The Giggle Factor (GF). Mention "Planetary Defense" and you'll soonunderstand. Even without invoking the sinister vision of alien beings arriving to enslave or destroy humanity, the eyebrows of serious and senior members of the national defense and scientific communities go askew when the subject is broached, whether at cocktail parties or congressional budget hearings. Even the most ardent supporters of defending the Earth from cataclysmic cometary...