Use this for questions relating to the proper use of physics terminology or nomenclature.
2
votes
1answer
83 views
What is the name for the whistling “musical” sounds that change stepwise in pitch when a hollow tube is spun like a lasso?
You have likely heard those sounds, science museums sometimes sell Flexible plastic tubes you can whirl like a lasso. The air rushing by the end of the tube causes these sounds, which are admitted in ...
2
votes
3answers
183 views
Weightlessness by a parabolic flight
Do you actually achieve weightlessness during a parabolic flight? Because I believe I heard somewhere did you achieve 'near-weightlessness' and not 'weightlessness' (if this is true, why is this?) ...
0
votes
3answers
145 views
Is it true that an isolated fundamental particle does not decay?
Is it true that an isolated fundamental/elementary particle does not decay?
It seems logical to me.
10
votes
1answer
671 views
What came first, Rice Crispy or “Snap,” “Crackle,” and “Pop”? [closed]
The fourth, fifth, and sixth derivatives of position are called "Snap" "Crackle" and "Pop". What came first, the rice crispy characters, or the physics units?
3
votes
2answers
442 views
Differences between classical, analytical, rational and theoretical mechanics
Can you explain me what are the differences between the four following subjects?
analytical mechanics
rational mechanics
classical mechanics
theoretical mechanics
1
vote
1answer
92 views
Is “Egyptian Year” the same as a modern sidereal year?
Copernicus uses the term "Egyptian Year" throughout his discussions of the movements of the Earth, and of his and other models of the movements of the planets; but is unclear from his text, or from ...
1
vote
1answer
91 views
What's the common consensus on the meaning of “physical change”?
I'm doing a textbook problem that shows a "molecular level" view of some matter, little colored balls, before and after, and there are, among the four questions, two that say: 1) Did a physical change ...
2
votes
3answers
1k views
What is the difference between Raman scattering and fluorescence?
What is the difference between Raman scattering and fluorescence?
Both phenomena involve the emission of photons shifted in frequency relative to the incident light, because of some energetic ...
0
votes
2answers
73 views
Is an electric lamp a transducer? [closed]
Silly thought.
A transducer, by definition, is a device that converts variations in one form of energy to another. An electric lamp converts electricity into visible light - the brightness may vary ...
0
votes
1answer
51 views
What is the reference spectrum?
What is the reference spectrum? I need to know how to calculate the reference spectrum of a wavelength 500nm.
0
votes
1answer
71 views
What is the pause called at the apex of an object's trajectory?
My apologies for such a basic question--I am a musician, not a physicist. But I cannot anywhere find the word, if one exists, that describes that elegant pause of an object such as a ball, thrown ...
7
votes
3answers
618 views
What does the dual of a tensor mean (e.g. dual stress tensor in relativistic ED)?
I know what the dual of a vector means (as a map to its field), and I am also
aware of of the definition a dual of a tensor as,
$$F^{*ij} = \frac{1}{2} \epsilon^{ijkl} F_{kl}\tag{1}$$
I just don't ...
3
votes
3answers
280 views
What is the difference between manifest Lorentz invariance and canonical Lorentz invariance?
I often read that the Lorentz symmetry is manifest in the path integral formulation but is not in the canonical quantization - what does this really mean?
0
votes
0answers
128 views
When the p-n junction of a transistor is reverse biased? [closed]
When the p-n junction of a transistor is reverse biased?
A. current flows from the p-type to the n-type.
B. no current flows from the p-type to the n-type.
C. conduction of current occurs.
D. ...
4
votes
1answer
368 views
Is there a difference between a postulate and a principle in physics?
Is there a difference between a postulate and a principle in physics?
Both seem unproved statements taken as true. If thats correct, why the different names?
2
votes
2answers
391 views
What the difference between “orbital” and “orbit”?
What's the difference between "ortibal" and "orbit"?
Which one should be used in physics?
In quantum mechanics, is "atomic orbital" or "atomic orbit" used?
And what about in classical mechanics? A ...
1
vote
1answer
119 views
Theorem or Conjecture? [closed]
I understand the definitions "theorem" and "conjecture" in mathematics, but I wasn't sure for physics. I mean, if it's proved mathematically, it's a theorem, otherwise it's a conjecture. But for ...
