C

Today I spent trying to put charge into completely MKS units. Yes, pretty much the whole day. There were breaks for lunch, seminars, and other similar things but mostly

1 Coulomb = m^a kg^b s^c

What are a,b, and c? Apparently, in SI units, current (A) is a "fundamental unit". What I'm wondering is, isn't the charge an observable independant of the parameters MKS?

One defines the current in terms of a force between two wires where the force is so many Newtons. The only problem is that force (per unit length) is given by

F \propto \mu_{o} I^2

and \mu_{o} has units of N/A^2. Thus if you give me the force between the wires I can give you a value for A but it will be in MKS+A units. A seems to depend on itself. Is this making sense? Where am I going wrong?

Today I am reading:
"Curved Space or Curved Vacuum?" by Eric Linder from gr-qc

PS: Would someone please write a Latex interpreter firefox plugin?

More lookups

cf.
→ abbrev.
compare with.
- ORIGIN from L. confer ‘compare’.

obtain is a formal and often pretentious word, and no one should be afraid of using the perfectly respectable word get in most contexts.

pre-empt

→ verb [with obj.]
1. take action in order to prevent (an anticipated event) happening; forestall: the government pre-empted a coup attempt.

• act in advance of (someone) in order to prevent them doing something: it looked as if she'd ask him more, but Parr pre-empted her.
2. acquire or appropriate (something) in advance: many tables were already pre-empted by family parties.

• (N. Amer.) occupy (public land) so as to have a pre-emptive right to buy it before others.
3. [no obj.] (Bridge) make a pre-emptive bid.


Above definitions from the Oxford Reference Online Premium.

bilking argument
→ n.
argument against backward causation posed by Max Black (1956) .
It goes as follows. If an event in the future causes an effect in the past it is possible to pre-empt the future cause between the events such that the effect occurs but not the cause. Thus, "assuming preemption is allowed, backwards causation cannot occur."
See an entry in the Stanford Encyclopedia of Philosophy. Still no word about the origin of the word bilking.


Weyl Curvature
→ n.
The curvature that exists in empty space. Why?

Green the Giant

What should I write about during the off season? I am deep into Classic Jackson and some Quantum problems with little time for fun reading like the burst I had during break. Maybe I will complain about how my sometimes favorite internet radio source, WMUC at University of Maryland, has seemed to be down for two days. I miss my Modest Mouse, Jens Lechman, and the occasional Dylan Hour.
I'm learning a lot of fun things about Green's Theorem and his first identity. Jackson presents this in the "look what happens when I do this" sort of framework. He just puts down a collection of scalar fields and their gradients and laplacians. He says its all based on the divergance theorem, which I believe. However why define the vector in that theorem as a scalar field times the divergance of another scalar field?
I was quietly awed by the Green's accomplishment. His identity and some clever manipulations give us this elegant form for the static potential from any charge distribution with simple support for Dirichlet or Neumann boundary conditions. A simple choice of guage in the Kernel/Green's function eliminates the unknown boundary condition. I wonder what they did for continous charge distributions before they figured this out.