| Sage |
[May. 14th, 2008|01:15 pm] |
Those of you who do scientific computation may be interested in this link:
Bye Matlab, hello Python, thanks Sage.
Short version: Sage is a bundle of all of the various numeric/scientific/graphing tools for Python, made easy to download and install (even if you don't have root access, apparently). According to the blogger linked above, it's now good enough to serve as a replacement for Matlab (and it has ambitions to be a replacement for Maple and Mathematica too, though I don't know how far along it is). It integrates with R, Gap, etc. And because it's Python, you get a real, high-level, well-designed programming language with a proper environment to do your coding in.
In other news, ![[info]](http://p-stat.livejournal.com/img/userinfo.gif) wormwood_pearl finished her Finals yesterday. As you can imagine, we're both pretty relieved. There's no tradition of meeting people outside Finals here like there is in Oxford, but I went along with a bottle of champagne anyway - and only then remembered that public drinking is against Glasgow bylaws. Drat it. We went out to lunch, the bottle went into the Department fridge, and we subsequently went round to her sisters' and drank it there while watching Layer Cake. Because we're that exciting. |
|
|
| In case you were wondering how I got this way... |
[May. 7th, 2008|11:30 pm] |
The tail-end of a conversation with my Dad last night:
[A discussion of scary-sounding nonlinear dynamical techniques my Dad has been studying, with Poincaré's name attached for extra scariness]
Me: Sounds interesting. Have you come across the idea of considering the Poisson bracket as a symplectic form on the cotangent bundle of phase space?*
Dad: No, I don't think so...
Me: Something like that, anyway. I went to enough lectures on this stuff to pick up the jargon, but not enough to really get my head around it.
Dad: Yes, I know that feeling.
Me: But it's interesting how quickly physics becomes geometrical, isn't it?
Dad: Yes, certainly. You know, one of these days you and I should put our heads together and try to properly understand General Relativity.
Me: Actually, that was my plan for after I hand in my thesis. That, and learning to ride a unicycle.
Dad: [laughs] ...and learn a foreign language and a musical instrument.
Me: thinks: I wasn't going to tell him about that bit...
* My office-mate, who does The Physics, tells met that I meant "configuration space" - phase space is the cotangent bundle of configuration space! |
|
|
| Too Much Information |
[Mar. 9th, 2008|12:04 pm] |
There's a new Fine Structure story out, called Too Much Information. In addition, the Crash stories have been incorporated into their own subdirectory, called 1970-. Some analysis of TMI and its implications has already started in the comments threads of my previous FS posts, and I'll have to revise my own thoughts in light of it, but for now:
( Discussion, including spoilers )
By the way, if anyone else is planning on blogging about FS, please leave a link here, so we can all follow what each other are saying :-) |
|
|
| More Fine Structure badgery |
[Feb. 29th, 2008|02:40 pm] |
It's become apparent to me that many of the mysteries in Fine Structure depend on the precise order in which the stories occur. Time to get systematic. Obviously, this whole post is full of spoilers.
( Plot summaries )
( Chronology )
I should probably put all this stuff into some sort of Hasse diagram, but right now I can't be bothered :-) |
|
|
| Thoughts on Sam Hughes' Fine Structure |
[Feb. 26th, 2008|02:10 pm] |
I've been reading some science fiction written by a guy called Sam Hughes1, and posted on his website Things of Interest. Most recently, I've been reading his Ed stories, about Sam and his (fictional) genius flatmate Ed, who builds battlemechs in their basement and saves the world from annihilation on a regular basis, and to whom Sam plays a sort of bemused Watson. It starts out as a fun bit of wish-fulfilment à la early Sluggy Freelance, and turns into something rather more. Well worth a read.
But I don't want to talk about that: I want to talk about his novel-in-progress, Fine Structure, and where I think it's going. It's a collection of loosely-linked short stories whose connections only become apparent later on, somewhat like Trainspotting: I don't want to give away too much of the plot, but let's just say it has elements of Contact, Superman and Strata, in a refreshingly hard-sf style. And it's garnered positive reviews from no less a person than David Brin (search for "Power of Two"). It's probably best to read them in order, but I started with Power of Two and it didn't do me too much harm (and it's one of my favourites).
