Interview of John Baez and Urs Schreiber

Bruce Bartlett

January 13, 2007

The following interview was done while Bruce Bartlett, Urs Schreiber and myself were at a Fields Institute workshop on Higher Categories and Their Applications. The main subject was our blog with David Corfield, the n-Category Café. You can also listen to this interview in the form of an mp3 file.

Bruce Bartlett also did an interview of James Dolan.

Bruce: I'm sitting here with Urs Schreiber and John Baez, two of the three founders of the n-Category Café - a group blog on mathematics, physics and philosophy. Guys, can you just maybe tell us, each of you, a bit from your personal point of view about the history of the blog and how it came to be created?

John: Urs should go first, since he had a blog first.

Urs: I spoke about this with Bruce already yesterday, but I might just repeat some things, is that okay? So I guess, similarly to John, I had long time ago an urge to communicate with other people on the web, for various reasons - mainly because I used to be at places where I didn't have that many people to talk to. So, I started using the newsgroup sci.physics.research, at the time when it was still...

Bruce: Still what? [laughs]

Urs: Yes, in the old days. I mean, it changed -

John: It was very active.

Urs: Yes, it was very active. And John was replying to almost every other post, and everybody was talking with John. I learnt a lot. Yes, I think I'm only slightly exaggerating when I say that I learnt more from sci.physics.research than I did at university. At least, more about where to read more and stuff like that. And anyway - so that helped me a lot.

Bruce: Why did you go to sci.physics.research in the first place?

Urs: Oh, at the time, that was the only thing there was.

Bruce: I mean, were your friends doing that? At that stage it was quite new to be spending time on the internet learning about your subject.

Urs: Well, learning, maybe yeah. At that time newsgroups were the only thing there was for this kind of discussion. I was reading various newsgroups, and then I got interested in physics more and more. At some point it just didn't help me so much anymore as it used to -

Bruce: Yes.

Urs: For two reasons, I guess. My personal needs changed, and also the character of the newsgroup changed when John left as a moderator, I think, and some other people came in who shouldn't have come in [laughter], maybe. Anyway, so I was crazy enough to start a PhD, which was supposed to be related to string theory without any string theorists around to talk to [laughs]. That's the craziest thing I've ever done in my life, I guess. I can't recommend it - don't try this at home! So I thought: I need some string theorists to talk to, there's no string theory newsgroup, so let's create one. That was a complete failure - that didn't work. But the process of creating sci.physics.strings, somehow Jacques Distler learnt of our efforts to create that group. And...

John: The String Theory Coffee Table... oh, wait - you're still talking about the newsgroups?

Urs : Yes, so we created that newsgroup which never really took off.

Bruce: Sci.physics.strings?

Urs: Yes. So then Jacques said, 'Okay, I'm using a blog, so if you like, I'll create a blog for you.' And I said, 'That's great'. We were looking for a name for it, and I said it should be like the discussions one has over coffee, so Robert Helling said, 'Oh, let's call it the String Coffee Table!' And the next moment, Jacques just created it, and we didn't know what was going on... you can see what I mean if you go to the archives. So everybody was sending their first message, and then [laughs] for most of them, that was their last message too. And then it was just me posting things there.

Bruce: [laughs] How long did the String Coffee Table last?

Urs: Oh, it still exists, but I stopped posting to it as soon as the n-category café was created.

Bruce: Okay, but how long was it from the beginning to the n-Category Café? Two years?

Urs: Oh, I'm not sure... I never can remember dates. Maybe over two years.

Bruce: I can't remember.

John: Something like two years. Roughly. I don't know.

[In fact the String Coffee Table was founded in December 2003, and the n-Category Café started in August 2006.]

Urs: Okay, so what happened was this. I kept posting things to the String Coffee Table, because I was just writing down any idea or anything I thought I would like to share. But few people actually... I guess nobody would read it. And, John at that time was having a very long discussion with David Corfield, on David Corfield's blog called Philosophy of Real Mathematics.

