Letters to the Editor

19187

After reading this article, I may have an answer for why a routine chest X ray indicated prominent scar tissue on my lungs even though I have never been a smoker during my 61 years. For the past 15 years, since a heart attack, I have jogged or ridden a bicycle for approximately an hour […]

19147

I am concerned about this article. It addresses the mass of fissile materials needed to “make a bomb,” yet it’s clear that the critical masses given–10 kilograms for plutonium-239, 50 kg for uranium-235, and 60 kg for neptunium-237–are for bare spheres with no neutron moderation, reflection, or other factors contributing to going critical.