Use this for questions relating to the proper use of physics terminology or nomenclature.

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2
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4answers
4k views

What does the magnitude of the acceleration mean?

I am a little confused as to what the magnitude of acceleration is and what it means.
0
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2answers
254 views

Conversion of ideal gas to real gas via $Z$ compression factor

The ideal gas equation $PV=nRT$ can be converted into real gas equation by compression factor $Z$ i.e $PV=Z~ nRT)$. My question is what is $Z$ and how does it arise? Is $PV/nRT$ a compression ratio of ...
0
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3answers
124 views

Meaning of invariable

Invariable means which is not variable i.e. can't be changed. Recently I have seen a sentence when reading a chapter based on measurement: The accepted standards must be accessible to those who ...
0
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1answer
21 views

Can Allan variance be generalized such that the “Oscillator model” is not presumed?

The definition of Allan variance, $\sigma^2[ \tau ]$, which relates to "stability of clocks" is described on the Wikipedia page as being derived in terms of an "Oscillator model": "The oscillator ...
3
votes
1answer
128 views

How to determine the order of indications of a clock?

Given the description of a clock $\mathcal A$, as (1) a set $A$ of all (more than 2) distinct indications of this clock, in no particular order (where the individual indications contained in set ...
0
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1answer
31 views

What does the term 'hyperbolic model' mean?

I am reading this non-linear discrete dynamical system paper. The authors mention the term hyperbolic model. What does that mean?
0
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1answer
98 views

Magnitude of a photon?

I encountered the following sentence in my textbook, which I don't quite understand, and after an unfruitful google search, I still can't figure out what they mean by magnitude in this context: ...
3
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3answers
226 views

Is it time or duration? [closed]

Taking this post: "Is there a proof of existence of time?", as a starting point. Therein was mentioned that there is confusion between: "time" and "flow of time". There was a comment (of mine) that ...
1
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1answer
55 views

Why is density an intensive property?

I am still trying to understand what are intensive and extensive properties. Possibly someone can give a pointer to a decent text (preferably on the web), as I am not too happy (to say the least) with ...
4
votes
3answers
387 views

Is speed an intensive property?

I remember being taught in elementary physics that while it makes sense to add volumes, masses, or heat, it makes no sense to add temperatures. As I wanted to use that to illustate some other issue, ...
2
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2answers
204 views

Why is it called “annihilation”?

The term "annihilate" literally means "turn into nothing". However, when a particle and antiparticle collide, they clearly do not turn into nothing; they simply transform into different particles. ...
0
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3answers
83 views

What is the work done against a force?

Suppose a particle travels a path $\gamma : I\subset \mathbb{R}\to \mathbb{R}^3$ subject to a force $\mathbf{F}: \mathbb{R}^3\to T\mathbb{R}^3$, then we know that we define the work done by the force ...
2
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3answers
83 views

Configuration manifolds and constraints

In Classical Mechanics there's this notion of configuration manifold. Although I've heard about that a lot and although I often use that concept, I'm not sure I really understand them well because ...
0
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1answer
24 views

Name of battery voltage when load connected/disconnected

If I had a 3V battery, and when no load connected it reads 3.2V, and with a load 2.8V (just a hypothetical example), what is the name for these two terms, with a load or no load? I know the voltage ...
11
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8answers
9k views

What is the difference between electric potential, potential difference (PD), voltage and electromotive force (EMF)?

This is a confused part ever since I started learning electricity. What is the difference between electric potential, potential difference (PD), voltage and electromotive force (EMF)? All of them have ...
8
votes
5answers
2k views

Is 'amp' a technically invalid term?

I've been told to use the term ampere in exams and class (I'm in high school), instead of amp as it's not a valid unit, although I've been using the amp for years along with all of my friends who do ...
5
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2answers
827 views

In layman's terms, what is a quantum fluctuation?

What causes it and how does it occur? If you do post some mathematics, please explain what each term means too please.
4
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3answers
665 views

Definition of a year

Is there an acceptable definition of a year (in number of days)? Google Calculator: https://www.google.com/search?q=seconds+in+1+year returns 3.15569e7 seconds and then ...
0
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1answer
26 views

What are “finely subdivided” substances?

