Articles

Note added in 2021. When I wrote this 10 years ago I had no idea that what I then saw as a fascinating side project would become my company, and sustain my family for years. I was wondering, back then, who would want these wonderful maps I was making. The answer ended up surprisig me beyond anything I could have imagined. The sky as seen from South Goa I’ve been obsessed for the last 24 hours, ever since I put on-line the version of http://greaterskies.com that I thought was the first one to deserve promotion. I knew that I shouldn’t really care; I knew that, most likely, nothing would happen; I knew that I should expect to be ignored in Hacker News. And I’ve done it because it was fun. I’ve had a good time figuring out how to build the puzzle of Common Lisp, Python and Javascript that serves the star chart PDFs. And hosting is free. But still. It’s hard not to give in to what I would naturally do at this stage: add features at a frantic pace, assuming that the next thing is the one that will make the difference. ...

I still remember my first fountain pen. It was a beautiful thing, green and blue, nice to touch, that would caress the paper when you wrote. To this day, holding a fountain pen in my hand puts me in writing mood, in thinking mood. It opens my mind, as Paul Erdös would say. I became conscious of this not long ago when, as I was reading Daniel Kahneman’s wonderful Thinking, Fast and Slow, I understood for the first time how prevalent this effect is, and how important it probably is in my life. ...

We cannot predict how the development of something large and complex is going to play out. We are not sure about what the right product architecture is, nor where the snags are hidden. In most cases we don’t even know what we’ll actually want by the time the product is done, when the compromises that reality will inevitably impose on us are bought off. Nor whether anybody will actually want what we envision today. ...

During the last three years I have managed a team of engineers doing ink-jet printer design at HP’s R&D lab in Barcelona. The excellent org-mode emacs package has helped me keep up-to-date with the work of the 12 engineers in my team, working in four different projects, without an obvious impact in my sanity. During this time some work-flows have evolved, and I have written helper functions for org-mode to support them. This is an account of the steady state at which I have arrived. Please let me know if any of what follows could be done or written in a simpler or more idiomatic way. ...

By Juan Reyero, Jaime Fernández and Utpal Sarkar. What is the maximum slope that a unicycle can climb? Trying to answer this question leads to some elegant results, and sheds some light on the dynamics of unicycle riding. Assumptions We shall assume the rotational inertia of the wheel, pedals and legs to be negligible. A further simplifying assumption is that the rider is putting all his weight into the pedal throughout its trajectory as it is going down, and that this is the only impulsion force. Which implies that the rider is not pulling up from the saddle, nor accelerating the body upwards with respect to the unicycle, nor making a horizontal force in the pedals. We know this assumption to be too stringent for expert unicyclists, who will typically be able to do all these things, but we hold it to be a reasonable approximation to what a unicyclist of normal skill would do when pressed to climb a slope at the limit of the unicycle’s possiblities. ...