one of the premises, or the conclusion, is general rather than particular in nature. The term analogy can also refer to the relation between the source and the target themselves, which is often (though not always) a similarity, as in the biological notion of analogy.

Analogy plays a significant role in problem solving, as well as decision making, argumentation, perception, generalization, memory, creativity, invention, prediction, emotion, explanation, conceptualization and communication. It lies behind basic tasks such as the identification of places, objects and people, for example, in face perception and facial recognition systems. It has been argued that analogy is "the core of cognition". Specific analogical language comprises exemplification, comparisons, metaphors, similes, allegories, and parables, but not metonymy. Phrases like and so on, and the like, as if, and the very word like also rely on an analogical understanding by the receiver of a message including them. Analogy is important not only in ordinary language and common sense (where proverbs and idioms give many examples of its application) but also in science, philosophy, law and the humanities. The concepts of association, comparison, correspondence, mathematical and morphological homology, homomorphism, iconicity, isomorphism, metaphor, resemblance, and similarity are closely related to analogy. In cognitive linguistics, the notion of conceptual metaphor may be equivalent to that of analogy. Analogy is also a basis for any comparative arguments as well as experiments whose results are transmitted to objects that have been not under examination (e.g., experiments on rats when results are applied to humans).
Analogy has been studied and discussed since classical antiquity by philosophers, scientists, theologists and lawyers. The last few decades have shown a renewed interest in analogy, most notably in cognitive science.

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  1. G

    Was the particle in a box analogy a recent one?

    Did the 'particle in a box' calculations come about when all those famous quantum physicists were forumlating the basics of quantum mechanics? It's the first thing taught in nearly all qm courses, but when was it first considered/published?
  2. F

    How does the swimmer analogy explain the movement of light in the ether?

    On the Ether "Swimmer Analogy" I am a high school student working through Lillian Lieber's The Einstein Theory of Relativity. She addresses Michelson's "swimmer analogy" (that light traveling through the ether could be compared to a swimmer traveling in a stream). I am confused as to how, in...
  3. G

    Intuitive Analogy to describe QM

    So I thought of an easy visual analogy to try and grasp the idea of quantum physics, and I wanted to see if this is accurate or if I am off base in my understanding (As I have mentioned, I'm not a physicist.) Picture a point. Draw lines from that point that moving away that are neither...
  4. B

    Exploring the Analogy of a Pond to Understand Quantum Physics

    As a novice to Quantum physics and as a working physicist in the oil industry this may be a stupid question but I find the whole subject of quantum physics fascinating. I have been pondering the missing mass in the universe and particle vs wave argument and came across a nice description...
  5. J

    Electricity/Water Analogy Fails?

    Hi All, I'm familiar with this analogy: "The voltage is equivalent to the water pressure, the current is equivalent to the flow rate, and the resistance is like the pipe size." -HowStuffWorks.com Power comes to our house on high-voltage, low current lines. Through a transformer, it gets...
  6. R

    Need a great analogy for Maxwells 1st eq

    The amount of electric field coming from a region of space is equal to the total electric charge in that region of space, (divided by a number). Imagine a point charge all by itself in space. It has a charge of 1C. According to the above statement, the electric field coming from the 1C point...
  7. P

    Rubber sheet analogy - density change

    When the rubber sheet with the bowling ball in it stretches, the density of the rubber is lowered as the rubber molecules become more widely separated by empty space. Are there particles of space time(?) that are similarily separated by more empty space when when the amount of nearby mass(?)...
  8. J

    Problem with Rubber and Metal Ball Analogy

    I'm struggling to understand how the stretched rubber & metal ball analogy explains the relativistic conception of gravity. It's possible that there is a simple and obvious solution to my confusion. It's also possible that this question has been answered many times. But I'll go ahead and ask...
  9. S

    Quantum Mechanical analogy of Newton's third law

    Greetings the venerable PF society, I have a question that has been lingering in my mind for a while, so I thought I'd ask it here. Firstly, how far below does the action-reaction (Newton's third law) principle go down fundamentally? How far below can I take it with me so that I don't make...
  10. T

    Exploring the Limits of the Balloon Analogy for Cosmology

    The analogy always used is to draw two points on the surface of a balloon and then blow air in the balloon. The points move away as the balloon expands. The issue I have with this is: now draw a "meter stick" on the surface of the balloon. It expands too, at the same rate, so that the number...
  11. L

    Distance analogy - am I being accurate?

