Letters to the Editor

19567

Why slam a copper impactor into Comet Tempel 1? Wouldn’t copper vapor contaminate the spray? Why not a high-temperature ceramic? P.M. deLaubenfelsCorvallis, Ore. According to Casey Lisse of the Deep Impact team, copper was chosen because its density put a lot of mass into a small package, its relative softness reduced bounce at impact, and […]

19566

I have experienced sleep paralysis in almost all of its forms, from terrors to vibrations and auditory hallucinations to out-of-body experiences. Most often it is completely terrifying, but I did have one episode that was elating. Sweet dreams. Kathleen MilroyOntario, Canada The manifestations reported by sufferers of sleep paralysis are eerily similar to the visitation […]

19565

Why should the whale study lead scientists to “change the way we view sleep”? Among whales, the priority is that babies not drown in the first weeks of life.