### The Week in Science and Engineering

March 3rd, 2008 -- A weekly look at science, engineering, and fringe science happenings from the week before!
Levitation: Fact or Fiction? Pravda.run ran an interesting article on levitation. It presented a chronological history of accounts of levitation. The initial accounts were more mystically slanted including various swamis, nuns, and saints. As time progressed, the coverage moved towards anecdotal and scientific accounts. These included accounts of levitation by Daniel Douglas Hewm that were verified by people such as Mark Twain and William M. Thackeray. Finally, the article discussed modern 'scientific' example of levitation such as the Meissner effect.

Another physical phenomenon that can result in levitation and was not covered in the article is diamagnetism. It was used most spectacularly to levitate a frog in the Netherlands. This experiment was carried out at the Nijmegen High Field Magnet Laboratory.

The moon-bound art museum: greg.org reported on an art museum left on the moon by Apollo astronauts. The miniature museum attached to the leg of on of the lunar landers included works by Andy Warhol and Robert Rauschenberg among others.

The spy satellite: The Pentagon confirmed that it had indeed succeeded in shooting down an errant spy satellite. The linked post also contains an interesting chronology of other articles about the spy satellite.

The Ray Gun: And, finally, 60 Minutes reported on a ray gun used by the military to disperse crowds which creates an uncomfortable burning sensation.

The Locations:

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Digg the sources:

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### 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…

### Lost Phone

We were incredibly lucky to have both been in university settings when our kids were born.  When No. 1 arrived, we were both still grad students.  Not long after No. 2 arrived, (about 10 days to be exact), mom-person defended her dissertation and gained the appellation prependage Dr.

While there are lots of perks attendant to grad school, not the least of them phenomenal health insurance, that’s not the one that’s come to mind for me just now.  The one I’m most grateful for at the moment with respect to our kids was the opportunities for sheer independence.  Most days, we’d meet for lunch on the quad of whatever university we were hanging out at at the time, (physics research requires a bit of travel), to eat lunch.  During those lunches, the kids could crawl, toddle, or jog off into the distance.  There were no roads, and therefore no cars.  And, I realize now with a certain wistful bliss I had no knowledge of at the time, there were also very few people at hand that new what a baby…

### Lab Book 2014_07_10 More NaI Characterization

Summary: Much more plunking around with the NaI detector and sources today.  A Pb shield was built to eliminate cosmic ray muons as well as potassium 40 radiation from the concreted building.  The spectra are much cleaner, but still don't have the count rates or distinctive peaks that are expected.
New to the experiment?  Scroll to the bottom to see background and get caught up.
Lab Book Threshold for the QVT is currently set at -1.49 volts.  Remember to divide this by 100 to get the actual threshold voltage. A new spectrum recording the lines of all three sources, Cs 137, Co 60, and Sr 90, was started at approximately 10:55. Took data for about an hour.
Started the Cs 137 only spectrum at about 11:55 AM

Here’s the no-source background from yesterday
In comparison, here’s the 3 source spectrum from this morning.

The three source spectrum shows peak structure not exhibited by the background alone. I forgot to take scope pictures of the Cs137 run. I do however, have the printout, and…