Edit: further posts on this topic can be found here.
( MAJOR spoilers. Go and read the stories first! )
A word of warning: I have literally lost days to browsing Sam's website. Interesting days, mind :-)
1 Some of you might even know him: he was a maths student at Corpus, Cambridge a few years ago. Or you might have encountered him on some online community or other: he generally goes by the username "sam512". |
|
|
| *ping* BBC R&D types |
[Feb. 15th, 2008|09:49 pm] |
You are appreciated.
Didn't some of you guys work on this? |
|
|
| Bad Science on serotonin |
[Jan. 28th, 2008|01:28 pm] |
It seems the link between depression and serotonin levels is far less proven than generally assumed. More here.
[BTW, if you don't already read ![[info]](http://p-stat.livejournal.com/img/syndicated.gif) bad_science, you should.] |
|
|
| *ping* physicists and engineers... |
[Dec. 10th, 2007|10:16 am] |
markdominus, who is a mathematician by training and a programmer by profession, has been attending undergraduate physics lectures and coming out more confused than he went in. It's a feeling I remember well from the last time I studied physics, and actually part of the reason I did my degree in mathematics - clearly I was never going to get to the bottom of this stuff if I were taught it by the physicists! :-) But then it turned out that physical applied maths was Really Really Hard, so I retreated back into pure maths.
Anyway, in one of his latest posts, he asks a series of questions about electromagnetism, and I realise to my shame that I don't know the answers to any of them. I did do a course with "electromagnetism" in the title once, but the other half of the title was "relativity", and wouldn't you know it, but relativity took up nearly all the teaching time. Anyway, I'd greatly like to know the answers to these: perhaps one of you physics or engineering types can help?
On the theory that I'll probably gain more understanding by thinking about it myself rather than just asking others, here are ( my guesses. ) |
|
|
| An exceptionally simple theory of everything |
[Nov. 17th, 2007|12:56 pm] |
Yesterday, elvum brought to my attention a paper called An Exceptionally Simple Theory of Everything by the physicist Garrett1 Lisi. Entertainingly, Lisi appears not to be your typical physicist, spending most of his time surfing in Hawaii. And the title's a pun: he claims to have unified the Standard Model of particle physics and gravity using the "exceptional simple Lie algebra" E8 (about which more later). If true, it looks like very cool stuff; mathematically rather elegant (though I really don't understand most of the mathematics behind it), satisfying some very desirable criteria (as elvum put it, it's like he's reeling off desirable features from the GUT checklist), and likely to make testable predictions.
But the main reason I mention it is so I can link to this slashdot comment, which is just about one of the best bits of pop science writing I've ever seen, and seriously raises the bar for me in my occasional attempts to explain maths and science. It's very light on details, but it explains in non-technical language what's actually going on here, and how symmetry arises in the study of particle physics. I learned a lot from it, and recommend it unreservedly. Edit: just to clarify, I didn't write the slashdot comment! I wish I had, though.
I wrote a somewhat more technical explanation of Lie algebras and the mathematical significance of E8 for elvum, and I might as well ( repost it here )
The highly-regarded mathematical physicist John Baez has written an explanation of some previous attempts at unification here, with some explanation of why exceptional Lie algebras/groups might arise. It mostly goes over my head, though. The physics blog Not Even Wrong has also written about it, somewhat more cautiously: the author thinks that Lisi's probably only shifted old problems into different places. This blog post also looks pretty informative, but I haven't worked through it yet. And the string theorist Luboš Motl thinks it's nonsense, but then Luboš is an unpleasant troll, so I take that as mild positive evidence.
Garrett (or someone) has produced this rather lovely video of E8: it shows a projection of the root system (which is a collection of vectors in some higher-dimensional real space) as it's rotated.