As in the title, what does it mean for a substance to be finely subdivided, or finely grained? For example: It is only in the cases for which the ratio area/volume is very large (for example, a ...
3
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1answer
56 views

Hot Big Bang vs. Big Bang

This should hopefully be a quick one. Is there any difference between the Big Bang Theory and the Hot Big Bang Theory? Around Cambridge I hear everyone using "Hot Big Bang Theory", for example ther ...
10
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0answers
267 views

Gauge invariant but not gauge covariant regularization

I'm not sure if someone's already asked this before, but I was wondering, in field theory, when we say that a certain field is gauge invariant but not gauge covariant, what does this mean? In ...
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0answers
16 views

Is there some other name used for “ping rigidity”?

In MTW, p. 398, "Box 16.4 (continued)", there's an interesting sketch (which can also be seen on p. 15 of this excerpt (www.pma.caltech.edu/~ph236/yr2008/readings/MTW_Chapter16.pdf). (It's not the ...
2
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1answer
48 views

Are there more distinctive names of “null curves” with certain additional properties (absence of “chord curves”)?

In this answer (to the question "In general relativity, are light-like curves light-like geodesics?", PSE/q/76170) a particular example of a curve is discussed whose "tangent is everywhere null" and ...
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2answers
38 views

In terms of physics, does the phrase “time slows down” mean the same thing as “things happen more slowly?”

The common definition of "time" is a type of measurement, like size. But the sentence "size gets bigger" doesn't make any sense. Is "time slows down" an odd phrasing of "events occur more slowly" or ...
2
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0answers
119 views

Why supra-conductivity became super-conductivity?

The original article by the Kamerlingh Onnes team in Leiden does not give a name to the new effect: Kamerlingh Onnes, H. Further experiments with liquid helium. C. On the change of electric ...
2
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2answers
68 views

Is there a difference between Hertz and 'frames per second'?

It's not uncommon that the term 'frames per second' (sometimes abbreviated as fps or FPS) is associated with, or even equated to, the unit Hertz (Hz). I'm not exactly sure how these two concepts ...
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2answers
107 views

Action and Action integral: Different kinds of variational principles

What are the difference between: the action $\int_{t_{1}}^{t_{2}}(L+H) dt$ that we use in the principle of least action, and the action integral $\int_{t_{1}}^{t_{2}}L dt$ that we use in ...
7
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2answers
860 views

What is “code” in “toric code”?

When I first heard people talking about using Kitaev's toric code to do topological quantum computation, I was thinking how many lines does the toric code have. Then I was told that the "code" really ...
7
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2answers
96 views

Is a “shift in the meaning” of Accuracy and Precision occurring?

Accuracy and precision are among the most fundamental concepts in experimental physics, and, I always believed, completely unambiguous. Recently I found that the Wikipedia article on Accuracy and ...
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2answers
62 views

Changing from potential to kinetic energy

During a conversation with a friend, I began to wonder if there's is a term for the transformation of potential energy to kinetic energy, and vice versa.Is there a term for the process of converting ...
3
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4answers
71 views

Measurement in reciprocal metres

I'm trying to name a measurement that is measured in reciprocal length, which is in a draft document for vehicle risk management. It currently says: ...
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2answers
63 views

Is fission reaction considered natural or artificial? [closed]

As I learned, nuclear fission doesn't occur without the control of a human made nuclear reactor, by hitting a neutron to a fissile isotope. Thus, the fission reaction is considedred as a part of ...
12
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3answers
752 views

The notion of an adiabatic process in thermodynamics -vs- quantum mechanics

I'm confused about the terminology in the two contexts since I can't figure out if they have a similar motivation. Afaik, the definitions state that quantum processes should be very slow to be called ...
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3answers
55 views

In Orbital Mechanics what is the quantity described below called?

