Letters to the editor

Fusion reactions
It is not true that fusion packs the highest punch of any known energy-generating process (“Ignition failed,” SN: 4/20/13, p. 26). Matter-antimatter annihilation far exceeds it (Star Trek had it right back in the 1960s). I believe that under certain conditions, matter falling into a black hole can also yield more energy than fusion.
Bobby Baum, Bethesda, Md.

The reader is right on both counts. But those approaches are impractical. Scientists have harnessed energy from fusion, even if it has not produced net energy. Energy has never been harnessed from matter-antimatter, and certainly never from a black hole. — Andrew Grant

The bigger problems [with fusion] are cost and size. It has been known since the 1970s that a successful tokamak machine would be so large and complex that the cost of its electrical output would be an order of magnitude more expensive than the power from the most expensive fission reactor. Moreover, fusion plants would produce radioactive waste. The structural steel would not be as dangerous as spent fuel rods, but it would constitute a low level waste. Fusion research has wasted the entire professional lives of literally thousands of brilliant physicists. It should be shut down.
Robert Sykes, via e-mail

“Conventional” fusion reactions produce copious amounts of neutrons, which are quite radioactive and, if not themselves “waste” in the sense that most people might picture, cause severe radiation damage to the structures of which the fusion reactor itself is built. Those structures then have to be disposed of and replaced. I’d call that radioactive waste, and it’s inescapable with conventional fusion reactions.
Roger Stout, Phoenix, Ariz.

Fusion does produce neutrons, which degrade structures and can cause radioactivity. But unlike fission, fusion doesn’t produce waste that needs to be stored in casks or buried under a mountain. Plus, fusion power plants could never have a nuclear meltdown that would contaminate a large area, as Chernobyl and Fukushima did. — Andrew Grant

Correction    
“Fossil embryos offer glimpse at dinosaur growth” (SN: 5/4/13, p. 5) incorrectly stated that recently analyzed dinosaur fossils may contain “some of the oldest preserved organic remains found.” Older remains, such as archaea preserved in stromatolites, also contain organic matter. The new finds may be the oldest organic remains found for a land-dwelling vertebrate.