An unusual Things of Science, both for the size of its booklet (a full U.S. letter size; 8.5″ x 11″) and also for how text-heavy this unit is.
The subject of this unit, topology, is a fairly complex concept in mathematics and Things of Science, as usual, gives it a very thorough treatment. Perhaps this unit was intended for a fairly sophisticated and advanced learner. While they approach the subject in easy to grasp terms, it is hard to see twelve-year-old me being very engaged.
Here is the diagram-heavy booklet (not too many “things” in this unit though):
More Things of Science scanned here.