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Looking at "cosmic hours," children have another way to grasp the concept of the relative amounts of time it took for Earth to form and for different types of life to develop.
Comes with a colored control (15" x 20") on poster board, pre-cut arrows and key, and a set of loose chart pieces for building the clock.
Revised in 2014 based on information from the International Commission on Stratigraphy. New colors match those used by ICS. This Notes for the Teacher PDF explains the rationale for the revision.