    Hi guys, I am giving a schools talk and would like your opinion on whether or not you think the following reasoning is accurate and roughly scientific. Lets we assume that on average there is only one hydrogen atom per cubic metre on average in the universe. The diameter of a hydrogen atom...
  12. N

    Bowling ball rubber sheet analogy

    The typical rubber sheet bowling ball analogy to "explain" gravity visually in layman's terms always seems to be two space dimensions. Why don't we use one dimension of space and the other of time? Both are curved by mass and everybody takes Eucledean/Cartesian type flat graphs of, say, x and t...
  13. J

    Circuit/Mechanical oscillator analogy

    Homework Statement I've been pondering the analogy between an RLC circuit and a damped harmonic oscillator. The inductor serves the role of the inertia, leading a finite charging frequency. What happens if we remove the inductor, so that the system consists just of a charged capacitor...
  14. B

    Classical Electron Oscillator Model, quantum analogy

    Hi, I originally posted this question in the homework section, but I really don't need any help calculating anything, my answers are right. I'm having conceptual trouble, so I figured that this question belongs here. So, let's say there is a field driving a single atomic oscillator (hydrogen...
  15. marcus

    Effort to get us all on the same page (balloon analogy)

    To have an enjoyable cosmo forum we needed a balance between mental freedom on the one hand and a shared knowledge base on the other. People should be free to imagine the universe the way they want, but everybody should try to understand the standard LCDM (Lambda-cold-dark-matter) model as a...
  16. atyy

    Analogy between vectors and covectors

    P1: A curve defines a vector at point. P2: A function defines a covector at a point. F1a: A congruence of curves defines a vector field. F1b:Every vector field corresponds to a congruence of curves. Statements F1 are analogous to P1. F2a: A "congruence of functions" defines a covector...
  17. Redbelly98

    Electronics: using water pressure & flow analogy to explain voltage & current

    Electronics / electrical engineering forums often get questions from novices who have trouble understanding the concepts of voltage and current. Invariably, a more knowledgeable person will explain it by giving the standard analogy between electricity and water: voltage <--> water pressure...
  18. Q

    Quantifying Entropy - an analogy

    My friend and I were playing cards, and he was shuffling the deck. He claimed that the longer he shuffled, the 'more random' the arrangement of the cards would become. I argued that at a certain point the cards would be sufficiently disorganised such that they were in a state with no pattern...
  19. S

    Possible Analogy for Objects Moving at C

    From my understanding of spacetime, space and time are one; an object cannot be displaced a distance without also being displaced in time. The only way to travel through space without also moving through time is to "curve" spacetime around you. Previously, I have had difficulty understanding...
  20. E

    Solving Analogy from the GRE: Tips & Tricks

    This is an analogy from the GRE (is this the best forum for this?). I knew what all the words meant but I still couldn't get it. :(
  21. N

    Analogy between E and B fields

    Hi, I was simply wondering this for some time now... I am constantly seeing similarities between electric (E) fields and magnetic (B) fields. A few examples, Coulomb's law and Biot-Savart's law: dE = \frac{1}{4 \pi \epsilon_0} \frac{dQ}{r^2} dB = \frac{\mu_0}{4 \pi} \frac{I dl}{r^2}...
  22. qspeechc

    Analogy to Damped , Driven Oscillator.

    Hi everyone. I have a project where I need to find a situation this is, or is similar to, a damped oscillator. That is, the Differential Equation (DE) for the system must follow: x'' + ax' + bx = 0 And, further, it must have some situation corresponding to being 'driven' or 'forced', that...
  23. H

    Why Does Reynolds Analogy Overestimate Heat Transfer?

