I just saw an “article about an astrologer in Russia who is proceeding to sue NASA because she believes that a future planned comet mission will disrupt the natural order of the universe”:http://news.yahoo.com/s/afp/russiausnasaspace.
Says the woman’s lawyer, “My client believes that the NASA project infringes upon her spiritual and life values as well as the natural life of the cosmos and would disrupt the natural balance of forces in the universe.”
Let me reassure her, the natural balance of the forces in the universe will not be disturbed. An impact on a distant comet involves the interaction of electrons in the comets surface with those of the probe; the electromagnetic force, while infinite in range, falls off in intensity as a function of the inverse-square of the distance. The effect on the surrounding universe (i.e. earth, sun, etc) is smaller than ambient electromagnetic disturbances (like lightening, or even a cell phone).
The impact is not energetic enough to break up atoms, so we don’t have to worry about the strong or weak nuclear forces (which are finite in range anyway). So that leaves gravity. Since the effect of this comet on the earth is vastly masked by the effect of the sun and moon on the earth (i.e. comets don’t cause tides, since they move past us quickly), and the comet’s material will merely be redispersed instead of totally annihilated, no problem there.
Let me assure you, Ms. Bai: there will be no disruption in the natural forces in the universe. Those forces have withstood much worse (i.e. the very creation of the universe) and this small probe will have no effect on us. Go back to your job with some satisfaction in that regard.