1 Garrett seems to be quite a good name for mathematicians: the only other Garrett I've heard of in any context was the mathematician Garrett Birkhoff, inventor of universal algebra.
2 I prefer to think of them as group objects in the category of manifolds and smooth functions, but that seems like too much of a digression for now :-) |
|
|
| Fun facts to know and tell |
[Nov. 13th, 2007|01:16 pm] |
The first London Bridge was built in around 600AD, and torn down in 1014 by the Norwegian King Olaf. Its replacement was destroyed by the London Tornado of 1091.
The British Antarctic Survey, despite being much smaller than (say) the US Antarctic Program, has the largest geographical reach of any national Antarctic programme. This is largely because BAS requires its field teams to camp in tents long-term (for months at a time), something no other Antarctic programme would require of its researchers. BAS, on the other hand, has too many volunteers.
[They also encourage their field staff to go on camping holidays...]
Edited to add: the Kiwis also do this, and other national Antarctic surveys use tents short-term or for emergencies. My informant was unable to confirm whether or not BAS actually has the largest geographical reach, but would be surprised if it doesn't.
Asbestos is a naturally-occurring mineral, which can be dug out of the ground in its fibrous state. Its fire-retardant properties were known to the ancient Greeks, who used to weave it into cloth. |
|
|
| Earth orbits sun integral number of times |
[Oct. 23rd, 2007|10:59 am] |
According to Archbishop James Ussher, Archbishop of Armagh and primate of all Ireland, the Earth was created at sunset on the night before the 23rd October, 4004BC (not at 9am, as many have claimed). Thus, I would like to wish the Earth a very happy (albeit slightly belated) 6010th birthday. :-) |
|
|
| Climate change in a nutshell |
[Oct. 9th, 2007|03:21 pm] |
I wrote this in a comment to a post on atreic's journal, and thought I'd repost it here.
If you don't have a friendly climate scientist you can ask, you can still get a good idea of whether climate change is real by following the money and asking yourself the following questions:- Is there much money to be made by convincing everyone that climate change is real when it isn't?
- Is there much money to be made by convincing everyone that climate change isn't real when it is?
- Who has the money for a big campaign of disinformation, the establishment or the green movement (or whoever their shadowy bankrollers might supposedly be)?
- Has the fossil fuel industry displayed any evidence of scruples before, ever?
The answers are, respectively:- Yes, a bit: wind turbines, insulation, etc.
- Yes, a fsckload.
- The establishment.
- No.
Hence, it seems clear to me that climate change is real, and sites like junkscience.org (beloved of the deniers) are, in fact, corporate shills. As a special case, which is more likely: that the IPCC exaggerates its claims to sound more important and advance people's careers (as the deniers claim), or that they are under huge pressure from governments to tone them down, as the green movement claims?
[Oh yeah: upcoming Climate Change bill. Write to your MP!]
Previously.
Edit: robert_jones was not impressed, and replied that he is "convinced by rational argument, rather than by anti-establishment paranoia." I replied,The problem with this "debate" is that there is potentially a lot of money to be gained and lost, and so people are able to lay down massive amounts of pharmaceutical-grade bullshit to confuse and deceive. You can try to follow the climatological literature and critically read the writings of the deniers: but ultimately, both sides have accused the other of outright fabrication of data, so if you really want to know you'll have to go to Antarctica and repeat the key experiments yourself. Much as I'd like to go to Antarctica, this would be a bit tricky to fit into my teaching schedule. It's at this point that the kind of simplistic, ad hominem, follow-the-money line of argument that I outlined becomes quite valuable. Is the kind of climate instability we're noticing significant and unprecedented, or is it just part of an ordinary cycle, like the Medieval Warm Period (or whatever)? I'm not qualified to judge. I am, however, qualified to listen to others and guess at their motivations, and thus at whether they're likely to be lying to me or not.
