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20 hours ago comment added Daniel Asimov The phrase "between A to B" is nonstandard English. It should be either "from A to B" or "between A and B". But neither of these locutions make clear whether A and/or B is included. To make that clear I would usually say "from A to B inclusive".
yesterday answer added Euro Vidal Sampaio timeline score: 4
Apr 8 at 12:57 answer added Euro Vidal Sampaio timeline score: 2
Apr 7 at 21:37 answer added P. Grabowski timeline score: 2
Apr 7 at 19:39 answer added Euro Vidal Sampaio timeline score: 2
Apr 3 at 18:28 answer added Euro Vidal Sampaio timeline score: 2
Mar 19 at 11:41 answer added Euro Vidal Sampaio timeline score: 5
Mar 3 at 22:27 answer added Euro Vidal Sampaio timeline score: 5
Mar 2 at 9:08 answer added Taras Banakh timeline score: 3
Mar 2 at 1:13 comment added Gerry Myerson @Gil, 2016 is the new 2006.
Mar 1 at 21:54 answer added Tomasz Kania timeline score: 5
Mar 1 at 17:21 answer added Euro Vidal Sampaio timeline score: 4
Feb 19 at 14:54 answer added Euro Vidal Sampaio timeline score: 8
Feb 5 at 17:48 comment added Gil Kalai @RolandBacher Let's update the requirement to: It was published or made publicly at least 10 years before the answer. (To avoid short-lasting conjectures.)
Feb 4 at 9:44 comment added Roland Bacher I was wondering about requirement 3 (before 2006): Start of Facebook etc.?
Aug 17, 2025 at 23:24 history edited Lucenaposition CC BY-SA 4.0
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Aug 24, 2024 at 16:49 answer added G. Melfi timeline score: 3
Aug 24, 2024 at 13:19 history protected Yemon Choi
Aug 24, 2024 at 13:10 comment added ming tsai Always a good idea to get another big list going. +1
Aug 24, 2024 at 13:08 answer added Joe Silverman timeline score: 9
Oct 27, 2023 at 4:28 answer added Pace Nielsen timeline score: 6
Oct 27, 2023 at 2:37 history edited Tim Campion CC BY-SA 4.0
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Sep 2, 2023 at 19:37 history edited Timothy Chow CC BY-SA 4.0
Updated the list
Apr 27, 2022 at 18:59 history edited Gil Kalai CC BY-SA 4.0
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Mar 26, 2021 at 8:58 comment added Dirk A conjecture from youtube.com/watch?v=BdHFLfv-ThQ is "$\pi^{\pi^{\pi^\pi}}$ is an integer". I don't know how old this conjecture is, but apart from its age it seems to fit the bill.
Mar 26, 2021 at 0:23 answer added Sam Hopkins timeline score: 6
Mar 25, 2021 at 16:13 answer added Timothy Chow timeline score: 17
Jun 15, 2020 at 7:27 history edited CommunityBot
Commonmark migration
Feb 27, 2020 at 10:57 history edited Gil Kalai CC BY-SA 4.0
a couple updates
Jan 16, 2020 at 14:59 answer added Gil Kalai timeline score: 15
Jun 2, 2019 at 18:28 answer added Daniil Rudenko timeline score: 30
Jul 29, 2018 at 23:47 comment added Maarten Derickx @FranzLemmermeyer I recently made a conjecture that if time goes to infinity trump will make a misspelling on twitter at some point and type abelian instead of a billion. The legend goes that this already happend and that this caused all multiplications at quantum level to be non-commutative, making the universe ridiculously hard to understand. On the other hand there are people thinking that trump tweeting about math is fake news.
Oct 24, 2017 at 5:05 answer added მამუკა ჯიბლაძე timeline score: 23
Apr 13, 2017 at 12:58 history edited CommunityBot
replaced http://mathoverflow.net/ with https://mathoverflow.net/
Mar 13, 2017 at 20:42 answer added Gerardo Arizmendi timeline score: 17
Mar 13, 2017 at 12:13 history edited Gil Kalai CC BY-SA 3.0
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Mar 13, 2017 at 11:20 vote accept Gil Kalai
Mar 13, 2017 at 11:20
Mar 13, 2017 at 10:19 answer added Mikhail Katz timeline score: 3
Mar 13, 2017 at 8:33 history edited Gil Kalai CC BY-SA 3.0
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Jan 29, 2017 at 18:55 comment added Gil Kalai Hmm, I see. This is indeed an outrageous conjecture about mathematics and its history :)
Jan 29, 2017 at 16:06 comment added Adam Spiers @GilKalai No, you misunderstood. I was proposing Fermat's quote about his Last Theorem as an answer to the question, not the Theorem itself. The implicit conjecture that there exists a marvellous proof which would have been attainable before 1621 is not settled (point 2), and IIUC is widely believed to be false.
