One of the oldest and most famous unsolved mathematical problems is the Goldbach conjecture. This is

*Every even number greater than 2 can be expressed as the sum of two prime numbers.*

This problem was first posed in 1742 by the German mathematician Christian Goldbach and nearly three hundred years later no one has managed to prove whether or not it is true.

*Christian Goldbach*

**Examples**

A prime number (or prime) is a positive number, which only has factors of itself and 1. For example: 2, 3, 5, 7, 11, 13, 17, 19 etc. By convention 1 is a not considered to be a prime number. Clearly all prime numbers other than 2 must be odd.

I’ve illustrated the Goldbach conjecture for some even numbers below:

4 = 2 + 2

6 = 3 + 3

8 = 3 + 5

10 = 5 + 5 *OR *3 + 7

100 = 3 + 97 *OR *7 + 93 *OR *11 + 89 *OR *13 +87 *OR *17 + 83 *OR *29 + 71 *OR* 41+ 59 *OR* 47 +53

In general, the larger the even number the more different ways it can be split between two primes.

**Proving the Goldbach Conjecture**

Shortly after the Goldbach stated the conjecture one of the greatest eighteenth century mathematicians Leonhard Euler said:

‘*That … every even integer is a sum of two primes, I regard as a completely certain theorem, although I cannot prove it’*

*Leonard Euler one of the greatest ever mathematicians – Image from Wikimedia Commons*

For the last 300 years mathematicians have tried without success to prove it, or to disprove it by finding an even number which cannot not be expressed a sum of two primes. Before the advent of computers, to try to disprove the conjecture, mathematicians had to laboriously check even numbers by hand to look for a number which could not be expressed as the sum of two primes. In 1938 the mathematician Nils Popping showed that all even numbers up to 100,000 could be expressed as the sum of two primes. This must have been an incredible tedious task.

Today, using super computers the Goldbach conjecture has been verified to be true for all even numbers less than four million trillion (4 000 000 000 000 000 000). However, this impressive feat does not ** prove** the conjecture is true for all numbers. All it shows is that the conjecture is true for all even numbers less than four million trillion. It is possible that there exists an even larger number which cannot be split into two primes. What has never been found is a mathematical proof that the conjecture is true for all even numbers

**The Bloomberg Prize**

In a 1992 novel Uncle Petros and Goldbach’s Conjecture by Apostolos Doxiadis the anonymous narrator describes his fascination with his reclusive Uncle Petros, who is considered a failure by his family. When his nephew shows an interest in mathematics, Petros offers him a problem to solve

**prove** that any even number greater than 2 is the sum of two primes.

The narrator works hard on trying crack this problem all summer without success. He later learns that it is more than 250 years old and has remained unsolved by the greatest mathematicians.

Enraged and frustrated, he confronts his uncle, only to discover that Petros has been psychologically crippled by the Goldbach conjecture for decades. When he was a young scholar determined to pursue distinction in the world of mathematics, Petros decided to tackle the proof. But as the proof revealed itself to be beyond him, his pursuit became a nightmare in which he imagined that numbers had taken human form and were speaking to him. As Petros lost hope of finding the proof, he lost his grip on his sanity and his livelihood as a professor at the University of Munich.

In March 2000 the publishers of the book (Bloomberg in the USA and Faber and Faber in the UK) offered a prize of one million dollars anyone who could prove the Goldbach conjecture and whose proof was accepted by fellow mathematicians. The prize was kept open for two years but nobody claimed it.

**Other unsolved problem****s**

In the year 2000 the Clay Mathematics Institute produced a list of of seven mathematical problems for which they would give a million dollar prize for the person(s) who solved them The Goldbach Conjecture was not among them. I have listed the seven problems below and I think that most of my readers will agree that they cannot be understood by anyone without a high-level knowledge of mathematics. To me the great attraction of the Goldbach conjecture is its simplicity to state and its impossibility to prove!

*From **http://www.ams.org/notices/200008/comm-millennium.pdf *

*I hope you have enjoyed this article. To find out more about Explaining Science, click here or at the Explaining Science Home link at the top of this page.*

For another unsolved (but less famous) problem see https://explainingscience.org/2017/08/12/196-an-unsolved-problem/

I was studying the Goldbach conjecture last year, but completely forgot the name! Thanks for reminding me.

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I’m leaning towards ‘flawedman’s final paragraph. 😀 … but this question did occur to me, if it was proved, or disproved, what would the consequences be, both practically (day-to-day life) and theoretically (science)?

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Hi Widdershins,

The Goldbach conjecture is a problem in pure mathematics. So the impact on day to day life and Science would be zero !!

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😀

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I looked up the last two prize problems are they not Physics problems ? I know physicists use mathematics a lot but physics is concerned with the real world mathematics is a world of its own.

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I would tend to agree with you,

the last two are really mathematical physics problems rather than pure mathematics problems

However, the Clay Mathematics Institute considered them to mathematics problems when offering the $1 000 000 prize 😉

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Is it not curious that simple numbers can display properties that are so difficult to prove.

I would mention Fermat’s theorem which most of us know as Pythagoras and learnt in one way or another at school.

The list you give is beyond me but I did understand that Fermat’s has at last been proved.

From what I understand Pythagoras was proved by geometry but it would be too difficult for me as my algebra and geometry are very elementary.

Goldbach seems true to me especially as computers have checked it for millions of cases.

It seems almost absurd to the layman that obvious truths need absolute proof but I’m told the absolute proof is mathematically possible.

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