[I'd also dispute your claim that doing things in a carbon-efficient way is going to be more expensive than doing things in a carbon-inefficient way. Most low-carbon technologies require higher up-front investment, but pay for themselves in the long term. One of the major obstacles to the improvement of, say, energy-efficient lightbulbs has been that the patents are held by the same people who hold the patents for incandescent bulbs, who don't want to endanger their revenue.] |
|
|
| A man, a jar, an oing - GNIONARAJANAMA! |
[Sep. 12th, 2007|11:20 pm] |
Me: What does "intrapleural" mean, anyway?
WP: Well, the pleura are the membranes that hold... basically, it's the poop that holds the tent wher it is. Or rather, the tent that holds the poop wher it is.
I love my girlfriend. She didn't even know about the DFC before she met me :-) |
|
|
| Fantasy Curriculum |
[Jul. 12th, 2007|12:47 pm] |
Several of my fellow PhD students here have to do a substantial amount of programming as part of their PhDs: unfortunately, most of them haven't done any programming before. The usual procedure, alas, is to hand them a Fortran compiler and tell them to get on with it, often hacking on a large mass of code written by someone else who was "taught" the same way. I try to do what I can to help, but there's a limit to the amount of time I can devote to someone else's project (and a limit to the amount of time they'd want me to devote, I suspect). But still, I see some horror stories: yesterday, for instance, an office-mate finally tracked down a bug due to a magic number which had been bothering her for longer than she cared to say, and which had been seriously undermining her confidence in her actual model. Not using magic numbers is basic programming practice, but nobody had told her this.
So I've been thinking about an introductory course on programming aimed at maths/science grad students. The emphasis would be on writing maintainable code and modern programming practices: modularity, use of libraries wherever possible, test-first programming, use of debuggers, source control systems and profilers, optimising later (if you have to at all), use of high-level languages, documentation, and so on. My real aim would be to break the cycle of abuse whereby each new generation of grad students is told to write 1000-line-to-a-function, opaque, untested, rape-and-paste Fortran by their supervisors, because it was good enough for their supervisors, and on and on...
Here's a first cut at a course catalogue entry for this fantasy course: I'd be very interested to hear everyone's comments.
( Practical Computer Programming for Scientists ) |
|
|
| Large databases, then and now |
[May. 21st, 2007|10:21 am] |
Back in 1998, I had a job at JET, the Joint European Torus, one of the world centres of research into nuclear fusion. The complex sprawled over most of the former RAF base at Culham, but the heart was the Machine: a huge torus of metal, machined to precisions of thousandths of an inch, which during experiments contained a few milligrammes of heavy hydrogen at a temperature ten times that of the Sun's core.
This machine pumped out what was at the time a daft amount of data: all the instrument readings and all the analyses of those readings came to around 120MB per run of the Machine (or "shot", as they were called). This was then fed into a wonderfully crockish home-brewed database system running on an IBM 390 mainframe. The system pre-dated the current ubiquity of relational databases, so it was actually a hierarchical database, something that most modern geeks haven't even heard of. The system operated in layers: recently requested data was held in RAM, data that hadn't been requested for a while lived on hard drives, data that hadn't been requested for longer than that lived on tape drives, and data that hadn't been requested for long enough was exiled to the Stygian depths of the tape store: your request for, say, deuterium-band emission spectra from May of 1983 would cause a small, red-eyed robot to trundle off into the tape store, fetch the tape with your data series, trundle back, and physically load it into the mainframe. I used to get lifts to work from the database administrator, and he hated the little robot: it was apparently always breaking down, and he'd then have to crawl in and fix it. "And the red eyes are really sinister! It looks like it's plotting against you."
An integral part of the JET database architecture. Possibly.
The JET Joint Undertaking had been founded in 1978, and had been collecting data for most of the time since. This all added up to a lot of data. My friend apparently used to go to conferences for administrators of large databases just to laugh at what everyone else considered "large".
By performing a simple ( calculation ) we get an estimate of 900 GB (which is to say nine hundred thousand megabytes) for the total amount of data collected by the JET project in twenty years.
As it happens, 900GB is only slightly larger than dreamstothesky's porn collection, which currently stands at around 880GB...
