Sunday, 29 March 2015

Musings on academic careers - Part 1

As promised, I'm going to put down some thoughts on academic careers. In doing this, I should put my cards on the table and point out that while I am a full-time professor of astrophysics of the University of Sydney, I didn't really plan my career or following the musings given below. The musings come from take a hard look at the modern state of play in modern academia.

I am going to be as honest as possible, and surely some of my colleagues will disagree with my musings. Some people have a romantic view of many things, including science, and will trot out the line that science is somewhat distinct from people. That might be the case, but the act of doing science is clearly done my people, and that means all of the issues that govern human interactions come into play. It is important to remember this.

Now, there may be some lessons below for how to become a permanent academic, but there is no magic formula. But realising some of these lessons on what is at play may help.

Some of you may have heard me harp on about some of these issues before, but hopefully there is some new stuff as well. OK. Let's begin.

Career Management
It must be remembered that careers rarely just happen. Careers must be managed. I know some people hate to realise this, as science is supposed to be above all this career stuff - surely "good people" will be identified and rewarded!

Many students and postdocs seem to bumble along and only think of "what's next?" when they are up against the wire. I have spoken with students about the process of applying for postdocs, the long lead time needed, the requirement of at least three referees, all aspects of job hunting, and then, just moments from the submission of their PhD, they suddenly start looking for jobs. I weep a little when they frantically ask me "Who should I have as my third referee?"

Even if you are a brand-new PhD student, you need to think about career management. I don't mean planning, such as saying I will have a corner office in Harvard in 5 years (although there is nothing wrong with having aspirational goals!), but management. So, what do I mean?

Well, if you are interested in following a career in academia, then learn about the various stages and options involved and how you get from one to the other. This (and careers beyond academia) should be mandatory for new students, and reminded at all stages of your career that you need to keep thinking about it. What kind of things should you be doing at the various stages of your career? What experience would your next employer like you to have? It is very important to try and spot holes in your CV and fill them in; this is very important! If you know you have a weakness, don't ignore it, fix it.

Again, there is no magic formula to guarantee that you will be successful in moving from one stage to another, but you should be able to work out the kind of CV you need. If you are having difficulties in identifying these things, talk with people (get a mentor!).

And, for one final point, the person responsible for managing your career is you. Not your supervisor, not your parents, and not the non-existent gods of science. You are.

Being Strategic
This is part of your career management.

In the romantic vision of science, an academic is left to toddle along and be guided by their inquisitive nature to find out what is going on in the Universe. But academia does not work that way (no matter how much you want to rage against it). If you want an academic career, then it is essential to realise that you will be compared to your peers at some point. At some point, someone is is going to have a stack of CVs in front of them and will be going through them and will have to choose a subset who met the requirements for a position, and then rank those subset to find the best candidate. As part of your career management you need to understand what people are looking for! (I speak from experience of helping people prepare for jobs who know little about the actual job, the people offering it, what is needed etc etc).

I know people get very cross with this, but there are key indicators people look at, things like the number of papers, citation rates, grant income, student supervision, teaching experience. Again, at all points you need to ask "is there a hole in my CV?" and if there is, fill it! Do not ignore it.

But, you might be saying, how can I be strategic in all of this? I just get on with my work! You need to think about what you do. If you have a long running project, are there smaller projects you can do when waiting to spin out some short, punchy papers? Can I lead something that I will become world known in? Is there an idea I can spin to a student to make progress on? You should be thinking of "results" and results becoming talks at conferences and papers in journals.

If you are embarking on a new project, a project that is going to require substantial investment of time, you should ensure something will come from it, even if it is a negative or null result. You should never spend a substantial period of time, such as six months, and not have anything to show for it!

Are there collaborations you could forge and contribute to? Many people have done very well by being part of large collaborations, resulting in many papers, although, be aware that when seeing survey papers on a CV now as "well, what did this person contribute to the project?".

The flip-side is also important. Beware of spending to much time on activities that do not add to you CV! I have seen some, especially students, spending a lot of time on committees and jobs that really don't benefit them. Now, don't get me wrong. Committee work and supporting meetings etc is important, but think about where you are spending your time and ask yourself if your CV is suffering because of it.

How many hours should I work?
Your CV does not record the number of hours you work! It records your research output and successes. If you are publishing ten papers a year on four hour days, then wonderful, but if you are two years into a postdoc, working 80 hours per week and have not published anything, you might want to think about how you are using your time. 

But I am a firm believer of working smarter, not harder, and thinking and planning ideas and projects. Honestly, I have a couple of papers which (in a time before children) were born from ideas that crystalised over a weekend and submitted soon after. I am not super-smart, but do like to read widely, to go to as many talks as I can, to learn new things, and apply ideas to new problems.

One thing I have seen over and over again is people at various stages of their careers becoming narrower and narrower in their focus, and it depresses me when I go to talks in my own department and see students not attending. This narrowness, IMHO, does not help in establishing an academic career. This, of course, is not guaranteed, but when I look at CVs, I like to see breadth. 

So, number of hours is not really an important issue, your output is. Work hours do become important when you are a permanent academic because all the different things, especially admin and teaching you have to do, but as an early career researcher, it should not be the defining thing. Your output is. 

Is academia really for me?
I actually think this is a big one,  and is one which worries me as I don't think people at many stages of their career actually think about. Being a student is different to being an postdoctoral researcher, is different to being an academic, and it seems to be that people embarking on PhDs, with many a romantic notion about winning a Nobel prize somewhere along the way, don't really know what an "academic" is and what they do, just that it is some sort of goal.

