Somewhere along the line, we all come to trust the numbers that come out of computers. After all, an infallible device told us it was true. So, let us start with a simple example, on a ten digit calculator enter the following:

1E12 + 1 - 1E12

If the 1 is in any position, but the last one, your calculator spits out 0. Despite the fact that the answer is very clearly 1. Using this example, and others, I try to have my students resist the urge to enter numbers into their calculators until the very end of the problem, and they will then usually avoid such problems. Despite my advice to my students, this bit me twice in two days, leading to a corollary to the first rule:

Science fiction has often relied on matter and antimatter annihilating each other as a power source. With current technology, producing anti-matter is prohibitively expensive, and most view this as the biggest hurdle for these types of power plants. Basic physics may provide another significant hurdle, however.

Physical Review Focus reports that upon reanalyzing data from 12 years ago, an Italian team discovered that – contrary to popular belief – antimatter and matter may bounce off each other before they’re annihilated (Original paper, subscription required). The key to this discovery was the annihilation events in their data were clustered into two groups: The first group occurred when the antiprotons interacted with the helium in their apparatus, and the second set of events (up to 25% of the total number) occurred at a later time. They determined this second set occurred because the antiprotons were reflected off of the back wall of their device to be later annihilated by the helium atmosphere, instead of either annihilating the aluminum in the walls or passing through entirely. This effect is called Rutherford scattering, and at the speeds they were working with (1 – 10 keV, or 0.14 – 0.46% of c) the antiprotons are more likely to find themselves scattered by the aluminum nuclei than they are to annihilate the nuclei. At lower speeds (500 eV, or 0.10% of c), this effect may peak with 50% of the antiprotons that make it to the back wall being reflected by it.

Being an academic, I regularly attend seminars on topics that may not be interesting to anyone else on the planet. Prior to the talk, an abstract is sent out by the speaker to give us an insight into what he/she will be discussing. A good abstract should be no more than an essential summary of what the speaker will discuss; it is usually no more than a paragraph in length, and is often tersely worded. The rare exceptions to this length requirement usually aren’t the best at conveying the essential information. For a seminar I attended recently, the abstract violated this "rule" by weighing in at a whopping four paragraphs. However, even considering this excessiveness, the opening sentence is what really drove me over the edge. The abstract began with the phrase, "One presents a critical analysis…" (Emphasis added).

In January, a jury in Connecticut found substitute teacher Julie Amero guilty of four felony charges of "risking injury to a minor or impairing the morals of a child" due to a 2004 incident in which her classroom PC became infected with pornographic pop-ups. Today, however, an upper judge effectively hit the reset button on the trial, claiming "information discovered after her conviction has direct bearing on whether she is responsible for risking harm to her students when pornographic pop-ups appeared on a classroom computer." Such information likely includes a pro bono complete forensic analysis of Amero’s classroom PC, which was performed by a group of independent security researchers and delivered to the defense attorneys in April. The results of the study, however, will not be released until any potential new trial concludes.

The universe operates on many different size scales, from intra-particle to inter-galactic. Most phenomena do not require more than one scale to be fuly understood. But, some phenomena operate along multiple scales. For example, the particles in a coronal mass ejection interact with each other (short scale) while they travel from the Sun to the Earth (long scale). In order to be correctly simulated, both length scales must be accounted for; making multi-scale problems difficult and computationally expensive to model.

After reading an article in Physics Today, it is easy to see why many view solar power as a panacea for our growing energy needs. "The enormous power that the Sun continuously delivers to Earth, 1.2 × 10⁵ terawatts, dwarfs every other energy source, renewable or nonrenewable." For a comparison, an estimate of the recoverable oil on Earth is approximately 3 trillion barrels containing "1.7 × 10²² joules of energy, which the Sun supplies to Earth in 1.5 days." Our current technology, though, is woefully inadequate to tap into the potential of this rich energy source.

In a study by the National Institutes of Health (NIH) that was ended last December, it was discovered that circumcised men were 50% less likely to become infected with HIV than uncircumcised men. As reported then, the NIH stopped the study only part way through because the treatment was so overwhelmingly effective that "it would have been unethical to continue without offering circumcision to all 8,000 men in the trials." For the studies that are to be published yesterday, the data was re-examined, "excluding a few men whose H.I.V. status was misdiagnosed during the trial and combining the results of three trials," producing "a protection rate of about 65 percent."

Introduction

Despite the continuing advances in the capabilities of computer languages, such as C++, Fortran remains the lingua franca of computing in physics. On the whole, I prefer the syntax and flexibility of C/C++, despite its potential for abuse.¹ With the appropriate libraries,² and some investment of time, C++ can be used to write code that is easier to understand than,³ and comparable in speed to,⁴ Fortran. However, despite the power and ease of use of the streams library in C++, it is difficult to read-in fixed width fields without modifying the streams’ behavior, unlike in Fortran.

According to Newtonian theory, the fate of the universe is clear: either the universe will keep expanding at an ever decreasing rate, or, if there is enough mass, it will eventually collapse in on itself. But, there is evidence that the rate of expansion is increasing. To explain this, phycisists have postulated the existence of a substance called dark energy that exerts a repulsive force counteracting the effects of gravity. According to cosmologists, the effects of dark energy should be observable as a short range force detectable at length scales around 85 µm.

The American Physical Society (APS) has recently announced a program where most of their articles can be made publicly available to anyone who wishes to read them. In order for an article to be made "Free to Read," the APS requires a modest fee ($975/Physical Review article and $1300/Physical Review Letter article), which anyone can pay, and the article will then be available for download by the general public for free. This does not mean that the APS surrenders the copyright to these articles, nor can they be posted on any other websites without prior permission.