Questions tagged [physical-constants]
This tag is for questions relating to physical constants which are any of a set of fundamental invariant quantities observed in nature and appearing in the basic theoretical equations of physics. Accurate evaluation of these constants is essential in order to check the correctness of the theories and to allow useful applications to be made on the basis of those theories.
685
questions
0
votes
0
answers
105
views
What natural processes are most sensitive to exact value of fine-structure constant?
My intuition (game theory PhD here, no serious background in physics) suggests that of all naturally observable processes protein folding should have the strongest dependence on exact value of $\alpha$...
1
vote
0
answers
98
views
Einstein's Box Argument [closed]
Freeman Dyson gave a talk where he updated Einstein's Box argument to defeat the energy-time uncertainty principle and contradict Bohr. This experiment and a few others along the same line are also ...
- 166
0
votes
0
answers
33
views
What is the evidence against a variable gravitational constant? [duplicate]
I understand that our main supporting evidence for dark matter is the anomalous speed of objects orbiting around the edges of distant galaxies. Is there a reason why dark matter solves this problem ...
- 101
-2
votes
2
answers
101
views
Why does the assumption that speed of light $c$ is constant exist? [closed]
This is I'm sure a very basic and juvenile question. Why do we take the assumption that $c$ is constant in all situations to be a law? It does work out that it fits the standard model well but it has ...
0
votes
1
answer
48
views
What is the name of the physical quantity which is the gyromagnetic ratio divided by $2 \pi$?
I am reading Abramowitz and Stegun's Handbook of Mathematical Functions and I come across Table $2.3$, Adjusted Values of Constants.
In there we see:
Gyromagnetic ratio of proton: $\gamma$, with value ...
- 446
2
votes
3
answers
93
views
How do we know that the speed of light is constant everywhere, not just here? [duplicate]
It might well be that universal constants, say the speed of light, are only constant as far as we can tell in our chunk of the universe - in the same way that the Earth looks flat in the area you live....
- 121
1
vote
1
answer
42
views
Does expanding universe length units also expand? [duplicate]
Information
I have read an explanation about the expanding universe which represents our universe as a metal plate that tends to expand simultaneously in all directions while being heated. One can ...
- 11
1
vote
1
answer
40
views
Are the physical properties of Tin-coated metals the same as of the substrate?
I am trying to perform a finite element analysis to plot static structural loading on a bare copper and compare the results with the tin plated copper. I do have the information about the electrical ...
- 111
-1
votes
1
answer
113
views
How to add Newton's constant to the metric function?
My main question is, is it possible to manually add Newton's constant $G$ to the metric function of a black hole? Is there such a possibility for Black Brane? How to add? Should it be added to the ...
- 65
4
votes
0
answers
34
views
How can i find the value of Planck's constant using Black body radiation?
I'm working for a physics project for Highschool, and i'm currently thinking about using black body radiation to measure Planck's constant. I know there is an option using the photoelectric effect but ...
- 41
0
votes
1
answer
114
views
Is there a reason the ratio of the Bohr speed to the speed of light approximates the fine structure constant?
$$\frac{Bohr_s}{c} \approx \frac{1}{137} \approx \frac{1}{137.035999084}
= \alpha$$
Where $Bohr_s$ is the speed of the electron in the Bohr model of the hydrogen atom and $\alpha$ is the fine ...
- 1,295
1
vote
0
answers
15
views
Curvature length and Newton's constant in AdS
What is the dimensions of Newtons gravitational constant in arbitrary dimensions in terms of teh curvature radius?
I am looking at entanglement entropy which goes as $S \sim \frac{ l_4^2}{G_4}$. This ...
- 83
4
votes
1
answer
102
views
Can double copy address the weakness of gravity?
I hope I didn't miss a post that already answers this question. I am simply wondering if there is a natural framework in the double copy approach to explain the weakness of gravity? I don't require ...
- 2,622
0
votes
3
answers
105
views
Fundamental constants
Alpha is one of the fundamental constants in physics. If it had not the precise value that it has, there would be no life in the universe.
One of these fundamental constants is the fine-structure ...
- 29
2
votes
3
answers
655
views
On constants that maintain proportionality [closed]
I do not consider my knowledge on mechanics higher than average, and average is perhaps as good as it gets; however, I ask this question to better my knowledge on the way physics has been modeled. I ...
- 197
-2
votes
1
answer
131
views
Is the fine structure constant a function of electron mass? [closed]
The main statement is: the EM coupling constant is energy dependent, and the fine structure constant (FSS) is the low energy limit. This means that the flow of the coupling constant vanishes when the ...
- 1
1
vote
1
answer
72
views
Definition of Planck area and Planck volume
According to https://en.wikipedia.org/wiki/Planck_units, the Planck area is defined as the square of the Planck length, and the Planck volume as the cube of the Planck length.
\begin{equation} l_\text{...