Jan 26, 2017 at 17:28 comment added Gil Kalai Adam, this was indeed a conjecture but it does not fit the question because: a) It was settled (point 2), b) it was not believed to be false (point 1). But I agree that beside the formalities Fermat's conjecture and Fermat's narrow margin claim were quite outrageous!
Jan 26, 2017 at 16:09 comment added Adam Spiers [Disclaimer: I haven't really done any serious maths since my degree many moons ago, and yes, I arrived here via the sidebar.] I'm surprised noone mentioned Fermat's famous "I have discovered a truly marvelous proof of this, which this margin is too narrow to contain" quote. I guess it's not technically a conjecture, but there's an implicit conjecture in there that there exists a marvellous proof which would have been attainable before 1621, and this fits all the criteria of the question, as well as being presumably in keeping with the spirit of the question.
Jan 25, 2017 at 10:09 comment added Gil Kalai Hi Damien, I agree with that. I also agree with Timothy's comment regarding unsettled conjectures. I am a little worried that adding settled conjectures would have made the question too board (but those can be mentioned in comments and also in other questions.)
Jan 25, 2017 at 3:36 comment added Damien Why 2006? It seems rather arbitrary. Perhaps instead "is at least 10 years old" which will allow for more recent "outrageous" answers as time goes on.
Jan 24, 2017 at 16:24 comment added Gil Kalai Dear Terry and Saal, indeed "all groups are sofic" is a famous conjecture which might be suitable. The Casas-Alvero conjecture strikes me as a good example as well but I dont know anything about it.
Jan 24, 2017 at 13:37 comment added Gil Kalai @Nzall, certainly it could be a good idea to add elementary explanations for at least some of the answers. It is not so easy but worth the effort.
Jan 24, 2017 at 11:31 comment added Nzall @GilKalai The biggest consequence is that the question gets a lot of new readers, votes, comments and potentially answers, many of which haven't had much more than high school or maybe first grade college education on the topic. Making the topic a bit more understandable for those users may introduce them to aspects of mathematics they didn't know exist and may encourage them to look further on the site.
Jan 24, 2017 at 11:26 comment added Nzall @GilKalai It means that the question has had enough activity on this site to be viewed as a "hot network question", which in turn means that it's eligible to appear in the list of questions which appear in the sidebar, beneath the meta highlights and the linked questions. This list is effectively a "best of Stack Exchange", and a lot of people tend to check out the questions on that bar, especially if the title is interesting or (like this question) clickbaity. It means that a lot of users from other exchanges on the network will look at the question and potentially give their input.
Jan 24, 2017 at 11:15 comment added Gil Kalai Dear @Nzall , what does it mean to reach the sidebar?
Jan 24, 2017 at 10:19 comment added Nzall This question reached the sidebar and as such has received a large influx of people who usually don't visit this site. Many conjectures in here are described in ways only mathematicians can understand them. I was wondering if the people who posted an answer already could clarify it in a way that people who aren't well versed in math could understand the conjecture?
Jan 22, 2017 at 21:26 comment added Timothy Chow @GilKalai : It's sort of too late now, but I wonder if another (and possibly better) way to phrase your question would be, what conjectures were regarded as impossibly bold or optimistic at the time they were first made? This would allow for both conjectures that have been settled and conjectures that are still open. It would also allow for bold conjectures that we've gotten used to but that were considered outrageous at first. And it would eliminate statements that nobody has ever believed.
Jan 22, 2017 at 10:42 comment added Gil Kalai Dear user36212, yes we both regards the conjectures (both for Boolean functions and for graphs) as fairly outrageous and would be very interested in counterexamples. Dear Timothy and Todd, these are good examples and I am certainly not too fussed about meeting all my conditions.
