maxwell's equations

ehrenfest

Are Maxwell's equations thought to be exact? I realize this question is very open-ended and loosely-phrased.

lzkelley

Yes they are. But keep in mind that each one of maxwell's equations inevitably contains some sort of fundamental constant (mu or epsilon usually; not to mention electric charge etc etc) which are measured quantities and therein not exact.
Does that answer your question?

ehrenfest

Yes.

Phlogistonian

They're not exactly exact. QED makes slightly different predictions from classical electromagnetism.

tgt

Mathematically, correct hence exact. Physically, it's a good approximation and only an approximation to model phenomena. Hence not exact physically. Is anything exact physically? No.

rbj

lz, be careful.

which constant in Maxwell's equation is measured and not defined (to an exact value)?

Poop-Loops

Epsilon-not.

Mu-not is defined. At least, that's what my professor said.

rbj

you mean this epsilon-not ?

Hootenanny

And the magnetic constant?

dst

I have one apple, I add another one, I have exactly two apples.

humanino

Well, if you take into account the masses of the apples, which is what is physically relevant when you buy apples, then you have less mass when the two apples are together, right ?

dst

Pfft, technicalities. If truth be told, the error is in disguise - it's either present in the definition(s) or as a constant in whatever expression you're using.

On the other hand, there is no match for the physics of two cows™.

You have two communist cows.

robphy

by the way, that's
epsilon-naught (epsilon-zero) and similarly for mu-naught.

rewebster

so, that applies, too, when two physicists get together?

ehrenfest

Umm--what? Are you using special relativity?

humanino

I guess so
edit
Actually, it depends. If they disagree on the status of "is string a theory ?", their interaction can be very exothermic.
They have gravitational biding energy, don't they ?