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> All real numbers, and all numbers of any other variety, can be written with a finite number of symbols. That's what it means to give something a name. This i
by WastingMyTime89 4y ago
> All real numbers, and all numbers of any other variety, can be written with a finite number of symbols. That's what it means to give something a name.
This is untrue and not particularly hard to prove by contradiction.
Suppose every elements in R can be named by a finite number of symbols.
You can build a bijection between R and the names of its elements (by definition a name points to a unique element and if elements have multiple names, you can easily well order a finite number symbols by building a lexicographic order and only consider the smallest name).
Or, you can also easily build a bijection between a finite number of symbols and N. That's just an encoding like ASCII or UTF-8. Therefore, the set of names is countably infinite.
Yet R is uncountable (see Cantor's diagonal argument).
Therefore, by contradiction, there has to exist elements in R which can't be named by a finite number of symbols.
- thaumasiotes 4y ago> Or, you can also easily build a bijection between a finite number of symbols and N. That's just an encoding like ASCII or UTF-8. Therefore, the set of names is countably infinite. You've confused two different senses of "a finite number of symbols". The requirement is that it takes a finite number of symbols to write down any given number, not that it takes a finite number of symbols to write down every number at once. (Though in fact that also takes a finite number of symbols; it is the precise meaning of ℝ.) Symbols are, in their simplest interpretation, bounded two-dimensional curves; there is no danger of running out of them before we run out of numbers.