Slashdot Mirror

Nope, he owned both domains.

I did a little searching and found a paper from 2011 [pdf] that addresses Jakobshavn specifically. It has this to say:

3.3. Jakobshavn Isbroe

Jakobshavn Isbroe was losing 8 Gt a1 of mass per year in 2000 (Figure 2). This rate increased over the following years to near 25 Gt a1 by the end of 2002. The loss rate then stabilized and declined back under 20 Gt a1 until 2006, when it increased to 33 Gt a1, reaching 34 Gt a1 by the end of 2007. Subsequently, the annual loss rate has fluctuated between 25 and 33 Gt a1. In total the glacier lost 321 ± 12 Gt by the end of 2010, equivalent to a basin!wide thinning of 3.5 m, with 2/3 of this loss occurring since June of 2005 (Figure 3). The 85 km2 of retreat accounts for nearly 20% of this loss. The rate of discharge is now such that the glacier is losing mass nearly throughout the year. As previously reported [Joughin et al., 2008a, 2008c; Luckman and Murray, 2005], annual oscillations in speed of ±20%, with a peak in June/July, correlated with seasonal retreat and advance of the ice front, become increasingly pronounced at the location of the fluxgate after 2005 (Figure S7). Seasonal oscillations in speed, SMB and front position cause annual fluctuations in mass of up to 50 Gt.

Of the other two glaciers reported on in the paper Helheim gained 17 +/- 13 Gt and Kangerdlugssuaq lost 152 +/- 10 Gt compared to Jakobshavn's 321 +/- 12 Gt in the 11 year period studied. Those are the three largest outlet glaciers in Greenland.

More generally the ice mass loss on Greenland has been well documented by the GRACE satellites. See the Total Ice Mass section of the Arctic Report Card: Update for 2013 for details.

So far, Go has made no choices regarding generics, besides the "we're working on finding out what kind of generic programming features is desirable for us to have in the first place". In fact, it's not even meaningful to talk about "no generics" since the term "generics" is highly contextual. The C# people talk about generics all the time when what they have in mind is actually a simple, 1980 vintage style rank-1 parametric polymorphism with no aspiration whatsoever to doing anything remotely useful in the context of what passes for generic programming today. (Or read this.)

There seems to be an awful lot of second hand record stores in Europe for something that is illegal. You seem to have missed the Exhaustion Principle/Rule which operates in a similar fashion to the first sale doctrine

Second hand software seems to more to be a grey area, where reselling a license for download is illegal but reselling a piece of boxed software (game disks, manuals, etc) seems to be fine.

Nobel Prize Gerard 't Hooft has already done that for you: HOW to BECOME a GOOD THEORETICAL PHYSICIST.

The Houqua, built in 1844 was $45,000. Though many other ships cost as much as $70,000.

What cost $45000 in 1844 would cost $1,024,086.13 in 2009.

Even galleons in the 1600's and 1700's were a huge investment of capital. Though admittedly these are far smaller than the cost of spacecraft, with reasonable payoff per ton in products shipped (which we obviously don't expect for spacecrat).

http://igitur-archive.library.uu.nl/student-theses/2007-1113-200356/FINAL%20-%20A%20comparative%20look%20at%20the%20funding%20of%20colonial%20enterprises%20in%20Asia.doc

But like I said, I wouldn't say ships are any more expendable than tankers of today simply because they were made of timber.

But yes, people WERE expendable. They actually designed ships that could be rigged and run by a bare minimum of crew simply because they expected some of the crew to die off.

And so I did.

Sure, a good first starting point is Carroll, Sean, "Spacetime and Geometry: An Introduction to General Relativity". 2003. ISBN 0-8053-8732-3

A good chunk of the book walks you through the maths you need to deal with GR, notably differential geometry. A decent library will have a copy you can leaf through before digging into your wallet; it's not really geared for outright beginners -- it helps to have a good understanding of quantum and classical electrodynamics, special relativity and calculus, but you won't need University-graduate-level maths or knowledge, and the book is no substitute for grad courses (although it might be used in one!)

