The contemporary great issue among cosmologists and astronomers is whether the Universe will collapse. The Universe started from an explosion and an expansion, and the reader who worries about the future in one or two billion years would like to know if the Universe will continue to expand and terminate as a gigantic freezer or else will collapse into a gigantic furnace. The answer is, it will continue to expand.
The second much debated question is whether the earth has any chance to disappear in a collision. This issue was exposed to public concern in a movie (Armageddon1) and the answer is no. Collisions are on the record but the expansion of the Universe is now so large that future annihilating collisions are unlikely.
The third inquiry is, how did it happen that, with only hydrogen, helium and traces of lithium initially present, so many different atoms have become available, to build life on. The answer is that the time during which the universal expansion has taken place was sufficient to allow the occurrence of secondary events, as the coalescence of matter into galaxies and the formation of celestial bodies (stars, supernovae, etc.) where the creation of heavy atoms from hydrogen and helium could proceed by fusion.
If the reader wants to delve deeper into the creation of atoms, he may read further, otherwise he should skip this arduous exposure as well as the next two chapters, which deal with the extremely large, the extremely small and the extremely complex.
1. Armageddon is derived from the Hebrew "Mount of Megiddo", located East of Haifa. According to the Bible, Megiddo will be the site of the final battle between God and his enemies when time comes to an end. Note that the noise, in the movie, is unwarranted: sounds do not propagate in a vacuum.