Pondering speedy neutrinos Regarding “Hints of a flaw in special relativity” (SN: 10/22/11, p. 18), there could be a simple explanation for neutrinos being measured as traveling faster than the speed of light in a vacuum. While a vacuum is typically defined as a space entirely devoid of matter, in fact a vacuum is a busy medium with virtual particles continually being created and destroyed. Light passing through a vacuum is affected by such activity.  Neutrinos have such low interactions that they can pass through a lead wall several hundred light-years thick without slowing do... (p. 35)

Sinking heavy ice The picture in “From the Archive” (“Self-experimenter didn’t suffer,” SN: 1/28/12, p. 32) shows heavy water ice sinking in a glass of water while alongside, light water ice floats. What is not clear is what kind of water is in the glasses. If heavy water ice were in a glass of heavy water, would it also float? Robert Chester, Tumwater, Wash. The picture shows a heavy water ice cube sinking in normal water. Like normal water, heavy water expands when it freezes, becoming less dense. An ice cube made of heavy water will thus float in heavy water. Christoph Sal... (p. 31)

Connecting the lincs As a physician, I was absolutely astounded reading “Missing lincs” (SN: 12/17/11, p. 22) and still am. We have been waiting since DNA was discovered to find this ‘what makes us human’ aspect of our biochemistry. Even in the infancy of this research, we are discovering the chemical reasons for a type of muscular dystrophy and other conditions. What I find especially illuminating is that this may be the etiology of what we call autoimmune diseases, among other problems. I am sure we will find it is a change in lincRNA balance or function that produces the change ... (p. 31)

Finding parasitic behavior Two adjacent stories, both by Tina Hesman Saey, at first glance may appear to be unrelated but in actuality show examples of a well-known phenomenon: parasites adversely affecting the behavior of the host so that the parasite can get to its next victim. The article “Belly bacteria can boss the brain” (SN: 10/8/11, p. 9) is an example of such behavior. A stressed-out wild mouse that clings to walls and avoids swimming is a mouse that lives to breed another day. Being relaxed is no more beneficial to it than climbing to the top of the tree is for the caterpilla... (p. 31)

The eyes have it Just finished the latest issue of your spectacular magazine. I’ve been a reader for many years, but this is the first time I’ve felt compelled to write in. In the article about the tadpole (“Tiny voltage grows eyes in strange places,” SN: 12/31/11, p. 5), the final sentence is a quote from Coffman: “The fact that a narrow range of voltage is enough to specify an eye is kind of amazing.” What might be even more amazing is if researchers find out the voltage level that prompts cells to initiate and grow malignant tumors. I hope someone will help me stir up some i... (p. 31)

Skaters slide Regarding the article “Skateboarders rock at physics” (SN: 12/3/11, p. 10), the skateboarders’ “intuitive” conclusion that the ball will roll faster down the blue ramp (which is longer but has two steeper sections compared with the shorter red ramp with a single shallower section) depends on the particular geometries chosen for the two ramps. I’ve programmed the solution for a point particle sliding (so no rolling) without friction down the two ramps and find that for certain ratios of the heights and lengths of the various ramps, it can actually be faster to slid... (p. 31)

Thinking probabilistically In the excellent article “Beware the long tail” (SN: 11/5/11, p. 22), the areas under each curve in the figure “Spotting the tail” should be unity (the total probability must be one). Therefore, the red curve should be lower in the center than the black one. Filson Glanz, Durham, N.H. Yes, the area under each curve should add up to one. In this case the graphic was shown without a y-axis to illustrate the basic point about the shapes of such curves; it would have been more appropriate to have shown the curves separately rather than superimposed. —Ra... (p. 35)

Predators inspire poetry and fear Regarding “Lopped off” (SN: 11/5/11, p. 26): One of the Tao Te Ching’s chapters (excerpt below) is very prescient on the unintended consequences of human behavior. It was written around 500 B.C., long before our innovative abilities threatened the entire planet. It is ironic that science both leads to innovations that cause the destruction, and now allows us to realize the full range of consequences. Woe to him who willfully innovates While ignorant of the constant, But should one act from knowledge of the constant One’s action will lead t... (p. 30)

Clocking neutrinos In response to “Hints of a flaw in special relativity” (SN: 10/22/11, p. 18): When supernova 1987a was detected in the Large Magellenic Cloud (a distance of roughly 168,000 light-years) an influx of neutrinos was detected simultaneously (or nearly so) in Japan, the United States and Russia. Had these neutrinos traveled at the same speed (about 25 parts per million faster than light) as the CERN neutrinos detected by the OPERA experiment in Italy, they would have arrived roughly four years ahead of the visual display from 1987a, rather than at approximately the same ti... (p. 30)

Defining the human species Having read “Humans benefited by interbreeding” (SN: 10/8/11, p. 13), I wonder if I have missed what, to me, seems a major change in the definition of “species.” I was taught that the attempted crossbreeding of animals of two different species could result in either no offspring or sterile offspring. If modern humans carry genetic information from Neandertal and Denisovan ancestors, stemming from successful interbreeding that resulted in fertile offspring, why aren’t the Neandertals and Denisovans considered to be merely of a different race or bre... (p. 31)