The JET Machine: red-hot nucleus-on-nucleus action |
|
|
| While I'm talking about philosophy.... |
[Apr. 9th, 2007|08:53 pm] |
I'd like to talk about a couple of simple thought experiments invented by the mathematician and philosopher Gottlob Frege, which for me really nail the relationship between mathematics and the physical world, and at the same time raise some fundamental questions in the philosophy of mathematics.
Suppose you have a vessel containing 2cc of liquid. To this, you add a further 3cc of liquid. How much is in the vessel now? Well, 2+3 = 5, so obviously it's 5cc. But the liquid you added wasn't the same as the liquid that was in there: the two underwent a chemical reaction, emitting some gas, and so the volume of the liquid in the vessel is actually less than 5cc. Or suppose you have five things, and you then add two more half-things. You've got six things, right? Except the "things" were pairs of boots, and the half-things were individual boots, but both individual boots were left boots. You have twelve boots, but only five pairs.
In both cases, you have some physical system (liquid in a vessel, pairs of boots in a rack) that you're trying to model using some mathematical formalism (whole numbers and addition, fractions and addition). In each case, it turns out that the model isn't a very good one, as it incorrectly predicts the behaviour of the system. But this doesn't mean that 2+3 is not equal to 5, or that 5 + 1/2 + 1/2 is not equal to 6! Nor does it mean that there's no mathematical model that would fit - in both cases, it would be pretty easy to construct one. It just means that we've chosen the wrong models. Standard arithmetic still works fine, it just happens to be the wrong thing in this case.
( SCIENCE! )
( PHILOSOPHY! )
Frege's story's rather a sad one, as it happens. He did pioneering work in the philosophy of language and in logic (he's got a solid claim to be one of the three great logicians of all time, along with Boole and Aristotle, and without his work much of modern mathematics would be literally unthinkable). In 1903 the culmination of his life's work, the Basic Laws of Arithmetic (Grundgesetze der Arithmetik), was on the verge of publication: in it, he claimed to show that arithmetic (and thus all of mathematics) could be derived from the obvious truths of logic. As it was about to go to press, he received a letter from Bertrand Russell informing him of what is now known as Russell's Paradox. This blew the entire enterprise out of the water. Frege inserted a preface to the effect of "This doesn't work any more, but I hope you find it interesting", then went off and had a nervous breakdown.
1 If you can get hold of a copy of his (sadly out-of-print) Foundations of Arithmetic, I strongly recommend it, if only for the chapter contra Mill. |
|
|
| Paradigm shifts and the Malayan Emergency |
[Jan. 12th, 2007|02:20 pm] |
I'm currently half-way through a fascinating book called The Utility of Force by the retired general Rupert Smith. I'll blog about it at greater length when I've finished it, but for now, here are a couple of IITESKAs to warm up:
( Paradigm Shifts )
Now, this next bit is way outside my area of expertise, but here goes:
( The Malayan Emergency ) |
|
|
| Space elevators |
[Jan. 5th, 2007|07:39 pm] |
Another Important Idea That Everyone Should Know About :-)
Capture a small asteroid. Stick it into geosynchronous orbit above a reasonably stable part of the Equator. Attach it to the ground with a big cable. It will need to be a very strong cable to support its own weight (to reach geosynchronous orbit, it would have to be nearly 36,000 km long), so you'd better make it out of carbon nanotubes. Run a railway line up the side. Ta-da! You've just reduced the cost of reaching geosynchronous orbit by a factor of more than 100.
What you have just built is called a Space Elevator.
This idea isn't actually as daft as I've just made it sound, and some very bright people (including NASA) are working on building one. In fact, if you want to go to Mars, it would probably be cheaper to build a space elevator first. These guys reckon they can do it by 2031. There's lots more information in the Wikipedia article linked; I'd also recommend Arthur C. Clarke's excellent novel The Fountains of Paradise, which is half about the construction of a space elevator and half about his beloved Sri Lanka. |
|
|