- 195
0
votes
0
answers
45
views
Why do the Stoney units of time, length, and mass differ with the Planck units by the squareroot of the fine structure constant?
The natural units of Planck and Stoney differ by the inverse of the finestructure constant.
For example, the Stoney-mass is:
$$m_s=\sqrt{\frac{k_e e^2}{G}}= 1.85921×10^{-9} kg,$$
where $k_e$ is ...
4
votes
1
answer
105
views
TOV equation constants
I am working on a project which requires solving TOV equation. The equation is as below:
$$
\frac{dP}{dr} = -\frac{G m \rho}{r^2}\left[
1+\frac{P}{\rho c^2}
\right]
\left[ 1+ \frac{4\pi r^3 P}{mc^2}\...
- 180
-3
votes
3
answers
54
views
Help with forming a dimensionless combination proportional to $e^2$ [closed]
I am currently working on a physics problem that asks me to form a dimensionless combination of the fundamental constants $e=\left|q_e\right|$, $\hbar$, $c$, and $\epsilon_0$ that is proportional to $...
- 25
2
votes
2
answers
124
views
Is $F=mg$ derived from Newton's law of universal gravitation $F=Gm_1m_2/r^2$?
If so, that means gravity is only 9.8 m/s^2 at the surface of the earth?
- 21
0
votes
1
answer
318
views
What is the full QED Lagrangian with physics units written out?
I wonder what the QED Lagrangian would look like if you carefully write out all units of the terms and make sure they are consistent. I think there is something missing about Coulomb.
Can you write ...
- 1,413
0
votes
1
answer
64
views
Problem with an equation in the context of black hole creation in high energy collisions
I am reading an article about possible black hole creation in high-energy collisions.
There's an equation: $b \le \sqrt{s}/ P^2$, where $b$ is the impact parameter of the collision, $\sqrt s$ its ...
0
votes
1
answer
171
views
What's the link between Planck Mass squared and $1/8πG$?
Good morning,
In an equation of an article, we said that 1/8πG = Mass of Planck^2. But 1/8πG = 596175243.8, is much larger than the Planck Mass^2 = 1.383*10-16 kg. Is there a conversion to do? If not, ...
6
votes
1
answer
1k
views
The universal value of Boltzmann constant?
So I'm quite confused about Boltzmann's constant $k_B$ being fundamental. From here:
... the Boltzmann constant. Its value is well known but even if its value were 10 times bigger or if it were ...
- 1,221
0
votes
0
answers
26
views
Is the Gravitational Constant $G$ really a Constant? [duplicate]
I'm a mere chemist, so I'm figuratively typing and ducking, as I ask this, but:-
If Dark Energy is increasing, then could this not be explained by the Gravitational Constant $G$ not being constant, ...
0
votes
0
answers
55
views
What is the average increase in entropy per unit space?
The second law suggests that averaged over a large enough space and time, entropy always increases.
The rate of increase obviously depends on local conditions. The increase in Entropy in a year in ...
- 299
1
vote
1
answer
115
views
How to rule out that the speed of light was different in the past?
The constancy of the speed of light is a fundamental principle in modern physics, and it is supported by a wide range of current experimental evidence.
There is no evidence to suggest that the speed ...
- 415
0
votes
0
answers
95
views
Is there a physical reason the fine structure constant should be 4 times ratio of a proton's classical to charge radius? [duplicate]
What is the physical relation, if any, that explains the factor of 4 in:
$\frac{\alpha}{4.001\pm 0.009} = \frac{r_{p_{Classical}}}{r_{p_{RMSCharge}}}$
where
$\alpha$ is the fine structure constant
$...
- 1,295
4
votes
4
answers
226
views
$ℏ$ in the canonical commutation relation
I am wondering what the physical meaning of the introduction of a "new" constant $\hbar$ in the CCR $[\hat{x},\hat{p}]=i\hbar$ is if you compare it to the classical Poisson-bracket $\{x,p\}=...
- 77
1
vote
2
answers
134
views
Is the Planck mass the minimum required to form a black hole?
I have heard this stated before, even that this is reason elementary particles do not collapse into a black holes no matter how much they are compressed and why we don't need to worry about them being ...
- 744
0
votes
1
answer
192
views
Has it been proven the fine-structure constant (FSC) changes with time?
I have heard this claimed over and over, even that the FSC was 1 at the Big Bang. Is there any actual consensus among scientists that this is so?
- 744
1
vote
1
answer
184
views
Why is there no law of physics that contains the Planck volume?
The Bekenstein-Hawking entropy of a black hole contains the Planck surface.
Mead's discussion of the gravitational microscope yields the Planck length as the length measurement limit.
