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2answers
66 views

What is the difference between a physical constant, a scalar, an invariant, and a conserved quantity?

I don't really know how to properly articulate this question. This question popped into my mind when pondering why the fact that a physical constant like the speed of light doesn't have an associated ...
-1
votes
1answer
59 views

Why $\epsilon_0 = 1/(4\pi k)$ instead of $\epsilon_0 = 4\pi k$? [on hold]

In my physics book, they consider a positive point charge $q$ and a spherical surface of radius $r$ centered on this positive charge. Then the flux through this surface is given by $$\Phi = \iint \vec{...
29
votes
6answers
4k views

Does the speed of light in vacuum define the universal speed limit?

Is light the thing causing the universal speed limit to be $299\,792\,458\,\mathrm{m/s}$? So the universal speed limit would be different if light travelled faster or slower? Or, is $299\,792\,458\,\...
1
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0answers
44 views

How Higgs Field is a constant in an Expanding Universe [closed]

Going through information on Higgs Field in various forums, it seems that the mass of an object is due its interaction with the Higgs Field which is constant throughout the universe. However it ...
12
votes
3answers
2k views

Why do universal constants have the values they do?

This is meant to be a generic question of the type that we get repeatedly on this site, in different versions: The origin of the value of speed of light The gravitational constant G theoretically? ...
0
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4answers
99 views

Is there an official list of independent units of measurements?

When I say 'independent units', I mean those which cannot be broken down anymore, and simultaneously forms the basis for any more, complex measurements. For example, height, length, and width can all ...
3
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1answer
50 views

Would order 1AU metric expansion of space begin if the solar system were not inside a galaxy?

In this question I describe the >30 years of laser ranging between lasers on Earth and the retroreflector arrays on the Moon. Amazingly, after comparing this data to simulation of all of the orbital ...
8
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4answers
1k views

Can the accuracy in Planck's constant ever be increased?

I guess I am having some confusion about the history of calculating Planck's constant. I see the mass of the electron may come into the equation here but isn't the measurement of mass based mostly ...
3
votes
1answer
115 views

Experimentally finding units of physical quantity?

Say you had a new physical quantity you wanted to determine the units for. How do you go about this? For the strength of an electromagnet for example, you could carry out a simple experiment like the ...
16
votes
4answers
859 views

Why isn't it $E \approx 27.642 \times mc^2$?

Sorry for the strange question, but why is it that many of the most important physical equations don't have ugly numbers (i.e., "arbitrary" irrational factors) to line up both sides? Why can so many ...
3
votes
1answer
42 views

Running Constant Values At Very Low Temperatures

From Wikipedia Coupling Constants, using QED as an example. I realise that the one-loop beta function in quantum chromodynamics is negative. If a beta function is positive, the corresponding ...
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0answers
36 views
0
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1answer
52 views

Are there any numerical predictions of the Newtonian gravitational constant $G$ from modern theories?

There are no established relationships between the Newtonian gravitational constant $G$ and other fundamental constants, so there is no way to derive its value from other quantities. Its value must be ...
0
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0answers
45 views

Fine Structure and Fine Structure Constant - intuitive relation?

How does the fine structure and fine structure constant relate to each other, intuitively? I've seen $\alpha$ extrapolated as a term in energy calculations for fine structure, but is there a ...
-1
votes
2answers
114 views

Do we have a better approximation of $c$ than 299792458 m/s? [duplicate]

All sites give this value as "exact" value. I mean, what's after the comma? 299792458,000 m/s?
0
votes
2answers
192 views

Is it possible for the Higgs Field strength, to increase with time? [closed]

Magnetic fields are created when an electric current flows: the greater the current, the stronger the magnetic field. What influences could affect the Higgs Field? If the Higgs field grew in ...
3
votes
2answers
796 views

Free parameters in the Standard Model

From my understanding of the standard model, I understand that there are 19 or 20 free parameters that we need to put in by hand as, and I'm guessing here, there is as yet no theoretical basis for ...
4
votes
2answers
99 views

If maximum speed limit $c$ is made infinite, will general theory of relativity become equivalent to Newton's gravitational theory?

