Are real numbers really real?

Re:Are real numbers really real? by thomasahle on Tuesday June 12, 2018 @02:38PM (#17296467)

It's counter-intuitive, but your algorithm actually only generate a subset of the rational numbers. That's because all of your numbers have a finite number of decimal digits. Most reals, like 1/3 or pi, will never appear in your list. (Though numbers close to them will.)

Most reals don't have a generating algorithm, since there is an uncountable number of reals, but only a countable number of algorithms. (Assuming an algorithm has to be a finite length program.)

[ Parent | on HN ]

Re:Are real numbers really real? by windows_tips on Tuesday June 12, 2018 @05:40PM (#17298307)

I'm not sure 1/3 is exactly a number. It seems to be an expression when written out. pi, likewise, appears to be a word, not a number.

[ Parent | on HN ]

Re:Are real numbers really real? by TJSomething on Tuesday June 12, 2018 @05:56PM (#17298434)

Numbers aren't lists of digits. They're abstract concepts that are referred to by lists of digits for the purpose of convenience. You can even have numbers without having invented digits. It's just annoying to write out one million, two hundred thirty-four thousand, five hundred sixty-seven and eighty-nine hundredths. So, we say 1,234,567.89 (or 1.234.567,89 for countries that use the comma for decimals).

0.5 in base 10 is the same as 0.1 in base 2, which is the same as 0.11111... in base 3. And the choice of base is completely arbitrary, with some societies using others, like base 12 or base 60.

[ Parent | on HN ]