Schutz, Bernard F., "A First Course in General Relativity". 1985 978-0521277037 is easier and more didactic, but shows its age a bit with respect to things like Einstein Lensing, and missing mass issues (after all it predates BOOMERANG by a decade or more...) Schutz's math books are good too (and so are Schaum's).

If you want much harder than Carroll, he has an excellent bibliography, and there's always arxiv's qc-gr :-) :-)

However, 't Hooft's bibliography is online http://www.phys.uu.nl/~thooft/theorist.html and also worth reading. 't Hooft also recommends Carroll, fwiw. He also recommends his own book, which is hard compared to Carroll's.

't Hooft is one of the people you will want to read if you find SR, GR and QED easy. (In fact, if you do, sign up as a part time student doing physical cosmology!)

While you're thinking, analytically, your relativistic journey is pretty similar to Supplee's paradox in the presence of nonuniform gravitation. Matsas's arxiv preprint is here and is very steep for anyone, which is why I'm not typing any mathmode stuff here (not that slashdot supports it...). Supplee's ocean is somewhat analogous to the natural realization of free space, and the sub is directly analogous to your relativistic space ship -- the analogy is closer if you fly a geodesic above the plane of the galaxy, such that the mass halo can be seen as the surface of the ocean and the more visible mass forms the ocean floor, with "neutral buoyancy" being a constant acceleration towards the plane of the galaxy.

This geodesic is necessarily something like an arc seen from a nonrelativstic observer looking edge-on at the galaxy, since there is more mass towards the middle of the milky way than towards the edge.

But what does the ship do as it accelerates? Does it follow this arc as planned, or is it accelerated downwards towards the plane of the galaxy or upwards away? Is this gravitational acceleration uniform (this is not in Supplee's paradox, it requires thinking about the distribution of matter) at a given speed? What happens to any non-uniformity as the ship accelerates along the planned arc? etc.

If you can grok the idea of different large clumps of stars in the galaxy influencing the spaceship flying over top of the galaxy, then narrowing that down to a spaceship flying through the galaxy (which because of the inverse square law is much lumpier spacetime!) should be straightforward. :-)

Sorry about drowning you in this stuff. You are right about Lorentz-Fitzgerald contraction happening, and would be right in an ideal flat spacetime about the practicality of relativistic interstellar or intergalactic travel with respect to the lifetime of a traveller. Unfortunately real spacetime is not flat at all, so special relativity is an insufficent toolset for this problem, and your traveller's lifetime would be dramatically shortened by a rather spectacular local shaking apart.

Sure, a good first starting point is Carroll, Sean, "Spacetime and Geometry: An Introduction to General Relativity". 2003. ISBN 0-8053-8732-3

A good chunk of the book walks you through the maths you need to deal with GR, notably differential geometry. A decent library will have a copy you can leaf through before digging into your wallet; it's not really geared for outright beginners -- it helps to have a good understanding of quantum and classical electrodynamics, special relativity and calculus, but you won't need University-graduate-level maths or knowledge, and the book is no substitute for grad courses (although it might be used in one!)

Schutz, Bernard F., "A First Course in General Relativity". 1985 978-0521277037 is easier and more didactic, but shows its age a bit with respect to things like Einstein Lensing, and missing mass issues (after all it predates BOOMERANG by a decade or more...) Schutz's math books are good too (and so are Schaum's).

If you want much harder than Carroll, he has an excellent bibliography, and there's always arxiv's qc-gr :-) :-)

However, 't Hooft's bibliography is online http://www.phys.uu.nl/~thooft/theorist.html and also worth reading. 't Hooft also recommends Carroll, fwiw. He also recommends his own book, which is hard compared to Carroll's.

't Hooft is one of the people you will want to read if you find SR, GR and QED easy. (In fact, if you do, sign up as a part time student doing physical cosmology!)

While you're thinking, analytically, your relativistic journey is pretty similar to Supplee's paradox in the presence of nonuniform gravitation. Matsas's arxiv preprint is here and is very steep for anyone, which is why I'm not typing any mathmode stuff here (not that slashdot supports it...). Supplee's ocean is somewhat analogous to the natural realization of free space, and the sub is directly analogous to your relativistic space ship -- the analogy is closer if you fly a geodesic above the plane of the galaxy, such that the mass halo can be seen as the surface of the ocean and the more visible mass forms the ocean floor, with "neutral buoyancy" being a constant acceleration towards the plane of the galaxy.

