Education
The nineteenth lecture in Dr Joel Feinstein's G11FPM Foundations of Pure Mathematics module covers a brief discussion of different sizes of infinity. (The video “Beyond Infinity” may also be helpful here.) Sets with the same cardinality. Countable sets and uncountable sets defined. Connections between functions and sequences. Countability in terms of sequences. The union of two countable sets is countable. (Proved at the start of next class.) These videos are also available on YouTube a