How Can Infinity Come in Many Sizes?

‘Infinity Comes in Sizes’—commenters demand more wow

TLDR: The piece explains that some infinities are “listable” while the real numbers form a bigger, unlistable infinity. Commenters loved the intro but blasted it for stopping at two sizes, demanding power sets, infinity arithmetic, and answers about “in-betweens,” sparking jokes, nitpicks, and math flamewars.

Infinity isn’t just endless—it’s apparently available in different sizes, and the comments section is having an existential crisis. The article tours Cantor’s wonderland: “small” infinity (you can list things one-by-one like the whole numbers) versus a “bigger” infinity (the real numbers like every point on a line), proved with a digit-flip trick. Cue the chorus: “Only two sizes? That’s it?” Top-voted math fans accuse the piece of stopping at the good part, teasing paradise and then slamming the door. One user points readers toward the big missing chapter: power sets (the set of all subsets), which blow up the size every time you take one.

Defenders clap back: “It’s an intro, not a PhD!” Meanwhile, chaos blooms: a wave of curious newbies asks if there are infinities between the two (hello, the legendary continuum mystery), while pedants spar over decimal quirks like whether 0.999… equals 1 and how to avoid that in the digit trick. Meme squad shows up with Hilbert’s Hotel “no vacancy” jokes, “infinite scroll is uncountable” quips, and one classic: “My inbox is a larger infinity than my free time.” The mood? Enchanted but impatient—the crowd wants the next level: power sets, set-size arithmetic, and the full drama of Cantor’s paradise, not just the lobby. Read the comments; bring popcorn and a number line.

Key Points

  • The article defines sets and cardinality, explaining that counting corresponds to creating a one-to-one match with natural numbers.
  • Even numbers and natural numbers are shown to have the same cardinality via a bijection, illustrating countable infinity.
  • Rational numbers are enumerated by arranging them in a grid and tracing a snaking path, proving they are countably infinite.
  • Real numbers are proven uncountable using a diagonal construction that contradicts any attempt to list them all.
  • The piece concludes that infinite sets can be the same size or different sizes, and there are infinitely many sizes of infinity.

Hottest takes

“The article asks… then proceeds to list just two sizes” — kccqzy
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