Bruce: Right. On Klein 2-geometry?

John: Yes. So David Corfield had his blog, and not too many people were posting comments to that... maybe people hadn't found out about it. And so I just sort of helped it out -

Bruce: Right.

John: I decided -

Bruce: I saw that - I read some of that.

John: So then we got quite a big discussion going on the topic of categorifying Klein geometry. It was a fun example of actually doing research on a blog. And I guess then somehow Urs noticed that...

Urs: Yes, I tried to join in. You two were discussing things very intensively, and I was looking at it - I think I didn't spend quite as much time as you did. I just tried to follow along and make a comment here and there, and I found it very hard to follow, because of the very inadequate web technology used on that blog. It was hard to see which comments were referring to which!

Bruce: Right, right.

Urs: There was no way to do it, and that's really hard, if you're trying to follow a discussion and someone says, 'Oh, I just told you, three comments above'. [laughter]

John: Yeah.

Urs: And I remember one day, I was walking home in Hamburg, and I somehow felt dissatisfied. And then, I had this idea. I said, 'why don't we have a new blog where we discuss these things'? And I think, before I even went home, I went to an internet café - because I don't have internet at home -

Bruce: [laughs]

Urs: I went to an internet cafe, and wrote an email to John and David, 'would you mind if I asked Jacques, or somebody, if they'd set up a blog?'

John: Right.

Bruce: You don't even have internet at home?

Urs: I still live in another city, with my girlfriend, so I have a very small place in Hamburg. It doesn't even have a telephone! I just work there, I don't actually...

Bruce: I see, I see.

John: So I had been feeling dissatisfied too, because I always like having a big conversation always going on around me, and I like to talk a lot, and I like to show off, and have a lot of people watching what I'm saying. And I'd been doing that on sci.physics.research for several years, and attracted quite crowd of people, and it was a lot of fun for a while. But then it fell apart, in various ways, that I don't want to go into too much -

Bruce: [laughs] Crackpots... or...?

John: I don't want to go into it too much. It has to do with all sorts of things. And you can look at the archives on Google, you can actually read it and see -

Bruce: Okay.

John: In addition to all those things, being a moderator took a lot of work. Discussing physics is fun, but there's all sorts of other stuff that's not so fun, like being an administrator. And when my wife moved to the same side of the country as me, I had less time than I did before, and I started getting more grad students, and being able to talk about things to them, and that seemed more productive than talking to people who didn't really do anything with the information...

Bruce: [laughs]

John: And so I quit being a moderator - in 2002, I think. And then, blogging -

Bruce: This Week's Finds.

John: Well, I continued doing This Week's Finds - but that's sort of different, its not a conversation, exactly.

Bruce: Right.

John: Anyway, this was around the time when blogs were just getting going, becoming very popular. And I started getting more dissatisfied when I would occasionally read people refer to me as 'John Baez, the proto-blogger, one of the first people to write a blog'...

Bruce: [laughs] I've heard about this, is that really on the internet somewhere, or...?

John: Yeah, yeah, that's right. And I'd been introduced at talks that way...

Bruce: [laughs]

John : ... and I mean, of course it's a great honour, and I think it's true that in some sense, This Week's Finds -

Bruce: So they were referring to This Week's Finds?

John: Yeah. This Week's Finds, of course, wasn't a blog, but it was a kind of... regular discussion of what I'm learning and doing, so in a sense it was a predecessor to blogs - but without the technology for people to easily make comments.

Bruce: Right.

John: So, I started getting a little frustrated about being called a 'proto-blogger'. [laughter] I would joke that I felt like being introduced as like, 'Homo erectus: Very smart for its time, with the first stone tools'. [laughter] It made me feel sort of old!

Bruce: So you thought the time had come, to...

John: Well, I thought, you know - do I want to just be remembered as someone who was ahead of his time once upon a time? So, I wanted to start a blog. But, my main example that I had of science or physics blogs, were Peter Woit's 'Not Even Wrong' and Lubos Motl's blog, and both of those are quite combative.

