Mark Thompson, age 11, of Eugene, Oregon, for his question:

How is helium manufactured?

Helium is one of the earth's natural elements and we cannot manufacture it in useable quantities. We must find it where we can. This is not easy. because on earth it is a very rare element, and the supplies are used to chill some of these gases to liquid and burn out the helium. This separates and extracts it from the natural gas mixtures in which it occurs. Most of the natural gas wells that contain useful amounts of helium are in the United States.

However, the earth constantly creates traces of helium as radioactive materials decay. Their alpha emissions are helium nuclei. When an alpha particle grabs two electrons from the air, it becomes an atom of helium. Some of these small, light atoms escape from the upper atmosphere as others are formed by radioactivity. The helium content of the air is a skimpy five parts per million.