Jan 22, 2017 at 9:46 answer added DKal timeline score: 10
Jan 21, 2017 at 23:40 comment added Saal Hardali I'm far from being an expert on this but perhaps Casas-Alvero conjecture is relevant. en.wikipedia.org/wiki/Casas-Alvero_conjecture . Although the most outrageous aspect of it is probably the date it was first conjectured (2001 !!!).
Jan 21, 2017 at 22:59 comment added Terry Tao Not an expert on this subject, but "all groups are sofic" might potentially qualify here.
Jan 21, 2017 at 22:43 answer added tomasz timeline score: 55
Jan 21, 2017 at 21:23 answer added Greg Martin timeline score: 38
Jan 21, 2017 at 1:05 answer added Jeff Strom timeline score: 17
Jan 19, 2017 at 23:58 comment added user36212 The Kahn-Kalai conjecture (the general one for Boolean functions) almost qualifies here, doesn't it
Jan 19, 2017 at 18:37 answer added Jan-Christoph Schlage-Puchta timeline score: 25
Jan 19, 2017 at 4:51 answer added dhy timeline score: 35
Jan 19, 2017 at 2:36 comment added Todd Trimble @TimothyChow The Tao example is a really good one (and with ample documentation), even if it doesn't meet all the conditions of the OP.
Jan 18, 2017 at 21:59 comment added Timothy Chow This one doesn't count because it status is settled, but from what I understand of the history of mirror symmetry, when the physicists first proposed it, Yau for one initially thought that it was too outrageous to be true. Along similar lines, I believe that Tao initially thought that the phenomenon of compressed sensing couldn't possibly be true, and that the Candes-Romberg-Tao paper was born out of Tao's attempts to find a disproof.
Jan 18, 2017 at 20:52 answer added mch timeline score: 15
Jan 18, 2017 at 18:10 answer added Adam Przeździecki timeline score: 48
Jan 18, 2017 at 13:58 answer added Wojowu timeline score: 42
Jan 18, 2017 at 13:40 answer added Mare timeline score: 11
Jan 18, 2017 at 13:33 answer added Rodrigo A. Pérez timeline score: 18
Jan 18, 2017 at 5:40 comment added მამუკა ჯიბლაძე I agree with Theo on that. E. g. Socrates was, I think, The asker number one. The way I understand it, the question is about conjectures of Socratic quality. If the things Socrates asked would be only pedagogic challenges and not the things he really burningly wanted to know, he would not be Socrates. And recall what happened to him. By the way there is a Socratic badge here on MO. A golden one ;)
Jan 18, 2017 at 5:39 comment added Gerry Myerson @Sam, I don't know about "philosophical", but I think there are good mathematical reasons for Collatz to be true.
Jan 18, 2017 at 5:39 comment added Franz Lemmermeyer What's next - a big list with Trump tweets concerning mathematics? Does this outrageous conjecture of mine count as an example?
Jan 18, 2017 at 4:56 comment added Sam Hopkins I feel like a number of famous, "elementary" conjectures, while often believed to be true, have no particular (philosophical) reason to be true, and thus from a cynical perspective might be described as likely false. Examples are the Collatz conjecture (en.wikipedia.org/wiki/Collatz_conjecture) and the union-closed sets conjecture (en.wikipedia.org/wiki/Union-closed_sets_conjecture)
Jan 18, 2017 at 3:51 answer added Joël timeline score: 68
Jan 18, 2017 at 3:18 answer added Jason Rute timeline score: 53
Jan 18, 2017 at 0:30 comment added Gerhard Paseman @Theo, in which case, let's rewrite the question to fit both a good intent of the asker and the good intent of MathOverflow. As it is currently written, I am not sure either is achieved. Gerhard "Being Ridiculous Can Serve Research" Paseman, 2017.01.17.
Jan 17, 2017 at 23:36 comment added Theo Johnson-Freyd And besides, I will learn things from reading it!
Jan 17, 2017 at 23:36 comment added Theo Johnson-Freyd @GerhardPaseman I think it is not too uncommon for good mathematicians, working in or near an area, to nevertheless not know about various conjectures. Especially if there has been recent development in tangentially-related areas, this type of list very well might lead to some of these conjectures being refuted. I support keeping the question open.