We know that special relativity tends to become equivalent to classical theory of relativity as the speed limit of nature becomes infinite. If this happens, clock will tick at the same rate ...
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votes
1answer
99 views

Must the fine structure constant be an irrational number? [closed]

This question concerns a conjecture on the nature of $\alpha = e^2/4\pi\epsilon\hbar c$ in light of black hole holes. Let me consider the Reissnor-Nordstrom metric for a charged black hole $$ ds^2 = \...
4
votes
4answers
727 views

What is the significance of Planck force?

I have been curious to find what could be the significance of Planck force? It is calculated by the formula $c^4/G = 1.21031359\times 10^{44} \, \mathrm{N}$, where $c$ is the speed of light and $G$ is ...
4
votes
3answers
307 views

Fundamental Constants in a theory of everything (TOE)

Do physicists ever expect to be able to derive the fundamental constants of nature from theory? For example, if string theory or some other theory unites the four forces, would the theory be ...
16
votes
7answers
2k views

Is there a limit to acceleration? [duplicate]

As we all know the speed of light is the limit at which energy/matter can travel through our universe. My question being: is there a similar limit for acceleration? Is there a limit to how quickly ...
8
votes
5answers
2k views

Planck mass is about the mass of one eyebrow hair

Unlike most Planck units named after "Planck" such as Planck length, Planck temperature, etc, the Planck mass seems more closed to daily life. It is about $10^{-5}$g, same order of magnitude of one ...
6
votes
4answers
609 views

Can the gravitational constant $G$ be calculated theoretically?

We know all that the gravitational constant is $$G=6.67428±0.00067\times 10^{-11}\mathrm{m^{3} \:kg^{-1} s^{-2}}.$$ But can we calculate it theoretically?
2
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2answers
149 views

The mass of the proton times its charge radius is very close to 4ħ/c. Is this a coincidence?

The claim is $r_p m_p = 4 L_0 M_0 = 4\hbar/c$, where $r_p$ and $m_p$ are the proton's charge radius and mass, and $L_0$ and $M_0$ are the Planck length and mass. Using the muon measurement $r_p=0....
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votes
1answer
97 views

When can the constant of proportionality in an eq be set equal to 1 and when not? [duplicate]

In $F=kma$, $k=1$ but in $F=kx$, $k$ is not equal to 1?So what are the conditions for the constant of proportionality to be set 1?
0
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0answers
54 views

Why Newton's gravitational constant remains unchanged in relativity though gravity is not a force?

I know that Einstein described gravity as a curvature of spacetime. So, It is not a "force" but why Einstein had to accept Newton's gravitational force constant?
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3answers
102 views

Are dimensionless physical constants predicted to be rational, irrational, or transcendental numbers?

Are dimensionless physical constants predicted to be rational, irrational, or transcendental numbers? Directly measured ones are obviously unknown, but according to Wikipedia many dimensionless ...
6
votes
1answer
280 views

Why is the gravitational constant so difficult to measure?

The gravitational constant seems to be very low precision. For example, in the Wikipedia article recent measurements are given as having the significands of 6.67 and 6.69, a difference of 2 parts in ...
0
votes
2answers
60 views

Proper units for physical quantities when $\hbar$=$1$

How to deal with the units of quantities if $\hbar=\tfrac{h}{2\pi}=1$? For example, the energy $E=\hbar\omega$: If I have chosen $\hbar=1$, how do I use the units to properly differentiate between ...
1
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0answers
40 views

Are there characteristics that distinguish our universe?

Are there any defining characteristics of our universe that could be different for other universes (or "instances of our universe") that operate under the same laws of physics? And which, if any, are ...
2
votes
0answers
38 views

Any method to determine the gravitational constant $G$ from observations in cosmological scale?

By the observations in cosmological scale, I mean observations by astrophysicists like motions of quasars in far distance from us, relative motions of our galaxy to others, etc. I know the famous ...
4
votes
1answer
689 views

What is the most natural definition of the weak hypercharge coupling constant if grand unification is wrong?