    Hi all. Why Reynolds Analogy and other empirical relations always overesimate heat transfer? I have done an experiment on turbulent pipe flow (smooth pipe) and I used Reynold Analogy (both the simple (Pr=1) and the modified one) and the Dittus-Boetler correlation equation to do the...
  24. M

    Exploring the Differences Between Water Flow and Current Flow

    What are the differences between the flow of water and current flow ? Besides the fact that the direction of current flow is opposite to the flow of e- where water molecules move in the same manner as flow of water... many Thanks.
  25. J

    Electricity and water analogy

    Hey guys: Consider the following water circuit: water is continually pumped to high pressure by a pump, and then funnelled into a pipe that has lower pressure at its far end (else the water would not flow through the pipe) and back to the pump. Two such circuits are identical, except for one...
  26. V

    Does Pipe Diameter Affect Water Flow Rate?

    Consider the following water circuit: water is continually pumped to high pressure by a pump, and then funnelled into a pipe that has lower pressure at its far end (else the water would not flow through the pipe) and back to the pump. Two such circuits are identical, except for one difference...
  27. M

    Analogy Between Conductance & Capacitance

    Hi all... I want more information about the analogy between calculating the capacitance C and the conductance G ?
  28. DaTario

    Is Rotational Kinetic Energy Analogous to Work in Torque Analysis?

    Hi all, If we take the integral of tau (the resultant torque) times the angular displacement theta, with respect to the angular variable theta, are we to expect the result to correspond to the variation in rotational kinetic energy? Is is this the case, does this integral have any...
  29. O

    Euclidean QFT and thermodynamic analogy

    I have been wondering now for quite some time about the meaning of Euclidean Quantum Field Theory. The Wick rotation t\to it allows us to transform a QFT in Minkowski space to a QFT in Euclidean space (positive definite metric). After that the expectation values of observables can be...
  30. Saladsamurai

    FINALLY A 4th dimension analogy for the layperson

    ...may frighten small children http://youtube.com/watch?v=6T0UQfKTcQw
  31. Helios

    How Does the Optico-Mechanical Analogy Explain Light Behavior in Physics?

    So, with the mechanical index of refraction n = \sqrt{ 1 - V/E } we plug into the optical ray equation, ( s = arc length ) \nablan - [ \nablan . ( d\vec{r}/ds ) ]( d\vec{r}/ds ) - n ( d^{2} \vec{r}/ ds^{2} ) = 0 and get \nablaV - [ \nablaV . ( d\vec{r}/ds ) ] ( d\vec{r}/ds ) + 2(...
  32. marcus

    Lee Smolin's molten gold analogy

    Smolin used a really interesting analogy for the big bounce transition here: http://cosmicvariance.com/2007/07/02/against-bounces/#comment-294116 the idea is a phase transition of the geometry of space which resets it to low entropy---and it looks like Bojowald's recent paper supports the...
  33. I

    Capacitor Analogy: Exploring William J Beaty's Water Analogy

    I have read this site by William J Beaty http://amasci.com/emotor/cap1.html It lucidly explains the functioning of the capacitor with a water analogy. I have a question with respect to this. If in a capacitor we introduce a dielectric with...
  34. M

    Mass,Spring, Damper vs Capacitor, Indcutor, Resistor vs ? analogy

    From a mathematic, linear differential equation point of view, and energy storage point of view, the concepts I mentioned in the topics are the same (I remember this being a concept in modeling control systems.) My question is, what are the same basic elements in other topics: thermal...
  35. H

    Understanding Flip-Flops: Analogy & Mechanical Terms

    Okay, I am having a difficult time understanding how flip-flops work. Can anyone give me an Analogy in mechanical terms like plumbing for each common individual Flip-Flop. I am really confused on how I read and follow the diagrams for FF's. :(
  36. A

    Analogy with Light: Total Internal Reflection & Quantum Tunneling

    Is there an analogy between total internal reflection and quantum tunneling? And did I spell tunnelling right?
  37. C

