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Major Advance Towards a Proof of the Twin Prime Conjecture

ananyo writes "Researchers hoping to get '2' as the answer for a long-sought proof involving pairs of prime numbers are celebrating the fact that a mathematician has wrestled the value down from infinity to 70 million. That goal is the proof to a conjecture concerning prime numbers. Primes abound among smaller numbers, but they become less and less frequent as one goes towards larger numbers. But exceptions exist: the 'twin primes,' which are pairs of prime numbers that differ in value by 2. The twin prime conjecture says that there is an infinite number of such twin pairs. Some attribute the conjecture to the Greek mathematician Euclid of Alexandria, which would make it one of the oldest open problems in mathematics. The new result, from Yitang Zhang of the University of New Hampshire in Durham, finds that there are infinitely many pairs of primes that are less than 70 million units apart. He presented his research on 13 May to an audience of a few dozen at Harvard University in Cambridge, Massachusetts. Although 70 million seems like a very large number, the existence of any finite bound, no matter how large, means that that the gaps between consecutive numbers don't keep growing forever."

248 comments

  1. Preprints not avaiable, but it seems legitimate by Anonymous Coward · · Score: 5, Informative

    The paper seems to have been accepted by Annals of Mathematics, which is basically the number one mathematics journal.

    Also, according to New Scientist, Henryk Iwaniec (a well-known analytic number theorist) has reviewed the paper and didn't find an error. This may or may not overlap with the review at Annals, though.

    1. Re:Preprints not avaiable, but it seems legitimate by boundary · · Score: 0, Offtopic

      Truncate your search by looking in the mirror.

    2. Re:Preprints not avaiable, but it seems legitimate by Anonymous Coward · · Score: 0

      If there are infinitely many pairs of prime numbers less than 70 million units apart then doesn't this prove the conjecture? The conjecture doesn't care how far apart the pairs are, after all.

      If the proof was that there are an infinite number of primes less than 70 million units apart (not pairs of primes), then we're really talking about two different things, because these are not pairs.

      Somehow it looks like the summary is letting us down.

    3. Re:Preprints not avaiable, but it seems legitimate by tolkienfan · · Score: 1

      Twin primes are primes that differ by exactly 2, e.g. 11 and 13.
      The twin prime conjecture is the conjecture that there are an infinite number of such pairs.

  2. Re:'2' - wrong, its 42 by Anonymous Coward · · Score: 0, Funny

    everyone knows the answer is 42

    -1

  3. Not in North Carolina by Anonymous Coward · · Score: 5, Funny

    No siree. Ain't non prime numbers at all here in North Carolina since we done banned them. Ain't no angels felled out of the sky, ain't no computers breakin', and my cousin's kisses never tasted sweeter. Prime numbers are a godless socialist conspiracy against Jedus and mah wallet.

    1. Re:Not in North Carolina by Mitchell314 · · Score: 4, Funny

      It's also against our state law that twin primes cannot cohabitate unless they're the same sex.

      --
      I read TFA and all I got was this lousy cookie
    2. Re:Not in North Carolina by Anonymous Coward · · Score: 0

      And the corollary to that is... if they're of opposite sexes, then they'll be able to breed and create more,
      and in doing so, there's a reasonable probability that the offspring will be of opposite sexes, and therefore
      will breed some more.

      Hence, there are (or will be) an infinite number of such pairs!

      QED (= Quite extraordinary divergence...)

    3. Re:Not in North Carolina by rasmusbr · · Score: 1

      So I guess in North Carolinian schools they only teach twin primes that consist of one odd prime and one even prime.

  4. Stories like this... by Anonymous Coward · · Score: 2, Interesting

    Stories like this only remind me of how ignorant I still am and how I've wasted my life.

    1. Re:Stories like this... by jamesh · · Score: 5, Funny

      Stories like this only remind me of how ignorant I still am and how I've wasted my life.

      Don't feel bad. Maybe you've made coffee for, served fries to, or unclogged the toilet of one of these great people? Every little bit helps!

    2. Re:Stories like this... by Anonymous Coward · · Score: 1

      Although funny, there seems to be some genuine wisdom bits.

    3. Re:Stories like this... by Anonymous Coward · · Score: 0

      maybe they made really *bad* coffee and some genius thought "urgh, I'll invent the latte"

    4. Re:Stories like this... by rwv · · Score: 4, Insightful

      So in addition to giants, there are great people standing on the shoulders of there own communities, too? That is somehow comforting.

    5. Re:Stories like this... by VortexCortex · · Score: 5, Insightful

      It's shoulders all the way down.

    6. Re:Stories like this... by faffod · · Score: 5, Insightful

      Um, one question that a person could ask is: If this proof is found, how does it change the world? How would being able to use the proof influence something in the real world? I'm not saying it can't or won't, only that simply picking a brainy subject does not mean that doing things in it aren't basically intellectual masturbation.

      The change to our world is this: we now know something that we didn't know before. Now we can teach this new knowledge to others (and by others I mean people smarter than me) who can find new places and ways to apply this new knowledge. They might never do anything interesting with it, or it might cause an avalanche of new findings, we don't know. But we, as a species, fundamentally know more today than we did yesterday.
      As an example, the ancient greeks studied prime numbers. Was there any immediate use of primes at the time? Did it allow them to improve harvest? Defeat the Roman army? Nope, they just studied them. At the time there is no way that they could have conceived their application for encryption. Yet today, all commerce on the web uses the mathematics of primes.
      It is not important to have an immediate use for knowledge.

    7. Re:Stories like this... by swillden · · Score: 4, Insightful

      It's shoulders all the way down.

      You were probably going for funny, but if I had mod points I'd call this insightful. It really is shoulders all the way down; no one accomplishes anything of significance without relying on many, many others.

      --
      Note to ACs: I usually delete AC replies without reading them. If you want to talk to me, log in.
    8. Re:Stories like this... by ShanghaiBill · · Score: 2

      If this proof is found, how does it change the world?

      Some encryption algorithms are based on large prime numbers. But how to you find a large prime number? One method often used is to pick a random large odd number, test if for primality, and if it is composite, increment by two and try again. The problem with this linear search method is that you are far more likely to pick a prime that is separated by a large gap from the previous prime, and you will almost never pick the larger prime of a twin pair. So a better understanding of the gaps between primes may lead to faster and more secure encryption and/or better methods of cracking encryption.

    9. Re:Stories like this... by SleazyRidr · · Score: 2

      Part of the art of humor is in being insightful while being funny. It why the greats are so great, they just tell you good life advice, but they frame it in an amusing way and we love them for it.

    10. Re:Stories like this... by fahrbot-bot · · Score: 1

      Stories like this only remind me of how ignorant I still am and how I've wasted my life.

      Don't feel bad. Maybe you've made coffee for, served fries to, or unclogged the toilet of one of these great people? Every little bit helps!

      I had a summer job as a cook at local Pizza Hut way back in the mid '80s and made George Takei lunch once (there was a Star Trek convention in town). He signed the lunch receipt and I still have it. (Definitions of "great" might vary, but I think Mr. Takei qualifies.)

      [ Note: Life since hasn't been a total waste; an senior system programmer/administrator. ]

      --
      It must have been something you assimilated. . . .
    11. Re:Stories like this... by Anonymous Coward · · Score: 0

      Which doesn't mean the garbage man has the same value as the scientist.

    12. Re:Stories like this... by Anonymous Coward · · Score: 0

      If this proof is found, how does it change the world?

      Some encryption algorithms are based on large prime numbers. But how to you find a large prime number? One method often used is to pick a random large odd number, test if for primality, and if it is composite, increment by two and try again. The problem with this linear search method is that you are far more likely to pick a prime that is separated by a large gap from the previous prime, and you will almost never pick the larger prime of a twin pair. So a better understanding of the gaps between primes may lead to faster and more secure encryption and/or better methods of cracking encryption.

      This.

    13. Re:Stories like this... by neonsignal · · Score: 1

      Understanding primes is fundamental to an understanding of number theory.

      Number theory itself is pure mathematics, which concerns itself with abstract concepts, so the immediate motivation is one of exercising our intelligence and playing with the puzzles that we discover. "Intellectual masturbation", to use your classy phrase, is fun. You should try it sometime.

      But of course, in turn number theory underpins many other areas of mathematics, including for example the discrete mathematics used in the development of computer algorithms, not to mention the numerical analysis we use in engineering.

      You seem to be making the mistake of thinking that research is best directed according to practical goals. Actually, it is more time effective to solve hard and fundamental problems that have general usefulness in the field than it is to pick off application specific tasks that won't have any relevance beyond next year.

      Of course, there has to be a balance here between general and specific. But since the number of people doing pure research is such a small fraction of the population, it is really up to you to justify why we don't have more people studying these matters.

    14. Re:Stories like this... by swillden · · Score: 1

      Which doesn't mean the garbage man has the same value as the scientist.

      I think that would depend who you ask.

      --
      Note to ACs: I usually delete AC replies without reading them. If you want to talk to me, log in.
    15. Re:Stories like this... by jamesh · · Score: 1

      Which doesn't mean the garbage man has the same value as the scientist.

      Theirs is a contribution that isn't fully appreciated until it ceases.

    16. Re:Stories like this... by Anonymous Coward · · Score: 0

      the proof exists in the real world.

      oh, what you meant by "real world" is the worthless little slice of the universe that you care about. well, yeah, i guess it doesn't influence anything there.

  5. Re:'2' - wrong, its 42 by Anonymous Coward · · Score: 0

    This. Slashdot definitely needs a "-1, Lame" mod.

  6. Gaps between numbers... by rew · · Score: 5, Funny

    To be perfectly honest the proof that the gap between consecutive integers doesn't grow forever is pretty simple. It stays 1.

    1. Re:Gaps between numbers... by kyuubi · · Score: 0

      He's referring to the gaps between the primes, not the integers.

    2. Re:Gaps between numbers... by rew · · Score: 2

      Yes. And I was joking, not serious. Duh!

    3. Re:Gaps between numbers... by Anonymous Coward · · Score: 5, Funny

      Traditionally, when you're joking you should write something that's funny.

    4. Re:Gaps between numbers... by Anonymous Coward · · Score: 5, Funny

      He may be English.

    5. Re:Gaps between numbers... by MadKeithV · · Score: 1, Offtopic

      Traditionally, when you're joking you should write something that's funny.

      Thank you mods for modding this comment funny.

    6. Re:Gaps between numbers... by Anonymous Coward · · Score: 5, Informative

      Joking aside, submitter is not a mathematician. This doesn't prove anything about the gap between arbitrary consecutive primes. That gap does indeed grow forever, by the known distribution of primes, but by "chance" one would expect a few pairs to lie close together. The proof is that this "chance" event still occurs as N tends to infinity. The same result would hold for random numbers whose distribution gets more sparse with increasing N so it just says that the primes are not "less random" than these (in a very informal sense).

    7. Re:Gaps between numbers... by auric_dude · · Score: 0

      So am I, obligatory XKCD reference https://xkcd.com/899/

    8. Re:Gaps between numbers... by tbird81 · · Score: 1

      Traditionally, when you're joking you should write something that's funny.

