←back to thread

God created the real numbers

(www.ethanheilman.com)
136 points Bogdanp | 2 comments | | HN request time: 0s | source
Show context
andrewla ◴[] No.45067770[source]
I'm an enthusiastic Cantor skeptic, I lean very heavily constructivist to the point of almost being a finitist, but nonetheless I think the thesis of this article is basically correct.

Nature and the universe is all about continuous quantities; integral quantities and whole numbers represent an abstraction. At a micro level this is less true -- elementary particles specifically are a (mostly) discrete phenomenon, but representing the state even of a very simple system involves continuous quantities.

But the Cantor vision of the real numbers is just wrong and completely unphysical. The idea of arbitrary precision is intrinsically broken in physical reality. Instead I am off the opinion that computation is the relevant process in the physical universe, so approximations to continuous quantities are where the "Eternal Nature" line lies, and the abstraction of the continuum is just that -- an abstraction of the idea of having perfect knowledge of the state of anything in the universe.

replies(10): >>45067843 #>>45068041 #>>45068086 #>>45068269 #>>45068318 #>>45068389 #>>45069577 #>>45070658 #>>45071417 #>>45075257 #
NoahZuniga ◴[] No.45068389[source]
You know it wouldn't be possible for us to tell the difference between a rational universe (one where all quantities are rational numbers) and a real universe (one where you can have irrational quantities).

The standard construction for the real numbers is to start with the rationals and "fill in all the holes". So why even bother with filling in the holes and instead just declare God created the rationals?

replies(8): >>45068658 #>>45068743 #>>45068954 #>>45068991 #>>45070837 #>>45070881 #>>45071862 #>>45073728 #
1. shonenknifefan1 ◴[] No.45068991[source]
I think this is right. Any measurement will have finite precision, so while we might be able to discover some maximum precision that the universe uses eventually, we won't ever be able to prove that the universe has infinite precision representations from finite precision measurements.
replies(1): >>45069008 #
2. andrewla ◴[] No.45069008[source]
Only so long as we use the rationals as an approximation. If we expect them to be exact then they are as bad as the integers.

The continuum is the reality that we have to hold to. Not the continuum in the Cantor sense, but in the intuitionalist or constructivist sense, which is continuously varying numbers that can be approximated as necessary.