Analogy Definition and 153 Threads

Can every QFT/CFT be interpreted at least approximately as a theory of gravity? If not, is it known which QFT/CFTs have gravitational counterparts?

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?

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...

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...

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...

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...

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...

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(?)...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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. :(

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}...

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...

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...

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.

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...

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...

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

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...

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...

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

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(...

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...

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...

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...

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. :(

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

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...

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

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?

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...

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...

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?

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...

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...

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...

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...

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...

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...

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