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.
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Can all physical quantities and units be derived from the seven base SI units? [closed]
I understood that from cesium that we derived the unit for second and procedurally with other universal constants we derived the other SI units. Can all other “physical” units be derived from the ...
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What would happen if $c$ wasn't constant, but the quotient of $c$ with the scale factor $a(t)$ was? [closed]
I'm supposing there are strong reasons to disregard this scenario but I can't understand exactly what would it imply, and why it is not at all considered in cosmology. What I'm talking about is: we ...
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Why is finding a mathematical basis for the fine-structure constant meaningful?
I was reading QED by Richard Feynman and at the end he mentions that:
There is a most profound and beautiful question associated with the observed coupling constant, $e$ – the amplitude for a real ...
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Why did we choose Coulomb's constant $k$ as $9\cdot10^9 \rm Nm^2/C^2$ while define unit of charge instead of any other number?
I understand that while defining charge, Coulomb had to choose any arbitrary value of $k$ to describe unit of charge. But, why did we chose $9\cdot10^9 \rm Nm^2/C^2$ as the value of $k$, but not any ...
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Definition of the gravitational constant in 1+1 gravity
In this paper, the author formulates a $(1+1)$-dimensional theory of gravity by taking the trace of the Einstein equations
$$\left(1 - \frac{D}{2}\right)R = 8\pi G_D T,\tag{2}$$
(where $G_D$ is the ...
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Is the Planck mass the "lower limit" for gravity?
The Planck units are often treated as being the "lower limits" to things: the Planck length for length, the Planck time for time, etc.
But the Planck mass, which is about $2.2\times10^{-5}$ ...
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Planck Length Calculation
On this question, from long ago, the Planck length is calculated as the length at which the Reduced Compton Wavelength is equal to the Schwarzschild Radius. However, in the calculation, the scalar &...
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Mass of the Prototype $\rm kg$
With the new SI kg based upon Planck's constant $h$, is there any plan to eventually measure the former IPK using a Watt Balance, and determine how far its mass deviates from the new definition of 1 ...
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Gravitational Constant with ENM Units?
To give some context, there's a conspiracy 'theory' that I saw called Electric Universe that says that gravity is not a fundamental force and instead is a "incoherent dielectric acceleration"...
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How is Planck's constant relevant in quantum mechanics?
Planck’s constant relates the frequency of a photon to its energy but how does that relate to other quantum particles? For example in the Schrödinger equation it is used according to my book “to ...
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Two values of Rydberg Constant
In my textbook I came across two values of Rydberg Constant:
\begin{align}
R&= 109\,677\ \mathrm{cm}^{-1}
\\
R_h&= 2.18 × 10^{-18}\ \mathrm J
\end{align}
when we are calculating energy of the ...
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Do we really know the universal gravitational constant?
We've all heard $$F_g=\frac{gm_1m_2}{r^2}.$$ However, since I took physics, we've discovered "dark energy," which if I have any concept of the current thinking is caused by space being ...
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What is the value of the ideal gas constant in J/(mol*°C)? [duplicate]
I've seen in some sites that it is the same as in J/(mol*K), is that true?
$8.314 \frac{J}{mol×K}=8.314 \frac{J}{mol×°C}$
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Why is the uncertainty of the Gravitational Constant $G$ many orders of magnitude larger than that of other important fundamental constants?
Why is the numerical range of uncertainty of the Gravitational Constant $G$ many orders of magnitude larger than that of other important fundamental constants?
What are the challenges in precise ...
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Ideal Gas law and Universal gravitational constant
In a hypothetical universe with a different Universal gravitational constant $G$, will the nature of ideal gas change by any means?
i.e, will $PV = nRT$ be no longer applicable in that case?
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