This geodesic is necessarily something like an arc seen from a nonrelativstic observer looking edge-on at the galaxy, since there is more mass towards the middle of the milky way than towards the edge.

But what does the ship do as it accelerates? Does it follow this arc as planned, or is it accelerated downwards towards the plane of the galaxy or upwards away? Is this gravitational acceleration uniform (this is not in Supplee's paradox, it requires thinking about the distribution of matter) at a given speed? What happens to any non-uniformity as the ship accelerates along the planned arc? etc.

If you can grok the idea of different large clumps of stars in the galaxy influencing the spaceship flying over top of the galaxy, then narrowing that down to a spaceship flying through the galaxy (which because of the inverse square law is much lumpier spacetime!) should be straightforward. :-)

Sorry about drowning you in this stuff. You are right about Lorentz-Fitzgerald contraction happening, and would be right in an ideal flat spacetime about the practicality of relativistic interstellar or intergalactic travel with respect to the lifetime of a traveller. Unfortunately real spacetime is not flat at all, so special relativity is an insufficent toolset for this problem, and your traveller's lifetime would be dramatically shortened by a rather spectacular local shaking apart.

Indeed. They should take advantage of the open-source textbooks that already exist... either by simply selecting one for their purposes, or putting together the best pieces from various sources into a coherent textbook that serves their purposes. Here are the open-source textbook (or related information) sites I'm aware of:

Pointers to Textbooks and Content:
http://textbookrevolution.org/
http://www.opentextbook.org/
http://www.theassayer.org/
http://spiff.rit.edu/classes/
http://globaltext.terry.uga.edu/
http://en.wikibooks.org/wiki/Main_Page
http://wiki.laptop.org/go/Books

Some available lecture notes:
http://ocw.mit.edu/index.html
http://www.phys.uu.nl/~thooft/theorist.html#languages
http://spiff.rit.edu/classes/

You're probably kidding, but the big difference is that biological processes are usually massively parallel and interdependent, while programs are primarily sequential or can easily be described as such.

Even a sequential, programming-language-like system that is slightly DNA-like but with lots and lots of helpful hints and things famiiar to programmers built in is actually quite challenging to reverse engineer.

1. The different masses almost certainly probably were (and remain) different, it's just that when they were manufactured, they were noted as varying from the IPK by a certain amountto the limit of measurement. Measurement technology has gotten better, and has exposed further differences in the masses of prototype copies to the IPK at BIPM. (Each copy is calibrated as a mass variation from the IPK).

Many individual PKs have been stable recently relative to other measurements of the kilogram; NPL (UK) in particular has been keen on investigating this with respect to the Watt Balance, for example. Some of the individual PKs have lost mass relative to the IPK and themselves -- the loss is on the order of tens of micrograms over a century -- almost certainly because of abrasion during handling and polishing.

2. The IPK mass variation is weird but it also shows a ~10 microgram mass deviation at various stages of polishing before being compared with a reference copy. A long tail on solvent evaporation is the likliest culprit. 10 micrograms is a bit more mass than a light fingerprint, and it is known that polishing techniques have improved enough to remove particles of dust and lipoprotein smears which would have been invisible in the early 20th century. Proving conclusively that the IPK suffered from contamination at the time of its establishment as a prototype is non-trivial, however.

However, even if there are "new physics" involved, it is unclear how a particular blob of material would lose or gain mass independently of similar blobs of material and all other blobs of material of the same mass. While the IPK is the official mass standard, other masses are routinely compared for periodic calibration of the cgs system (for example) and in physical sciences in which molar masses are in routine use.

3. Your shrinking cosmology exacerbates the hierarchy problem. In particular, if you vary the gauge couplings of the electromagnetic, weak, and strong forces to operate in the shrinking volume, you must also adjust gravity's field strength too, or your shrunken gravitationally bound systems quickly collapse into black holes. If you adjust gravity's local field strength to preserve stellar and galactic and cluster scale structures, you then run into a problem involving the peculiar redshifts within clusters (and within galaxies, for those galaxies whose rotational plane allows us to see a doppler difference between receeding and advancing arms).