Bruce: Right, yeah. I see.

John: There's a lot of arguing going on. And that's exactly one reason why I didn't want to be moderating sci.physics.research anymore -

Bruce: Right.

John: - so I thought, 'oh I don't want to start a blog, then I'll be back into being a moderator again, and each day I'll wake up and see a bunch of nasty email replies to what I said on my blog.' I didn't like that idea. But, I knew what Urs's blog was like and what David's blog was like, and neither of them had that kind of flaming on them. So when Urs suggested a group blog, I thought, 'Oh, maybe that would be possible'. Maybe it could work, without becoming unpleasant.

Bruce: Right. So, you didn't immediately take it up?

John: I'd been thinking about the idea. But when Urs mentioned it, I didn't immediately say yes. I asked a whole bunch of questions. Because I'd been worrying about it, so I wanted to know: could you run it in a way that only people you allow would make comments? Because I thought that maybe that would be necessary, to keep it polite.

Urs: That turned out not to be important.

John: Right. It turned out not to be! But, I had been thinking at the time that it would be necessary to do that - or might be. So they said, yes you could do that, and they said yes, you can also turn off comments on any particular thread if you want. You can also delete comments pretty easily. So I thought okay, there probably are enough safeguards in place that I could risk it. I was pretty nervous at first, that I would have to do a lot of work -

Bruce: Right.

John: And so we started it up! And one of the main good things about it, is that there really has been very, very little flaming. Not none, but very little.

Bruce: Okay.

John: And I'm very merciless about deleting any comments that are hostile. That helps.

Bruce: Now, physics, maths and philosophy seem like a bit of a strange combination.

Urs: What!

John: No, not to me. They're the things -

Bruce: They're the same thing?

John: We're trying to understand the universe -

Bruce: Do you think they work together on the blog? Do you think that there's some maths people that only listen to the maths things, and some philosophy people who only do the philosophy things, or...?

John: There are certainly people who do... who listen to the math, and maybe the physics, but don't listen to the philosophy. I was... [laughs] I was rather upset when, uh, Jim Stasheff - whom I like a lot -

Bruce: Right.

John: - posted to the topology mailing list, saying, 'Do you guys know there's this blog called the n-Category Café? You should check it out. Unfortunately there's a bunch of philosophy you have to wade around.'

Bruce: [laughs] I see.

John: But then I discovered later that he knows nothing at all about philosophy, because he was asking my opinion about some complete crackpot philosophy -

Bruce: [laughs]

John: - and he didn't seem to know the difference between that and what David was doing. Which made me even more nervous in some ways [laughter], but, it just means not everyone has a taste for the philosophy.

Urs: I must say too though, that, the kind of philosophy that David is writing about is completely different from what I'd usually associate with the term 'philosophy'.

Bruce: Right, I agree with you.

Urs: I mean, it's what I would like to call philosophy, but I before, you might have heard me say something similar to what Jim Stasheff said: that I don't want to read all this philosophy stuff, it's completely interesting. But I was surprised how much I actually gained from reading David's comments on his posts.

Bruce: It's very relevant philosophy!

John: Yes, I really enjoy it a lot. What's really fascinating is that on the one hand, I think he's the philosopher of mathematics who knows the most about mathematics of any whom I've met. So I can actually, like -

Bruce: Right, right. It's quite scary.

John: - talk to him about sophisticated topics, and he'll come up with good ideas. But on the other hand, he's not at all into analytic philosophy, meaning philosophy that tries to act like its mathematics, philosophy that tries to mathematically analyse concepts. In fact, he's very much opposed to that!

Bruce: I see, I didn't know that.

John: Instead, when he's talking about the philosophy of mathematics, he's very concerned about the sociology of mathematics, and how people interact, and how you can do mathematics well -

Bruce: Right, right.