      Let me demonstrate.

        "You want me to fix your toaster? Hold it firmly and run hot water over it, while putting its plug in the power outlet."
      This is only funny if you get it.

      Humor is suggesting a (absurd yet understandable) relation between unlikely things.

      It also needs a degree of originality and unexpectedness to it - absurdity is not enough. I found rew's comment funny because I wasn't expecting that reply.

      The toaster thing isn't funny at all. It's just nasty. Water + electrical appliances have been way overdone in both pop culture and humour.

    9. Re:Gaps between numbers... by twisteddk · · Score: 2, Funny

      Given that the only "real use" for large primes is cryptography, I was in my nerd mindset thinking that this means that there will now be a near finite amount of processing power required to break algorithms.

      However, I keep comming back to xkcd aswell: http://xkcd.com/538/

      --
      --- To err is human... Am I more human than most ?
    10. Re:Gaps between numbers... by JustOK · · Score: 0

      42!

      --
      rewriting history since 2109
    11. Re:Gaps between numbers... by Barryke · · Score: 1

      Its just what that US science guy once said, to highlight differences in understanding simply due to insights.

      And yes, originality/unexpectedness is key, i rather unsuccessfully implied that with "absurd yet understandable".

      --
      Hivemind harvest in progress..
    12. Re:Gaps between numbers... by Anonymous Coward · · Score: 0

      Stop! Stop thinking! *klets*

    13. Re:Gaps between numbers... by mortonda · · Score: 1

      Traditionally, it helps when the recipient has a sense of humor, too.

    14. Re:Gaps between numbers... by Impy+the+Impiuos+Imp · · Score: 1

      Given the bigger the number, the more smaller numbers that could divide into it, suggests primes should be getting further and further apart. So a proof they don't is important because it suggests the growing density of divisors (smaller primes) starts to lose out vs. the general increase in sheer quantity of all numbers.

      It approaches a limit that is neither infinity nor zero (since we know there are infinite primes.)

      I still feel this proof has to be wrong for that reason. Well let math at larege look at it for some years and we shall see.

      --
      (-1: Post disagrees with my already-settled worldview) is not a valid mod option.
    15. Re:Gaps between numbers... by jfengel · · Score: 1

      Given the bigger the number, the more smaller numbers that could divide into it, suggests primes should be getting further and further apart.

      Further apart _on average_, which they do. This result doesn't change that; the density of primes still goes to zero.

      The question is whether despite that increasing _average_ distance, there is also an increase in the _minimum_ distance. That was unproven, and now we know: the greatest minimum distance is at most 70 million. It could be as small as 2, and in fact I think most mathematicians strongly suspect that it is: no matter how high you go, there will always be some pair of primes larger than that, separated only by 2. But they'll be rarer and rarer, just as the primes themselves are harder and harder to find.

    16. Re:Gaps between numbers... by femtobyte · · Score: 3, Insightful

      The same result would hold for random numbers whose distribution gets more sparse with increasing N

      This is false --- depending on how fast the random numbers "spread apart", you can have an infinite number of random numbers but a finite number of "close pairs". Simple example: for each positive integer N, choose N to be in your set of random numbers with probability 1/N. This gives you an infinite expected number of such random choices: sum 1/N over positive integers diverges. But what's the chance of adjacent pairs? The probability of N and N+1 being in your random set is 1/N * 1/(N+1). The expectation value for this set is *finite*: sum 1/(N*(N+1)) converges to a finite value.

    17. Re:Gaps between numbers... by Anonymous Coward · · Score: 0

      He may be English.

      Thanks for making me spill my coffee.

    18. Re:Gaps between numbers... by SleazyRidr · · Score: 1

      Actually, it gets slightly smaller as you approach the speed of light.

    19. Re:Gaps between numbers... by iggymanz · · Score: 1

      the toaster thing would be hilarious if a slashdot member with four digit or less ID number really tried it and died.

    20. Re:Gaps between numbers... by Anonymous Coward · · Score: 0

      ...This doesn't prove anything about the gap between arbitrary consecutive primes...

      His proof bounds the liminf of the gaps, jackass.

  7. Open set it is! by idunham · · Score: 0, Redundant

    That means that prime numbers are an open set, since an infinite number of prime pairs with a finite difference means an infinite number of prime numbers.

    In other words: If you wanted to be recognized for finding the highest prime number, you can stop your computer now. There is no highest prime.
    But if you only care for a temporary entry, go ahead; you may well find one in a search of only 70 million numbers!

    1. Re:Open set it is! by Agent+ME · · Score: 2

      It was already proved that there were an infinite number of primes.

    2. Re:Open set it is! by phantomfive · · Score: 5, Informative

      There is a simple, ancient, proof that there are infinite prime numbers.

      Imagine that you did find all the prime numbers, every single one.
      Then, take them, and multiply them all together.
      Add 1.

      You now have a number that is divisible by none of the primes, which therefore must be a prime number.

      --
      "First they came for the slanderers and i said nothing."
    3. Re:Open set it is! by Nyh · · Score: 1

      The Greek knew in 300 BC there are an infinite number of prime numbers. The same proof also shows the gab arbitrary between two numbers can be arbitrary large (even larger as 70 million).

      This proof shows there are an infinite number of primes that are 70 million or less from each other.

      Nyh

    4. Re:Open set it is! by Anonymous Coward · · Score: 0

      That there are infinite prime numbers has been known since the old Greek.

      If there was a finite number of prime numbers, you could multiply all of them. Call this number X. Now add one to X. Now add one to X. As the numbers that can be divided by a prime number P are always P integers apart (e.g. the numbers that can be divided by 3 are 3, 6, 9, 12, and so on. 6 - 3 = 3, 12 - 9 = 3 and so on). Therefore, of all the prime numbers that X can be divided by, the only one that X+1 can be divided by is 1.

      Thus, X can only be divided by 1 and itself => X+1 is prime. But X+1 will always be larger than the largest prime, as X was found by multiplying every prime.

      As X+1 cannot both be prime and larger than the largest prime number, there cannot be a finite number of primes.

    5. Re:Open set it is! by Nyh · · Score: 3, Informative

      You now have a number that is divisible by none of the primes, which therefore must be a prime number.

      Or the number is divisible by a prime that wasn't in you initial set.

    6. Re:Open set it is! by Anonymous Coward · · Score: 0

      This isn't about whether there are an infinite number of primes. Rather it is a proof that there are an infinite set of pairs of primes which are at most a finite distance apart. This would mean that going into infinity the primes don't just get farther and farther and farther apart.

    7. Re:Open set it is! by Anonymous Coward · · Score: 0

      That would give you an even number.

    8. Re:Open set it is! by Anonymous Coward · · Score: 1, Insightful

      That was the point, yes. Are you unclear on the nature of the proof?

    9. Re:Open set it is! by wonkey_monkey · · Score: 1

      Or the number is divisible by a prime that wasn't in you initial set.

      GP has already used all the supposed finite number of prime numbers in constructing his contradictory bigger prime.

      --
      systemd is Roko's Basilisk.
    10. Re:Open set it is! by Anonymous Coward · · Score: 0

      2 is prime, so you'd also multiply by 2. Anything times 2 + 1 is an odd number.

    11. Re:Open set it is! by Anonymous Coward · · Score: 1

      http://primes.utm.edu/notes/proofs/infinite/euclids.html

    12. Re:Open set it is! by Your.Master · · Score: 1

      No it wouldn't. 2 is a prime number. Any positive integer multiplied by 2 is an even number, thus the result of multiplying "all" primes is an even number. Any even number, plus 1, is not an event number. QED.

    13. Re:Open set it is! by c.r.o.c.o · · Score: 1

      That would give you an even number.

      Wrong. Multiplying all the known prime numbers will always give you an even number, so adding 1 to whatever result will give you an odd number.

      Hint: 2 is a prime number. You figure out the rest.

    14. Re:Open set it is! by Nyh · · Score: 4, Informative

      GP has already used all the supposed finite number of prime numbers in constructing his contradictory bigger prime.

      The proof constructs a number that is not divisible by any of the prime numbers in the set of all prime numbers. Therefore it proofs there are an infinite number of prime numbers. The conclusion the constructed number must be prime is wrong.

      Nyh

    15. Re:Open set it is! by Anonymous Coward · · Score: 0

      Wait.
      Not that I don't trust you or the proof, but how do you know that adding one doesn't result in an even number?
      Or, in other words, how do you know that multiplying all the primes will get you an even number?

    16. Re:Open set it is! by wonkey_monkey · · Score: 1

      Now add one to X. Now add one to X.

      Oops. Just add one, not two ones. Two shalt thou not add.

      --
      systemd is Roko's Basilisk.
    17. Re:Open set it is! by sgunhouse · · Score: 1

      May. There is a trivial proof that there exist gaps larger than any given number ...

      Pick any number n. Consider n! (that's "factorial", for the non-mathematicians). Now, n! - 1 might be prime (or not), but as n! is divisible by k for all k x and a prime q > p with q - p = 70 million, not that there will always be a prime within 70 million of x.

    18. Re:Open set it is! by z3alot · · Score: 1

      To be pedantic, we still cant conclude the product + 1 is prime, only that it is a contradiction that it is divisible by no prime (which is all we need anyway). The GP is correct in that a proof more similar to Euclid's original is given by considering an arbitrary finite set P of primes, letting N be the product of the P plus 1, and then concluding that a prime divisor of N must not be in P.

    19. Re:Open set it is! by locofungus · · Score: 5, Informative

      Or the number is divisible by a prime that wasn't in you initial set.

      GP has already used all the supposed finite number of prime numbers in constructing his contradictory bigger prime.

      The GP's correction is right.

      The GGP said that his number was prime. It might be, but it might not. But if it's composite then it cannot be divisible by any of the primes in his initial set so there must be a prime not in his set.

      For example, if we assume 13 is the last prime then multiply them all together and add 1 we get 30031. But 30031 is not prime - it's divisible by 59 (which is a prime not in our set)

      Tim.

      --
      God said, "div D = rho, div B = 0, curl E = -@B/@t, curl H = J + @D/@t," and there was light.
    20. Re:Open set it is! by Anonymous Coward · · Score: 0

      Same AC here.
      I got it now, since you end-up multiplying by 2, one of the primes.
      Nice :)

    21. Re:Open set it is! by sgunhouse · · Score: 2

      I gather the comment system doesn't like all those symbols. It removed half of my reply. Let me try words ...

      n! is divisible by k for all k less than or equal to n, so n! - k is divisible by k and (if k is not 1) is not prime. So n! - 1 to n! - (n + 1) are two numbers with a difference of n with no primes between them.

      The result must show that for any x there are primes p and q with q > p > x and q - p less than 70 million, ...

    22. Re:Open set it is! by locofungus · · Score: 3, Insightful

      Your proof as written is wrong.

      I claim there are a finite number of primes viz:
      2 3 5 7 11 13.

      You construct 2*3*5*7*11*13+1 = 30031 and claim that this is a new prime in my list.

