Figure 1b. A basic concept of the origin of the solar system. Evolution of the protoplanetary nebula according to O. Schmidt. Left side: Sequence of transformations of the original gas-dust disk in blobs growing into rocks and coalescing in clumps of planetesimals. The time span is approximately 104–105 years. Right side: These embryos of planets continue to grow through mutual collisions, eventually to become protoplanets and ultimately a planetary system, here attributed to the solar system. The time span is about 108 years.