Doubt

Tuesday, 30th October.

I'm holding a talk this afternoon about measuring heart pulse (that expansion of the artery you feel when you put your finger on your throat/wrist). I guess that any medical doctor will see that I know fuck all about arterial blood flow. Any electrical engineer will see that I know fuck all about electronics. And any physicist will see that my error bars are way too big.

I can see it, as I'm a physicist. You don't need to know anything about the subject to say that this graph is bullshit. Nature don't work like that.


If you're not a physicist, let me tell you a secret. If those error bars show one standard deviation, then if you fit a line through all the points, about one third of the points shouldn't touch the line with their error bars. A plausible plot looks something like this:



I didn't make the plots, and couldn't be bothered to sort out the error analysis. I'm just the gimp who does the talk. My worst case scenario is to tender my resignation on the spot (with 3 months' notice), go for a juggle in central park, and find a good strip club.

What the hell am I doing here?

I spent two hours this morning trying to solve an exam question, and completed a quarter of it. Students are supposed to be able to solve the entire exercise in 20 minutes. I kept writing alphas instead of gammas (90 degree rotation syndrome) and 3s instead of epsilons (180 degree rotation syndrome, aka mirror reversal syndrome, aka L337n3ss syndrome). This is not good, at all.

I've done pretty much nothing useful this week, and spent most of Monday morning in tears. These things aren't very good at all.

EeeyEe0e

Yesterday I had a confidence crisis at work. It started off with an equation with too many E's in it. It looked to me pretty much like the post title, and described an electric field entering a region, whilst oscillating according to a power of Euler's number (e), and pointing in the direction of the y-axis, but only one unit (einheit) long.

So in summary, Electric (E), Einheit (e), Eintritt (e), Euler (e). I looked at this equation and was thrown into despair. It is an amazing ability to be able to look at an equation and immediately recognise the significance of each term, to see that the direction of a vector doesn't depend on a constant value, or that the time-dependence doesn't depend on the direction. I looked at the equation, and could only see and say "EEEEEE". That was it. The same understanding as a five-year-old.

I recovered slightly, read the foreword to Calculus made Easy by Silvanus P. Thompson, and found a book where they used "Incidence" instead of "Eintritt", and worked around the e for "Einheit". With most of the E's gone, things made sense again.

This happened to me once before, when I found an equation consisting of 17 J's and pretty much nothing else. I remember intensely wishing to never see a physics book again. The next time this happens, I will try to remember this advice: drop the book (or lecturer), but keep at the subject.