In focusing on the insufficiently rigorous academic preparation of math and science teachers in the U.S. in “Building a Better Science Teacher,” Pat Wingert neglects larger issues. The head of a charter school is quoted saying that for every five candidates she observes in teaching demonstrations, she hires only one. What qualities does she look for beyond math mastery? I'd bet they are social and emotional ones.

If a person with deep knowledge lacks empathy and relationship management skills, he will fail as a teacher. Having taught and served as a department chair, I have seen people with expertise extinguish children's nascent interest and others with less knowledge but a greater repertoire of social and emotional skills inspire them.

The article refers to nearly two thirds of math and science teachers departing the profession each year who cite job dissatisfaction, but it doesn't point out some of the factors that fail to attract and retain good teachers: disrespect for the profession and poor or stressful working conditions in public schools, including large class sizes, endless test preparation, lack of autonomy and authoritarian management styles.

Derek Stolp
Math faculty member Inly School, Scituate, Mass.


“The Benevolence of Black Holes,” by Caleb Scharf, refers to a relationship in which a galaxy is a “host” to a black hole, such as the supermassive one at the center of the Milky Way. Are we really certain which is the host and which the “guest”?

Francis Jones
Amarillo, Tex.

SCHARF REPLIES: Two of the biggest unsolved mysteries of supermassive black holes are: Where did they come from—and when? There is clear evidence that such holes existed at the very dawn of the formation of galaxies and stars. It seems that they already inhabited galaxies or the clumps of material that were merging to form bigger galaxies. The largest of such holes seem unlikely to have had time to grow from smaller, star-mass holes by eating matter, which suggests they started out pretty big. One of several theories about how this could happen is that the conditions of a young, element-poor universe could produce black holes of about 100,000 to a million times the mass of the sun in the dense regions inside forming galaxies. These “seed” holes could then grow rapidly while the rest of the galaxy assembled and gravity coalesced cooling matter from the surrounding universe. So their relationship is perhaps better described as being “symbiotic”!


Michael Shermer defends free will in “Free Won't” [Skeptic] by arguing that although the individual may not be making choices, he is free to veto choices presented by the brain. Yet a veto is simply a choice to reject a previous choice. Similarly, in arguing that the veto takes place in a separate part of the brain, Shermer ignores that all locations within the brain are part of that organ—there is no outside authority.

James Leritz
San Francisco

SHERMER REPLIES: The fact that we can be conscious of the consequences of our choices means that we can choose to veto them, and we can even train ourselves to have more self-control over temptations to make choices that we know will not be good for us. Through practice and positive feedback, I can train myself to resist eating fatty foods and can even choose to design my lifestyle to avoid such temptations. All these choices happen in a determined universe, but they are nonetheless my choices.


“Cracks in the Bone Test,” by Deborah Franklin, refers to the online fracture-risk calculator FRAX. I am surprised that it does not include exercise level as a risk factor, which other sources indicate is important in preventing fractures.

Richard Polinsky
Barton, Ohio

FRANKLIN REPLIES: FRAX remains an imperfect, though useful, tool that its developers agree does not include every factor. On the upside, it still provides more context than the DXA (dual-energy x-ray absorptiometry) bone mineral density test, which also does not include physical activity. Perhaps as doctors become better at quantifying exactly how much and what kinds of physical activity provide exactly how much protection, it will be included in a future update of the FRAX calculator.


In “Deadly Rays from Clouds,” Joseph R. Dwyer and David M. Smith rule out sprites—brief, high-altitude electrical discharges—as the source of gamma rays produced by such thunderstorms.

I was a member of the team that discovered another high-altitude optical phenomenon, called blue jets. A gamma-ray burst could explain many of their features. Have the authors considered the blue jets as manifestation of such bursts?

Daniel L. Osborne
Fairbanks, Alaska

The authors describe the radiation dose received while flying through a thunderstorm as potentially a lifetime's worth within a fraction of a second. Would it be possible to estimate the radiation dosage received while flying above a thunderstorm, which airlines routinely do?

Omri Guttman
Haifa, Israel

If the storms here on Earth are producing gamma rays and antimatter, I wonder what the lightning storms on Jupiter and Saturn are doing. Could they be the source of some cosmic rays seen on Earth or even have an effect on the sun?

Steven Brennervia
via e-mail

DWYER AND SMITH REPLY: After terrestrial gamma-ray flashes (TGFs) were found to originate from lower altitudes than sprites, blue jets were considered as an alternative. Blue jets, however, last about 1,000 times longer than TGFs, so it is not clear what part of the blue jet, if any, might be responsible. Although we cannot rule out that some TGFs might be produced by blue jets, recent radio observations of TGFs now show that most are associated with lightning processes within thunderclouds.

Regarding Guttman's question: our simulations suggest that if the airplane is just above the electron acceleration region, the radiation dose from gamma rays is about 10 percent of the worst case inside the storm. As you get higher, this drops off quickly, and any horizontal distance reduces the dose even more sharply.

As for storms on Jupiter and Saturn, calculations show that thunderstorms within their hydrogen-helium atmospheres are probably efficient particle accelerators. Thunderstorms in those outer planets, however, take place deep within their atmospheres, so any energetic electrons and gamma rays are probably absorbed before they can escape to space. Although Jupiter's magnetosphere does accelerate particles by other mechanisms, which can be detected throughout the solar system, we doubt that these could have a significant effect on solar flares and the solar cycle because the particle and energy densities are so much greater in the solar corona than anything Jupiter would contribute at that distance.

On the other hand, the magnetospheres of “hot Jupiters” in other solar systems—circling red dwarf stars in extremely close orbits—could possibly have a strong influence on magnetic activity in those stars.