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September 27

Why are there constants in the forces of electric, magnetic and gravitational fields

Is there an explanation for the constants associated with the inverse square law in the forces acting within the electric, magnetic and gravitational fields? Or is it simply an observation verified experimentally? Malypaet (talk) 09:15, 27 September 2022 (UTC)[reply]

Electrostatic and gravitational forces are found to be proportional to the inverse square of distance. It is only when a constant has been verified experimentally that their proportional relations can be expressed as quantitative laws useful to predict real situations, within a consistent system of units.

Inverse square force laws
Force	Constant of proportionality
Electrostatic	Coulomb's constant $k e \approx 8.988 \times 109 N\cdotm 2 \cdotC -2$
Magnetic	Not reducible to an inverse square law. See Introduction to electromagnetism and for a more detailed mathematical treatment, see electromagnetic field.
Gravitational	Gravitational constant $G$ ≈ 6.674×10⁻¹¹ m³⋅kg⁻¹⋅s⁻².^[1]

Philvoids (talk) 11:37, 27 September 2022 (UTC) [reply]

References

^ "2022 CODATA Value: Newtonian constant of gravitation". The NIST Reference on Constants, Units, and Uncertainty. NIST. May 2024. Retrieved 2024-05-18.

Generally it is because units of measurements of length, time, charge etc. were chosen arbitrary. For instance, in CGS system there are much fewer constants compared to SI. Ruslik_Zero 20:33, 27 September 2022 (UTC)[reply]

I think there are just as many; their magnitudes differ merely by factors of the form 10^$n$, where

n

is each time a whole number. Compare the values in the table in Centimetre–gram–second system of units § Physical constants in CGS units with the SI ones. For example, the gravitational constant

G

is given as 6.67430×10⁻⁸ dyn⋅cm²/g². --Lambiam 22:26, 27 September 2022 (UTC)[reply]

Regrettably, "no..." (cgs actually has fewer constants). ...Although in fairness, the abbreviation "CGS" can refer to many different conventions - so let's be precise about what we're talking about: cgs typically refers to a specific system - the Gaussian units, also known as the cgs units or CGS - that differs from SI in other ways beyond a simple "factor-of-ten" conversion. Among the details we find a different convention to express physical laws, and this permits users to operate with some of the constants (especially the electrodynamics constants) defined equal to "1"; and still other constants are defined as unitless/dimensionless. (The most obvious example is that in cgs, there is no vacuum permeability μ0: it's not even "equal to one", it simply is a constant that does not exist in this formulation).

Our article says: "The CGS system variant avoids introducing new base quantities and units, and instead defines all electromagnetic quantities by expressing the physical laws that relate electromagnetic phenomena to mechanics with only dimensionless constants."

It's really quite an obtuse system and it's very challenging to explain in way that is both concise and correct... but certain physicists (especially astrophysicists, of all people) prefer to use this system professionally... For an external citation outside of Wikipedia's article, Jackson's Electrodynamics book is the go-to reference. World of Physics also has some more useful information, and they also cite Jackson, pointing our readers straight to Appendix 4.

I also seem to recall that certain famous peer-reviewed publications made a big deal about forbidding these cgs formulations in their journals (because they are confusing and horrible). I cannot locate sources for this (though I did recently say, I am trying to be less opinionated, my efforts to cite "confusing and horrible" fall short... let's just attribute that opinion to me.); and neither are sources cited in our article's history section; but I think it was recent enough that it took place during my lifetime.

Nimur (talk) 21:22, 28 September 2022 (UTC)[reply]

See also Natural units, describing alternative systems of units based on rational considerations. Some, such as the Hartree atomic units, are in actual use. --Lambiam 22:12, 27 September 2022 (UTC)[reply]

Geo coordinates - other interpretation?

In Top Gun: Maverick, the aircraft carrier radar screen displaying the enemy airstrip to be destroyed gives the geo coordinates 48°52.6-S 123°23.6-W. This means 48 degrees, 52.6 minutes South and 123 degrees, 23.6 minutes West... which is located - not exactly meaningfully - in the Indian Ocean, south of Australia. Right? Or is there any other interpretation of those coords? --KnightMove (talk) 13:42, 27 September 2022 (UTC)[reply]

That seems to be an Easter egg. Those coordinates are considered to be the point on Earth farthest from land. It is sometimes referred to as Point Nemo, the location of Capt. Nemo's secret base,[1] (Jules Verne's Mysterious Island).[2] 136.56.52.157 (talk) 17:57, 27 September 2022 (UTC)[reply]

Link: Pole of inaccessibility § Oceanic pole of inaccessibility. --Lambiam 22:14, 27 September 2022 (UTC)[reply]

It's mentioned at Talk:Pole of inaccessibility#Top Gun: Maverick. It's unclear whether it was a suggestion for the article. I guess the film deliberately chose a location far from land so no nutjob could go there and cause trouble, or whoever is located there could complain and maybe sue the studio. Maybe Point Nemo has been or will be used by others like fictitious telephone numbers 555-xxxx. PrimeHunter (talk) 03:09, 28 September 2022 (UTC)[reply]

[physconst-G-1] "2022 CODATA Value: Newtonian constant of gravitation". The NIST Reference on Constants, Units, and Uncertainty. NIST. May 2024. Retrieved 2024-05-18.

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