# Links down to PlanetMath.org? [closed]

I have been unable to reach PlanetMath for a couple of days now. I get "This site can't be reached; planetmath.org took too long to respond" in my browswer.

Has something happened to the site? If so, this is disturbing, because Mathematics StackExchange answers sometimes link to proofs in PlanetMath.

• It is true that there are more than two hundred posts on Math.SE of that kind. Knowing something about the situation might well be useful to the Community. I'll see what can be learned. – hardmath Jan 26 '18 at 22:03
• I found that there have been at least a couple of previous periods of downtime. One involved a loss of domain registration at the end of 2012, and another was noted in a Math.SE answer from 2015, where substantial archived material was regurgitated. The Wayback machine suggests that the site may have been out for a considerable period since 2016. – hardmath Jan 27 '18 at 18:40
• Here's the most recent Wayback scrape of the PlanetMath homepage, from Dec. 27, 2017. There were scraping errors on some days in November and October, so perhaps there are ongoing issues related to the software transition begun in 2015. – hardmath Jan 27 '18 at 18:48
• The Talk:PlanetMath Wikipedia page has a more comprehensive account of downtime periods for the site. The frequency of outages seems to have significantly shaped the approach to curating the main Wikipedia article about PM. – hardmath Jan 28 '18 at 1:31
• Nice work, @hardmath! – amWhy Jan 28 '18 at 2:19
• "What happened to PlanetMath?" is decidedly not a question about Mathematics Stack Exchange or the Stack Exchange network. The fate of PlanetMath may have some bearing on the site, but questions about PlanetMath itself don't really fit here. In contrast, a question along the lines of "PlanetMath seems to be gone for good so what should we do with all the posts that link to PlanetMath?" would be a question about Mathematics Stack Exchange. (I'm not certain if it is time to ask that question yet, but at least it would be on topic.) – sie es er Jan 28 '18 at 18:34
• @palladium : As I commented, knowing more about the Planetmath situation would be useful to Math.SE. I had in mind exactly the potential for mitigating dead links you mention (also hinted at in the Question). – hardmath Jan 29 '18 at 14:23
• For what it's worth, I can't reach PlanetMath right now either. I'm using Google Chrome on Windows. – Mr. Brooks Jan 30 '18 at 22:53
• @hardmath: I think the point trying to be made here is that it is better to post a question that is explicitly relevant to Math.SE, rather than to post a question about PlanetMath in the abstract. – user14972 Jan 31 '18 at 8:41

This site has the best granularity for recent PlanetMath outages that I found so far.

There is a GitHub developer issues page for bug reports on the PlanetMath software, but it has been moribund since 2014, possibly because of software revisions in 2015. The Google Groups Planetary Developer forum is similarly moribund.

I reached out to Aaron Krowne, one of the PlanetMath founders, by email to see if more information is available. He replied promptly and CC'd a number of individuals most recently involved with the site's design and maintenance. Joe Corneli responded with information that included the Dec. 2016 site backup on GitHub.

Aaron mentioned that discussions have been underway for several months to "[get] the content up in a new environment." I'll try to stay involved and report back here when we could decide about efficiently revising dead links within existing Math.SE posts.

Update(01/31/18): We should have an estimate "in a few days" of WHEN "the dead links should come back to life." (Turns out they are only MOSTLY DEAD.) Discussion of whether extensive edits will be needed or desired can wait for that.

Update(07/09/18): The PlanetMath site came back online in March, 2018, and I optimistically thought that most of the links here would return to working. However (prompted by a recent Comment from Alex W.) sampling of these links shows that the simplified structure of the site probably leaves a large number of the existing links broken. A query shows about 800 links to planetmath.org. I've seen a couple of patterns in older versions of those links which won't work: linking to a folder planetmath.org/encyclopedia (189 cases) and linking to a folder planetmath.org/sites/default/files (25 cases). I'll refine my queries to give more detailed counts.

• 1) Currently, the PM main page only displays a "Welcome!" message and all mathematical content seems to have vanished. 2) It seems that "downanalyze.com" (referenced in your first link) no longer exists. – Alex M. Jul 8 '18 at 12:57
• @AlexM. Thanks for the note. I think their site is up in a new format, mainly different in not supporting online editing as the old format did. One has to drill down through the subject or alphabetic index to find mathematical content. For example, I picked this topic on probabilistic proof from the General subject index. When I last looked (March?) it seemed that a sampling of links from Math.SE were working reasonably, and I wasn't feeling much enthusiasm here on Meta.Math for pursuing the issue. – hardmath Jul 8 '18 at 14:49
• @AlexM. Sampling further suggests that some of our links were to underlying PDF files that are no longer supported. For example, I find PlanetMath has an article on Dynkin's lemma, but this Question linked to a PDF version in a way that is now broken. – hardmath Jul 8 '18 at 15:00
• @AlexM. For contrast here is one of our Answers that embeds a working link. I voted to reopen the Question some time back for the purpose of triaging what's working and what isn't. Just having some counts (which I could add to my existing "answer") might be useful. – hardmath Jul 8 '18 at 15:07