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> We don't know if pi is a normal number. Sure we do. There are plenty of proofs out there that pi is an irrational number.
by SteveGoob 6y ago
> We don't know if pi is a normal number.
Sure we do. There are plenty of proofs out there that pi is an irrational number.
- andreareina 6y agoIrrational does not imply normal. For example, 1.01001000100001... is irrational but it's certainly not normal.
- x3c 6y agoTechnically, 1.01001000100001... can be normal depending on what ... stands for. :)
- coddle-hark 6y agoOr what 1 or 0 or . stands for.
- bscphil 6y agoWell, obviously. But presumably the ... is meant to imply that this is the summation of 1/(10^(x(x+3)/2)).
- landryl 6y agoActually I'd argue the example you provided is normal, as long as you authorise a particular encoding where every number n you're looking for is encoded as a string of n zeros. It's then trivial to see that every number you can think of is encoded in there, and therefore any data, piece of music or movie that ever existed. (I'm not sure we're allowed to fiddle with the encoding, but since we allow ourselves to represent a piece of music into a number, we're already talking about encoding anyway, so it doesn't seem like cheating to me...)
- enedil 6y agoNormality of a number is with respect to number bases, so your trick with encoding is invalid. Otherwise, every computable number could be considered normal - take an algorithm for generating of it, supply a random string (this is the encoding), disregard the random string, and you have a perfectly valid normal representation of your number. So it is cheating.
- NieDzejkob 6y agoI agree that normality is a specific formalized concept, but you could always require that an encoding function like this is injective.
- dheera 6y agoEncoding doesn't count. Normality is a very specific mathematical concept: https://en.wikipedia.org/wiki/Normal_number https://en.wikipedia.org/wiki/Normal_number Also, 1.01001000100001... is a good example of a number that is both irrational and transcendental but not normal.
- jimktrains2 6y agoNormal in this sense means that all the frequency of all digits approaches a uniform distribution as the length of the sample increases towards infinity. Basically if we could see "all of" π and count all the 0s, 1s 2s, 3s, &c to 9 all the counts would be equal.
- gugagore 6y agoThat on its own can't be right, because 0.12345678901234..... According to wikipédia, you gave a definition for "simply normal", and for normal numbers the distribution of any sequence of digits is uniform. So 00, 01, ..., 99 each occur uniformally too.
- enedil 6y agoMoreover you need to consider it with regards to all other bases than 10 too.