      I say - no it's not 30031 is composite. (59*509)

      --

      The correct proof is to say that X+1 is either prime or is divisible by a prime not in the list thus proving that the list is incomplete. If the list contains all the primes up to N then there must be a prime bigger than N.

      --
      God said, "div D = rho, div B = 0, curl E = -@B/@t, curl H = J + @D/@t," and there was light.
    23. Re:Open set it is! by bierik · · Score: 1

      This isn't pedantic at all. The constructed number does not have to be a prime (as shown below in locofungus' example) and thus the additional step (there must be another prime, contradicting the assumption) is needed.

    24. Re:Open set it is! by k.a.f. · · Score: 1, Informative

      You now have a number that is divisible by none of the primes, which therefore must be a prime number.

      Or the number is divisible by a prime that wasn't in you initial set.

      No, the assumption was that you have all prime numbers. You're not allowed to violate assumptions within a formal proof, you're only allowed to point out self-contradictions.

    25. Re:Open set it is! by dkf · · Score: 1

      You now have a number that is divisible by none of the primes, which therefore must be a prime number.

      Or the number is divisible by a prime that wasn't in you initial set.

      The operation itself is guaranteed to give you a number that is coprime with the initial set. However, if you were to believe that there were a finite set of prime numbers and were then to use that finite set as the input into the coprime generator, you'd get something that is coprime with "all" prime numbers, which would therefore consequently show that there must be at least one prime number that is not in that set, and establish the result as a candidate for the missing prime. (If you previously believed that there are no prime numbers, the product-over-set-and-add-one operation produces 2.) The assumption that must have been false, given that everything else is a basic mathematical or logical operation, is that there is a finite set of prime numbers; there must be an infinite number of primes.

      But TFA wasn't talking about this. It was talking about the number of pairs of primes where the difference between the pair is 2, and that's a very non-trivial property.

      --
      "Little does he know, but there is no 'I' in 'Idiot'!"
    26. Re:Open set it is! by Anonymous Coward · · Score: 0

      That means that prime numbers are an open set

      Apart from everything else wrong with your statement that has already been pointed out, "open set"
      doesn't mean what you think it means. It is a term from topology; a set is "open" if none of the points
      on its boundary is a member of the set (like the interior of a circle, excluding the circle itself). Considered
      as a subset of the real line, no nonempty set of integers is open.

    27. Re:Open set it is! by Barryke · · Score: 0

      Mod parent up. He got antiproof.

      --
      Hivemind harvest in progress..
    28. Re:Open set it is! by Anonymous Coward · · Score: 0

      Not only are you forgetting the classical proof of the infinity of the primes (as pointed out passim elsewhere), you also don't know what an open set is.

      An open set is a concept from topology, and means a set which does not contain its closure. It does not mean an "open-ended" set of (natural) integers. There's a word for those sets, and it is "infinite".

    29. Re:Open set it is! by Anonymous Coward · · Score: 1, Informative

      His proof is fine, you're just not familiar enough with how proofs by contradiction work. It's true that 30031 is composite. Within the formal context of his proof by contradiction, it is simultaneously true that 30031 is prime. It is prime because it is not divisible by any other prime. It is composite because you found a non-trivial factorization. Both statements are true. That's why it's a proof by contradiction - there is a contradiction. Your wording is correct too, but it is not necessary to add the case that you did where X+1 is not prime, though that extra bit may be helpful for less mathematically experienced readers.

    30. Re:Open set it is! by Anonymous Coward · · Score: 1

      Can people stop trying to point out the flaw in this comment please? The poster is correct and if you look up the proof you will find this rider.

      You, sir, are not a mathematician. The person you are replying to is because he gets why the stated proof was incomplete.

      If the new number is not divisible by any of the primes in the initial set, then either it is a prime (contradiction - the initial set is not complete) or it is composite (contradiction - another prime exists outside the initial set).

      The stated proof assumes the new number is prime. This is not a valid assumption.

    31. Re:Open set it is! by locofungus · · Score: 2

      No! Why is this causing so much confusion.

      I claim that SEO (Some enormous number) is the largest prime.

      You construct 2*3*5*7*11*...*SEO+1 and claim that it is a prime not in my list.

      I run a quick probabilistic primality test and prove that your number is composite. (which it almost certainly is)

      Conjecture: There are no numbers of the form 2*3*...*P_{n-1}*P_n + 1 that are prime for P_n greater than 11.

      --
      God said, "div D = rho, div B = 0, curl E = -@B/@t, curl H = J + @D/@t," and there was light.
    32. Re:Open set it is! by Anonymous Coward · · Score: 0

      GP has not constructed a bigger prime. He has constructed a bigger number which may be prime or may be composite. The guy you're "correcting" is pointing this out, unfortunately in terms you're too mathematically naive to understand.

    33. Re:Open set it is! by Anonymous Coward · · Score: 0

      Nyh, I would personally like to thank you for correcting the original proof, and I would personally like to shoot the non-mathematicians who keep telling you you're wrong.

      Sheesh, Slashdotters discussing math is like blind people discussing the Mona Lisa.

    34. Re:Open set it is! by Anonymous Coward · · Score: 0

      This would mean that going into infinity the primes don't just get farther and farther and farther apart.

      That is implied but hardly proven.
      This doesn't say anything about the distance between the pairs or the number of non-paired primes between those pairs.
      The average distance between the primes could still increase as far as we know but if we look at prime density graphs we can guess that the average distance increment decreases.

    35. Re:Open set it is! by evilbessie · · Score: 1

      This whole proof is much easier if you use factorials as you can always prove there must be a prime bigger than N, as N! + 1 is not divisible by any number less than N. Which sort of gets around this weird way of attacking this problem y'all seem to be using which involves ephemeral 'set of known primes' which is weird in proofs.

    36. Re:Open set it is! by A+Nun+Must+Cow+Herd · · Score: 1, Insightful

      So you don't have the set of all primes after all... that's the point. The proof goes like this:
      1) suppose you have a set of all primes, and the set is finite.
      2) show that there's another prime not in your set - that contradicts (1).
      3) therefore, there is no finite set that contains all primes.

      All you've done is demonstrate one example of step 2. The original proof given by phantomfive gives a different example of a prime not in the set. Either works - the proof is valid.

    37. Re:Open set it is! by Splab · · Score: 1

      Nope, still with the missing stuff there it doesn't make sense :-)

      But that might just be because I'm slightly blind when it comes to mathematical proofs.

      (Kinda like Zaphods sunglasses, but build into the brain, blacking out when stuff gets complicated)

    38. Re:Open set it is! by locofungus · · Score: 3, Insightful

      I don't see why it gets around this problem.

      The equivalent claim would be that
      N!+1 is prime.

      The correct claim is that N!+1 is prime or is divisible by a prime larger than N

      The faulty proofs are trying to construct a prime not in the set. The correct proofs are showing that a prime exists that is not in the set without making any claims about what that prime is other than it's bigger than N.

      I'm pretty sure that it has been proved that there cannot be a constructive proof that there are an infinite number of primes - i.e. there is no way to construct a prime larger than N for arbitrary N.

      Tim.

      --
      God said, "div D = rho, div B = 0, curl E = -@B/@t, curl H = J + @D/@t," and there was light.
    39. Re:Open set it is! by mrvan · · Score: 3, Interesting

      Or more elegantly in haiku form:

      Top prime's divisors'
      product (plus one)'s factors are?
      QED, bitches!

      -- http://xkcd.com/622/

    40. Re:Open set it is! by evilbessie · · Score: 1

      I was just objecting to the use of set of all primes, as you say there is no easy way to construct (or test) primes, however by showing that there must be a prime greater than an arbitrary value you have demonstrated there are an infinite number of primes* without requiring that you know all the primes in the first place.

      *(N!+1)! +1 ad infinitum.

      The proof in the article is that there exists an infinite subset of the primes where members are separated from at least one other member by less than 70 million. Which is a pretty hard thing to even get close to proving.

    41. Re:Open set it is! by Arrepiadd · · Score: 1

      Actually, Euclid's proof for the infinitude of primes says that the number itself is either a prime (which your example shows isn't always the case) or that the number can be factored by a prime not in the list provided (thus proving other primes exist). In your case both 59 and 509 are primes, showing the original list of primes was incomplete. Rinse and repeat.

    42. Re:Open set it is! by Arrepiadd · · Score: 1

      Oh god, I saw the "--" in your comment and assumed it was the signature... only then I realized it was the final section of your comment. Sorry about that.

    43. Re:Open set it is! by Anonymous Coward · · Score: 0

      why exactly can we be sure the constructed number isn't divisible by any of the primes in our initial set? i know it's a valid claim, however it isn't obvious to me. mind to elaborate?

    44. Re:Open set it is! by locofungus · · Score: 1

      It's as much my fault. I'll try not to do that again!

      --
      God said, "div D = rho, div B = 0, curl E = -@B/@t, curl H = J + @D/@t," and there was light.
    45. Re: Open set it is! by Anonymous Coward · · Score: 0

      Yeah, but I worry the "top prime's divisors' ( plus one)'s" is unparseable

    46. Re:Open set it is! by Sockatume · · Score: 4, Insightful

      You've misunderstood the proof as a test to see whether a subset of primes up to prime n is complete. That's not the case. You start by taking the entire postulated finite set of primes.

      The condradiction you receive - that it's possible to create a prime outside of the complete set of all primes - indicates that any finite set is incomplete. (Or alternatively that addition, multiplication, or sets work very differently than we assume, but let's stick to the form of mathematics the problem addresses.)

      --
      No kidding!!! What do you say at this point?
    47. Re:Open set it is! by tbird81 · · Score: 1

      If you take all the primes from 2 to 23, and multiply them all then and one, you get 223092871 a non-prime, with 317 and 703763 as its prime factors.

      I don't, however, see how it is obvious that multiplying all the primes in a list, then adding one, should mean that the result cannot be factorised by the original component primes.

    48. Re:Open set it is! by Sockatume · · Score: 1

      You don't have to know all the primes in the first place for the proof to work, you just have to postulate that such a finite set exists. (Which you then disprove by contradiction.)

      --
      No kidding!!! What do you say at this point?
    49. Re:Open set it is! by Sockatume · · Score: 2

      It can't be composite if it's a product of all of the primes plus one. It could only be a composite if it was a product of a subset of the primes, plus one.

      --
      No kidding!!! What do you say at this point?
    50. Re:Open set it is! by twisteddk · · Score: 4, Interesting

      From a purely mathematical point of view you are incorrect.

      The proof isn't that there's less than 70million units between each prime (like there's a lot of primes with a gap of two units eg 29 and 31, 41 and 43 etc). the proof is that there's in infinite number of prime pairs with a maximum of 70 million units between them.
      You can still find gaps significantly larger. Those gaps are present between numbers that are NOT prime pairs.

      eg: 29 30 31 32 33 34 35 36 37 39 40 41 42 43 44
      Here there is a prime pair with a 2 unit gap between them (41 and 43), however the number 37 has a larger gap on either side, because it is not a part of a "prime pair". In your thinking you are excluding the primes that are NOT paried, and the gaps between where one pair ends and another begins. Each of which, according to the proof still has the ability to exceed 70 million units.

