Unsolicited Advice, Volume I

So you want to be a physicist?  Hey, me too!  While I don’t know everything there is to know about getting there, I might be farther along than you are, and have some wisdom that I’ve accrued along the way that I can impart to you, even though you never asked for it.  Hence, this series of Unsolicited Advice.  (I would be remiss if I didn’t mention the inspiration I got from Cosmic Variance.  Plus I borrowed stole the name.)

Since this is Volume I, we’ll start early: before college.

Nurture Your Interest

If you’re reading this, and you’re not yet in college, then I’m willing to bet that you got interested in physics by reading one of the many popular books on physics.  It’s a great way to get into physics (it’s the way I got into it all those years ago).  You should continue to feed that interest in any way you can: read more books, watch tv specials, and discuss what you’ve learned with anyone who will listen.

You’re Like School in the Summer…

No class!

Or at least that’s how the corny old Fat Albert joke goes.  Of course, there’s always summer school… In high school, these were remedial classes that you wanted to avoid.  In college, maybe you’re trying to improve a grade, or maybe stay on track to graduate in four years.  But in grad school, summer schools are something entirely different.

Summertime is a time to focus on your research, without the distractions of tests, homeworks, and (hopefully) teaching duties.  But many grad students, at least in physics, take the summer as an opportunity to attend summer schools, which are short, intense sessions aimed at advanced grad students that are held at various institutions around the country and the world.  These schools bring in lecturers to present short courses on different topics within a certain subfield, often focused on a particular theme for that year.  The purpose is primarily to broaden the students’ exposure to the field, getting them out of the narrow focus that dissertation research requires.

Not everyone has the resources or the ability to attend one of these schools, but, thanks to modern technology, you can still participate by watching the lectures online.  In particular, the Theoretical Advanced Study Institute in Elementary Particle Physics (TASI) is going on now, in Boulder, CO.  You can find the links to lecture videos and notes here.  So far, it looks like they are getting the videos posted the day after the lectures occur, so you can make time to take a course or two that looks interesting (the upcoming lineup of talks is also found on the same site).  I have started the course on Supersymmetry and the MSSM, but I am particularly looking forward to the lectures on the AdS/CFT duality, as that pertains to my summer research project.

What is a Particle?

For my money, particle physics is just about the coolest thing in the world.  The scientifically curious public evidently thinks it’s pretty cool too, as evidenced by the books and articles aimed at the general public that far outnumber the coverage given to other areas of physics, much to the chagrin of the people who study those fields.

So you’ve probably heard about many concepts about particle physics.  I’m sure you know about atoms, electrons and the nucleus.  Maybe quarks, neutrinos, and the higgs boson sound vaguely familiar.  And the media hype around the LHC startup has been hard to ignore.

In this series of posts, I hope to give you a better understanding of what particle physics is about.  I hope these posts will be of interest to both the novice and the relative expert — anyone who wants to explore the question of just what it is we mean when we talk about a fundamental particle.

ATOMS

Before we talk about particle physics, we have to have a little context.  Let’s start with the universe.

Okay, now let’s zoom in juuust a little bit, down to the level of atoms.  This is where I will begin our discussion of what it means to be a particle.  Atoms were originally posited to be the smallest, “uncuttable” building blocks of all matter, the first candidate for a fundamental particle.  This idea, originally put forth by philosophers such as Democritus, was in opposition to the idea that matter was a continuum that could be divided into smaller pieces ad infinitum.  As chemistry developed and new elements were discovered and isolated, the atomic hypothesis moved from the realm of philosophy and became an essential scientific concept.

However, we’re not all that interested in the development of chemistry.  I want to focus instead on what sort of a mental picture this model gives us.  In other words, just what sort of properties does a “fundamental particle” have in this atomic theory?

You Load 16 Tons, and What do You Get?

Another day older, and deeper in debt…  Or so the song goes, but is that realistic?

Man, loading 16 tons of coal in a day sounds like a lot of work… But is it as much work as it seems?

Fortunately, physics gives us a way to calculate the amount of work done.  In this case, we will assume that the only work done is to lift the coal against the force of gravity.  As the direction of motion is parallel to the direction of the force, the formula for work done is simple:

Work = Force x Distance

Hip Hop and Error Analysis

There’s sixteen ounces to a pound, twenty more to a ki

–Mos Def, “Mathematics”

Crack cocaine has long been a scourge of America’s inner cities, and as such, often makes its way into hip hop lyrics.  For whatever reason, drug dealers measure large amounts of cocaine in kilograms (usually abbreviated as a “kilo” or a “ki”), while smaller amounts are measured in ounces (“O’s” or an “O-Z”).  This leads to some pretty unusual unit conversion, as illustrated above.

How close is this conversion?  Well, 36 ounces is 2.25 pounds, while a kilogram is approximately 2.2 pounds.  This is about a 2.3% excess, so somebody’s getting ripped off here.  My hunch is that it’s the user who gets the short shrift.  Maybe we can dub 36 ounces the “drug dealer’s kilo,” along the same lines as a baker’s dozen being equal to 13.

