I am a “retired” postdoc in particle physics, trying to transition into the tech industry. I started out programming with Java around 1999, and more recently I’ve been doing a lot of work with Python, C, and C++, although I do occasionally dabble in PHP, Perl, shell scripting, and other languages.

  1. 2013
    Oct
    09

    Obligatory musings on the Nobel Prize

    Posted by David Zaslavsky on — Edited

    You’ve probably heard that the Nobel Prize in Physics was awarded yesterday to François Englert and Peter Higgs, for the theoretical prediction of the Higgs boson. You’ve probably also heard all the commotion leading up to the announcement, about how silly it is that Nobel Prizes are awarded only to three people. And you may have noticed that I didn’t weigh in.

    Frankly, that’s because I didn’t really care. I’m sure it’s a big deal to the recipients and non-recipients of the prize, but to the rest of us, the work done by all six authors stands on its own merits. The community of physicists doesn’t need a prize to tell them whose research leads to a better understanding of the universe — and in the end, even if you ask most Nobel Prize winners, understanding the universe is what makes doing science worthwhile, not getting recognition.

    If this year’s debate gets people to look more closely at the actual science being done, and put less emphasis on who gets labeled a Nobel Prize winner, that can only be a good thing.

    I’ll leave you with the links to the Nobel-winning …

  2. 2013
    Sep
    24

    Interpreting Fourier transforms

    Posted by David Zaslavsky on

    Before you ask: yes, I do know I’ve been absent from blogging for too long. About a month, actually, which roughly coincides with the start of the fall semester here at Penn State. I’m TAing a class this semester, and also working overtime to push out a paper about my group’s current research (a followup to this one, which I will be writing about soon), and still moderating Physics Stack Exchange, and many other things which just haven’t left time for blogging as much as I would have liked.

    There are some recent nifty bits of physics I do plan to write about, but until I get time to do that, enjoy this picture:

    (adapted from XKCD). I was inspired by last week’s physics colloquium speaker, Patrick Drew, who actually works on neural engineering. Not very physicsy, you’d think, but actually physics has ties to all sorts of other fields of study because in the end we’re all just trying to make models that describe reality.

  3. 2013
    Aug
    21

    The story of open access

    Posted by David Zaslavsky on

    I was all set to make a grand post on reddit on why scientific research isn’t publicly accessible. Type type type, submit, “the link you are commenting on has been deleted.” Moderation, sometimes you suck. (I kid.) But it’s a shame to waste four perfectly good paragraphs, so here you go:

    Why is scientific research hidden from the public by paywalls?

    First, let’s be clear on one thing: the “public” that scientific research is hidden from is not nonscientists. So it’s not like scientists are involved in some conspiracy to keep their results out of public scrutiny. Paywalls — the restriction of having to pay a fee to read a scientific article — hide research from the “public” that is anyone who hasn’t paid to access it. That includes other scientists. Yes, any time you’ve wanted to read a paper and been blocked by a paywall, I guarantee that some scientist has already had the exact same experience and has been even more pissed off about it than you.

    The reason we have paywalls at all is largely historical. In the olden days before the internet, scientific research was shared primarily through printed journals. Scientists would …

  4. 2013
    Aug
    07

    B meson decay confirmed!

    Posted by David Zaslavsky on

    Time for a blog post that has been far too long coming! Remember the Quest for B Meson Decay? I wrote about this several months ago: the LHCb experiment had seen one of the rarest interactions in particle physics, the decay of the \(\mathrm{B}^0_s\) meson into a muon and antimuon, for the first time after 25 years of searching.

    Lots of physicists were interested in this particular decay because it’s unusually good at distinguishing between different theories. The standard model (which incorporates only known particles) predicts that a muon and antimuon should be produced in about 3.56 out of every billion \(\mathrm{B}^0_s\) decays — a number known as the branching ratio. But many other theories that involve additional, currently unknown particles, predict drastically different values. A precise measurement of the branching ratio thus has the ability to either rule out lots of theoretical predictions, or provide the first confirmation on Earth of the existence of unknown particles!

    Naturally, most physicists were hoping for the latter possibility — having an unknown particle to look for makes things exciting. But so far, the outlook doesn’t look good. Last November, LHCb announced their measurement of the branching ratio …

  5. 2013
    Jul
    15

    Have we really found a tetraquark?

    Posted by David Zaslavsky on

    Hooray, it’s time for another blog post! What I’m writing about this time is kind of old news — and don’t worry, there’s more to come on just why I haven’t been able to write about it for so long — but very interesting nonetheless.

    A few weeks ago, two separate physics experiments announced that they had discovered a tetraquark, a composite particle made of four quarks. Or rather, that’s what all the popular news coverage said. But what really happened? The discovery of a real tetraquark would be huge news, so I’m sure not going to trust the media reports on this one. As always, I’m going straight to the source: the original papers by the BES III and Belle collaborations.