A tricky question. Here is the famous graph of the running of the three coupling constants in the standard model: The graph shows, in its top curve, the running of the coupling constant $\alpha_1$. ...
1
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1answer
174 views

Difference between theoretical equations and empirical equations

Some equations are theoretical in the sense that they are derived from an underlying theory. Other equations are empirical in the sense that they were selected only because they fit experimental data ...
3
votes
1answer
57 views

How is a result of no time variation in the gravitational constant $G$ related to a measurement of no local expansion?

In this answer @PhillS linked to the paper Progress in Lunar Laser Ranging Tests of Relativistic Gravity which has given me a great start. While its main focus is on the Equivalence Principle (EP) ...
3
votes
3answers
333 views

Physical Significance of the Planck Density

The Planck density is the Planck mass devided by the Planck volume, approximately 1093 g/cm3. Does this quantity have any known physical relevance? The Planck mass is believed to be the smallest ...
2
votes
3answers
497 views

Why do we need constants? [closed]

This question is driving me crazy because I cannot find a straightforward answer. I want to know what a physical constant exactly is. I know that it’s a value that doesn’t change, but what is it? Why ...
5
votes
1answer
106 views

Proportionality Constant in Einstein Field Equations

The Einstein Field Equations: $$G_{ab}~=~8\pi T_{ab}.$$ I am familiar with how to obtain the $8\pi$ proportionality factor through correspondence with Newtonian gravity, but am wondering if this ...
0
votes
3answers
174 views

Why did Einstein took speed of light unit or constant in his equation of relativity?

We can find that no object can have speed more than light from Einstein's equation of relativity because if anything have speed more than light then we get -ve value within square root. But why did ...
3
votes
0answers
85 views

Experiment measuring vacuum permittivity and permeability in high speed

Suppose that we do NOT know anything of constancy of speed of light, to say nothing of special relativity. It is that we acquired a constant speed of light from Maxwell's Equations that we finally ...
1
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5answers
171 views

What in nature causes Newton's gravitation constant to have its given value?

Does the value of Newton's universal gravitational constant $G$ remain a mystery? Why does it have the value that it has?
1
vote
1answer
69 views

About Planck tension in strings theory as stated in “The Elegant Universe”

In the book "The Elegant Universe" by Brian B. Greene, on chapter 6 it is stated that there's the so called "Planck tension" in string theory, and it is given a value of $10^{39}$ tons. This value is ...
2
votes
0answers
26 views

Do time/location-dependent fundamental constant exists? [closed]

Throughout history people have been carrying out experiment after experiment to test many of the known constant, so I like to know if there are any oddities among the known fundamental constants. If ...
0
votes
3answers
69 views

What does the $k_e$ in Coulomb's law and $G$ in Newton's Universal Gravitation Law mean?

I very well understand the proportionality relation that was used to derive these laws like $F$ is proportional to product of masses and inversely to radius squared and hence its proportional to the ...
-1
votes
1answer
71 views

Which was the first Coulomb's constant value? [closed]

Which was the first Coulomb's constant value? I didn't found any info in the Internet. I need the first value of K to compare it with my experiment. Could you please help me?
1
vote
0answers
35 views

Where does the square root of two in the conversion between the Fermi constant and the weak coupling constant come from?

As in the title, where does the square root of two in the conversion $$ G_{F}=\frac{\sqrt{2}g^{2}}{8m_{W}^{2}} $$ between the Fermi constant and the weak coupling constant come from? I was able to ...
1
vote
1answer
29 views

How are the constants in hydraulics calculated? [closed]

I would like to know (out of sheer morbid curiosity) how constants in hydraulics are calculated. The constants are, for good ol' 'Merican units; 63025, 5252,and 231. These constants came out of "...
1
vote
1answer
80 views

Can the value of $c$ be calculated from Relativity? [duplicate]

I have three related questions about what theories or equations can calculate and what is an input parameter/constant to the theories. This question is not about parameter units (as another similar ...
5
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2answers
139 views

String models of particle physics

What general features of particle physics are derived/replicated by constructing string models of particle models? How do such models address the fixing of free parameters like the masses and the ...
3
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2answers
73 views

Does the speed of light change? [duplicate]

I know that there is a similar questions, but I think mine is a bit different. I wonder if with the expansion of the universe the speed of light changes. It seems that the speed of light is very ...