      Disclaimer: I did not fully read the proof posted in annals of mathematics, but I'm pretty certain that this is the gist of it

      --
      --- To err is human... Am I more human than most ?
    51. Re:Open set it is! by Sockatume · · Score: 2

      It occurs to me that my comment below is rather demonstrating your point, actually. If it's a composite then we've successfully proven that the complete set of primes is an incomplete subset of the complete set of primes, which is another contradiction.

      --
      No kidding!!! What do you say at this point?
    52. Re:Open set it is! by Anonymous Coward · · Score: 0

      The first contradiction follows from the original assumption, which is why it disproves the assumption.

      Your second contradiction follows from arbitrarily assuming the contrary of the original assumption, i.e. "if we assume a contradiction then there is a contradiction". It is a meaningless tautology which neither proves nor disproves anything.

    53. Re:Open set it is! by tr897 · · Score: 1

      You really don't get it, do you? And you tell other people that they're not familiar enough with how proofs by contradiction work...

    54. Re:Open set it is! by xorsyst · · Score: 2

      p is any of the primes, x is the result of multiplying all the other primes in the list.
      If px+1 was divisible by p, then px+1 = py, for some whole number y
      dividing by p, y = x + 1/p. This cannot be a whole number as p >= 2 and x is a whole number.

      I'm sure there's a better proof, but that's just off the top of my head.

      --
      Get free bitcoins: http://freebitco.in
    55. Re:Open set it is! by cryptizard · · Score: 1

      Depends on what you mean by "construct". You can just start at N+1 and test everything for primality. We know now that primality testing is in P, and the prime number theorem tells us that the distribution of primes is dense, so this is even efficient.

    56. Re:Open set it is! by Anonymous Coward · · Score: 0

      There is no largest prime.

    57. Re:Open set it is! by locofungus · · Score: 1

      Yes, Sorry. My comment wasn't very well written.

      What I was trying to say is that given a purported complete set of primes, it's impossible to construct a prime not in the list other than by first assuming that there is a prime not in the list.

      Any algorithm that tests N+1, N+2... will not terminate if N is the largest prime.

      Tim.

      --
      God said, "div D = rho, div B = 0, curl E = -@B/@t, curl H = J + @D/@t," and there was light.
    58. Re:Open set it is! by Anonymous Coward · · Score: 0

      Sure there is:

      use sieve of Eraosthenes to find all primes p_i {i = 1 ... k} up to N (i.e. sieve to N^2)
      N' = 1 + product p_i {i = 1 ... k}
      use sieve to find all primes p'_j {j = 1 ... k'} up to N'
      pick smallest p_j > N.

    59. Re:Open set it is! by Anonymous Coward · · Score: 0

      You, sir, are not a mathematician. The person you are replying to is because he gets why the stated proof was incomplete.

      First problem: Appeal to authority. Whether he is or is not a mathematician has no bearing on the argument.

      Second problem: You don't actually know whether he is a mathematician.

      Third problem: "Getting" why one particular particular proof is allegedly incomplete does not define whether someone is a mathematician.

      or it is composite (contradiction - another prime exists outside the initial set).

      Fourth problem: If we assume that there are no prime numbers outside the initial set (which we are) it follows that is not composite.

      The stated proof assumes the new number is prime. This is not a valid assumption.

      It is not an assumption at all. The only assumption is that the set of all prime numbers is finite. And we know that the new number is not a multiple of any number in that set (do you challenge this?), it follows that the new number is not composite unless you also assume that there are at least two other prime numbers that do not belong to the set of all prime numbers, and that is not a valid assumption.

    60. Re:Open set it is! by Anonymous Coward · · Score: 0

      Except most of these people are arguing over something rather pointless. It is not so much they are wrong and Nyh is right, or visa versa. The logic that results from making an assumption that is incorrect leads to a contradiction. Once the contradiction is established, there is not much point in going further, otherwise you will be able to prove an infinite number of further things that are true but contradicted other things that you've also prove true from the same premise.

      It is like that silly proof that divides by zero to get that 1=0, and people are then arguing over whether it should be 1=0 or 25=24 or 6=0, etc. You can't really argue which one is more correct or should be a correction, because they are all missing the point.

    61. Re:Open set it is! by Anonymous Coward · · Score: 0

      Once you've introduced an assumption that produces a contradiction into such a system, you usually can end up creating an infinite list of statements that said assumption will prove that contradict with other such statements, or with statements based on a system without that assumption. One of them is not more or less true than the other, and it is pointless to argue over that. The only point is there is a contradiction, it doesn't matter which contradiction you use.

    62. Re:Open set it is! by CodeHxr · · Score: 1

      Your math is correct. What I believe is being discussed is that while multiplying the primes from 2 to 23, you're making the (admittedly invalid) assumption that the primes from 2 to 23 are all that exist. We know that there are more primes than that, we're intentionally making that assumption to prove a point...

      If {2, 3, 5, 7, 11, 13, 17, 19, 23} are all the primes that exist (we know that they aren't, but just assume for the moment that they are), then the total 223092871 is indeed prime when compared to all of the primes that "exist", thus invalidating the original assumption and proving it false because now we have another known prime. If you count the fact that 317 and 703763 are indeed prime factors, this also invalidates the original assumption in that there are primes in addition to all that "exist", also proving the assumption false.

      Given that numbers are infinite, there would be no point in which you could truthfully say "here is the set of all existing prime numbers", thus proving that there are an infinite number of them. That's all that's being said by the proof posted so far above: There are an infinite number of prime numbers, and here is my proof as to why that is so.

    63. Re:Open set it is! by xigxag · · Score: 3, Informative

      Euclid's Theorem in actuality does refer to the case where X+1 is not prime. It's essential to the proof.

      It goes something like this:

      ---------
      Take a finite list of prime numbers, A, B, C etc. (The assumption that they are "all the primes" is unnecessary.)
      Find the smallest common multiple of them, X.
      Add 1 to that.
      The new number, X+1, is either prime or composite.
      If it's prime, then that's it. We've generated a new prime not on the list.

      If it's composite, then it is divisible by some prime, G.
      Could G be one the primes (A, B, C. etc.) already on the list?
      But remember, X is divisible by A, B, C etc. So if G is one of those primes, then that means that both X and X+1 are divisible by prime number G, which is impossible.
      Therefore G would have to be a new prime, not on the list.

      Now we have a larger list, A, B, C, G, etc. and can repeat the process.

      We can always generate a new prime not on the list, and therefore the list of primes is without bound.
      ---------

      --
      There are two kinds of people: 1) those who start arrays with one and 1) those who start them with zero.
    64. Re:Open set it is! by VortexCortex · · Score: 1

      The thread of comments attached to parent reminds me of folks on Yahoo Answers trying to apply order of operations to basic equations -- Don't look it up, humanity needs your hope.

    65. Re:Open set it is! by Anonymous Coward · · Score: 0

      Including the number 1 as a prime:
        1+2+1 = 4. 4 is divisible by 2.

      Not including the number 1 as a prime:
        2+3+1 = 6. 6 is divisible by 2 and 3.

      You should always test your hypothesis on the simplest possible data set before you open your mouth.

    66. Re:Open set it is! by Anonymous Coward · · Score: 0

      1*2+1=3. 3 is not divisible by 2.
      2*3+1=7. 7 is not divisible by 2 or 3.
      You should at least read the hypothesis that you're trying to refute, lest you look like an idiot.

    67. Re:Open set it is! by dcollins · · Score: 1

      You should have explicated how the contradiction establishes that the original assumption must be wrong (i.e., the primes cannot be finitely listed). Not everyone understands proof by contradiction, so leaving it unstated was asking for trouble.

      --
      We know where leadership by an anti-intellectual "strongman" who scapegoats minorities and likes boisterous rallies goes
    68. Re:Open set it is! by Anonymous Coward · · Score: 0

      But if it's composite then it cannot be divisible by any of the primes in his initial set so there must be a prime not in his set.

      However, that's not the case because it is not composite, by definition of that initial set.

    69. Re:Open set it is! by wonkey_monkey · · Score: 1

      The stated proof assumes the new number is prime. This is not a valid assumption.

      Isn't it, at least under the stated conditions? The assumption that the new number is prime is made because it is not divisible by any of the supposedly complete set of primes used in its construction. I don't quite see why you need to add the "...or it is composite" to complete the reductio ad absurdum*.

      *which is either what they told me proof by contradiction is called in Latin, or something Harry Potter was taught in Transfiguration.

      --
      systemd is Roko's Basilisk.
    70. Re:Open set it is! by phantomfive · · Score: 1

      Thanks for the tip.

      --
      "First they came for the slanderers and i said nothing."
    71. Re:Open set it is! by nedlohs · · Score: 1

      You should learn what multiply means before opening your mouth.

    72. Re:Open set it is! by phantomfive · · Score: 1

      I will take your advice, but it is interesting because just last night I was reading Dijkstra who said that in the Netherlands, order of operations puts multiplication before division.

      --
      "First they came for the slanderers and i said nothing."
    73. Re:Open set it is! by Anonymous Coward · · Score: 0

      The product is divisible by all the primes in the set. If the product plus one is divisible by a prime in the set, then two consecutive numbers N and N+1 are divisible by the same prime, which is obviously wrong.

    74. Re:Open set it is! by locofungus · · Score: 1

      No!

      The original proof is flat out wrong.

      It claimed that the product of all the primes up to N and then adding 1 is prime.

      The product of all the primes up to 13 is 30031.
      2^30030 mod 30031 is 21335
      Therefore 30031 is not prime. (Fermat's little theorem)

      The proof as stated is insufficient. I have proved that 30031 is not prime but I have not found any prime factors of 30031. Therefore, to complete the proof you need to include the case that 30031 contains a prime factor not in my original list because I have proved that 30031 does not belong in my list.

      Tim.

      --
      God said, "div D = rho, div B = 0, curl E = -@B/@t, curl H = J + @D/@t," and there was light.
    75. Re:Open set it is! by Anonymous Coward · · Score: 0

      It's simply because the resulting number is so much larger than the supposed "last" prime, so you haven't found a legitimate prime in between the "last" one and the resulting number which definitely exists.

    76. Re:Open set it is! by Anonymous Coward · · Score: 0

      You just blew my fucking mind!

    77. Re:Open set it is! by Bigby · · Score: 1

      If there is a 70m gap between prime pairs, then there is a 70m gap between primes. Prime pairs are made up of primes. So it effectively proves that every series of 70m numbers has at least 2 primes and 1 prime pair. Is there a proof that narrows basic primes to a smaller maximum?

    78. Re:Open set it is! by Anonymous Coward · · Score: 0

      You can't create a new prime from every existing prime, that's self contradicting. The SEO+1 shouldn't be prime.
      Just to illustrate, here's a mock list showing a flaw in the assumption the end resulting SEO+1 would be prime.
      (2*3)+1=7 prime
      (2*3*5)+1=31 prime
      (2*3*5*7)+1=211 prime
      (2*3*5*7*11)+1=2311 prime
      (2*3*5*7*11*13)+1=30031 not prime (actual nearest primes are 30029, 30047)
      (2*3*5*7*11*13*17)+1=510511 not prime (actual nearest primes are 510481, 510529)

      You now have a number that is divisible by none of the primes, which therefore must be a prime number.