John: - and things like that. Instead of trying to say, make up and prove theorems about philosophy, or something like that -

Bruce: [laughs]

John: - which some people actually try to do, and they usually don't get anything very useful out of that.

Urs: Or if you do, then you no longer call it philosophy. [laughter]

John: Then it's just mathematics. Yeah, that's right.

Bruce: So, recently I've heard about some other similar blogs: apparently Clifford Johnson has one on string theory, and so on. Can you say anything about the philosophy of your blog, which might, you know, distinguish it from the philosophy of other possible blogs out there?

John: The main blogs I know about - the main ones I read, besides Not Even Wrong - are one called Cosmic Variance, written by a number of people...

Bruce: So these are real physicists, cosmologists, string theorists or whatever?

John: Right. Anyway, that blog is nice, but they don't actually do cutting edge research on the blog. They tend to explain ideas from physics in ways that laymen can understand. So as a result their blog's much more popular than ours -

Bruce: Oh, really?

John: - in terms of the number of readers. And they get a lot more posts.

Urs: Yes, they get a huge number of comments.

Bruce: Can you say something about the number of readers that you have?

John: I don't keep track of the number of readers. We know how many people post things, but I don't pay attention to the number of hits.

Urs: I don't actively count. But at times when we are actively discussing things - as opposed to times like now, when John and myself are at a conference and not doing anything [laughter], there are like, maybe, ten or twelve comments a day?

Bruce: Right.

John: Yeah, about twelve comments a day. As science blogs go, I think ours has among the largest number of blog entries per week. There are lots of them that only have, say, one entry per week. We like to talk a lot more than most people. [laughs]

Bruce: But, it's more of a research blog?

John: Right. So the number of people reading our blog is, I think, much smaller than some. But the more popular blogs get a lot of people who are non-physicists and non-mathematicians discussing things, so the conversation rambles much more.

Bruce: I see.

John: So, ours is serving a different purpose. Those other blogs are very good. They're a great way for people to learn about physics. But we're doing something a little different.

Urs: Many blogs are run as a kind of magazine or newspaper. Right? As a journalist would do. You know, recording all sorts of things. But that's not what we're doing. And that's part of the reason we don't get as much traffic.

Bruce: Right. Can you guys say something about the implications for research ethics that blogs have - especially research blogs? For example, if a silent reader who didn't actually engage in any actual blog conversation were to pick up some valuable information from the blog, write a paper, and not reference it, no-one would ever find out that he had taken your ideas. Do you have anything to say about these ethical issues?

John: That hasn't happened yet. So, we'll probably have a lot more to say about it when it does [laughs]. I'm sure someday something like that will happen, and then I guess we'll see what happens.

Urs: Yes... but let me just say one thing, maybe -

John: Urs has a philosophy about this.

Urs: I'm probably crazy. I don't really think about 'should I, should I not', I just...

Bruce: You just let it all hang out.

John: Well my theory is that Urs figures he can generate ideas so much faster than anyone else can possibly catch up with them, that - [laughter]

Urs: Well, actually sometimes I would rather like somebody to catch up with them [laughs]. I mean, I would like to throw away an idea like a ball and see it come back to me.

John: Yeah, that's it.

Urs: You see, everyone's afraid they need to hide their ideas -

John: Sure, yeah.

Urs : - but see, I've posted all this stuff to the blog, and now I just came to this conference and gave a four hour talk on what I've been doing, and people are approaching me and saying: 'Oh, now that I've heard your talk I finally understand what you kept blogging about'. So, it isn't really the problem of giving away too much information: the problem is really of giving away too little! Of course, it's very esoteric stuff...

Bruce: Right.

Urs: And its not just like you can read something off a blog and write a paper about it, like finding the winning ticket to a lottery and cashing it in! [laughter]

John: Right, right. Even if you try, it's actually very hard to give away ideas that require knowing both string theory and n-categories to appreciate. For example, I could tell you some wonderful fact that I've learned from Urs, like 'The key to elliptic cohomology is to study things like vector 2-bundles where the fiber lives in the 2-category not of 2-vector spaces but of bimodules, because the string 2-group has a natural representation in there'. Okay? I just gave away a precious piece of information. But how many people in the world are ever going to know what to do with that?