Another example of shady unit conversion:

Collection of Traffic-Related Science

In my last post about the 35W bridge and the traffic problems it caused, I promised that I would look for some traffic-related science.  So here’s a collection of links I’ve found, plus some memories of older stuff that I’ve read that I haven’t taken the time to track down.

Assume a Spherical Physicist

In physics, it is often necessary to make certain assumptions to simplify a complicated problem to make it tractable.  We might make assumptions about symmetry, say that a certain small value is essentially zero, talk about what happens when a certain value is infinity, or any of a host of other simplifications that would make a mathematician cringe and make a layman wonder how he can take our results seriously.

We often make light of this tendency by talking about spherical cows.  Obviously, a spherical cow is a pretty ridiculous picture:

A cow only a physicist could love.

However, in certain situations, estimating the cow as a sphere with a characteristic radius might not be as ridiculous as it seems.  For example, if the car were flying through the air (or standing in a strong wind, if flying spherical cows are too much for you to accept), the air resistance on a sphere the size of a cow would be a pretty accurate approximation.

But of course, the spherical cow is most useful as a metaphor for the approximation techniques we do use.  So what are these simplificaton techniques?  Read on to find out.

First Week of Class

So I’ve got the first week of grad classes under my belt.  Not that I had expected a huge difference from undergrad, but the classes aren’t qualitatively different.  Of course, there are significantly more students in my classes than at my small undergrad program where I had six people in my classes.

Taking notes

I’ve been struggling somewhat with the chronic problem of physics classes: Do you try to really understand what the professor is doing during the lecture, or do you try to copy down everything, hoping that you’ll understand it later?

Of course, in principle I should know, for example, where Lagrange’s equations come from and how to derive them, but I also know from experience that I probably won’t be required to reproduce this in homework or exams, but rather how to use them to solve problems.  And when the professor is tossing around all kinds of cross products and indices, and arguing why this or that term equals zero, it’s very easy to miss the forest for the trees.  I’d say that in many traditionally taught classes, it’s pretty much impossible to both understand what’s going on and to get everything in your notes.  Most students tend to opt for the latter, hence the addage that “Lecture is the place where the class notes are transferred from the notebook of the professor to the notebook of the students without passing through the brains of either.”

Thinking Like a Physicist: Super Mario and Problem Solving

My two-week orientation with the physics department began this week.  This program entails some getting acclimated to the program, the department, and the university at large, as well as our first free shot at the qualifying exam (more on that after I finish failing it tomorrow).  However, the bulk of the time will be devoted to learning how to be an effective TA for labs and discussion sessions.  The first part of the TA training has been to think about what the phrases “thinking like a physicist” and “problem solving” mean to us.  In order to help me crystallize some of these thoughts, I have decided to blog about them.

Thinking Like a Physicist

We were told to ask our advisers their opinion on these topics when we met with them to discuss course selections for the upcoming semester.  My adviser had some interesting ideas about “thinking like a physicist.”  The main thing that he said is that he finds learning physics to be more personal than learning math.  By this, he means that physics is done more by feel and concept than symbol manipulation, which he thinks is more emphasized in math.  Because of this personal basis for physics, the instructor is very important, as the students try to emulate him when they set out to solve problems for themselves.  The students must also work to go beyond simply solving the problem and make sure that they can extend the conceptual reach of the problem.

I agree with this idea to a certain extent.  I do believe that a conceptual understanding of the system is the key in understanding a system.  Simple “plugging and chugging” may get you the right answer, but this is useless if you don’t have an idea what this answer means.  This is why physicists often employ the “limiting case” concept: if you can understand how the system behaves as certain parameters get very large or very small, then you go a long way to understanding how the system really works.  I disagree, however, that math is very different in this regard.  My best undergrad math teachers repeatedly emphasized the importance of understanding what was going on by visualization and drawing pictures of the situation, rather than depending on some formulaic “recipe” to spit out the right answer.

How Super Mario Saved the Princess

An important distinction made in our Instructor’s Handbook is the distinction between completing exercises and solving problems.  I think that for my generation, a handy analogy can be drawn to video games.

First Protons in the LHC this Weekend!

As reported by Scientific American:

The Large Hadron Collider (LHC), nearing readiness outside Geneva, Switzerland, was designed to smash protons together at the highest energies ever achieved in hopes of unlocking new secrets of the universe. But to date, all that’s traveled through its circular beam pipe are ping-pong balls to test for obstructions.

That’s all about to change. This weekend, CERN, the European Organization for Nuclear Research, plans to test a key component of the accelerator by injecting a low-intensity beam of protons clockwise into the LHC and letting it travel three kilometers (two miles) through the machine.

Assuming all goes as planned, the lab announced today that it will send the first beam around all 27 kilometers (17 miles) of pipe on September 10, the machine’s official start-up date.