801. How do fletchings stabilize an arrow in flight after it is shot from a bow? — SH, Newton, TX
Like all isolated objects, the arrow naturally pivots about its own center of mass, a point located near its geometric center. If the arrow had no fletchings (or fins) it would tend to rotate wildly in flight. But the fletchings experience substantial aerodynamic forces whenever the arrow isn't flying point first and these aerodynamic forces twist the arrow back toward its proper orientation. Thus whenever the arrow begins to rotate so that its point isn't first, the air pushes hard on the fletchings and returns the arrow to its point-first orientation. The same effect keeps airplanes and birds flying nose (or beak) forward.