      It could be divisible by non-primes. A prime is only divisible by one and itself.

    79. Re:Open set it is! by Anonymous Coward · · Score: 0

      The whole point is it produces a contradiction. Of course it can produce a number that is not prime but calls prime, that is a contradiction that shows the initial assumption is wrong. It can also produce a number that should be prime, which contradicts the assumptions all primes were already accounted for.

      Arguing over which contradiction is more right or wrong is completely pointless. You could generate a list of many more potential contradictions too. No one of them is right or wrong. They're all contradictions, and the point is that one exists, not that any particular one exists.

    80. Re:Open set it is! by Anonymous Coward · · Score: 0

      You, sir, are not a mathematician. The person you are replying to is because he gets why the stated proof was incomplete.

      I am actually paid to be a mathematician, and both sides here are essentially wrong. Both sides are arguing over something silly that doesn't matter and doesn't add to the proof. Of course there is a contradiction and there are problems like it produces a number that "should be" prime but isn't. The reason it isn't prime is not because the proof is wrong, but because it is derived from a false assumption, as is the entire point of proof by contradiction.

      The analogy another AC had further down hits the nail on the head. There is a "proof" that 1=0 by allowing for division by zero. Instead of coming to the conclusion that a false result means the proof is built upon something false, both sides here are busying arguing whether the result should be 1=0 or 2=1. It doesn't matter, misses the whole point, and is a waste of effort to really argue either side.

    81. Re:Open set it is! by Anonymous Coward · · Score: 0

      All non-prime numbers are divisible by at least one prime number, so if a number is divisible by a non-prime, it must also be divisible by a prime. If a number is not divisible by any element of the set of all prime numbers, then it can only be divisible by itself and one and must therefore be a prime number. Proving that the set of prime numbers is infinite works by assuming that the set of all prime numbers is finite, creating a number that is not in that finite set and not divisible by any number in that set. By the conclusion above, this number must be prime, but it can't be, because it's not in the set of all prime numbers. This contradiction disproves the assumption. The set of all prime numbers is therefore infinite.

    82. Re:Open set it is! by Anonymous Coward · · Score: 0

      You now have a number that is divisible by none of the primes, which therefore must be a prime number.

      Or the number is divisible by a prime that wasn't in you initial set.

      No, the assumption was that you have all prime numbers.

      Yes, and the whole point is to show that that assumption can't be true. The product-plus-one must be either prime itself or divisible by some prime that isn't in your original set, but either way it gives you a prime number that isn't in the original set, so it proves that no matter how many prime numbers you have there's always another to find.

    83. Re:Open set it is! by Anonymous Coward · · Score: 0

      It's also not prime, by definition of that initial set. Which is a contridiction, which is the whole point.

    84. Re:Open set it is! by Anonymous Coward · · Score: 0

      Or more elegantly in haiku form:

      Top prime's divisors'
      product (plus one)'s factors are?
      QED, bitches!

      -- http://xkcd.com/622/

      Except it's shite. "Top prime's divisors' product" is equivalent to "top prime", and while we know that there's no such thing, hypothetically adding one and taking the factors of the result doesn't help in proving that.

    85. Re:Open set it is! by Asmor · · Score: 2

      That clarification was important. GP said:

      > You now have a number that is divisible by none of the primes, which therefore must be a prime number

      This is incorrect. The number must have a prime factor not in the initial list, which is a different (and more general) statement than "it must be a prime number."

      The existence of a prime factor not in the original chosen set is proof that the set was not, in fact, all the primes. Thus you've shown that the original premise leads to a contradition, so the original premise is impossible.

    86. Re:Open set it is! by dcollins · · Score: 1

      Hmmm, I guess you must mean "for n greater than 11" (not "P_n greater than 11").

      --
      We know where leadership by an anti-intellectual "strongman" who scapegoats minorities and likes boisterous rallies goes
    87. Re:Open set it is! by Anonymous Coward · · Score: 0

      If there is a 70m gap between prime pairs, then there is a 70m gap between primes.

      Think you need "some" and "can be" in there somewhere, nigger.

    88. Re:Open set it is! by Anonymous Coward · · Score: 0

      Proof by contradiction proves that the assumption is wrong. In this case, the assumption is the existence of a finite set of primes. Obviously the constructed number C mod (any prime) is 1, since C = (2*3*5*7*...) + 1. and equally obviously, (2*3*5*7*...) mod (any prime) = 0 - assuming C is finite, which in turn means the set of primes is finite.

      In other words, C is either prime or composite. If we assume it's composite, C = prime * C'. That means C mod prime = 0. Yet we know that C mod prime = 1.

    89. Re:Open set it is! by Smurf · · Score: 1

      No, you are not getting it. Suppose that P[i] denotes the i-th prime number. The proposed theorem does not say that P[i+1]-P[i] <= 70 million for all values of i, as you believe.

      What it does say is that for every index k for which P[k+1]-P[k] > 70 you can find a number m greater than k such that P[m+1]-P[m] <= 70 million.

    90. Re:Open set it is! by Roachie · · Score: 1

      Man, it kills me when someone quotes a great mathematician/great proof and the neckbeards come out to tell you that you are wrong.

      I made the mistake of describing cardinality to a coworker and had him unwittingly suggesting that Cantor is wrong, he thought he was arguing with me.

      Its all a big bologna measuring contest.

      --
      This sig is not paradoxical or ironic.
    91. Re:Open set it is! by locofungus · · Score: 1

      I did. I've also now tested it more fully and I think it's wrong.

      The product of the first 75 primes (up to 379) is X=1719 620105 458406 433483 340568 317543 019584 575635 895742 560438 771105 058321 655238 562613 083979 651479 555788 009994 557822 024565 226932 906295 208262 756822 275663 694110

      2^X mod X+1 is 1 so X+1 is probably not prime.

      Tim.

      --
      God said, "div D = rho, div B = 0, curl E = -@B/@t, curl H = J + @D/@t," and there was light.
    92. Re:Open set it is! by locofungus · · Score: 1

      Gah. ... so X+1 is probably prime.

      --
      God said, "div D = rho, div B = 0, curl E = -@B/@t, curl H = J + @D/@t," and there was light.
    93. Re:Open set it is! by Anonymous Coward · · Score: 0

      The assumption that the new number is prime is made because it is not divisible by any of the supposedly complete set of primes used in its construction.

      If it's not divisible by any of the "complete" set of primes then it can't possibly be prime, just as much as it can't possibly by composite.

    94. Re:Open set it is! by dcollins · · Score: 1

      Wolfram Alpha agrees: says it's a prime number.

      --
      We know where leadership by an anti-intellectual "strongman" who scapegoats minorities and likes boisterous rallies goes
    95. Re:Open set it is! by strikethree · · Score: 1

      Hm. I am not a math major nor a history major. How does multiplying prime numbers and adding 1 create a guaranteed prime number? I can think of smaller examples of multiplying primes and adding 1 that does not equate to a prime: (3*3)+1=10.

      --
      "Someone needs to talk to the tree of liberty about its ghoulish drinking problem." by ohnocitizen
    96. Re:Open set it is! by phantomfive · · Score: 1

      It only guarantees that you will have a number that is not divisible by any of the numbers you multiplied together. Thus if you multiply every prime number in existence together, and add 1, you will end up with a number indivisible by every prime number in existence.

      --
      "First they came for the slanderers and i said nothing."
  8. Re:'2' - wrong, its 42 by Anonymous Coward · · Score: 2, Funny

    That would make it 41?

  9. Conclusion seems wrong by Anonymous Coward · · Score: 1

    That there are infinitely many pairs of prime number which are at most 70 million numbers apart does not guarantee that you'll find another prime number within 70 million from a given prime number. There are (infinitely many) prime numbers for which you'll find another one within 70 million, but it's not true for every prime number, so there can still be increasingly large gaps.

    1. Re:Conclusion seems wrong by wonkey_monkey · · Score: 0

      There are (infinitely many) prime numbers for which you'll find another one within 70 million, but it's not true for every prime number

      Nope, it is true. Consider only the prime pairs. There are, we now know, no gaps larger than 70 million. Add the rest of the prime numbers and there can still be no gaps larger than 70 million.

      --
      systemd is Roko's Basilisk.
    2. Re:Conclusion seems wrong by locofungus · · Score: 2

      Not only can there be increasingly large gaps but there are increasingly large gaps.

      (N+1)!+2 to (N+1)!+N+1 are N consecutive composite numbers - divisible by 2..N+1 respectively.

      Therefore there are arbitrarily long sequences of composite numbers.

      Tim.

      --
      God said, "div D = rho, div B = 0, curl E = -@B/@t, curl H = J + @D/@t," and there was light.
    3. Re:Conclusion seems wrong by Anonymous Coward · · Score: 0

      Maybe I wasn't clear.
      This is wrong: For all P prime exists P' prime greater than P with P'-P<=70000000. (i.e. maximum distance between two consecutive primes is less or equal 70000000)
      This is true: There exist infinitely many P prime such that there exists P' prime greater than P with P'-P<=70000000. (i.e. infinitely many prime pairs with distance less or equal 70000000)

    4. Re:Conclusion seems wrong by Anonymous Coward · · Score: 0

      Nope, OP was right. The statement is that for any N, there exists primes p and q greater than N such that the difference between p and q is less than 70 million. The statement is not that if p is prime then there will be a prime in the interval between p and p + 70 million. In fact, by considering 70 million factorial, you'll see that the latter statement is false.

    5. Re:Conclusion seems wrong by Anonymous Coward · · Score: 0

      Not only can there be increasingly large gaps but there are increasingly large gaps.

      (N+1)!+2 to (N+1)!+N+1 are N consecutive composite numbers - divisible by 2..N+1 respectively.

      Therefore there are arbitrarily long sequences of composite numbers.

      Have you considered the possibility that you might have misunderstood something? I mean, whenever I find that I have a trivial proof for something that has been an important open problem for decades (or centuries as in this case), the first question that I ask from myself is: "Why haven't the brilliant guys who have researched this problem before me found this solution?"

      The usual answer is that my proof doesn't work. The second most common thing is that I'm proving the wrong thing.

      Here, you are doing the second thing. You are proving that for each natural number n, there is a pair of primes with that many composite numbers between them. On the other hand, the article is proving that there's an infinite number of pairs of primes with a limited gap between them.

      It's quite obvious that the pairs involved in your proof are different from the pairs involved in the article's proof.

    6. Re:Conclusion seems wrong by locofungus · · Score: 1

      Have you considered the possibility that I might be replying to a particular comment in the parent my post was attached to?

      The comment in particular that I was replying to had:

      "but it's not true for every prime number, so there can still be increasingly large gaps."

      To which my reply said:

      "Not only can there be increasingly large gaps but there are increasingly large gaps."

      Tim.

