129 Essays on Infinite Lifespans   Marvin L. Minsky Fortunately, we would not need to know every minute detail. If that were so, our brains would not work in the first place. In biological organisms, generally each system has evolved to be insensitive to most details of what goes on in the smaller sub- systems on which it depends. Therefore, to copy a functional brain, it should suffice to replicate just enough of the function of each part to produce its important effects on other parts. Suppose that we wanted to copy a machine, such as a brain, that contained a trillion components. Today we could not do such a thing (even were we equipped with the necessary knowledge) if we had to build each component separately. However,  if  we  had  a  million  construction  machines  that could each build a thousand parts per second, our task would take only minutes. In the decades to come, new fabrication machines will make this possible. Most present-day manu- facturing  is  based  on  shaping  bulk  materials.  In  contrast, the field called ‘nanotechnology’ aims to build materials and machinery by placing each atom and molecule precisely where we want it. By such methods, we could make truly identical parts – and thus escape from the randomness that hinders convention- ally made machines. Today, for example, when we try to etch very small circuits, the sizes of the wires vary so much that we cannot predict their electrical properties. However, if we can locate each atom exactly, then those wires will be indis- tinguishable. This would lead to new kinds of materials that current techniques could never make; we could endow them with enormous strength, or novel quantum properties. These products in turn will lead to computers as small as synapses, having unparalleled speed and efficiency.