I seem to recall that $r^2 \dot{\theta}$ is a conserved quantity in orbital mechanics, which I just proved using the Euler-Lagrange equations. Namely via: $ \mathcal{L} = \frac{m}{2} (\dot{r}^2+r^2 ...
0
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1answer
24 views

The meaning of “heralded photon”

I am not a native English speaker, and I have just started to study physics in English. However, I came across the term heralded photon while I was reading a review article about optical quantum ...
2
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0answers
33 views

Since “coordinate time” has a very specific meaning, how to call more general parametrizations?

Recently I've learned that "coordinate time" assigned to a particular time-like spacetime path is not only required (1) to be monotonous and continuous and even differentiable wrt. the "proper time" ...
3
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1answer
79 views

Supersymmetry definition

Can someone outline the difference between supersymmetry and supersymmetric quantum mechanics? I often hear the two used interchangeably but I'm almost certain they are not the same.
1
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2answers
71 views

Why is scattering vector $\vec{q}$ called vector of 'momentum transfer'?

In the world of scattering the angle at which you detect the scattered radiation is known as $q$, where $$ \vec{q} = \frac{4\pi\eta}{\lambda}\sin(\theta/2) $$ I read in a lot of books that this is ...
1
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1answer
37 views

Usage of the terms Raman, Stokes and anti-Stokes scattering

I am confused over the correct usage of the terminology for "Raman scattering", "Stokes scattering", "anti-Stokes scattering", or even "Stokes-Raman scattering" and "anti-Stokes-Raman scattering". Is ...
0
votes
1answer
45 views

Is there a name for a substance that is a gas at room temperature?

Is there a name for a substance that is a gas at room temperature, such as Hydrogen, Helium, Neon, Argon, Krypton, Xenon, Chlorine, Fluorine, Bromine, Nitrogen, and Oxygen. I am writing a paper where ...
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0answers
60 views

Why is the $SO(4)$ symmetry of the Hydrogen atom called dynamical?

Why dynamical? My previous quantum mechanics teacher could not answer it.
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1answer
47 views

Parity of a system composed of 2 particles

I have read that for a system of 2 particles, the total parity is given by: $P=P_1 P_2 (-1)^L$ where $ P_1, P_2$= insisec parity of particle 1, 2 $L$ = relative angular moment what's the meaning ...
2
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0answers
22 views

What does unfolding of attractor mean?

What does unfolding of attractor mean? Effect of time scales on the unfolding of neural attractors paper talks about Takens embedding theorum. It says that the embedding dimension should be large ...
6
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1answer
187 views

History of the names “Feynman-gauge” & “Landau-gauge”. How arised & how settled?

Warning: Students, stay away from antiquities. The aim to learn is to survive. Hi. Today the nomenclatures Feynman gauge and Landau gauge seem established, but could you explain the history? It's ...
4
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3answers
324 views

What are the differences between indistinguishable and identical?

What is the difference between indistinguishable particles and identical particles?
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1answer
36 views

Totally antisymetric wavefunction: clarification about terminology

Pauli's Principle says: "The wavefunction of two identical fermions must be totally antisymmetric". I know that, for a antisymmetric wavefunction, $(-1)^L*(-1)^{S+1}*(-1)^{I+1}=-1$ "totally ...
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1answer
107 views

Looking for the name of a physical phenomenon in fluids' mechanics

I have not even an idea about how I would search for that on Google, that is why I'm trying my chance here. As electrical engineer I have no clue about fluid mechanics. We all now that when water is ...
2
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1answer
58 views

What is a 'height field'?

I encountered a few times the expression of 'height fields' in statistical physics, without ever reading a proper definition. My textbooks don't seem to talk about that, and googling it hasn't been ...
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2answers
38 views

Terminologies for moment of inertia

Perhaps someone can suggest the right terms for the following mathematical objects related to moment of inertia? A inertia tensor $I$. $$I \equiv \begin{bmatrix} I_{1,1} & I_{1,2} & I_{1,3} ...
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1answer
83 views

What is the name for the “nothing particle”? [closed]

What is the name for a particle with zero mass, zero charge, no strong force, no weak force and has no energy?