Urs: Right, and I kept saying that. Precisely that statement!

John: Right, and today I finally understood what you meant!

Urs: I repeated, and repeated, and repeated it [laughter]. Every time somebody would mention something about one kind of 2-vector space or something I would say 'Yes, but we also have bimodules'. And now I finally give this talk, and I tell everyone about this [laughter], and Nils Baas comes up to me and says, 'Ah, no but what you're doing is not what we are doing'. And I say yes, it's precisely this! You're using bimodules implicitly [laughter]. So it's an important piece of information which people didn't figure out, even though I told them.

John: Right.

Urs: But maybe I'm just not explaining it well. That's the problem.

John: Well, you're being a bit harsh on yourself. I've spent a whole bunch of time trying to figure out how to explain things. And you know, it takes a lot of work to convey ideas in a way that people can easily pick them up. If someone wants to learn about something, they can go after it, and find out about it. But if they're just sitting there, and you tell them something that they're not expecting, it will almost always just bounce right back off them, unless you work really hard to get them interested.

Bruce: Okay. So you're an expert, in the art of explaining things?

John: I'm trying to become an expert in that. But I don't do too much of it on the n-Category Café, actually! When I was at sci.physics.research I put a lot of work into making my posts very fun: pretending to be fictional characters, telling stories, and things like that. That's because I was trying very hard to get as many people involved as possible.

But I don't really want to have flame wars and moderation problems on the n-Category Café. So, I've deliberately refrained from being very inviting on the n-Category Café. Sometimes I feel that I'd like to change that, and do more fun things... but usually I think that if I start popularizing science, and stuff like that, it belongs on some other blog.

Bruce: Right.

John: So, right now I just talk in a way so that only people who are already interested could ever possibly understand what I'm saying! [laughter] I talk about things like relations between higher categories and computation, and stuff like that: not the kind of thing that many people get very excited about.

Bruce: John, how do you see This Week's Finds going into the future- say, interacting with the n-Category Café? I mean, what is your vision for This Week's Finds for the next ten years?

John: I'm sort of confused about it now. I'm going to keep writing it, I love writing it. It's one of the few things that I always enjoy writing. Papers always start becoming hard work when you're about three quarters done, and you have to sort of suffer... [laughter]. But the great thing about This Week's Finds is I don't need to do anything I don't wanna do. So it's very easy and fun.

Bruce: Right.

John: But I do worry about it in various ways. I'm always worrying about who is my audience. I always try to make it fun for both nonexperts and super-experts. So, I start out with things that are really easy to understand, like pretty pictures or fun facts, and then slowly -

Bruce: [laughs]

John: - and then slowly, as you read on, it gets harder and harder. I think some people will maybe always only read the first paragraph. I hope different people can get different things out of it. But I always worry about whether it's working, especially as I keep learning more and trying to talk about more advanced stuff. There are some really big things I want to tackle now, like the Langlands program, and the stuff Jim Dolan and Todd Trimble are doing on categorifying quantum groups... it's a bit hard to know where to start.

There are also technical worries. I started out by writing This Week's Finds purely in ASCII, back in the days of newsgroups [laughter]. And then I started doing web versions too, which requires turning them into HTML. So to some extent I have a script for that, but I also need to do a lot of things by hand.

Bruce: Right.

John: In particular, there's still a lot of pictures drawn in ASCII there -

Bruce: String diagrams in ASCII [laughs]!

John: Yeah. So then at some point I decided, okay now I'm actually going to really start using photographs, in the web version. But I've been trying to keep a low bandwidth approach -

Bruce: Okay.

