Skip to main content

When The Shoe's on the Other Foot... Literally

As our 'just under OSHA's safe hearing limits' subway hummed to a stop, I felt a gentle nudge at my left side.  Turning to find a kind but concerned looking fellow passenger, I raised my eyebrows quizzically.  She pointed at the kids.  "Ah," I thought, "she's about to comment on how awesome the kids are!"  It was the obvious answer, but why did she look so concerned?

She leaned in conspiratorially. "Their shoes might be on the wrong feet," she whispered.

"Hunh, would you look at that?  Cool!  Thanks!"  I replied with a big grin.  Off the train went roaring through the tunnels of San Francisco again.

At the next station, the train doors slid open letting the bright platform lights flood in.  I felt another nudge.  This time my fellow passenger leaned back in contemplation, staring at the kids' shoes.  For fun, I leaned back with her.  We studied the footwear in question in some detail.  She nodded her head, then leaned back in to whisper, "No, no, their shoes are definitely on the wrong feet." The doors on the train slid back shut.

I gave my best conspiratorial yet contemplative nod.  It felt kind of like being in a spy movie.  I whispered back, "I think your right.  No, no, you are right.  They're definitely on the wrong feet."

Our station was next, so I happily shouted "Next station is ours!" alerting my gang of three that they needed to jump up and run out of the train the next time the doors opened.

We all piled out of the train, and onto the platform where I hollered, "Hard left!" to direct the kids to the escalator we were headed up next.  Out of the corner of my eye, I could just make out our well-meaning fellow rider, still gazing forlornly at the kids' shoes.  Her face, pressed close to the glass of the train's window, was a palette of concern and confusion.  Why, oh why hadn't their shoes been changed back?

Here's why:

  1. 'Cause it's so easy!  The kids dress themselves.  Woohoo!  I focus on getting me ready!
  2. It makes the kids happy!  Yes, I've told them which shoes go where.  They don't care. 
  3. And finally, we meet so many interesting people this way!  Who would I talk to on the train otherwise?  Well, probably everyone, but that's beside the point :)


Popular posts from this blog

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…