Data loss bug in iTunes Backup with Leopard

Using iTunes backup and restore can cause thousands of your music tracks to be lost.

The procedure for transferring your iTunes music library from your old Windows PC to your brand new iMac is very simple:

1. On the PC, use the Backup command in iTunes to write your 5,016 songs onto 6 DVDs.
2. On the iMac, insert each DVD in turn and let iTunes restore all the songs.
3. Enjoy your songs, all 3,679 of them.

If you compare step 3 with step 1, you will see one snag: only 73% of your songs have survived the process. More than a quarter of your music library has been silently lost.

Time and power

One thing I discovered last week was how important it is to think of time as well as power.

Before now, I’ve tried a move, been countered by my opponent, and therefore immediately gone on to try something else. Only last week did it occur to me to ask myself: how much is this costing him?

Because if it doesn’t cost me much to maintain the pressure, and he’s in a weak position and using every ounce of his strength to resist me, it makes a lot of sense for me to wait a few seconds and see if time is on my side.

Like all big discoveries it’s utterly obvious but it’s made a big difference to my game. Whenever we reach a momentary stalemate I make this test – and if I think that he’s going to run out of steam before me (usually because I’m in a better position than I thought, but it might just be that he’s weaker than I thought) then I apply less strength but more weight, count to five and see how things evolve.

Now I have to get rid of the related bad habit: when trying a move you’re not sure of, try it at half strength first and if it feels OK then really commit yourself to it. In other words, give your opponent notice of what you’re doing! It’s an easy habit to get into if you’re not confident and surprisingly hard to kick.

A dedicated follower of fashion

Walking across the City of London I came across a huge glossy clothes shop in a brilliantly lit modern building. It was evening and the shop was closed, but as I looked at the window I saw a movement.

One of the local residents was investigating the latest fashions. He rummaged around under the jacket for a good long while, but then he turned his attention to the material the shirt was made of, and that’s when I was able to take his photograph.

His tail is unclear because he was waving it and it’s only a camera phone, but you can see that he was serious about his research.

Cyprian’s Last Theorem – proved?

To recap: we know that 3²+4²=5² and 3³+4³+5³=6³. Cyprian’s Last Theorem states that these are the only cases of n consecutive nth powers adding up to the next nth power.

I’ve nearly proved it.

Specifically, I’ve proved it for all values of n that are not of the form 16m+2 or 8m+3, and, in addition, for all values of n (of whatever form) that are less than . This is not the same as proving it for absolutely all values of n, but it’s enough to be going on with.

The final gap in that proof was proving Part B of the problem described here. I floundered around for a while, getting nowhere in particular, and then submitted it to the American Mathematical Monthly for publication in its problems page. In accepting it, the editor sent me a proof by one of his colleagues of a weaker version of Part B, and I was able to strengthen it to prove the result I needed.

So now I have a 45-page paper describing the whole adventure in a chatty and discursive style: I think it’s important that mathematics should work as a spectator sport as long as the spectators can be helped to participate a little bit in what’s going on. I’m letting the paper infuse for a few weeks and then I’ll tighten it up a bit and smooth it out.

Royler and Helio

This is a lightweight documentary clip that’s good for explaining to your friends what this BJJ thing is all about. It’s good to watch how Helio moves.

Thanks to B Stuff et cetera for pointing it out.

Principle: weight placement

Over the past two weeks my BJJ game has changed fundamentally. Suddenly, instead of thinking in terms of the moves we’ve been taught, I find myself thinking in terms of the underlying principles.

For example: when on top in side control, I stopped thinking about putting my arm under his head (item 3 on my “side-control” checklist, as if I was a pilot preparing my aircraft for flight). Instead there came the simple idea that it would be good to arrange things so that if he turned a way I didn’t want, he’d choke himself without me having to do anything.

If you like, it’s a process of forgetting the moves so that you can invent them for yourself as you go along.

I’m rather at the forgetting stage just now, so the overall performance can end up worse than it was, but deep down it really is progress. I’m moving from doing a less good thing well to doing a better thing less well. Eventually, once the process is complete, I’ll be able to think about moves once more, but the way the blue belts do. Listening to them talk, they do talk about moves, but the moves are a description of what they’re doing, not a definition of it.

Eventually.

Anyway, the new thinking has had its successes. Yesterday, rolling with Luciano and practising getting out from under his side control (he’s 83.5kg on the scales but 120kg when he’s on top of me), I suddenly felt, in the middle of my shrimp-and-shove attempt to get him into guard, that the position was unstable. I gave it a bit of a push in the right direction and sure enough, we toppled over and I was in a side control position on top of him. I couldn’t tell you what the move was called and I don’t want to know just yet because the knowledge would confuse me, but that moment of “something funny in the equilibrium here, let’s try to use it” is exactly the sort of principle thing I’m trying to convey.

Here, appositely, is a YouTube clip about weight placement:

Being a principle, you can bear it in mind anywhere – as opposed to a move, which only fits in one place. I saw this on B Stuff et cetera (thanks, and good luck with the operation!).

Sex education poster

 

Seen in the weight room at Cannons Gym in Covent Garden.

A mathematical problem

I submitted the problem outlined here to the American Mathematical Monthly and they seem willing to publish it in their monthly problems page. One of the collaborating editors has provided a proof of part (b), which is delightful news. It takes a route I considered briefly but then discarded as being impassable!

The only thing missing in the editor’s proof is that the error in the approximation is proved to be , whereas I really need and a good idea of what multiple of 1/n is involved. Perhaps one of the solvers will improve the error term once the problem appears in the magazine.

The transactional interpretation of quantum mechanics

An entry in Ars Mathematica has alerted me to John Cramer’s Transactional Interpretation of Quantum Mechanics [see also Wikipedia]. It feels exactly right.

The trouble with quantum mechanics has always been that it makes accurate predictions but doesn’t make sense. People make a virtue of this. It shows how far above our heads the whole theory is. “My thoughts are not your thoughts, my ways are not your ways, says the Lord”.

This is self-indulgent obscurantism and it leads to such New Age loopiness as The Dancing Wu Li Masters (in which, among other delights, every chapter is called Chapter One).

The transactional interpretation is solidly and sensibly based on mathematics – specifically, on a bit of mathematics that has mostly been ignored because it’s embarrassing.

How we learn

Now that I’m beginning to get the ghost of an inkling of what BJJ is all about (and so I should, since I got awarded my third stripe on Wednesday: thank you Luciano, I’ll try to deserve it), I think I can understand the learning process a little better.

Our class is fairly standard. Our instructor shows us a move – armbar from side control, or whatever. He breaks it up into the individual stages, the grips, the shifts of weight, and then he puts it back together again. Then we pair off and practise.

By then we’ve already completely forgotten how it’s meant to go. It was obvious when we watched it. It was so obvious that we were bored with being shown and impatient with the one guy in the class who wanted to see it just one more time. And now – our minds and bodies are blank. We have to call the instructor over and get him to show us on our own bodies what to do.

The same comes when you try to learn any physical activity and the reason is always the same. They can teach your mind, but it’s your body that has to learn.