John: - so I still have the ASCII versions without pictures, and I have the web versions with pictures, and now though there's this other possibility, which is that I could also do a version, either at The n-Category Café, or somewhere else where I could write equations in TeX -

Bruce: Right.

John: But I'm not doing that yet. And I don't really want to be writing three different versions of the same thing. It already takes me quite a lot of time just to do the processing. So, so far I'm just sort of announcing them at the n-Category Café, and then having a link.

Bruce: It kind of works, though.

John: I think it works. But I've been learning about some new mathematics typesetting systems on the web, so that maybe on my own computer I could have math symbols in This Week's Finds, and other places, more easily, -

Bruce: Right, I see.

John: - and that would be the next 'generation' of This Week's Finds. And then I might, like, hire a work study student or someone to go back through all the old ones and update them, to make them look nicer.

Occasionally publishers ask me, do I want to turn them into a book? And I always say that I don't really want to do that, because... Well, first of all, they want me to turn it into a book because they'll make money off of it. But writing a book in mathematics doesn't make the author very much money - about ten percent of what the publisher makes.

Bruce: [laughs] So its just a money thing, basically.

John: Well, they would make money, but I wouldn't make much money.

Bruce: Right.

John: And, the book would basically be less useful than the web version! The web version now has links to the papers on the archive. I think that's useful, because you can read about things and then just jump over there and look at them. But if you had a book, it wouldn't wouldn't have that feature. So then to make it interesting you'd have to do something else instead. So, it's just too much work.

Bruce: Absolutely. Okay, so now for the final question. How do you feel about how the mathematics and physics establishment views your blog? Are there any hard feelings from some quarters, like 'old school' academics, or string theorists?

John: I don't really know. Urs might know a little bit. Jacques Distler is a hard-core string theorist and he's the one who got the blog going: he provided the technical infrastructure for it. So, obviously he's okay with it.

Bruce: What I'm trying to get at is that maybe some people will feel that research blogs are just not what an academic should be doing. You know, maybe mathematicians should be stuck in an office and do their work silently until finally they send off their paper in an envelope to the journal.

John: Okay. Maybe some mathematicians are like that; string theorists sure aren't like that. They invented the arXiv!

Bruce: Right. Okay, well, have either of you picked up any bad vibes from certain quarters - people that would rather have you shut down?

John: I don't think anyone ever said that.

Urs: No. I don't receive any messages like that. But I guess people who aren't interested in it - they won't send you an email saying 'please stop that blog!' [laughter]. It's people who are interested in it that give you feedback, and this is often good. Sometime when I go to a conference or something, someone whom I've never met before will approach me and say 'hey I know you from your blog, I like reading your blog'. Or maybe they don't like reading it, or whatever, but -

Bruce: It gives you a good introduction.

Urs: - they know me, and yes, they sort of know what I'm thinking about, so we can immediately talk about something. For example, a couple of weeks ago I was, in Göttingen I guess, at a lecture that Michael Hopkins gave. I'd never met him before. And I was standing in the hall, and he approached me and said, 'oh you're Urs Schreiber, I've been reading your blog, and - '

John: That's great.

Bruce: That's really cool.

Urs: - so I liked that! And that's an advantage for me, yes.

John: Yeah, I've gotten a lot of benefits from writing This Week's Finds. It basically seems that almost every place I go there are mathematicians who know about it. And I've also gotten a lot of other benefits: when I write about things, I get email from people correcting me and telling me other interesting stuff. So, it's a great way to learn about a lot of things.

Bruce: Okay.

Urs: Well that's certainly the main reason I'm doing it. I mean I could have just typed all these things and saved them on /dev/null or something! [laughter]. But the reason for putting them out there is that I -

Bruce: You want to learn.

Urs: - I want other people to look at it. There are people like Bruce Bartlett out there who actually read this [laughs], and they come up with interesting comments, and it really helps a lot.

John: Yeah, I think all three of us - Urs, David and I - are pushing a new way of thinking: a very n-categorical way of thinking about a large bunch of ideas in math and physics. I'm very excited about this, because I can see how much potential it has. But we're also simultaneously pushing a new idea of how to communicate ideas. And the combination is actually really, really interesing.