      --
      God said, "div D = rho, div B = 0, curl E = -@B/@t, curl H = J + @D/@t," and there was light.
    7. Re:Conclusion seems wrong by Anonymous Coward · · Score: 0

      You're the one that's misunderstood.

      People seem to think this result means every prime is within 70 million of another prime. This is not the case. The grandparent tries to disabuse people of this notion by demonstrating that you can construct an arbitrarily long sequence of composite numbers, hence you can construct a sequence of 7,000,001 composite numbers, hence there must be a pair of primes that are more than 70 million apart.

      The actual result, as you seem to realise, but many other people didn't, is that for any number there is some pair of prime numbers both greater and within 70 million of each other. There's room for both of these constructions because infinity.

    8. Re:Conclusion seems wrong by gnasher719 · · Score: 1

      Nope, it is true. Consider only the prime pairs. There are, we now know, no gaps larger than 70 million. Add the rest of the prime numbers and there can still be no gaps larger than 70 million.

      Blatant nonsense. Not only has someone already posted how to find 70 million consecutive non-primes, but it has been long proven that the number of primes less than N is about N / ln (N) (the ratio of number of primes = exp (70,000,000) the _average_ gap between primes is more than 70,000,000.

    9. Re:Conclusion seems wrong by wonkey_monkey · · Score: 1

      finds that there are infinitely many pairs of primes that are less than 70 million units apart.

      Doh. I read "pairs of primes" as "twin primes" - as in pairs of twin primes less than 70 million apart.

      --
      systemd is Roko's Basilisk.
    10. Re:Conclusion seems wrong by wonkey_monkey · · Score: 1
      Yeah, it confused me as well (see below...)

      means that that the gaps between consecutive numbers don't keep growing forever.

      What I see now is that it really means that while gaps can (and presumably do) keep to a general trend of growth, there will always be a gap of less than 70 million somewhere up ahead.

      --
      systemd is Roko's Basilisk.
  10. Primes closer together? by allypally · · Score: 0, Interesting

    Also means that there must be at least one prime in every sequence of 70 million integers.

    Means I can put an upper bound on my prime search script....If it searches 70,000,001 consecutive integers and claims to have found no primes, I'll know the bugged little script is lying.

    That's a helpful debugging heuristic. Thank you, Pure Math.

    1. Re:Primes closer together? by ledow · · Score: 1

      I'm not sure it does.

      "there are infinitely many pairs of primes that are less than 70 million units apart"

      It just means that the individual primes in the pairs must be 70 million units apart (from each other) or less. (and where the hell did "unit" come from? Do they mean integer?)

      Not that single primes must be. Not that one pair from the next must be. You could have twin prime pairs at any interval so long as the other half of the pair is within 70 million integers.

      Unless I'm reading it wrong. The thing about maths is, you have to be VERY precise and not leap into assumptions without testing them very, very, very thoroughly first. 99.99999% certain isn't good enough for a mathematician.

    2. Re:Primes closer together? by As_I_Please · · Score: 5, Informative

      Not quite.

      The new result, from Yitang Zhang of the University of New Hampshire in Durham, finds that there are infinitely many pairs of primes that are less than 70 million units apart...

      This means that for every prime p such that p+q (where q is less than 70 million) is also prime, there exists another prime r bigger than p such that r+s (where s is also less than 70 million) is also prime. Note that there is no limit to the distance between p and r.

    3. Re:Primes closer together? by Anonymous Coward · · Score: 1

      There is an easy proof that there can be arbitrarily large gaps between consecutive primes:

      For example, suppose you want to find a prime gap of size at least 1000000. Let N = 1000000!, so,
      in particular, N is divisible by every integer from 2 to 1000000. Then N + 2 isn't prime because it's
      divisible by 2, ..., N + 157 isn't prime because it's divisible by 157, ..., N + 1000000 is divisible by
      1000000. So there are 999999 consecutive composite numbers from N + 2 to N + 1000000. The
      gap between the largest prime before them and the smallest prime after them is at least 1000000.

      What the new proof shows is that as we go through the primes, the prime gaps aren't eventually
      all huge: there will always be some further prime gaps that are smaller than 70000000.
      This is perhaps more impressive when you realize that the Prime Number Theorem says that
      the average size of the gaps does get as big as you like: for billion-digit numbers, the
      average size of the gap between primes is about 2.3 billion. Nevertheless, close pairs of primes
      will still occasionally occur.

    4. Re:Primes closer together? by Anonymous Coward · · Score: 0

      Nope. Large intervals without such pairs are allowed, similar as that there is no prime pair with distance two in the range 90-96. However, there will always be a prime pair with distance two later on (e.g. 101,103) , if the twin prime conjecture is correct.

      Similarly, if Yitang Zhang is right, even if you find a 1e20 big interval without primes (I did not check if this exists), after that, there will be a prime number followed by another prime within 70 million integers.

    5. Re:Primes closer together? by bigg_nate · · Score: 1

      Not quite.

      What he proved is that given any number n, there exist prime numbers p and q that are (1) greater than n and (2) within 70 million of each other. For example, for a particular n, perhaps p = n + 1,000,000,000 and q = n + 1,069,000,000.

      This is not quite the same as saying there's necessarily a prime between n and n + 70,000,000. In fact, since the average density of primes decreases as 1 / log(n), I'm pretty sure that statement is known to be false.

    6. Re:Primes closer together? by Anonymous Coward · · Score: 0

      Following sibling post, the interval from N!+2 to N!+N is a range of N-1 numbers, all trivially composite. Set N = 1e20+1 and you are done.

    7. Re:Primes closer together? by Kjella · · Score: 2

      Yes, it's more like this: Imagine if you took a sack of marbles and spread them infinitely thin, you'd expect that the distance between any two marbles to also grow to infinity. This is proof that primes are not like this, no matter how thin they're spread they'll cluster in pairs less than 70 million apart. The conjencture is that you'll always find another pair 2 units apart (like 5 and 7, 11 and 13 etc.) no matter how big the numbers get.

      --
      Live today, because you never know what tomorrow brings
    8. Re:Primes closer together? by gnasher719 · · Score: 2

      Yes, it's more like this: Imagine if you took a sack of marbles and spread them infinitely thin, you'd expect that the distance between any two marbles to also grow to infinity. This is proof that primes are not like this, no matter how thin they're spread they'll cluster in pairs less than 70 million apart. The conjencture is that you'll always find another pair 2 units apart (like 5 and 7, 11 and 13 etc.) no matter how big the numbers get.

      It would of course depend on _how many_ marbles there are and _how thin_ they are spread. In the case of prime numbers, there are still so many of them that we _expect_ two that are close together from time to time.

      The number of primes If you pick a random integer around N, the chance that it is a prime number is about 1 / ln (N). If you pick an odd number, the chance is about 2 / ln (N). Now if you pick an odd number x, then the chance that x is prime is about 2 / ln (N), the chance that x + 2 is prime is about 2 / ln (N), both are not quite independent (if x is not divisible by 3, then x + 2 is more likely divisible by 3, same for 5, 7 etc. ), but the chance that (x, x+2) is a twin prime pair is roughly 1 / (ln (x))^2.
      The sum of (1 / ln (x))^2 over all even integers x diverges; if you sum it for all x The same is true for every pattern like (x, x+2, x+6), or whatever pattern you choose, except for those patterns where it is obvious that these primes can't exist, like (x, x+2, x+10), where one of the three numbers must be divisible by 3.
      Proving it is of course an entirely different matter. However, if there are infinitely many pairs of primes with a gap
      So if you take the (x, x+2) conjecture aka twin prime conjecture, the (x, x+4) conjecture, the (x, x+6) conjecture and so on, which are _all_ assumed to be true, then we now know that at least one of them _is_ indeed true.

    9. Re:Primes closer together? by gnasher719 · · Score: 1

      Bloody html.

      The number of primes less than N is about N / ln (N).

      If you pick a random integer around N, the chance that it is a prime number is about 1 / ln (N). If you pick an odd number, the chance is about 2 / ln (N).

      Now if you pick an odd number x, then the chance that x is prime is about 2 / ln (x), the chance that x + 2 is prime is also about 2 / ln (x), both are not quite independent (if x is not divisible by 3, then x + 2 is more likely divisible by 3, same for 5, 7 etc. ), but the chance that (x, x+2) is a twin prime pair is roughly 1 / (ln (x))^2.

      The sum of (1 / ln (x))^2 over all even integers x diverges; if you sum it for all x less than N then the sum is more than N / (ln (N)^2, which diverges.

      Something similar is true for every pattern like (x, x+2, x+6), or whatever pattern you choose, except for those patterns where it is obvious that these primes can't exist, like (x, x+2, x+10), where one of the three numbers must be divisible by 3.

      Proving it is of course an entirely different matter.
      However, if there are infinitely many pairs of primes with a gap less than 70,000,000 then at least one of the possible gaps must come up an infinite amount of times (because 70 million times a finite number is still finite).

      So if you take the (x, x+2) conjecture aka twin prime conjecture, the (x, x+4) conjecture, the (x, x+6) conjecture and so on, which are _all_ assumed to be true, then we now know that at least one of them _is_ indeed true. There is a K 70,000,000 such that there are infinitely many pairs of primes (x, x + K).

    10. Re:Primes closer together? by Anonymous Coward · · Score: 0

      In fact, it is easy to construct a sequence of 70 million integers which are all composite. Let N = 70,000,001. Then

      N!+2, N!+3, N!+4, ..., N!+N-2, N!+N-1, N!+N

      is a sequence of 70 million composites.

  11. Amusing. by idbeholda · · Score: 0

    I've been using a similar practice for a few years when implementing the API database for TT Livescan.

    http://tot-ltd.org/API/
    http://tot-ltd.org/API/main.db

    Use prime numbers 2 or higher to map API calls to a "number" specific family (add the collective values of the API calls from main.db, then convert the value to hexadecimal), based on the API functions (Windows 3.11 to Windows 7). The rate at which it can catch malware based on API calls alone is grotesquely efficient.

    1. Re:Amusing. by cryptizard · · Score: 1

      You mean multiply? If you add then you get ambiguous cases, i.e 2+3=5 where you don't know if it was just five or if it was two and three. If you want to add you would have to do powers of two. Pretty cool, but it has nothing to do with the article :D

  12. Re:TFS by Raenex · · Score: 5, Funny

    This is probably the worst written summary that I have ever read on Slashdot.

    You must be new here.

  13. Conclusion wrong by enriquevagu · · Score: 4, Informative

    "the existence of any finite bound, no matter how large, means that that the gaps between consecutive numbers don't keep growing forever"

    Actually, I disagree with the unfortunate writing of the sentence. The gaps between consecutive prime numbers are variable, and on average they DO tend to keep growing forever. This is a widely known result, the density of prime numbers decreases as the numbers grow. However, since the gap between consecutive primes is variable and it does not follow a regular function (otherwise, it would be very easy to calculate prime numbers), even with a very low density of prime numbers we can find a pair of consecutive prime numbers with a gap of only 2.