Jan 17, 2017 at 23:20 history reopened Lucia
Joel David Hamkins
Carlo Beenakker
Joseph Van Name
Daniel Loughran
Jan 17, 2017 at 23:02 comment added Gerhard Paseman It depends on the utility of this question. As a short term diversion to appeal to some of the forum community it serves quite well. As part of a database of questions and answers for future reference by the interested-in-mathematics consumer, I think it is too based in opinion and belongs on a blog. If the intent were to set some challenge questions to spur research, then I think the question should be reworded. As it stands now, it isn't much better than an opinion poll. Gerhard "MathOverflow Isn't Question And Opinion" Paseman, 2017.01.17.
Jan 17, 2017 at 23:00 review Reopen votes
Jan 17, 2017 at 23:24
Jan 17, 2017 at 22:49 comment added Lucia The answers below all look of interest, as does the question. And, to boot, this is Community Wiki. Why not keep it open?
Jan 17, 2017 at 22:42 history closed Denis Nardin
CommunityBot
Steven Landsburg
Igor Pak
Chris Godsil
Opinion-based
Jan 17, 2017 at 22:32 comment added Federico Poloni I don't understand what you mean by point 5. By definition, the negation of any commonly-believed-false statement is a commonly-believed-true statement, isn't it?
Jan 17, 2017 at 22:19 comment added Gerry Myerson I don't think anyone has disproved the ridiculous ideas that there are only finitely many Mersenne composites, or that all the decimal digits of $\pi$ from some point on are sixes and sevens, or that the partial quotients for continued fractions of real algebraic irrationals are always bounded, but I don't think anyone has proposed any of these ideas genuinely suggesting they are true.
Jan 17, 2017 at 22:14 answer added Gerry Myerson timeline score: 146
Jan 17, 2017 at 22:01 comment added Joel David Hamkins Incidentally, my question at mathoverflow.net/q/101821/1946 was asked in the spirit of this question (but it is too recent to qualify for your 2006 requirement).
Jan 17, 2017 at 21:59 comment added Gerry Myerson It seems to me there is a conflict between "you can't even disprove this ridiculous idea" and "the proposer proposes the conjecture genuinely suggesting that it is true", so it's not clear to me what exactly you're after.
Jan 17, 2017 at 21:18 history edited Gil Kalai CC BY-SA 3.0
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Jan 17, 2017 at 21:05 history made wiki Post Made Community Wiki by Todd Trimble
Jan 17, 2017 at 21:04 answer added T. Amdeberhan timeline score: 41
Jan 17, 2017 at 20:32 answer added Mark Lewko timeline score: 76
Jan 17, 2017 at 20:25 comment added Joseph O'Rourke There is a fine line between an outrageous conjecture and a bold conjecture. But still I see the spirit of your interesting question.
Jan 17, 2017 at 20:22 comment added Gil Kalai Right! I prefer examples where it is still now commonly believed that the conjecture is false and where the proposer proposes the conjecture genuinely suggesting that it is true. But these two requirements may be too harsh.
Jan 17, 2017 at 20:20 comment added Steve Huntsman "In this paper we try to convince the leader that there is no good reason to believe that the Jacobian Conjecture holds. Although there are several arguments in favor of this conjecture, we show that these arguments haven't got the power to justify the statement that the Jacobian Conjecture holds in general." -van den Essen (1997): seminariomatematico.unito.it/rendiconti/cartaceo/55-4/283.pdf
Jan 17, 2017 at 20:20 comment added T. Amdeberhan The Berman–Hartmanis conjecture.
Jan 17, 2017 at 20:19 review Close votes
Jan 17, 2017 at 22:42
Jan 17, 2017 at 20:12 comment added Gil Kalai Hmm, I think it qualifies as a comment but not as an answer. For an actual answer I would like "most likely false" to represent a large consensus and not a personal view of the answerer. But once I asked the question my view about what qualifies is just one view in the crowd...
Jan 17, 2017 at 20:08 answer added Joel David Hamkins timeline score: 134
Jan 17, 2017 at 20:03 comment added Steve Huntsman Does the Jacobian conjecture qualify?
Jan 17, 2017 at 20:00 answer added Carlo Beenakker timeline score: 97
Jan 17, 2017 at 19:55 history asked Gil Kalai CC BY-SA 3.0