I’ve occasionally posted here about my involvement with Physics Stack Exchange — in fact, don’t be too surprised to see more posts of that nature in the upcoming weeks. But today I would like to bring your attention to another potential Stack Exchange site that will be of interest to many physicists and others: Scientific Computing.

As some of my regular readers (let us assume for the moment that these “regular readers” exist) will know, Stack Exchange is a network of question and answer websites on various topics. It started with Stack Overflow for computer programming, then expanded to Server Fault and Super User for sysadmins and power users respectively, and based on the success of that model, the people in charge have created about 70 more based on proposals from community members. The proposal for a scientific computing site came about because the topic occupies a niche between general-purpose programming and the specific science. To take computational physics as an example, these sorts of questions don’t quite fit on Physics Stack Exchange, which is about physical principles, but they don’t get a particularly good response on Stack Overflow, because they get swamped by all the questions …

A pharmacologist at Oxford, Susan Greenfield, is putting forward a theory that computer games cause dementia in children. The theory itself doesn’t really concern me, but I do notice that often when someone comes out with a theory like this, people tend to be pretty dismissive — you hear things like “How can you possibly think that?” Well, every fact we know about the world had to be thought by someone first, and just because it sounds ridiculous or even offensive doesn’t necessarily make it wrong.

However, any theory, especially a controversial one, does need to be verified or rejected with plenty of evidence, and that’s where publication comes in. At the Bad Science blog post linked above, Dr. Goldacre makes a good point

Science has authority, not because of white coats, or titles, but because of precision and transparency: you explain your theory, set out your evidence, and reference the studies that support your case. Other scientists can then read it, see if you’ve fairly represented the evidence; and decide whether the methods of the papers you’ve cited really do produce results that meaningfully support your hypothesis.

…

In this regard, I don’t mean peer …

An interesting article in the New York Times has been making the rounds of the internet lately. It talks about the tiny theoretical increase in weight of a Kindle when its memory is full as opposed to when it’s empty. Since I’ve previously written about the weight of data on a magnetic hard drive, I couldn’t resist taking a look at the equivalent effect for flash memory.

To begin with, we need to know a little about how flash memory works, and to do that, we need to know how transistors work. A transistor is just a tiny electrical switch. It has two contacts, the source and the drain, that are separated by a layer of material with an excess or lack of electrons. Normally this configuration blocks any current from flowing between the source and the drain. But when the right kind of voltage is applied to the separation layer, it removes the excess (or fills the lack) of electrons, allowing current to pass through. (For the record, I know I’m not doing justice to semiconductor physics here.)

As described in a pretty good article on Explain That Stuff!, and several other sources I’ve …

If you’re like me, you’re used to thinking of Mathematica as an interactive calculator, where you type in an expression and Mathematica evaluates it and spits out the result. But the Mathematica system actually incorporates a whole programming language, and as you might expect of any programming language, it’s possible to write Mathematica programs (scripts) that run non-interactively.

In order to write a Mathematica script, you create a text file which contains the expressions you want to evaluate (in normal programming terminology, the statements to execute). The conventional file extension for Mathematica scripts is .m. Each expression that you would normally type into the Mathematica window, you type into the script file, one per line. (Line breaks are allowed within expressions under certain circumstances.) You can then run the script using

math -script filename.m

(on Linux). The evaluated expressions, which Mathematica would normally show you right below where you typed in the input, are printed to standard output, so I recommend ending lines with a semicolon (which suppresses the output) by default. Only leave the semicolon off for the results you actually care about.

Keep in mind that a Mathematica script file is not what you …