Skip to content
HHackerTube.videoSurprise me

Numberphile v. Math: the truth about 1+2+3+...=-1/12

Numberphile v. Math: the truth about 1+2+3+...=-1/12 on HackerTube: recommended by 4 Hacker News commenters across 4 separate months, 2020–2023.

Mathologer

explainer · intermediate · evergreen

Open on YouTube

Mathologer examines the infamous Numberphile claim that 1+2+3+... equals -1/12, explaining what is wrong with the calculation and how it connects to real math like the zeta function and analytic continuation.

Why Hacker News recommends it

HN points to it as the in-depth rebuttal to the Numberphile video that explains why the 'proof' is wrong yet the result is meaningful.

people recommended it
4
separate months
4
strong recommendations
0
discussed on HN
2020–2023
“Mathologer did a fairly in-depth video[1] into why this proof is wrong”
— cyphar, Nov 2020, in “1.5 is the midpoint between 0 and infinity in Ruby”

What HN commenters said

7 Hacker News comments link this video. Each one links back to its thread.

jonnytranJul 2022Recommends

I know you're asking about Computerphile, but this video explains how one of the Numberphile videos is wrong: ▶ this video

in “Ask HN: YouTube Channels for the Intellectually Curious” · View on HN

crvdgcOct 2021Recommends

I find a response video to it more enlightening. It's often found as the number one related video. ▶ this video

in “Conterintuitive facts in mathematics, CS, and physics” · View on HN

cypharNov 2020Recommends

That proof (and the more general statement) is not correct because it makes assumptions about infinite summation of divergent series that are not true. There is a link between the sum of natural numbers -- namely, the analytic continuation of the Reimann Zeta function has Z(-1) = -1/12. But the Zeta function is only defined to equal the sum of inverse powers for Re(z) > 1. And under a specific definition of summation (Ramanujan summation) you can say that "the sum is equal to -1/12" but that isn't the same as normal summation. Mathologer did a fairly in-depth video[1] into why this proof is wrong and what the actual link is between the infinite series and -1/12. The upshot is that even if you use more complicated definitions of summation, you cannot define sums of the kind 1+2+3+... to equal a finite number. If you assume the infinite sum of 1+2+3+... converges to a finite number you can easily prove a contradictory statement using the same summation properties assumed by that proof. Namely: S = 1 + 2 + 3 + ... = -1/12 S2 = S-S = 0 = 1 + 2 + 3 + ... - 1 - 2 - 3 - ... = 0 = 1 + 2 + 3 + ... - 1 - 2 - ... = 0 S2 = 1 + 1 + 1 + 1 + ... = 0 S3 = S2-S2 = 0 = (1-1) + (1-1) + ... = 1 - 1 + 1 - 1 + ... = 0 But we "derived" in the original proof that S3 is equal to 1/2, which is a contradiction. (You could derive S3 is 1/2 from S but that's what the article does in reverse.) [1]: ▶ this video

in “1.5 is the midpoint between 0 and infinity in Ruby” · View on HN

stan_rogersFeb 2020Recommends

Burkard Polster's (Mathologer) videos on the subject are probably going to be more useful than Numberphile. Numberphile merely presents a trick; Mathologer points out both that it's patent nonsense [0] and that it's useful patent nonsense [1]. [0] ▶ this video [1] [link]

in “Ramanujan Surprises Again (2015)” · View on HN

djaychelaJul 2022Cites it

Just spent 5 minutes making a script to find all the links in this thread and then 'score' them on the number of votes. Here's all the channels with 2 or more: 6 Votes: [link] [link] 5 Votes: [link] [link] [link] [link] 4 Votes: [link] 3 Votes: [link] [link] [link] [link] [link] [link] [link] [link] [link] [link] [link] [link] [link] [link] 2 Votes: [link] [link] [link] [link] [link] [link] [link] [link] [link] [link] [link] [link] [link] ▶ this video [link] [link] [link] [link] [link] [link] [link] [link] [link] [link] [link] [link] [link] [link] [link] [link] [link] [link] [link] [link] [link] [link] [link] [link] [link] [link] [link] [link] [link] [link] [link] [link] [link] [link] [link] [link]

in “Ask HN: YouTube Channels for the Intellectually Curious” · View on HN

OldGuyInTheClubSep 2023Critical

Yes, I kept waiting for them to "fess up" at the end but they didn't. Mathologer called them out on it. ▶ this video

in “A Duodecade of Numberphile” · View on HN

Show 1 more comment
t_mannJul 2022Critical

It's similar. Two issues with Numberphile videos I can remember: Their video on 1+2+3+... = -1/12 was so bad that another Math channel (Mathologer, which is highly recommendable btw) did a whole 40min video tearing it apart: ▶ this video In their video on fluid mechanics, they say that the Navier-Stokes equations describe all fluids on earth, while they only show the incompressible version (without clarifying). The examples shown on screen at that moment also include a Ketchup bottle, and they don't discuss non-Newtonian fluids either (Ketchup is non-Newtonian, that's why you can get a lot of it coming out at once if you shake a bottle too hard). It's a bit nitpicking though, because apart from these missing caveats it's a great video (with a guest lecturer from Tom Rocks Maths, another great math channel).

in “Ask HN: YouTube Channels for the Intellectually Curious” · View on HN

Topics & tags

Recreational & visual mathPure mathematics-1/12zeta functionanalytic continuationramanujanmathologer