    The problem under study is not wether the gap between consecutive primes keeps growing forever (which is true only on average, considering a long secuence of integers), but wether there are infinite such pairs of primes with gap 2. The new result found says that there exist infinite pairs of primes with gap 70M or less. However, this does not imply at all that no consecutive pairs of primes with gap > 70M exist (which, in fact, they do).

    1. Re:Conclusion wrong by Anonymous Coward · · Score: 0

      It depends. The exact interpretation of "the gaps between consecutive [prime] numbers don't keep growing forever" is true. There can not be an infinite sequence of increasing gaps between consecutive prime numbers. In any infinite sequence of gaps between consecutive prime number, there are infinitely many gaps which are less or equal 70000000. That means there is no point from which the gaps only increase.

      However, the other interpretation, that the gaps grow for a while but are bounded, is wrong.

    2. Re:Conclusion wrong by tulcod · · Score: 2

      It /is/ very easy to calculate prime numbers. The apparently hard thing is to list them all, and to factorize non-prime numbers.

    3. Re:Conclusion wrong by Anonymous Coward · · Score: 0

      To a computer scientist, easy doesn't mean you can write down an easy algorithm which does the job. To us it means that running the algorithm has to be feasible. There is no such algorithm for big prime numbers, hence the attention being paid to the search for ever bigger largest known prime numbers.

    4. Re:Conclusion wrong by tulcod · · Score: 2
    5. Re:Conclusion wrong by Anonymous Coward · · Score: 0

      For large numbers, these all require a lot of processing time. Often only probable primes are generated. That should tell you that there's some problem with provable prime generation. There's even a $150000 prize on the first person or group to come up with a prime number that is at least 100000000 digits long. If generating large primes is easy, what are you waiting for?

    6. Re:Conclusion wrong by Anonymous Coward · · Score: 0

      The new result found says that there exist infinite pairs of primes with gap 70M or less.

      It would indeed haves been better if the summary made more clear that this is the gap between the two primes that form the pair instead of any other gap.

    7. Re:Conclusion wrong by Anonymous Coward · · Score: 0

      According to this research, you can take any number that's 100000000 digits long, then the next 70 million numbers, and submit them all.

      One of them will be prime.

    8. Re:Conclusion wrong by Anonymous Coward · · Score: 0

      After further reading, I believe I misunderstood.

    9. Re:Conclusion wrong by Raenex · · Score: 1

      There's even a $150000 prize on the first person or group to come up with a prime number that is at least 100000000 digits long. If generating large primes is easy, what are you waiting for?

      Oh, so you're only asking for a prime number with 100 million digits? Yes, if you make the number large enough, many algorithms that are O(N) are infeasible in practice. In the meantime, as far as I know there is no practical reason to need primes of this size.

    10. Re:Conclusion wrong by Demonantis · · Score: 1

      After reading this comment I think I get it now. Thanks for that, but man does my head hurt.

  14. Re:First? by Anonymous Coward · · Score: 0

    You sound mad.

  15. Re:First? by Chrisq · · Score: 1, Offtopic

    good to know that while the country is almost 17 trillion in debt that such important endeavors take priority

    What do you mean - they can now say "17 trillion dollars in debt is close to two dollars in debt when you consider infinity, the mathematicians say so!"

  16. Re:'2' - wrong, its 42 by Anonymous Coward · · Score: 0

    you obviously have never watched 'the hitch hiker guide to the galaxy'

  17. Re:'2' - wrong, its 42 by Anonymous Coward · · Score: 0

    Watched? Hand in your geek card!

  18. Re:'2' - wrong, its 42 by tbird81 · · Score: 2

    Yeah, that movie right?

    Saying 42 might have been funny if they were researching a number that had some abstract relationship to the meaning of life - but even then it would be predictable and overused.

    But it's not funny just to answer 42 to any mathematics question. It's not funny at all.

    42

  19. Re:First? by Anonymous Coward · · Score: 0

    That's because it is.

  20. Twin Primes by spaceman375 · · Score: 2, Funny
    My favorite example of twin primes is "867-5309/Jenny" performed by Tommy Tutone in 1982.

    Thanx xkcd!

    --
    On the one hand you take life too seriously, and on the other, you do not take playful existence seriously enough. Seth
  21. Why do we believe the twin prime conjecture? by bigsexyjoe · · Score: 1

    Do we have good reasons to think it's true? Or do we just see lots of twin primes and figure they never run out?

    1. Re:Why do we believe the twin prime conjecture? by mjr167 · · Score: 0

      A better question is why does it matter?

    2. Re:Why do we believe the twin prime conjecture? by cryptizard · · Score: 1

      Sort of, in that it would be really weird if it wasn't true. It is generally thought that primes follow a certain distribution (i.e. any given odd number has a certain probability of being prime, decreasing as the number gets larger). We know there are an infinite number of primes. That means this probability never reaches zero. If it is always non-zero, then there is also always some non-zero probability that we get two primes in a row (just the square of the probability). If there were not infinite twin primes, then it would mean that the "prime event" is not i.i.d., which is not impossible but would be strange. For there to be a point where there ceases to be twin primes would imply some weird arbitrary limit, beyond which primes don't want to "clump" any more.

    3. Re:Why do we believe the twin prime conjecture? by Anonymous Coward · · Score: 0

      Yes, there is very convincing evidence for believing the twin primes conjecture. Hardy and Littlewood back in the 1920s formulated a famous heuristic that predicts how many pairs of twin primes there are up to x: it is about x/(log x)^2 times a certain constant that can be accurately computed. An even better integral approximation follows from the same method, much like Li(x) versus x/log x for the Prime Number Theorem.

      Back in the 1920s, there were hand-computed tables of twin primes, but not much numerical evidence to support this conjecture: it was more like an educated guess (assume that primes behave randomly except in the obvious ways they are not) that led to a precise prediction. Since then, other people (such as Thomas Nicely who discovered the Pentium bug while doing calculations with twin primes) have calculated the twin primes up to 10^15 and found the actual count to agree with the Hardy-Littlewood prediction to within one part per million.

      So it's not just that we see lots of twin primes. It's that the number of twin primes we see falls EXACTLY in line with our expectations (when I say exactly I don't mean there is no error, but that we also have predictions about how large the error will be on average). If the prediction continues to be this accurate for larger numbers, then there surely would be infinitely many twin primes.

  22. Re:'2' - wrong, its 42 by gatkinso · · Score: 1

    You sound like the life of the party.

    --
    I am very small, utmostly microscopic.
  23. Trivially constructive by ebcdic · · Score: 1

    N!+1 either is prime or has prime factors not in 1...N. Try factorizing the integers N+1 ... N!+1 in turn until you come to one that is prime.

    1. Re:Trivially constructive by locofungus · · Score: 1

      N!+1 either is prime or has prime factors not in 1...N. Try factorizing the integers N+1 ... N!+1 in turn until you come to one that is prime.

      Why on earth would I do that?

      PRIMES is in P. So if I want a prime bigger than N I'd start testing numbers of the form N+s for increasing s for primality until I found one. (Actually for very large values of N there are better candidates to test which have special case tests for primality that are particularly fast)

      I wouldn't try to find a prime bigger than N by trying to factor a number greater than N! While the algorithmic complexity of factoring isn't known it's almost certainly not in P.

      Tim.

      --
      God said, "div D = rho, div B = 0, curl E = -@B/@t, curl H = J + @D/@t," and there was light.
    2. Re:Trivially constructive by locofungus · · Score: 1

      Oops, sorry, I misread your algorithm.

      But it still doesn't help. You've assumed that it will terminate (i.e. there is a prime larger than N). So you cannot use it to prove that there is a prime larger than N.

      Tim.

      --
      God said, "div D = rho, div B = 0, curl E = -@B/@t, curl H = J + @D/@t," and there was light.
    3. Re:Trivially constructive by ebcdic · · Score: 1

      I'm pointing out that the existing proof is constructive, not giving another proof.

    4. Re:Trivially constructive by locofungus · · Score: 1

      http://www.math.psu.edu/sellersj/courses/math035/fa11/handouts/07_infinitely_many_primes.pdf

      1) This proof is not a âoeconstructiveâ proof. We do not build an infinite list of primes in the process. This is a proof by contradiction.

      --
      God said, "div D = rho, div B = 0, curl E = -@B/@t, curl H = J + @D/@t," and there was light.
    5. Re:Trivially constructive by ebcdic · · Score: 1

      it provides the contradiction by constructing a list of numbers at least one of which must be a new prime. It's simple to test each of them. If you want to construct an infinite list of primes, just repeat indefinitely.

  24. Re:'2' - wrong, its 42 by IndustrialComplex · · Score: 2

    He would be, but he doesn't get invited to those sorts of parties.

    --
    Out of modpoints but really liked a post? 1BDkF6TtmmeZ3yqXbz9yhdYVqRYnwFoXDj
  25. Re:Primes are precious by Anonymous Coward · · Score: 0

    Do you seed your encryption keys with non-prime numbers?

  26. The Question by wonkey_monkey · · Score: 5, Informative

    Researchers hoping to get '2' as the answer

    In case anyone's as confused as I was, I think I've finally figured out The Question, which is:

    What is the smallest gap between consecutive primes which occurs infinitely many times?

    Or something like that. Everyone thinks it's probably 2.

    --
    systemd is Roko's Basilisk.
    1. Re:The Question by Anonymous Coward · · Score: 0

      No. Can it be proven that there are infinite pairs of primes spaced nn apart, where nn is 2? Distant second prize for nn of your choosing.

    2. Re:The Question by wonkey_monkey · · Score: 1

      What do you mean, "no"? The article already posited "2" as the hoped for answer, which doesn't make sense as an answer to your question. Also what's with using a double-character name for your variable? Crazy.

      --
      systemd is Roko's Basilisk.
    3. Re:The Question by c++0xFF · · Score: 1

      If the Answer is 42, then maybe you found the Question to Life, the Universe and Everything. Douglas Adams fans rejoice!

    4. Re:The Question by Anonymous Coward · · Score: 0

      It has to be.

      This isn't rigorous, but my view:

      Prime numbers are those which fall through the cracks when plotting repeated sequences on a number line (2,4,6... etc)
      As the old proof goes, to demonstrate that there are an infinite number of primes: Multiply the first N primes together then add 1 - the result is a number not previously divisible by any of the first N primes.

      My reasoning - why doesn't that also hold for "multiply the first N primes together then SUBTRACT 1", with the notable exception of "1" as that's only divisible by itself.

      Multipling the N primes together locates a nexus, but the immediately adjacent numbers cannot be divided easily.

      2*3 = 6, 5 & 7 are primes
      2*3*5 = 30, 29&31 are primes
      2*3*5*7 = 210, 211 is prime but 209 isn't. (it's 19*11)

      Ah hell. Well, still...

    5. Re:The Question by wonkey_monkey · · Score: 1

      This isn't rigorous, but my view:

      Conjectures don't stand or fall on "views".

      As the old proof goes, to demonstrate that there are an infinite number of primes: Multiply the first N primes together then add 1 - the result is a number not previously divisible by any of the first N primes.

      But that doesn't mean it's prime.

      My reasoning - why doesn't that also hold for "multiply the first N primes together then SUBTRACT 1", with the notable exception of "1" as that's only divisible by itself.

