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

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What is the relationship between harmonic motion and the harmonics of a wave?

I learned about harmonic motion and harmonic oscillators a long time ago in physics, but I can't remember what the relationship between that and and the definition of harmonic in a wave. A harmonic ...
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1answer
27 views

What is the difference between a measurement and an experiment?

For example, say I want to determine the atomic structure of a bio molecule. I purify the molecule, get it to crystallize (probably though trial and error), shoot it with X-rays, observe the scatter ...
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2answers
65 views

Do the matrices $S^{\mu\nu} = \frac{1}{4}[\gamma^\mu, \gamma^\nu]$ have a name?

Do the matrices $S^{\mu\nu}$ defined by $$ S^{\mu\nu} = \frac{1}{4}[\gamma^\mu, \gamma^\nu] $$ have a name ($\gamma^\mu$ are the gamma matrices)? They feel very important to me since they form a ...
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1answer
72 views

What is a “fundamental thermodynamic relation”?

My professor handed me a quiz in which he said something like (I don't remember exactly) "write down the four fundamental thermodynamic relations for $A,G,H,U$". I showed the differential elements of ...
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1answer
111 views

What's the difference between binding energy and separation energy?

My understanding of the two was as follows: the binding energy of a nucleus is, classically speaking, the energy needed to put together/take apart that nucleus completely (i.e. a measure of the strong ...
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2answers
81 views

Name for Earth?

What is the proper word for 'Earth', as in 'Solar' and 'Lunar'? I cannot find this anywhere; I am guessing there is a word that starts with geo?
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127 views

What is meant by phase, phase difference, in (and out of) phase in wave terminology?

What is meant by phase, phase difference, in (and out of) phase in wave terminology? How do you get the relation $$y=A\sin(\omega t + \phi)?$$ Since the graph of sin function is identical to that of a ...
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5answers
169 views

A reference frame is any coordinate system or just a set of Cartesian axes?

In Physics the idea of a reference frame is one important idea. In many texts I've seem, a reference frame is not defined explicitly, but rather there seems to be one implicit definition that a ...
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2answers
144 views

What is the difference between leptons and baryons?

I am learning about the formation of the first atoms and, from what I am reading, before heavy particles, like neutrons and protons could form, there were already other types of particles, called ...
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1answer
55 views

What is a self adjusting force?

What is a self adjusting force? I searched it everywhere on internet but not got my answer and I have no other source to get its answer except this site so please help me.
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3answers
357 views

Given the Wikipedia notion of “arc length”, how is its manifestly real “signed variant” to be called and denoted?

I am dissatisfied with the presentation (not to say "definition") of "arc length", in its "Generalization to (pseudo-)Riemannian manifolds", as given in Wikipedia. (Who isn't?. But I'll sketch it here ...
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5answers
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Why are electromagnetic waves called waves even though they don't travel through a medium?

If waves are defined as the oscillation of a medium, why are electromagnetic waves called waves as they do not need a medium to travel through?
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1answer
38 views

Mutually Commutative

What is the definition of a Mutually Commutative set of operators? I've found articles describing a complete set of mutually commutative operators, but I can't actually find what mutually commutative ...
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0answers
38 views

Motion Integrals of a Particle in a Force Field

I am trying to wrap my head around the following problem: A point particle is moving in a field, where its potential energy is U=-α/r. Find first motion integrals. In our university we have no ...
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1answer
78 views

Why oobleck does not obey Newtonian dynamics? [duplicate]

In the following post we can see that some guys are walking on Non-Newtonian fluids. As far as I know that, we can not predict the exact amount of strain if we predict some forces. therefore the curve ...
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2answers
52 views

Is a constant transformation still considered a gauge transformation?

I've never even considered the possibility that a constant transformation would not qualify as a gauge transformation. But I'm reading a paper that seems to make exactly this distinction. In ...
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4answers
52 views

Who is said to do Work, me or the body?

If I subject my force to a body and it is displaced then the work is said to be done. What is that work done by? Is it said to be done by me or that body?
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1answer
73 views

What is the difference between the diffusion equation and the heat equation?

I know that the diffusion equation is a more general version of the heat equation. But what is the exact difference informally?
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1answer
54 views

What does it mean the term “probe brane”?

What does it exactly mean the term "probe brane"? People say for example: We put a stack of N branes at some point and then a probe brane ..." How do they appear in AdS/CFT? Can you give me an ...
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0answers
70 views

How can we count 17 particles in the standard model

This may be a bit of numerology, but I'd like to be able to make a statement like "There are 17 particles in the standard model" with some logical definition of a particle. But this statement is ...
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0answers
41 views

How would you define a difference in potential?

I'm currently in 12th grade, and am required to write an essay about physics and biology. The topic of the essay is the artificial brain (with the researches of the Human Brain Project in Switzerland ...
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3answers
1k views

What is basically the difference between static pressure and dynamic pressure?

What is basically the difference between static pressure and dynamic pressure? While studying Bernoulli's theorem, I came before these terms. The law says: When the fluid flows through a small ...
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1answer
52 views

What are the differences between special and general relativity? [duplicate]

What are the differences between special relativity and general relativity? I am looking for a naive, non-mathematical explanation.
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0answers
27 views

Definition of a semiconductor

Originally I had learned that solids are split into two categories: isolators/semiconductors, and metals. The fundamental difference between the two is the existence of a bandgap. Metals don't have ...
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1answer
29 views

Forgotten word meaning susceptability to direction

A little over a year ago, I encountered a descriptive word with respect to experimental physics, describing the phenomenon in which calibrating an instrument from one direction will yield a different ...
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1answer
29 views

In astronomy, what is a 'reflex orbit'?