A variety of elucidations of quintessence-like expansion fields work better because the energy needed to drive the metric expansion of spacetime is extremely small compared to gravitation, so there is no need to "protect" observed structures at large and small scales (gravitationally bound systems remain gravitationally bound, electromagnetically bound systems remain EM bound, nucleons aren't ripped apart, and so forth), and no reason to protect future structures from "big rip" like events. That is, introducing a new low-energy slow-rolling field is much more conservative than introducing variations of the fields in the standard cosmology.

4. You have a gauge problem involving your explanation for redshift. While you could tune the fine structure constant to allow for the downshift in frequencies emitted by distant compactified astronomical objects, that does not shift the absorption lines. In particular, we have views of bright astronomical objects occluded by absorbing molecular clouds at different distances along the line of site; each such cloud leaves a "Hubble fingerprint" that shows absorption line shifting redward with distance.

These problems alone are enough to sink your proposed cosmology as described.

If you care to be rigorous in your proposal, I think you will find people who are prepared to be equally rigorous in analysing it.

Please see http://www.phys.uu.nl/~thooft/theorist.html

The League for Programming Freedom was formed by Stallman around the Apple UI lawsuits -- http://en.wikipedia.org/wiki/League_for_Programming_Freedom

As for gcc -- NeXT refused to contribute its patches back to the FSF for a while. http://faqs.cs.uu.nl/na-dir/Objective-C/answers.html has some info on that.

As an aspiring astronomer your profile will strongly resemble that of a theoretical physicist. And you'll certainly need to know about just about everything he lists on that page: from classical mechanics, optics, special and general relativity, quantum mechanics, statistical mechanics, thermodynamics, plasma physics, plain old electromagnetism, to electronics. 't Hooft lists freely downloadable high-quality reading material on just about every topic!

And although you didn't ask, don't forget the computational side of things! Most astronomers I know are heavy computer users and very good programmers.

So make sure you know about Fortran and the libraries that are written in it (e.g. have a look at http://www.netlib.org/liblist.html and acquaint yourself with Lapack, Sparsepack, fftpack, cephes etc). Many of those routines can also be found in Matlab, Octave, Scilab, etc., but if you need full control and a standalone executable on a big supermini you might have to go back to Fortran and C++), And make sure (well ... I hardly need tell a mathematics undergraduate but I can't omit it) that you know about Maple and/or Mathematica.

But ... if I may be so bold ... whilst reading and self-study are an indispensable element of learning physics they are rarely sufficient. You'll also need to learn a special way of thinking that sometimes comes hard to people with a background in mathematics. Which is to know when and where to cut corners and use approximations, and sometimes even go beyond the mathematics you know.

Think of Paul Dirac (of the Dirac Delta function). His "function" isn't a function at all, it's a distribution, and trying to think of it as a function will lead you to contradictions. But Dirac set up a formalism using it (and got the properties right !) without knowing about distributions (they were invented later partly to put what he had done on a firm mathematical basis). He simply let mathematical firmness go hang at the appropriate moment. Now I'm not comparing you to Dirac (and I'm certainly not encouraging you to take liberties with mathematics), but Dirac was a physicist first and a mathematician second. That's what I mean. Someone suggested the Feynman Lectures ... they're great (if sometimes a tough read) exactly because Feynman makes this very point.

You see ... in Physics, the physics comes first and the mathematics second; meaning that in thinking about physics problems you'll have to think in terms of physics (of course greatly helped by the mathematical formalisms in which physical laws are couched) but if you'll need to be able to think through a physical line argument without necessarily working through all the maths. Physicists do this as a second nature, and you'll need to learn how.

