Maxwell's equations

  • Thread starter ehrenfest
  • Start date
  • #1
ehrenfest
2,020
1
Are Maxwell's equations thought to be exact? I realize this question is very open-ended and loosely-phrased.
 

Answers and Replies

  • #2
lzkelley
277
2
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?
 
  • #3
ehrenfest
2,020
1
Yes.
 
  • #4
Phlogistonian
87
0
They're not exactly exact. QED makes slightly different predictions from classical electromagnetism.
 
  • #5
tgt
520
2
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.
 
  • #6
rbj
2,227
9
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.

lz, be careful.

which constant in Maxwell's equation is measured and not defined (to an exact value)?
 
  • #7
Poop-Loops
721
0
Epsilon-not.

Mu-not is defined. At least, that's what my professor said.
 
  • #8
rbj
2,227
9
  • #10
dst
379
0
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.

I have one apple, I add another one, I have exactly two apples.
 
  • #11
humanino
2,490
8
I have one apple, I add another one, I have exactly two apples.
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 ? :biggrin:
 
  • #12
dst
379
0
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 ? :biggrin:


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.
 
  • #13
robphy
Science Advisor
Homework Helper
Insights Author
Gold Member
6,550
1,921
Epsilon-not.

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

by the way, that's
epsilon-http://www.answers.com/naught&r=67" [Broken] (epsilon-zero) and similarly for mu-naught.
 
Last edited by a moderator:
  • #14
rewebster
843
2
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 ? :biggrin:

so, that applies, too, when two physicists get together?:wink:
 
  • #15
ehrenfest
2,020
1
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 ? :biggrin:

Umm--what? Are you using special relativity?
 
  • #16
humanino
2,490
8
so, that applies, too, when two physicists get together?:wink:
I guess so :rofl:
edit
Actually, it depends. If they disagree on the status of "is string a theory ?", their interaction can be very exothermic.
Umm--what? Are you using special relativity?
They have gravitational biding energy, don't they ?
 

Suggested for: Maxwell's equations

  • Last Post
Replies
3
Views
498
  • Last Post
Replies
4
Views
136
  • Last Post
Replies
6
Views
515
Replies
4
Views
269
Replies
1
Views
282
Replies
3
Views
640
  • Last Post
Replies
4
Views
726
Replies
8
Views
613
  • Poll
  • Last Post
Replies
21
Views
3K
  • Last Post
4
Replies
125
Views
11K
Top