### Getting Started with Amateur Satellites and Satellite Mapping

Progress! See Part II.
I'm helping to plan an amateur radio special event on November 5th to raise awareness of the effort by The Friends of Science East to save Tesla's last lab, Wardenclyffe, in Shoreham, NY. One idea for the event is to operate from some of the buildings that Tesla occupied either as labs or as homes in Manhattan. I'm thinking an easy means of operation from there might be satellite. This brings up the interesting question of "which satellites are visible from which rooftops?" I've perused the net a bit and haven't found a program that will display amateur satellite orbits in relation to the NYC skyline, so I decided to plunk around and see if I could come up with my own. So far, I have a list of references I intend to start with and I know what technology I'm going to try to use.

Google Earth is now avaiable on web pages as a JavaScript plugin. I'll be using that as the programming framework. The docs for the portion of the API I plan on using can be found at:

Satellite trajectories are described by Keplerian data. The Keplarian data for amateur satellites is availabe at:
http://www.amsat.org/amsat/ftp/keps/current/nasa.all

Amsat also has an fb explanation of the Keplerian data elements at:
http://www.amsat.org/amsat/keps/kepmodel.html

The author of the site http://www.barnabu.co.uk has already written a great satellite debris tracking framework I'll be using as a code basis. To see more about it, go to:

For an in-depth description of the algorithms used in the code, check out Wikipedia at:
http://en.wikipedia.org/wiki/Simplified_Perturbations_models

Finally, if you just absolutely positively have to find an amateur satellite right now, then the site you want is the excellent one by N2Y0.

### Cool Math Tricks: Deriving the Divergence, (Del or Nabla) into New (Cylindrical) Coordinate Systems

The following is a pretty lengthy procedure, but converting the divergence, (nabla, del) operator between coordinate systems comes up pretty often. While there are tables for converting between common coordinate systems, there seem to be fewer explanations of the procedure for deriving the conversion, so here goes!

What do we actually want?

To convert the Cartesian nabla

to the nabla for another coordinate system, say… cylindrical coordinates.

What we’ll need:

1. The Cartesian Nabla:

2. A set of equations relating the Cartesian coordinates to cylindrical coordinates:

3. A set of equations relating the Cartesian basis vectors to the basis vectors of the new coordinate system:

How to do it:

Use the chain rule for differentiation to convert the derivatives with respect to the Cartesian variables to derivatives with respect to the cylindrical variables.

The chain rule can be used to convert a differential operator in terms of one variable into a series of differential operators in terms of othe…

### The Valentine's Day Magnetic Monopole

There's an assymetry to the form of the two Maxwell's equations shown in picture 1.  While the divergence of the electric field is proportional to the electric charge density at a given point, the divergence of the magnetic field is equal to zero.  This is typically explained in the following way.  While we know that electrons, the fundamental electric charge carriers exist, evidence seems to indicate that magnetic monopoles, the particles that would carry magnetic 'charge', either don't exist, or, the energies required to create them are so high that they are exceedingly rare.  That doesn't stop us from looking for them though!

Keeping with the theme of Fairbank[1] and his academic progeny over the semester break, today's post is about the discovery of a magnetic monopole candidate event by one of the Fairbank's graduate students, Blas Cabrera[2].  Cabrera was utilizing a loop type of magnetic monopole detector.  Its operation is in concept very simpl…

### Unschooling Math Jams: Squaring Numbers in their own Base

Some of the most fun I have working on math with seven year-old No. 1 is discovering new things about math myself.  Last week, we discovered that square of any number in its own base is 100!  Pretty cool!  As usual we figured it out by talking rather than by writing things down, and as usual it was sheer happenstance that we figured it out at all.  Here’s how it went.

I've really been looking forward to working through multiplication ala binary numbers with seven year-old No. 1.  She kind of beat me to the punch though: in the last few weeks she's been learning her multiplication tables in base 10 on her own.  This became apparent when five year-old No. 2 decided he wanted to do some 'schoolwork' a few days back.

"I can sing that song... about the letters? all by myself now!"  2 meant the alphabet song.  His attitude towards academics is the ultimate in not retaining unnecessary facts, not even the name of the song :)

After 2 had worked his way through the so…