      It does hold - you do end up with another number which is not divisible by any of the first N primes. But, again, that doesn't make it a prime.

      --
      systemd is Roko's Basilisk.
  27. not sure... by Toonol · · Score: 1

    Ok, this isn't rigorous at all (obviously), but it seems to me that if the size of the gap continuously grew, but fluctuated randomly, you would still have an infinite number of primes close together even though the average distance between them never stopped increasing. They would become fewer and fewer, but never stop, and hence would be infinite.

    Not doubting the guy's work, but I'm doubting the summary's "the gaps between consecutive numbers don't keep growing forever."

  28. Re:'2' - wrong, its 42 by SupplyMission · · Score: 1

    Exactly this.

    Also, I was not in the mood to handle these parrotsheep who bleat out, "42! Get it?? Haha!" on cue, any time there is any remotely math-related discussion taking place.

    Also, I see what you did there at the end, but I will not gratify it with a response.

  29. Newbie question by V!NCENT · · Score: 1

    I have a question: (excuse me for the realy bad formatting)

    If the result of prime numbers (plotted), can be formulated as e^x, where Xaxis = numbers (zero to infinity) v Yaxis = [amount of unique distances observed] ;
    and plotted against the plotting of prime numbers themselves ;
    and plot a formula_3 that averages the coordinates that both euclidean functions output, towards infinity, through where they almost intersect ;
    and form a formula_4 that equals the offset of the two euclidean function, relative to formula_3, towards infinity ;
    and plot two fomulas that offset formula_3 by formula_4 in both 'directions' ;
    then Doesn't it make a lot of sense?

    I'm terribly sorry for my bad mathmetics and would welcome a rant in which someone would explain why and where I'm making a mistake.

    --
    Here be signatures
    1. Re:Newbie question by dcollins · · Score: 2

      "Doesn't it make a lot of sense?"

      No.

      --
      We know where leadership by an anti-intellectual "strongman" who scapegoats minorities and likes boisterous rallies goes
    2. Re:Newbie question by Anonymous Coward · · Score: 0

      You're first sentence makes no sense. Where did you get e^x from. Are you trying to say that in the numbers from 1 to 1000, there are e^1000 unique distances observed? You sir are a moron.

    3. Re:Newbie question by V!NCENT · · Score: 1

      No, but that's not the point.

      What is do is play Sudoku with knowledge. And the problem I'm usualy having with math (aside from not having a very broad understanding of the logical implementation) is that it can become a very... very... very tough (from my perspective) Sudoku puzzle.

      But the real problem I'm having is just not giving up. That, combined with so little understanding of it, drives me nuts. So yes; you're right.

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    4. Re:Newbie question by Anonymous Coward · · Score: 0

      I don't know if English is your second language (if it is, maybe try finding a mathematician or math professor that speaks the same language to discuss things with first, so there is one less language barrier), but what your wrote was nearly nonsensical word salad of math and non-math terms. Like any other field, math has its share of jargon. But one of the points of the jargon is it very precisely conveys what is meant in a field where specifics matter a lot. Without that precision, people have to guess at what you are meaning or asking, over even worse, any possible legitimate meaning is lost like a needle in a haystack.

      The basics are at least easy to get access to. While there is plenty of stuff online, it might be hard to tell who is being sloppy and who is being precise if you are trying to learn jargon, etc. But for math up to calculus level, you can usually get textbooks really cheap if you live anywhere near a community college or university, as old versions end up in book stores. They are cheap because they are not useful in a course where homework problems are assigned out of a different version, but are just fine for learning math out of. Wikipedia is pretty good to learn a lot of random higher level math, as long as you already have a foundation and spend a lot of time clicking on links to make sure you know what a word means instead of just assuming something based on it looks like (there are a lot of higher level math jargon words that look like an every day word, but means something really specific and probably unrelated to the every day use).

      If you can get the communication part down, it makes it 100x easier to converse with someone with a math background, and hence much more likely they will put in effort into answering questions instead of just trying to figure out what you are saying (or in extreme cases assuming someone is a crackpot purposely using nonstandard terminology out of ignorance/spite/misdirection).

    5. Re:Newbie question by RockDoctor · · Score: 1
      Your Sudoku analogy is flawed in many many respects, but one clear one is this : Sudoku puzzles as published always have at least one solution , and you know that, because it's part of the rules of the game. But not all arrangements that look like Sudoku puzzles actually have a solution under the rules of the Sudoku game. however, there is no "easy" way of deciding whether a particular putative Sudoku puzzle has a valid solution, or doesn't. ("easy" meaning "No way that is easier than trying to solve the puzzle." Which isn't terribly hard. I like doing 16x16 Sudokus in hexadecimal : a factor of around 10 harder than a 9x9 one.)

      In mathematics, you don't ever know if the conjecture that you're trying to prove really is true, or false. Until you've proved it. You don't know if your pattern is a Sudoku, or a random jumble of numbers on a grid.

      For example, Fermat's famous Last Theorem has been proved true ; but given the detail of the work that was taken to achieve the proof, and that many of the tools were not discovered until long after Fermat's death. So Fermat's plea that "this margin is too small", is true (by a factor of several thousand), and his claimed proof was very probably wrong. Or maybe he did have a proof that is remarkably simpler than Wile's 1995 proof? Nobody knows.

      --
      Birds are not dinosaur descendants;birds are dinosaurs, for all useful meanings of "birds", "are" and "dinosaurs"
  30. Re:'2' - wrong, its 42 by PoolOfThought · · Score: 2

    Which is... back on topic... prime!

    --
    My present is the activity I am currently engaged in with the purpose of turning the future into a better past.
  31. How useful is this? by davidwr · · Score: 0

    Although 70 million seems like a very large number, the existence of any finite bound, no matter how large, means that that the gaps between consecutive numbers don't keep growing forever.

    I did not read the paper, but the statement above doesn't mean that gaps between consecutive groupings of prime numbers won't keep growing forever.

    It's basically like saying there are an infinite number of "star pairs" in the universe that are less than 70m light-years from each other. That doesn't mean that the spacings between these star-groups (let's call them "galaxies") isn't getting larger over some way of measuring (let's call that way "age of the universe").

    Perhaps the paper does make some guarantees in this area that aren't made in the simplified /. summary.

    --
    Knowledge is how to play a game, intelligence is how to win, wisdom is knowing what game to play.
  32. Re:First? by Anonymous Coward · · Score: 0

    That's because I am.

    Fixed that for me?

  33. From Infinity to 70 Million? by Anonymous Coward · · Score: 0

    We're half-way there!

  34. Re:'2' - wrong, its 42 by SleazyRidr · · Score: 0

    Yessiree! Forty one is a prime number. (Big whoop. Lots of numbers are prime.) I bet I could make more money if I just sold homework answers... Get out of here kid, you bother me.

  35. Polignac Conjecture by Anonymous Coward · · Score: 0

    Rather proving the twin prime conjecture (which is only for the case concerning prime numbers with a gap of n=2), is it more likely it is the first proof for any case of Polignac's conjecture (n = 70 million)? A large step though to proving the special case of twin primes.

    1. Re:Polignac Conjecture by wonkey_monkey · · Score: 1

      Well, yes, that's exactly what this is. Which is what the summary says.

      --
      systemd is Roko's Basilisk.
  36. Re:Primes are precious by similar_name · · Score: 1

    I only use irrational numbers as there are fewer rational numbers.

  37. This is a question? by suutar · · Score: 1

    I didn't think that "there's an infinite number of twin primes" was in question. Like so: Let S(k) be the set of all prime numbers less than or equal to k, where k is at least 3 [S(3) would be {2, 3}]. Let P be the product of them all. Then P+1 and P-1 are prime and not in S(k). Therefore S(P+1) is at least two larger than S(k) (and probably much more than 2; finding those others, that's the tricky part). Rinse, repeat. What part of this is difficult?

    1. Re:This is a question? by suutar · · Score: 1

      nevermind, I had a bad assumption (P+1 and P-1 are prime) because I'd never noticed a counterexample. But 2*3*5*7 = 210, and 209 is not prime.

    2. Re:This is a question? by dcollins · · Score: 1

      Good lesson: You're probably not going to solve a math problem that's been open for millennia with 3 lines of work and a snarky conclusion.

      --
      We know where leadership by an anti-intellectual "strongman" who scapegoats minorities and likes boisterous rallies goes
    3. Re:This is a question? by suutar · · Score: 1

      yeah, that's what made me go back and check it. Now if I could just delete the comment... oh well, as stupid posts go it could have been worse.

  38. How do you count the irrational numbers? by Anonymous Coward · · Score: 0

    You are only exchanging one problem for another.

  39. Re:'2' - wrong, its 42 by PoolOfThought · · Score: 4, Insightful

    Yes, but if you read the article, or hell, even the summary, then you'd know it was about primes.

    Some AC felt the need to make a lame '42' reference. Then, against all odds, it somehow managed to get back around to being on topic when someone else gave it a -1, thus rendering it a nicely prime 41. Then you came along and decided to be an ass. Well done.

    But wait! With 41 you don't just get an "on topic" prime number. You'll also find that 41 is actually a twin in the twin prime pair of (41, 43)! That's right, it is completely on topic... so.... nah nah nahnah nah.

    Now, as far as I can tell I've managed to make two relevant posts on the topic out of a seemingly impossible "42 duh duh" comment. On the other hand, you've managed only to be an asshole and contribute nothing other than bad karma. As far as you comment about making more money goes, I'm confused, who knows, maybe I got whooshed or missed a meme or something. Or maybe I've just been trolled. But, maybe you'd make more if you weren't such an asshole and instead just let people have a good time without trying to piss on 'em. Especially when it doesn't even matter.

    --
    My present is the activity I am currently engaged in with the purpose of turning the future into a better past.
  40. Elvish italic by epine · · Score: 1

    If the set of primes is finite, form the product of all primes and add 1, creating a number not divisible by any prime (making the number formed prime by definition) yet not included in the set of all primes by construction. At this point you can smoke some weed or you can begin to suspect that the set of primes is not finite.

    Let p = 10^-googolplex.

    With enough patience, you can win this lottery 100 times in a row, and you can do that as many times as you like.

    All this new result gives us is further evidence that in the unextinguished coincidence of short spacings, the distribution of primes resembles a random process. There's a structural reason why both N and N+1 are never prime at the same time. It appears, however, to be rather difficult to identify any other structure of the distribution of primes taking the form of permanently extinguished gap distances.

    Our list of viable gaps grows thin. (I did wish momentarily to mark that up as <e>thin</e> for Elvish italic.)

    1. Re:Elvish italic by Anonymous Coward · · Score: 0

      (making the number formed prime by definition)

      No.

  41. Re: Preprints not avaiable, but it seems legitimat by Anonymous Coward · · Score: 0

    You are not smart.

  42. Re:'2' - wrong, its 42 by SleazyRidr · · Score: 1

    Sometimes I get too far out with my humor, I apologise for making you feel that way.

    is.41.aprimenumber.com has something stupid like that about a lot of numbers.