“The Stars are Too High” and Gravity Waves

Rumor has it that LIGO is finally going to announce the discovery of gravity waves on Thursday!  The author of “The Stars are Too High”, Agnew Hunter Bahnson Jr. helped to fund one of the first general relativity conferences where the existence of gravity waves was discussed.  In 1957 at the Chapel Hill conference.  Not all the physicists present considered gravity waves to be a possible physical reality.  Details were hashed out outside of conference sessions, and the physicists, while not reaching a consensus, were able to easily share ideas  by the simple expediency of being in the same location.

All of this was made possible by Bahnson.  Reaching out Bryce DeWitt after reading his Gravitation Research Foundations prize-winning essay, Bahnson proposed that DeWitt head up an academic institute for the study of gravitation.  Bryce was at first inclined to decline, but accepted after speaking with his mentor John Archibald Wheeler, (originator of the term Black Hole), who implored him to “Take the money!”. Shortly thereafter, using his own money, as well as funds from the military and other private industrialists, the Institute for Field Physics was born.  A few years later after Hunter’s untimely death in a plane crash, funding to the Institute would be cut by his family, but in the intervening time, it played host to early gravity wave discussions, as well as some of the work of visiting scholar, Peter Higgs, (yes, THAT, Higgs!)

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…

Kids R Kapable

Just a little note to concerned ‘grownups’ everywhere.  If you look at a kid—and I mean really look—I don’t mean notice a person shorter than you, I mean make eye contact, notice their facial expression and observe their body language—If you look at a kid, don’t assume they need your help unless they’re obviously distressed, or ask for it.  You might think this is difficult call to make.  You might think, not having kids of your own, that you’re unable to make this determination.  You are.  You do in fact, already have the skills even if you’ve never been around kids  It’s a remarkably simple call to make, just use the exact same criteria you would for determining if an adult was in distress.  Because, guess what, kids and adults are in fact the same species of animal and communicate in the same way.  Honest.  If someone—adult or child—doesn’t need your help, feel free to say hello, give a wave, give a smile, but don’t—do not—try to force help on anyone that doesn’t want or need it.

Y…