I think this is for you, MOBE: http://www.phys.uu.nl/~thooft/theoristbad.html

Gibson, in an interview by Lance Loud in an article on the 10th anniversary of "Blade Runner" for the magazine "Details" (October 1992 issue), had the following to say:

"About ten minutes into Blade Runner, I reeled out of the theater in complete despair over its visual brilliance and its similarity to the "look" of Neuromancer, my [then] largely unwritten first novel. Not only had I been beaten to the semiotic punch, but this damned movie looked better than the images in my head! With time, as I got over that, I started to take a certain delight in the way the film began to affect the way the world looked. Club fashions, at first, then rock videos, finally even architecture. Amazing! A science fiction movie affecting reality!"

"Years later, I was having lunch with Ridley, and when the conversation turned to inspiration, we were both very clear about our debt to the Métal Hurlant [the original Heavy Metal magazine] school of the '70s--Moebius and the others. But it was also obvious that Scott understood the importance of information density to perceptual overload. When Blade Runner works best, it induces a lyrical sort of information sickness, that quintessentially postmodern cocktail of ecstasy and dread. It was what cyberpunk was supposed to be all about."

I like the ones sugested at http://www.phys.uu.nl/~thooft/theorist.html#pmathematics . For the basics there's Texas A&M's http://www.wtamu.edu/academic/anns/mps/math/mathlab/beg_algebra/

IANAL, but this may be about the moral rights of the authors, which includes things like the right of attribution. In some countries/jurisdictions these rights can go quite far and cannot be transfered or waived. For instance, in The Netherlands, artists can object to defilement of their work. This can have nasty implications, for instance, when you want to alter a building you own in a way that the architect or interior designer objects to. My alma mater cannot alter the interior design of one of its libraries for this reason.

That early this morning (long before I read this) while surfing an article about Google Scholar I happened across mention of the intriguing article Can quantum-mechanical description of physical reality be considered complete?(PDF) by the aforementioned Einstein Podolsky and Rosen, and read it.

Having read that article, and this one, I feel Albert Einstein and company were guilty of some flat thinking here. I hope this guy gets his bucks. I doubt he'll find what he's looking for, but even a negative result can add to the pool of human knowlege. Sometimes results can serendipitous.

This is one of those grand myths that the public just can't shake. Photovoltaic's have a very good energy return on investment (EROI).

The energy payback peroid for various PV cell types are:
Crystal Silicon: 3.3 years
Multicrystal Si: 0.8 years
CIS: 0.4 years

To put that is perspective of EROI:
Photovoltaics (Si): 60:1 - 10:1 (based on above)
Wind: 60:1
Coal(US average): 9:1
Nuclear (light water): 4:1
Oil (mid-east): 10:1 - 30:1
Oil (US): 3:1 or less

And that is keeping in mind that the lifespan of PV is calculated at 30 years, an arbitrary number picked to equalize it with the life of a coal or nuclear power plant, however are panel warranties are 20-30 years alone. There is no reason to believe that the average lifespan of a PV panel won't be 40-60 years or more.

This is one of those grand myths that the public just can't shake. Photovoltaic's have a very good energy return on investment (EROI).

The energy payback peroid for various PV cell types are:
Crystal Silicon: 3.3 years
Multicrystal Si: 0.8 years
CIS: 0.4 years

To put that is perspective of EROI:
Photovoltaics (Si): 60:1 - 10:1 (based on above)
Wind: 60:1
Coal(US average): 9:1
Nuclear (light water): 4:1
Oil (mid-east): 10:1 - 30:1
Oil (US): 3:1 or less

And that is keeping in mind that the lifespan of PV is calculated at 30 years, an arbitrary number picked to equalize it with the life of a coal or nuclear power plant, however are panel warranties are 20-30 years alone. There is no reason to believe that the average lifespan of a PV panel won't be 40-60 years or more.

This is one of those grand myths that the public just can't shake. Photovoltaic's have a very good energy return on investment (EROI).

The energy payback peroid for various PV cell types are:
Crystal Silicon: 3.3 years
Multicrystal Si: 0.8 years
CIS: 0.4 years

To put that is perspective of EROI:
Photovoltaics (Si): 60:1 - 10:1 (based on above)
Wind: 60:1
Coal(US average): 9:1
Nuclear (light water): 4:1
Oil (mid-east): 10:1 - 30:1
Oil (US): 3:1 or less

And that is keeping in mind that the lifespan of PV is calculated at 30 years, an arbitrary number picked to equalize it with the life of a coal or nuclear power plant, however are panel warranties are 20-30 years alone. There is no reason to believe that the average lifespan of a PV panel won't be 40-60 years or more.