    Understanding the Expanding Universe: A Simple Analogy for Kids

    Its confusing to think that the Universe is 78 billion light years across considering that we think its only 13.7 billion light years old. So I tried to construct an analogy that I could tell to kids. Can you tell me if this analogy is ok? I'm in the back of a pickup truck facing...
  38. M

    Making analogy between fluid mechanical and electrical system

    Hi, Because of pictures that are drawn, I find easier to make question completely in pdf document. Thanks for help and understanding
  39. S

    Argument From Analogy in Science

    Do you guys think that argument of analogy belong in sciences like physics, chemistry and biology? I don't, because its doesn't seem to have any logical basis. What are your guys' views on this topic?
  40. D

    Exploring the Analogy of Negative Energy in Physics: The Jack-in-the-Box Example

    I seem to recall reading an analogy describing the total mass/energy of a jack-in-the-box. This said that a compressed spring insided a box would "weigh" more than the same when relaxed (albeit immeasurable small). This makes sense given the equivalence of energy and mass. But what if the spring...
  41. C

    Understanding the Energy Conservation Principle in Roller Coaster Physics

    I'm not sure if this question belongs to this forum or advanced phsyics.. but since I'm still in high school, I think this is the right forum. I'm doing physics questions based on roller coaster and am just a little bit confused on how to answer some questions. You know : Mass of each...
  42. D

    Simple physics analogy question (circuits)

    would the positive end of a battery be the top or bottom of a water slide? my guess is bottom because electrons flow from negative to positive. so that would be from top (-) to bottom (+) of a slide. is that accurate logic?
  43. A

    Capacitance Analogy: Thinking About Resistors Like Pipes

    My Physics TA said that a good way to think about resistors is to also think about pipes: the circuit is a pipe with water flowing thru it (water being charge) and a resistor acts like a section of pipe that is smaller than the rest... it slows down the current of charge and water. using a...
  44. S

    Exploring the Analogy between Liquid Crystals & Cosmic Strings

    http://arxiv.org/abs/gr-qc/0509091 A liquid crystal analogue of the cosmic string "We consider the propagation of light in a anisotropic medium with a topological line defect in the realm of geometrical optics. It is shown that the effective geometry perceived by light propagating in such...
  45. M

    How can Thevenin equivalent circuits be represented using a mechanical analogy?

    My lecturer mentioned something about how you can represent Thevenin equivalent circuits with forces etc. As a mech eng student, this would be easier to understand than stupid resistors and voltages. :) Does anyone know what I am on about? I can't think of how you could do this, but then...
  46. T

    Conceptualizing the analogy of gravity

    Hi there, I have a question about something that has been bothering me for quite some time now: Doesn't the notion of gravity being a curvature (or "warp") in the fabric of the universe created by a body of matter presuppose the idea of an already larger gravitational force/curvature acting upon...
  47. D

    Does anybody have a better analogy of describing space-time curvature?

    The old 2D paper describing 3D curvature is a little lame because it uses gravity to describe gravity. You know, the little ball circling the 2D psuedo-black hole, well remove gravity and the ball would fly off the 2D paper, you can't use gravity to describe gravity. It would be like saying...
  48. F

    Meaning of "A Good Analogy is like a Diagonal Frog"

    I love Kai Krause's quote "A good analogy is like a diagonal frog"...to me it's one of those oxymorons...like "astronomically small" or "authentic replica" Is that why it's so popular...because it's a clever oxymoron...or did this guy Kai Krause have another intent for the quote that I...
  49. E

    Analogy and its applications

    Analogy can be considered as one of the idea-generating techniques. Can you describe how analogy influence the idea-generation and its application?
  50. J

    20,000-lb. vs. Pedestrian - Analogy Sought

    Hi, Here's a true scenario: A 50 year-old female of average height and weighing 160-lbs. steps off a curb and is hit square-on by a 20,000-lb. bus going a steady 10-mph. The bus impacts the woman at 10-mph, then stops. The woman is first knocked up into the windshield of the bus, then...
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