1
vote
1answer
125 views
What do I call the inverse of a propagator?
Let's suppose I have a theory described by a Lagrangian as follows:
$ \mathcal{L} = A_\mu \underbrace{\left( \partial^2 g^{\mu\nu} - \partial^\mu \partial^\nu + m^2 g^{\mu \nu} \right)}_{K^{\mu \nu}} ...
2
votes
2answers
389 views
What is the difference between parallel universe and multiverse?
What is the difference between parallel universe and multiverse? Is it parallel universe or universes?
14
votes
2answers
700 views
Definitions: 'locality' vs 'causality'
I'm having trouble unambiguously interpreting many answers here due to the fact that the terms locality and causality are sometimes used interchangeably, while other times seem to mean very different ...
3
votes
3answers
187 views
What is “A” in AGeV?
AGeV means GeV per nucleon. But why A letter is used for such a short cut? Why not NGeV, for example?
2
votes
1answer
481 views
What is Dalitz decay?
What is Dalitz decay?
I know there are Dalitz $\pi^0 \to e^+ + e^- + \gamma$ decay, $w \to \pi^0 + e^+ + e^-$ decay, may be more. But is there a rule to say which decay is Dalitz and which is not?
...
5
votes
1answer
380 views
What does the concept of phase space mean in particle physics?
I came across the concept of phase space in statistical mechanics.
How does this concept come about in particle physics?
Why was it introduced and how is it used?
What does it mean when ...
0
votes
2answers
169 views
Why equivalence principle is principle and not law?
We can prove that the inertial mass and the gravitational mass should be the same (equivalence principle) from the $f=mg=ma$ then $g=a$, so we have equivalence law! But why we said equivalence ...
1
vote
2answers
237 views
A basic confusion about what is an atom
Wikipedia defines atom as
The atom is a basic unit of matter that consists of a dense central nucleus surrounded by a cloud of negatively charged electrons.
and defines electron as:
The ...
1
vote
0answers
208 views
What is the relationship between Luminosity, Intensity, and Flux?
I am always confused by the terminology:
In high energy particle scattering, and in particular, in the context of collider physics, what is the relationship between luminosity, intensity and flux? ...
1
vote
2answers
128 views
Magnitude refers to number or number with units?
This question is about terminology for physical quantities.
When we talk about magnitude (while talking about scalars and vectors) do we refer to just number or Number along with units?
example: If ...
0
votes
0answers
309 views
When is a quantity “non-physical”? [closed]
The wikipedia says
A physical quantity is a physical property of a phenomenon, body, or substance, that can be quantified by measurement.
Formally, the International Vocabulary of Metrology, 3rd ...
7
votes
1answer
231 views
What's the relation between perturbative and nonperturbative QFT?
In case of any miscommunication let me describe my understanding of the meaning of "perturbative" and "non-perturbative", and correct me if something is wrong:
In a perturbatively defined QFT the ...
2
votes
2answers
216 views
Should the term Watt's Law be used?
I'm revising some electrical curriculum for a technical training program. In the curriculum students have to calculate values using Ohm's law and the equation Power = Current * Voltage (or P = IV).
...
2
votes
3answers
292 views
Probability vs. degree of belief in facts of nature (“Plausibility”)
I just came across a line in a paper:
"Assume the probability that a Lagrangian parameter lies between $a$ and $a + da$ is $dP(a) = $ [...]."
This reminded me again of my single biggest qualm I have ...
1
vote
2answers
113 views
What should I call an n>4 dimensional Minkowski metric?
I am manipulating an $nxn$ metric where $n$ is often $> 4$, depending on the model. The $00$ component is always tau*constant, as in the Minkowski metric, but the signs on all components might be ...
1
vote
1answer
113 views
What does anthropic mean as in Anthropic principle? [closed]
I'm reading a book about string theory, and it describes anthropic principle. Idea is clear to me, I understand this principle describes certain constants in modern physics that are so fine tuned as ...
2
votes
2answers
321 views
Where do the terms microcanonical, canonical and grand canonical (ensemble) come from?
