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Physics question, is a true DC or constant magnetic field truly possible?
Kleinstein:
The earths magnetic field is not 100% stable. Good magnetometers can measure the variations in the earths field. On the slow scale they observe that the magnetic poles are wandering a little.
Circlotron:
If we assume the universe had a beginning, then our DC current or magnetic field must have gone from zero to a steady value at that point or sometime after that. Would that not disqualify it from being truly constant?
jpanhalt:
--- Quote from: BrianHG on March 28, 2024, 12:38:39 am ---Can we or the universe ever achieve an authentic 0hz unchanging charge with 0 AC characteristics?
--- End quote ---
Sure, but how would you prove it? Any method of measure would disturb it (not Heisenberg's uncertainty principle but a similar argument).
tggzzz:
--- Quote from: nctnico on March 28, 2024, 09:11:23 pm ---
--- Quote from: BrianHG on March 28, 2024, 12:38:39 am ---Well? I guess you might call this a philosophical question, but, no matter the power source creating your DC power, it will eventually die meaning no longer a DC signal as it has an AC attribute. (Heat death of the universe and all that...) Even a permanent magnet's field fades over time, hence they are not truly constant.
Can we or the universe ever achieve an authentic 0hz unchanging charge with 0 AC characteristics?
--- End quote ---
How about the earth's magnetic field?
--- End quote ---
It reverses periodically. The record of such reversals provided early compelling evidence for plate tectonics. Also spot how fast the magnetic North pole is moving: at >30 miles/year (i.e.>10 furlongs/fortnight).
As for the original question, the answer is yes, repeat no, unask the question.
I remember a school maths lesson (age 12?) where we spent the entire lesson discussing whether it was possible to have a flat plane. After I pointed out that even the smoothest surface would have atoms sized variations, we eventually came to realise that the mathematical abstraction was real, but there could be no physical embodiment.
I hope the relevance is obvious.
SiliconWizard:
There is nothing much constant in the universe anyway, except possibly the speed of light (and a few other constants that can more or less be derived from it), and even that is not certain.
As I and others have said, a physical constant value is whatever varies little enough that the variation doesn't matter from the perspective of the observer.
The rest is inevitably not a physics question, but metaphysics.
The flatness and atoms example is relevant. But so is the "constant" attribute of the "amplitude" (envelope) of some oscillation, when the oscillation itself is a value that is permanently changing. What that means is that one defines, arbitrarily, some "macro" property that helps abstracting what happens at a lower level, but those abstractions are models, not an expression of something real.
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