    Two or Three is Company, Four’s a Crowd

    Before delving into the discovery itself, I’m going to tackle the burning question on everybody’s mind: what’s so special about a particle made of four quarks?

    To understand that, we have to look to quantum chromodynamics (QCD), the theory of how “color-charged” particles interact. In some ways, QCD is superficially similar to quantum electrodynamics, the theory of how electrically charged …

  6. 2013
    Jun
    17

    Quick plotting

    Posted by David Zaslavsky on — Edited

    While I was writing my last Mythbusters blog post, I realized that it’d be really useful to have a “quick and dirty” plotting program — one that just takes the output of another program and plots it, no questions asked. Actually, let me rephrase that: I knew it would be useful, it just never occurred to me that I don’t have one. Most of the common plotting programs people tend to use, like GNUplot, expect to be configured with the format and syntax and display options and all that junk that you don’t really care about when you just want to turn numbers into a picture.

    If you have GNUplot installed, here’s a little script to do just that:

    #!/bin/bash

using=""

shopt -s extglob
if [[ "$1" == +([[:digit:]])*(,+([[:digit:]])) ]]; then
        using="using ${1//,/:} "
        shift
fi
shopt -u extglob

plotopts=""

if [[ "$*" == *title* ]]; then
        next_is_title=""
        for word; do
                if [[ -n "$next_is_title" ]]; then
                        plotopts="$plotopts title '$word'"
                        next_is_title=""
                        continue
                fi
                if [[ "$word" == "title" ]]; then
                        next_is_title="1"
                else
                        plotopts="$plotopts $word"
                fi
        done
else
        plotopts="$* title 'STDIN'"
fi

gnuplot -p -e "plot '-' ${using}${plotopts}"

    Save it as plot, make it executable, and put it in your $PATH, and then you can …

  7. 2013
    Jun
    12

    Riding on water

    Posted by David Zaslavsky on

    The Hyneman has a new line to add to his resume:

    I kid, of course. Still, the Mythbusters’ demonstration of a motorcycle riding on water in last week’s episode was seriously cool. I have to admit, I didn’t expect it to work! But physics says otherwise — both the experiment, as we saw last week, and as I’m about to show you, the theory.

    Underneath all the complicated fluid dynamical effects, a motorcycle can ride on water for much the same reason a speedboat does: it presents an upward slanted surface for water to bounce off of. For a speedboat, that surface is the hull; for a motorcycle, it’s the bottom of the wheels, especially the front wheel. But wheels are complicated. It’ll make things easier to start by examining the behavior of a speedboat-like slanted flat surface as it moves through water.

    Conveniently, I’ve already done that calculation. It comes from another episode of Mythbusters a few years back, when they tried skipping a car across a lake. The calculation went like this: water molecules hit the lower surface of the car with a horizontal momentum \(-mv \unitx\) and bounce off in a downward …

  8. 2013
    May
    29

    Drag under the Indy car

    Posted by David Zaslavsky on

    As you might be able to tell by the lack of activity on the blog, I’ve been pretty busy the past couple weeks. Which makes it kind of hard to write about Mythbusters at my usual level of detail.

    Fortunately, Rhett Allain has already done it for me. He analyzed last week’s episode to figure out whether air pressure is enough to pick up a manhole cover. And it is: an air pressure of \(\SI{101325}{Pa}\), normal atmospheric pressure, applied to a manhole’s surface area of \(\SI{0.369}{m^2}\) (seriously, click the link), gives a force of \(\SI{37400}{N}\) — over eight thousand pounds! That’s way more than enough to pick up a 300-pound manhole cover.

    Of course, that would only happen if the manhole cover had a near-perfect vacuum above it. Perhaps if it were a manhole on a spaceship. But that’s not the situation on Mythbusters. (How cool would that be? Mythbusters in space… but I digress.) The manhole cover under an Indy car has air on both sides; the pressure of the air above is reduced, though, due to Bernoulli’s principle.

    $$P_1 + \frac{1}{2}\rho v_1^2 …
  9. 2013
    May
    16

    Careful, the rope is out to get you!

    Posted by David Zaslavsky on

    I know, I know, this blog post is very late! If I’m going to post about a Mythbusters episode, I usually try to do it before the next one airs. But this topic — calculating the circumstances under which a rope will pull a person’s leg — turned out to be pretty complicated. Which of course made it impossible to give up on.

    And after days of toil, I think I finally figured it out! If you’re the kind of person who finds complicated physical interactions fascinating, you’re going to love this post. The math isn’t too complicated; if you know what a differential equation is, you’ll be fine, but the physical reasoning is something you could probably spend a while wrapping your head around.

    The setup

    On the Deadliest Catch-themed Mythbusters episode which came out last week, one of the myths being tested was that if a person steps in a coil of rope, and that rope is attached to a crab pot (trap) that gets dropped over the side of the ship, the rope will be pulled tight enough around the person’s leg that it will drag them overboard, and down to the …