Second, atoms are notoriously “individualistic”. When a batch of atoms in a material has been raised to higher energy levels there is no way to know in what order, or in what direction, they will release their energy. This kind of process is called _spontaneous emission_, since each atom “makes up its own mind”. All we know is that within a certain period of time—a short period, to be sure—a certain percentage of these higher energy atoms will release their photons. [Illustration: Figure 10 _Ordinary light is a jumble of frequencies, directions, and phases._] What we have, then, is incoherent radiation—a jumble of frequencies (or colors), directions, and phases. Such light, symbolized in Figure 10, works well enough in lighting up this page, but is almost worthless as a carrier of information (and in other ways, as we shall see shortly). About the best that can be done with it is to turn it on and off in a sort of visual Morse code, which is exactly what is done on the blinker communication systems sometimes used for ship-to-ship communication. In other words, ordinary light cannot be modulated as radio waves can. It is of interest to note, however, that ordinary white light _can_ be made coherent, to some extent, but at a very high cost in the intensity of the light. For example, we might first pass the light through a series of filters, each of which would subtract some portion of the spectrum, until only the desired wavelength came through. As can be seen in Figure 11, only a small fraction of the original light would be left. [Illustration: Figure 11 _Obtaining coherent radiation the hard way. Filters and pinhole block all but a small amount of the original radiation._] Incoherent Filters Coherent in time Pinhole Coherent in time and space We would then have monochromatic (one color) light, which is temporally coherent radiation, but it would still be spatially incoherent. In our diagram, we show three monochromatic waves. If we then passed this light through a tiny pinhole as shown, most of these few remaining waves would be blocked; the ones that got through would be pretty much in step. (In a similar manner, a true point source of light would produce spatially coherent radiation; but, as in the process described here, there wouldn’t be very much of it.) We have, finally, obtained coherent light. The important thing about the laser is that, by its very nature, it produces coherent light automatically. Now.... WHAT’S SO SPECIAL ABOUT COHERENT LIGHT? So desirable are the qualities of coherent light that the complicated filtering process described above has actually been used. For example, one British experimenter, Dennis Gabor, used it in the 1940s in an attempt to make a better microscope. But so great was the effort, and so meager the resulting light, that this project was abandoned.