In astronomy, what is a reflex orbit? The term is used in one of my books, but u don't find a definition for it. Googling it gives me articles about 'Oculocardiac reflex' which is not what I want. ...
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1answer
63 views

Does reverse biasing hold any meaning in case if both terminals are n type semiconductors?

When we talk about an n-p-n transistor in common emitter configuration, we often say that emitter-collector circuit (the one towards right) is reverse biased. In what sense it is reverse biased? Here, ...
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1answer
103 views

What is the difference between a parameter, a variable, and an operator in QM?

On the question why time isn't an operator, people will usually say that time is a parameter in QM (Time as a Hermitian operator in QM?) and not a variable. Can someone please distinguish between a ...
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1answer
36 views

Definition of a symbol $s_{NN}$ appearing in particle physics

What is the meaning of $s_{NN}$ in particle physics? See e.g. here http://www4.rcf.bnl.gov/brahms/WWW/thesis/karabowicz_phd_thesis.pdf page 18 in the pdf. What is its relation to energy? I ...
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1answer
65 views

Statistical mechanics vs. many-body theory

Where is the basic difference of statistical mechanics with many-body physics? What are the systems which cannot be studied in statistical mechanics but in many body theory? After all we know ...
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3answers
169 views

Is my conceptual understanding pertaining to heat & temperature correct?

From what I've understood: Heat is the total sum of translational energy possessed by individual atoms in an object. Temperature is the average translational energy possessed by individual atoms ...
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2answers
99 views

What is a full cycle in damped oscillation?

Maybe it seems a dumb question, but I can't understand what the cycle in a damped oscillation is? Let's take an example: In harmonic motion, one cycle is the smallest distinguishable part of wave ...
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1answer
51 views

What does multi-periodicity mean in stellar pulsations?

How can there exist multi-periodicity in stellar pulsations? http://www.kitp.ucsb.edu/sites/default/files/kitp/preprints/moskalik2.pdf How can one visualize a multi-periodic pulsation or oscillation?
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134 views

Why does the classical electrodynamics Lagrangian density equation have a “field” term and an “interaction” term?

On Wikipedia's page on classical electrodynamics, they state the Lagrangian density equation as follows \begin{equation} \mathcal{L} = \mathcal{L}_{\text{field}} + \mathcal{L}_{\text{int}} = ...
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3answers
146 views

Kinematic Viscosity

How would you define kinematic viscosity? What does it physically represent? Around the Internet I've found it defined as just a ratio, and that's it. I saw in an answer that I can think of it as ...
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2answers
115 views

What does memorylessness mean as a postulate of special relativity?

I was reading the wiki page on special relativity postulates. And wiki says, The two-postulate basis for special relativity is the one historically used by Einstein, and it remains the starting ...
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2answers
83 views

Definition of Duality (opposed to Symmetry)

I'm learning basic string theory right now and we came across T-duality which was presented as a symmetry of the formula for the mass of a string in the context of compactification. There was a remark ...
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3answers
118 views

Ideal, isotropic fluid and stress tensor

An ideal fluid is the one which cannot support any shearing stress. It also doesn't have viscosity. My question is what does it mean by a fluid to be isotropic? Is an ideal fluid necessarily isotropic ...
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1answer
52 views

What exactly is an image?

When we say several rays meet to form an image, what is that which is formed? Is it an arrangement of unknown entities? What exactly am I looking at when I see my image in a plane mirror?
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27 views

Frame dependence

I was reading an article about magnetospheres, and came across this quote: This supersonic ionized gas, or plasma, called the solar wind carries with it a magnetic field and a frame dependent ...
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3answers
144 views

Eternal Black Holes

What is the definition of an eternal black hole? Studying white holes and the term appears in relation to this field of research.
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169 views

Locally flat coordinate and Locally inertial frame

I am having some doubts on myself regarding the above concepts in General Relativity. First, I want to point out how I understand them so far. A male observer follows a timelike worldline ($\gamma$) ...
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1answer
61 views

What does 'channel' mean?

I see many plots like the following that graph counts per channel, I know what a 'count' is, but I don't know what a 'channel' is. Could somebody please explain to me? My guess is that it is that ...
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3answers
105 views

What is the 'normal/standard' formulation of quantum mechanics called?

I know of at least three equivalent formulations of QM: The "normal/standard" one, dealing with Hilbert spaces and state vectors. The Feynman path-integral formulation. The Wigner-Weyl phase space ...
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1answer
38 views

Semantics: alternative word for long-ranged interaction? [closed]

I am working on wording for a report. I need to a word to describe long ranged interaction that is constant in strength. But I am aware that people sometimes use 'long-ranged' to mean decaying ...
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1answer
48 views

What is a geocentric altitude?

In NAO TN no.69, Yallop defines ARCV as geocentric difference in altitude between the centre of the Sun and the centre of the Moon for a given latitude and longitude, ignoring the effects of ...
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1answer
92 views

Difference between harmonic oscillator & coupled oscillators

Coupling, according to wiki, is the condition of two systems when they interact with each other. Now, I came across the terms harmonic oscillator and coupled oscillators. Now,what is the difference ...
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48 views

Why is special relativity so special? [duplicate]

The title says it really. Why is special relativity so special? I'm just curious as to how and why the term 'special' came to describe the theory of relativity where gravitational forces are ...
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1answer
70 views

Is 'grapheme' a substance or a typo?

While reading Ref. 1 I came across the sentence Below we focus on the physics of ideal (single layer) grapheme. I did google search 'grapheme' but the results tended towards a completely ...
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53 views

The name of effect of liquid flow inducing flow to neighboring layers of liquid?

How do you call an effect, when liquid or gas stream is involving the neighboring layers of matter also move? Like on videos of rocket engines testing, when exhausting gas sucks an air and steam from ...