The Lattice of Sets of Natural Numbers Is Rich
Explore the power set lattice of natural numbers, a Boolean algebra where every possible set of natural numbers exists. This structure is universal for all countable orders, meaning it contains a copy of every countable order, including the rationals. Surprisingly, it also embeds the real continuum and contains an uncountable antichain. Moreover, the lattice exhibits homogeneity: above any cofinite set or below any infinite set, it looks the same, and there are automorphisms mapping any infinite coinfinite set to any other.
Every countable order that occurs anywhere at all occurs in the lattice of sets of natural numbers.