Single Slit Diffraction

Light plays a key role in Physics. The study of the interaction between light and matter has caused many breakthroughs in in Physics. At a fundamental level, waves spread out after they pass through a gap. This process is called diffraction. When laser light passes through a narrow rectangular slit, and the pattern observed on a screen, most of the energy is found arriving on the screen in a bright area called the central maximum. This is flanked on each side by a dark area and then the pattern becomes brighter on each side at a location called the first order maximum. The first order maximum has an intensity of 4.7% that of the central maximum. Higher order maxima also form, the next two of which have intensity ratios of 1.7% and 0.83% respectively. Why doesn't all of the energy "land" in the central maximum? Why do we get higher order maxima?