When one illuminates them by a narrow light beam so as to alternately increase and decrease their length, the strings could move the balls along a corrugated surface. Motion in two perpendicular directions is achieved by adding more balls and strings to the system. While no prototype is yet available, the device holds a promise of great possibilities in medicine and in the design of mechanical microdevices.
Many molecules come in two varieties, one the mirror image of the other.
True, an excess of one variety over the other may be created by shining circularly polarized light on chemically reacting substances, but polarized light is too rare in nature to be a factor in biological evolution. Exposing a complex unstable chrome compound to the combined action of an ordinary unpolarized light beam and a magnetic field of the same direction, they saw the molecules of one variety to dominate in the solution. The result is the same if polarized light is used, and if the magnetic field is reversed, the other variety builds up. If the light beam is perpendicular to the field, no asymmetry is observed. Some believe it is this effect which is behind the right to left-hand asymmetry in living organisms.