In fact, this is such a big one, I think this might be a good place to stop and think about later musings.

Saturday, 21 March 2015

Moving Charges and Magnetic Fields

Still struggling with grant writing season, so another post which has resulted in my random musings about the Universe (which actually happens quite a lot).

In second semester, I am teaching electricity and magnetism to our First Year Advanced Class. I really enjoy teaching this class as the kids are on the ball and can ask some deep and meaningful questions.

But the course is not ideal. Why? Because we teach from a textbook and the problem is that virtually all modern text books are almost the same. Science is trotted out in an almost historical progression. But it does not have to be taught that way.

In fact, it would be great if we could start with Hamiltonian and Lagrangian approaches, and derive physics from a top down approach. We're told that it's mathematically too challenging, but it really isn't. In fact, I would start with a book like The Theoretical Minimum, not some multicoloured compendium of physics.

We have to work with what we have!

One of the key concepts that we have to get across is that electricity and magnetism are not really two separate things, but are actually two sides of the same coin. And, in the world of classical physics, it was the outstanding work of James Clerk Maxwell who provided the mathematical framework that broad them together. Maxwell gave us his famous equations that underpin electro-magnetism.
Again, being the advanced class, we can go beyond this and look at the work that came after Maxwell, and that was the work by Albert Einstein, especially Special Theory of Relativity.

The wonderful thing about special relativity is that the mix of electric and magnetic fields depends upon the motion of an observer. One person sees a particular configuration of electric and magnetic fields, and another observer, moving relative to the first, will see a different mix of electric and magnetic fields.

This is nice to say, but what does it actually mean? Can we do anything with it to help understand electricity and magnetism a little more? I think so.

In this course (and EM courses in general) we spend a lot of time calculating the electric field of a static charge distribution. For this, we use the rather marvellous Gauss's law, that relates the electric field distribution to the underlying charges.
I've written about this wonderful law before, and should how you can use symmetries (i.e. nice simple shapes like spheres, boxes and cylinders) to calculate the electric field.

Then we come to the sources of magnetic field. And things, well, get messy. There are some rules we can use, but it's, well, as I said, messy.

We know that magnetic fields are due to moving charges, but what's the magnetic field of a lonely little charge moving on its own? Looks something like this
Where does this come from? And how do you calculate it? Is there an easier way?

And the answer is yes! The kids have done a touch of special relativity at high school and (without really knowing it in detail) have seen the Lorentz transformations. Now, introductory lessons on special relativity often harp on about swimming back and forth across rivers, or something like that, and have a merry dance before getting to the point. And the transforms are presented as a way to map coordinators from one observer to another, but they are much more powerful than that.

You can use them to transform vectors from one observers viewpoint to another. Including electric and magnetic fields. And these are simple algebra.

where we also have the famous Lorentz factor. So, what does this set of equations tell us? Well, if we have an observer who sees a particular electric field (Ex,Ey,Ez), and magnetic field (Bx,By,Bz), then an observer moving with a velocity v (in the x-direction) with see the electric and magnetic fields with the primed components.

Now, we know that the electric field of an isolated charge at rest is. We can use Gauss's law and it tells us that the field is spherically symmetrical and looks like this
The field drops off in strength with the square of the distance. What would be the electric and magnetic fields if this charge was trundling past us at a velocity v? Easy, we just use the Lorentz transforms to tell us. We know exactly what the electric field looks like of the charge at rest, and we know that, at rest, there is no magnetic field.

Being as lazy as I am, I didn't want to calculate anything by hand, so I chucked it into MATLAB, a mathematical environment that many students have access too. I'm not going to be an apologist for MATLAB's default graphics style (which I think sucks - but there are, with a bit of work, solutions).



Anyway, here's a charge at rest. The blue arrows are the electric field. No magnetic field, remember!
So, top left is a view along the x-axis, then y, then z, then a 3-D view. Cool!

Now, what does this charge look like if it is moving relative to me? Throw it into the Lorentz transforms, and voila!


MAGNETIC FIELDS!!! The charge is moving along the x-axis with respect to me, and when we look along x we can see that the magnetic fields wrap around the direction of motion (remember your right hand grip rule kids!).

That was for a velocity of 10% the speed of light. Let's what it up to 99.999%
The electric field gets distorted also!

Students also use Gauss's law to calculate the electric field of an infinitely long line of charge. Now the strength of the field drops off as the inverse of the distance from the line of charge.


Now, let's consider an observer moving at a velocity relative to the line of charge.
Excellent! Similar to what we saw before, and what we would expect. The magnetic field curls around the moving line of charge (which, of course, is simply an electric current).

Didn't we know that, you say? Yes, but I think this is more powerful, not only to reveal the relativistic relationship between the electric and magnetic fields, but also once you have written the few lines of algebraic code in MATLAB (or python or whatever the kids are using these days) you can ask about more complicated situations. You can play with physics (which, IMHO, is how you really understand it).

So, to round off, what's the magnetic field of a perpendicular infinite line of charge moving with respect to you. I am sure you could, with a bit of work, calculate it with usual mathematical approaches, but let's just take a look.

Here's at rest
A bit like further up, but now pointing along a different axis.

Before we add velocity, you physicists and budding physicists make a prediction! Here goes! A tenth the velocity of light and we get
I dunno if we were expecting that! Remember, top left is looking along the x-axis, along the direction of motion. So we have created some magnetic structure. Just not the simple structure we normally see!

And now at 99.99% we get
And, of course, I could play with lots of other geometries, like what happens if you move a ring of charge etc. But let's not get too excited, and come back to that another day.