In “The Coding Revolution,” Annie Murphy Paul reports on discussions and initiatives related to teaching computer science to all public school students, with a distinction made between coding and “computational thinking,” which is described as “habits of mind that include breaking down a problem, designing systems, and running small experiments.”

Enough hand-wringing, please! From my experiences as a teacher and a former senior adviser to the Commonwealth of Virginia for STEM initiatives, I can say that while certain areas of computer literacy are required for today's students, in general they don't need a deeper than basic understanding of how computers work any more than they need a mechanic's knowledge of how a car works to prepare for driving. All students do need some fundamental programming skills, and those planning on a STEM major in college would benefit from an introduction to computational methods for science and engineering. But to get tied up in deep angst about such issues as computational thinking and to talk about a massive involvement of such thinking in all disciplines will stall any implementation of appropriate levels of computer literacy in grades K–12 for many years as focus groups are created, data taken and reports written.

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In the social and medical fields, a researcher has to demonstrate that there is empirical evidence supporting that an intervention may work and that he or she has thought through all possible harms that may accrue before experimenting on humans (or even animals). In education, though, it seems as if we can introduce an intervention that affects tens of thousands of students simply on the basis that it seems to make sense. We have seen disastrous effects from such massive educational experiments, such as teaching set theory instead of basic mathematical skills.

The rationale given in Murphy Paul's article for teaching computational thinking is that it fosters other skills, such as “a flexible set of mental tools.” Similar arguments were given more than a century ago for teaching penmanship and Latin. But in 1913 this was proved to be wrong by psychologist Edward Thorndike, who concluded that “a change in one function alters another only in so far as the two functions have as factors identical elements.”

Department of Psychiatry and Behavioral Neurosciences McMaster University, Ontario

It's nice to see what was called “critical thinking” is now being promoted in elementary and secondary schools. It is better to teach the concepts of programming via computational thinking than to focus on teaching kids to write code. The teaching methods for such computational thinking sound very similar to those I used in a general education class that I taught at the University of Arizona in the late 1980s and the early 1990s. Early on, I realized that teaching the particular subject matter was not the purpose of the course. Rather it was to teach critical thinking to students who, for the most part, relied on the rote memorization they had been drilled in while in their elementary and secondary schools.

Petrolia, Calif.


“The Seven-Year Mission to Fetch 60 Grams of Asteroid,” by Dante S. Lauretta, states that the “safest regions” of the asteroid Bennu for NASA's OSIRIS-REx spacecraft to visit “will likely be near the equator, where the spacecraft can more easily match the velocity of the spinning asteroid to touch down on the surface.”

I would think that the easiest spots to land on or hover over would be at the poles, especially if the spin rate of the asteroid is fairly high.

Cody, Wyo.

LAURETTA REPLIES: For a spacecraft to safely make contact with a spinning asteroid, it must match the transverse velocity of the surface, which is greatest at the asteroid's equator and drops to zero at its poles. One would thus think that touching down at a pole would be easiest for OSIRIS-REx, but this is not so for a number of reasons.

Most important, the scientific requirements for the illumination of the touch-and-go (TAG) site are not met. The site must have a solar phase angle of more than 85 degrees, and Bennu's pole is closely aligned with the ecliptic plane, which makes that impossible.

Another constraint is imposed by the fact that the spacecraft departs for TAG from an orbit in the terminator plane, which means that the desire for the TAG transfer trajectory to be four hours and for the checkpoint maneuver that initiates descent to the surface to be near periapsis is much harder to fulfill for polar sites.

For meeting the TAG contact velocity requirements, there are some sites that are more challenging than others, but variations in topographic features in the site's vicinity and in the terrain that is overflown during the approach to it have the largest effect on TAG dynamic performance.


In “Zombie Neuroscience,” Christie Wilcox describes how jewel wasps attach eggs to cockroaches so that their offspring can devour them alive, which involves injecting dopamine into the cockroaches' brain.

Wilcox could have further elaborated on an imagined cockroach's nightmares before and after the dopamine loading. Rather than sensing horror, it could instead feel the approach of a hijack wasp as the ultimate emotional high, despite ensuing certain death.

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In “The Emptiest Place in Space,” István Szapudi explains that because of the accelerating expansion of the universe, photons experience a net loss of energy as they traverse a supervoid, a very large expanse of space with relatively little matter or galaxies. If this phenomenon is not to violate the law of conservation of energy, then where does the photons' energy go?

Portland, Ore.

Szapudi says the cosmic microwave background (CMB) can be observed by tuning an old TV between channels. But unless the TV's signal detector is cryogenically cooled to extremely low temperatures, the thermal noise of the detector will overwhelm the CMB, making it impossible to observe.

Indianapolis, Ind.

SZAPUDI REPLIES: In answer to Luckett's question: The photon is not a closed system; it interacts with the expanding universe, and the expanding universe takes up the excess energy from the photon. This is why it does not regain the full energy it originally had before starting to cross the changing potential of the supervoid.

Regarding Carroll's letter: It has been estimated that about 1 percent of the “snow” in analog TV static comes from CMB radiation. This signal to noise is small but nonnegligible, and it isn't a stretch to call it an observation.