In Defense of Infinity
The Glencoe Algebra II study materials (p. 10) make an amazing claim (Reddit).
This statement is in a math textbook, but it is horrifyingly wrong. A statement like "the letters A--Z cannot be matched up with the numbers 1--26" would be similarly wrong. These two sets of the same size (here, 26) can be matched up as A1, B2, C3, ..., Z26. Can the rational numbers be matched up with the integers? Both are infinite, which allows for the tricks of a technique called Hilbert's hotel, a hotel with infinite numbered rooms that can always make room for one more guest. The Glencoe claim asks if the cardinality of the integers and rationals is the same. Both are , or Aleph-0, which Georg Cantor proved in the 1870s.