See previous posts if you’re confused:
Part 1: Normal numbers in base ten
Part 2: Numbers in base φ and π
Part 3: One is normal in base π
This post is also available on LessWrong.
This wasn’t supposed to be a whole series of posts, so we’re going to speed through the punchline:
One is a normal number.
“No it’s not.”
In base π, I mean.
“No, it’s still just 1.“
Don’t be so greedy. Start with 0. and go from there.
“So it’s 0.222… or 0.333… or something?”
Nope, it’s 0.3011021110…
“That’s… bad. Does it repeat?”
I think it’s normal, but that seems hard to prove.
“So each digit occurs equally often?”
No, normal numbers in base π are about a 37%-30%-29%-4% split of 0, 1, 2, 3.
“Where did that distribution come from?”
Integrals of this weird function:
“And where did that come from?”
It’s the distribution of remainders when computing a random number in base π.
“What are the x coordinates of those discontinuities?”
Sequence of remainders when computing 0.3011021110…
“um”
which are dense in [0, 1], by the way.
“Can you prove that?”
No, and neither can you.
“…And the y coordinates?”
The discontinuities get smaller by a factor of π each time.
“And almost all numbers have this distribution of remainders?”
Yup.
“Including 1, if you use the 0.3011021110… representation.”
Yup.
“So the histogram of x-coordinates of the N largest discontinuities in this function approaches… this function itself, as N goes to infinity.”
Yup.
“Which has derivative zero almost everywhere, but has a dense set of discontinuities.”
Yup!
“Any other neat facts about it?”
It’s a fractal.
“How?”
Stretch out the colored regions by a factor of π horizontally, shrink by π vertically, and add them to each other. You get the original function back:
“And this is all because π is normal, or transcendental, or something?”
Nope, I think analogous statements are all true for base 3.5.
Dear Adam,
Thank you for the mathematical information. I used to be good a math, but not that good! Keep it up — Enjoy it! love, Grandma