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B1 متوسط انگلیسی 7:50 Educational

ASTOUNDING: 1 + 2 + 3 + 4 + 5 + ... = -1/12

Numberphile · 9,684,421 بازدید · اضافه شده 3 روز پیش

آمار یادگیری

B1

سطح CEFR

5/10

سختی

زیرنویس‌ها (136 بخش‌ها)

00:00

I'm gonna give you an astounding result

00:02

Astounding?

00:03

An astounding result

00:04

So I'm just gonna write down a little sum

00:06

I'm just gonna see what answer it gives.

00:08

1 + 2 + 3 + 4 + duh duh duh duh duh

00:13

And I include all the natural numbers, so all the way up to infinity

00:18

So what do you reckon the answer to this is, Brady?

00:21

-Well I would say it would go to tend towards infinity.

00:25

Yeah, that makes sense, doesn't it.

00:26

The answer to this sum is -- remarkably -- minus a twelfth.

00:32

It's amazing! I mean, I first saw this result when I start learning a bit of String Theory

00:37

And what's even more bizarre is that this result is used in many areas of physics

00:44

This is a very well known string theory textbook by Joe Polchinski. As you can see,

00:48

sort of quite early on, page 22, we have this statement here which is that the sum of

00:53

all this is --- basically saying the sum of all the integers ---

00:56

all natural numbers all the way up to infinity, is, minus a twelfth.

01:00

Alright so we're going to prove now,

01:02

Without getting our knickers in a twist with Riemann zeta functions, we gonna prove

01:06

in quite simple way, why the sum of all the natural numbers is indeed minus a twelfth.

01:12

So, to do that we're gonna do this in a number of steps.

01:15

We're gonna to look at a few different sums.

01:16

The first sum that I want to look at, I'm gonna call it S1.

01:20

And it's 1 -1 +1 -1 +1 -1 and so on.

01:28

That's the first sum I wanna look at in principle.

01:30

The second sum I'm gonna look at is 1-2+3-4 and so on

01:39

Carry on in that process all the way up.

01:41

And the third one is of course going to be

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