As Meinard Kuhlmann points out in “Physicists Debate Whether the World Is Made of Particles or Fields—or Something Else Entirely” particles and fields are not real but are analogies developed to describe another realm of reality, one that is not accessible to our senses but inferred from observation, measurement, mathematics and theory. An electromagnetic wave is not really like a wave on the ocean, but it is in many ways analogous to such a wave, and through such an analogy, it seems more comprehensible. We must remember that such representations do not describe the true, alien reality of the quantum-mechanical world. We are like fish studying the stars.

John Ball
Huntsville, Ala.


The articles in the special report Learning in the Digital Age neglect two crucial aspects of teaching. The first is motivation. The digital-learning methods espoused by many of the articles may work well for the highly motivated students highlighted, but most of their peers are not well motivated.

When I read that massive open online courses (MOOCs) and other computer-based learning systems rely on lectures by “good” teachers, I wonder if the definition of “good” is producing students who score well on standardized tests. Good teachers first motivate their students, and motivation does not come from a computer screen but from when students see their instructors deeply involved in learning.

The second aspect is developing critical thinking skills. A few years after I began teaching a general education science course, it became obvious my students weren't learning anything from a template of information-based lectures and multiple-choice tests. I changed my testing format to essay-type questions that required understanding and instituted an optional “review” session outside of regular class hours, which was two hours of intensive interaction with my students, designed to help develop their critical thinking skills. Almost every student dramatically improved in this area by the semester's end.

The facts and knowledge learned in any course will become obsolete well before you retire. The ability to think critically is a skill that will last a lifetime.

Kenneth C. Young
Retired associate professor
University of Arizona

As a high school student, I am excited by the great potential of personalized education technology as described in “How Big Data Is Taking Teachers Out of the Lecturing Business,” by Seth Fletcher, but a couple of things concern me.

First, in my experience, school boards aren't very good at choosing effective technologies, and students are often forced to use frustrating and buggy applications. Second, I fear adaptive software would force all students to plod through poorly executed videos and explanations. The promise of “adaptivity” is that every student could work at her or his own pace. I have doubts, however, that educational companies would make effectively different sets of material for students of different ability levels instead of providing the same one-size-fits-all content in a more high-tech, high-cost format.

Kaylene Stocking


In “The 5 Myths of Terrorism—Including That It Works” [Skeptic], Michael Shermer claims that the ideas that terrorism is deadly and that “it works” are a “fiction.” Shermer expresses a lack of concern over a mere 33 deaths since 9/11 (conveniently subtracting the thousands on 9/11). But how many is too many? Maybe one if you knew and loved that person.

As to terrorism's efficacy: two close friends of mine are suffering from serious leg injuries, and one is now a double amputee because of the recent act of terrorism cited by Shermer. These young, innocent people are only at the beginning of a lifelong physical and emotional struggle. It worked, my skeptical friend.

Lori E. Hurley
South Hampton, N.H.

I suggest terrorism does work. It has spawned a governmental department that employs tens of thousands of people with a budget of almost $7.7 billion to screen airline passengers. More than a million people stand in line every day and have to take off their shoes prior to being able to board an airplane, with hundreds of thousands of hours of otherwise productive time lost daily because of terrorism. Global terrorists have created a situation that seriously impacts our economic and productive environment.

Gary Morrison
San Antonio, Tex.

SHERMER REPLIES: Hurley's understandable response illustrates the difference between anecdotal and statistical analysis. Anecdotally, of course, even one death from terrorism is a tragedy to the victim's family and friends, and outrage is an appropriate response. My analysis was on a statistical level in which the numbers of people who have died from terrorism are far below dozens of common causes of death that we have grown accustomed to (such as automobile accidents).

Morrison's observation is well made, but my larger point in showing the failures of terrorists to achieve their political objectives is that we do not need to invest such time and resources combating terrorism.


In “Smartphones Mean You Will No Longer Have to Memorize Facts” [TechnoFiles], David Pogue argues that technology has made memorization obsolete.

Having access to information is not the same as knowing it. We learn big things by dividing them into chunks. Some parents think it's easier for kids to learn American history if they organize it around the list of presidents (whose memorization Pogue dismisses). Anyone who can't name a majority of the presidents in approximate order usually knows little about the rest of American history. Joshua Foer describes the right way to memorize in Moonwalking with Einstein (reviewed in the March/April 2011 Scientific American Mind).

R. C. Mark
Athens, Ohio


Researchers Explain Why Exercise Works Magic,” by Shari S. Bassuk, Timothy S. Church and JoAnn E. Manson, stopped short of adding to the recent bad news that high-intensity workouts don't make up for six hours of sitting. If the authors can't explain the mechanism, could they please at least return to your pages with a verdict on what lying down does? Could my seven hours in bed at night be as bad as my hours before a computer screen?

James Guest
East Melbourne, Australia

THE AUTHORS REPLY: Sleeping and sitting are very different. Sleep restores brain function and helps to regulate the body's energy balance. Well-designed bed-rest studies, however, suggest that once the need for sleep is met, lying around all day has similar adverse health effects to sitting—especially if accompanied by snacking.


In “Diane Ravitch: 3 Dubious Uses of Technology in Schools” [Learning in the Digital Age], Diane Ravitch meant to note that hundreds of thousands, perhaps millions, of teachers regularly use the Internet to exchange ideas about enlivening classrooms. The printed article put the number at “thousands.”