Where do the terms microcanonical, canonical and grand canonical (ensemble) come from?
When were they coined and by whom? Is there any reason for the names or are they historical accidents?
4
votes
2answers
230 views
What does a non-perturbative theory mean?
I'm a science writer and I'm having difficulty understanding what a non-perturbative approach means. I thought I understood what perturbative meant, but in looking for explanations of ...
6
votes
3answers
2k views
Why is Higgs Boson given the name “The God Particle”?
Higgs Boson (messenger particle of Higgs field) accounts for inertial mass, not gravitational mass.
So, how could it account for formation of universe as we know it today? I think, gravity accounts ...
2
votes
0answers
292 views
de Sitter and anti de Sitter metric
Is the following correct for the distance $d$ from the origin $(0,0)$ to point $(t,x)$ in the 2-dimensional
de-Sitter and anti de-Sitter spaces? Here, $t$ is time and the distance may be called the ...
2
votes
2answers
106 views
May molecules of ideal gases have an inner structure?
The following question is probably very elementary:
whether molecules of ideal gases may have optic properties?
As far as I understand, when one discusses optic properties, one assumes that molecules ...
5
votes
0answers
163 views
Physical interpretation: weighted eigenvalues of the Laplacian with a potential
I'm a mathematician with only the basic knowledge of Physics, so my question may be trivial: in this case, mercy me. :-)
Let $\Omega \subseteq \mathbb{R}^N$ be a domain and let $V,m:\Omega \to ...
4
votes
4answers
5k views
What's the difference between Fermi Energy and Fermi Level?
I'm a bit confused about the difference between these two concepts. According to Wikipedia the Fermi energy and Fermi level are closely related concepts. From my understanding, the Fermi energy is the ...
0
votes
4answers
154 views
Isotropy and Noise
If you have a field which value is just Gaussian noise plus a constant do you call it isotropic?
there is no preferred direction
however it is not "the same" in all directions if "the same" means ...
1
vote
3answers
249 views
What does “nearly infinite mass” mean?
I am sure this is a silly question, but I was reading something that described the pre big-bang universe as having "nearly infinite mass."
How can something be "nearly" infinite? The term seems to ...
0
votes
1answer
161 views
What is the difference between observer, frame of reference, and gauge?
It seems to me that there is considerable relationship between the three concepts: frame of reference, observer, and gauge. How do they overlap?
My current understanding is that an observer with a ...
5
votes
2answers
504 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 ...
3
votes
3answers
195 views
What is a “Center Of Mass” issue of a Gorillapod?
I read somewhere that a Gorillapod may have "Center Of Mass" issues when used with the long lenses.
So, I wish to understand what is a "Center Of Mass" issue?
I have to clarify that I am NOT a ...
0
votes
1answer
135 views
Spectroscopic notation $s$, $p$, $d$, $f$, $\ldots$
$s$ is sharp, $p$ for principal, $d$ for diffuse, $f$ for fundamental.
Where do all those term come from? I do not see any link with the corresponding shapes.
-1
votes
1answer
164 views
Is a uniformly charged conducting plate the same as a uniformly charged conducting sheet?
Is it correct that a uniformly charged conducting plate is made up of two charged conducting sheets, that is, a charged conducting plate consists of four surfaces?
5
votes
2answers
94 views
Is the “dimension” in dimensional analysis the same as the “dimension” in “three spatial dimensions”?
When we talk about the dimension of a quantity (e.g. the dimension of acceleration is$[ L \ T ^ {-2}]$) are we talking about the same "dimension" as when we talk about three dimensional space?
Are ...
1
vote
1answer
178 views
What is the difference between quantum cryptography and quantum teleportation?
Generate two entangled photons, send one to a message sender and the other to the intended receiver. Both the sender and the receiver recover the same piece of quantum information from the photons, ...
0
votes
0answers
50 views
Taylor approximation of e(v) [closed]
Relativistic mass $\displaystyle m(v)=\frac{m_o}{\sqrt{(1-(v/c)^2}}$
$m_o$ = mass of object measured at rest
$c$ = speed of light ($3\times 10^8\;m/s$)
$v$ = speed
If the total relativistic energy ...