Bruce: Yes.

John: It's sort of funny to be simultaneously doing new kinds of math and physics, but also doing it in a new way. I think it's... I don't know... it's sort of an exciting combination.

Bruce: Right.

Urs: Uh-huh. And I think having three people who do philosophy, math and physics is also nice. Like you said at the very beginning: 'what's the relationship between philosophy, and math, and physics'? It's a nice coincidence, right, that we've got three of us doing those three things. I didn't look for it. There's David the philosopher, and me the physicist, originally at least, and John the mathematician. So, I like to think of it as a triangle. It's very nice, you know!

Bruce: Okay.

John: Yes, I think it will keep being very interesting. There are lots of people who read it, who are too shy to post anything. But hopefully some of them will become less shy, and...

Urs: Yeah, from time to time I receive emails that say, 'Oh I read that entry by you, here's a comment', and I think, well, let's make that comment on the blog! Because I might not know the answer, but -

John: Right.

Urs: - but someone out there will. And it happens! Some expert - there may be one or two in the world - will read what I wrote and and say something, like 'This is completely wrong'. That doesn't happen when you're sending messages just by email.

Bruce: So you'd prefer them to post anonymously, or something like that, instead of sending email.

Urs: Yeah, I certainly do.

John: When I get emails from people, if they say something interesting, I often ask them, 'is it okay if I post this on the blog for you?' They usually say yes. And so then I do that.

Urs: I have this agreement with Jim - Jim Stasheff, right? He had some problems with his equipment, reading or posting to the blog, so he kept sending me emails, and he said, whatever you find interesting, just forward it to the blog.

Bruce: Oh, okay! [laughs]

Urs: So many of the messages by Jim were actually posted by me - I can just insert his email address.

Bruce: Oh right. I see.

John: Does he still do that? Or does he post also himself now?

Urs: Yeah, from time to time he also posts himself.

Bruce: Well you can see the difference: if it's all written in lower case... [laughs]

Urs: Anyway, that's fine with me. That's great.

John: Yup. I mean, it's great having his posts there. It brings more prestige to the blog! [laughter] I mean, he's a serious mathematician. And he loves to communicate with people. He's constantly sending email to hundreds of people.

Urs: You were asking about the advantages of running this blog. Well, at one point we were talking about that supergravity Lie 3-algebra [laughter], and I was...

John: I wanted to write a paper with you about that, but I'm so busy that I probably will never do it! [laughter]

Urs: I was trying to do something with that Lie 3-algebra. And in order to do that I needed to recall a lot of things I had done in my thesis and I'd read in John's papers, on free differential algebras and Lie n-algebras. So at some point I said, 'I'm forgetting all these things, just partially remembering them!' So, just for my own convenience I created a file, which has become that 'free differential algebra laboratory' - right? I just packed in all the examples that I could come up with, just to remind myself of what was actually going on. But because everything I type, I want to share with everybody, I created a link on my blog to that file.

I was completely surprised when, quite a bit later, Jim came across this and said it would be worth turning into a paper! I wasn't aware that there would be anything in there that would be of interest to a wide audience. I thought I had just summarized things that were sort of known, even if scattered around in the literature. But he actually told me that he thinks it's interesting. So now I'm writing a paper with him about this stuff! [laughter]

I would never have considered that on my own. I mean, for me it was just a means to get to that supergravity Lie 3-algebra.

Bruce: Right, right.

Urs: Having all these examples was just sort of a stepping stone. So for me this was a real revelation: that even before you arrive at the point where you want to arrive, what you're doing can be of interest already! Not to mention the fact that the great Jim Stasheff is writing a paper with me! [laughs].

Bruce: Okay, on that positive note we'll end the interview. Thanks, guys.

© 2007 Bruce Bartlett, Urs Schreiber and John Baez