Is there any ...
- 617
1
vote
1
answer
95
views
Is the running of electric charge the same as the running of the fine structure constant?
This is a simple question - maybe too simple. If I recall correctly, Feynman wrote about the running of the electric charge with energy (or 4-momentum). Nowadays, one hears more about the running of ...
- 617
0
votes
2
answers
152
views
What is the logic behind Planck units?
I was curious to know the logic behind “Planck Units”, I read this question but did not understand it. Do you have a better (simpler) explanation for setting $c = G = \hbar = 1$?
- 117
0
votes
0
answers
34
views
Solving for Geodesics in Dynamic Ellis Wormhole
Is it possible to make a coordinate transformation to the metric $$ds^2=-dt^2+dp^2+(5p^2+4t^2)d\phi^2$$ that would reveal constants of motion that can be used to solve for geodesics analytically? ...
- 135
1
vote
0
answers
47
views
Different limits of string theory parameters
So in (perturbative) String theory, it is my understanding that we have the following parameters (taking natural units).
The string length : $\ell_s$, which appears in front of the world-sheet action, ...
- 2,230
-4
votes
2
answers
74
views
Why $cG = 0.02 \rm N$? [closed]
The unit of their product is Newton and its value is precisely (up to their uncertainty) equal to 1/50.
And I know! It is tempting to re-think that they might not be constant, but their product must. ...
- 145
1
vote
2
answers
142
views
The Planck length squared $\ell^2_P$ in the Friedmann Equation
I noticed in this thread:
Implications of a comoving Friedmann equation
Aside from the error of him having curvature term on the wrong Friedmann equation, I'm still interested in what literature ...
0
votes
2
answers
164
views
Does the Reynolds number uses the velocity of the fluid or the velocity of the object going through it?
On the Wikipedia page for the Reynolds number, it is defined as:
$$
Re = {\frac {\rho uL}{\mu }}
$$
where:
...
- 483
1
vote
1
answer
44
views
When tweaking values of physic's fundamental constants, how are outcomes observed?
I often read about the concept of the "Fine-Tuned Universe".
From my understanding, the universe's existence is sensitive to the values of certain fundamental physical constants, which are ...
- 111
1
vote
0
answers
97
views
Does vacuum displacement field imply space filled with Planck particle/antiparticle pairs?
Consider natural Gaussian units such that $\hbar=c=1$ and the electron charge $e=\sqrt{\alpha}$ where $\alpha\approx1/137$ is the fine structure constant.
In Gaussian units the vacuum displacement ...
- 5,507
1
vote
0
answers
84
views
In principle, "how much" of the path integral is required to match the electron $g$-factor experiment?
As Dirac was the first to realize (Dirac 1933, page 69), the reason the quantum path integral converges to the classical action principle as $h\rightarrow 0$ is that
The only important part in the ...
- 2,363
1
vote
0
answers
129
views
Has the fine structure constant been derived from theory? [closed]
The following paper from this year claims to have derived the fine structure constant:
Singh, T.P. Quantum gravity effects in the infrared: a theoretical derivation of the low-energy fine structure ...
- 19
-1
votes
4
answers
253
views
Should the empirical Newton's gravitational constant $G$ be considered as the independent fundamental physical constant?
It is known that the effect of gravitational waves generation in collisions of (black holes)/(neutron stars) pair follows from the predicted consequences of Einstein's General Theory of Relativity.
...
- 386
1
vote
0
answers
89
views
What are the beta functions for electroweak and strong constants of interactions?
As the title says I want to find beta function for electroweak and strong constants ($g$ for W-boson, $g'$ for B-boson and $g_s$ for gluons)
Beta function is the function that describes change in ...
- 907
1
vote
0
answers
75
views
Derivation of Coulomb's constant
I am searching for the derivation of the Coulomb constant.
In most of the parts of internet, they just explain the experiment, and How force is proportional to $q1q2$, and Force is inversely ...
- 11
-1
votes
1
answer
55
views
How characteristic length scale affects continuum treatment of matter?
I understand that by choosing a particular system with a given characteristic length, the smaller the mean free path ($\lambda$) the greater will be the validity of continuum treatment. Thus,
$$...
- 501
0
votes
3
answers
153
views
What is the mechanism responsible for the value of the speed of light in vacuum? [duplicate]
First of all, I've read almost all of the similar questions and duplicates given under them. And the question is never answered properly in any of them so please don't just share duplicates and leave ...
- 368
-3
votes
1
answer
131
views
Is a running coupling constant a natural consequence in QFT, or is it a consequence of the "dressing-up" of particles?
The running coupling constant ("hold that constant!) is a well known phenomenon in quantum field theory. The constant varies with the energy of the interacting particles. I think this is rather ...