There are various Logo environments, some are free. They are great for kids that know a few letters (see http://el.media.mit.edu/Logo-foundation/)

There used to be a free program by Prof. Mark Overmars called Drape (see http://www.cs.uu.nl/people/markov/kids/drape.html) but unfortunately it is no longer available for free download (though there might be ways to get a copy). It's advantage over Logo is that it is used through a graphic interface and does not require the child to know anything about letters (perhaps it has some value as a preparation to reading as it makes a child realize how sequences of sybols arranged in different ways have different meanings.

The real reason to let kids use these is that it gives them more ways to be creative. It is not supposed to completely replace things like building blocks or Legos.

Game Maker (see http://www.gamemaker.nl/) by the same Prof. Overmars is suitable for older kids. My 6 year old child can do some things with it (actually he did when he was 5) but it's really not for his level and his success owes a lot to help from his 12 years old brother. For older kids it is a great way to learn programming in an environment that balances their needs for fast results with the ability to do complicated programming (and I've seen my older son progressing from simple graphic UI programming by dragging icons around and editting their property sheets to using more and more scripting). It's Windows only and the author claims it is not suitable for open sourcing or porting to other platforms as the code is too Windows-centric, but I think it can serve as a good model for creating a similar open source alternative - a programming environment that grows with the child.

Finally: even a standard graphics program such as MS Paint can let a child be creative, especially if a child learns to use Google images and copy/paste images to his/her own work. My younger son convinced himself at the age of 4 that he needs to learn to read because this is the key to obtain images from Google, and that he needs to learn English because searching in English produces more and better search results.

Prof. OverMars has one more cool program that kids can use to be creative and it is "Drawing for Children" (see http://www.cs.uu.nl/people/markov/kids/draw.html). It is not a replacement for a standard graphics program but it lets kids be creative in a different way (composing images from erady made components.) I think it has some cool things like fractal-based generation of trees, letting the child "draw" a forest with each tree a randomly generated fractal. (I haven't followed Tux paint too much. Does it have these things? Tux paint have a problem of "too many penguins". It makes a child's drawing look like a Windows desktop after an ISP instalation disk has been run, assuming the ISP's logo is a penguin ;-) ).

There are various Logo environments, some are free. They are great for kids that know a few letters (see http://el.media.mit.edu/Logo-foundation/)

There used to be a free program by Prof. Mark Overmars called Drape (see http://www.cs.uu.nl/people/markov/kids/drape.html) but unfortunately it is no longer available for free download (though there might be ways to get a copy). It's advantage over Logo is that it is used through a graphic interface and does not require the child to know anything about letters (perhaps it has some value as a preparation to reading as it makes a child realize how sequences of sybols arranged in different ways have different meanings.

The real reason to let kids use these is that it gives them more ways to be creative. It is not supposed to completely replace things like building blocks or Legos.

Game Maker (see http://www.gamemaker.nl/) by the same Prof. Overmars is suitable for older kids. My 6 year old child can do some things with it (actually he did when he was 5) but it's really not for his level and his success owes a lot to help from his 12 years old brother. For older kids it is a great way to learn programming in an environment that balances their needs for fast results with the ability to do complicated programming (and I've seen my older son progressing from simple graphic UI programming by dragging icons around and editting their property sheets to using more and more scripting). It's Windows only and the author claims it is not suitable for open sourcing or porting to other platforms as the code is too Windows-centric, but I think it can serve as a good model for creating a similar open source alternative - a programming environment that grows with the child.

Finally: even a standard graphics program such as MS Paint can let a child be creative, especially if a child learns to use Google images and copy/paste images to his/her own work. My younger son convinced himself at the age of 4 that he needs to learn to read because this is the key to obtain images from Google, and that he needs to learn English because searching in English produces more and better search results.

Prof. OverMars has one more cool program that kids can use to be creative and it is "Drawing for Children" (see http://www.cs.uu.nl/people/markov/kids/draw.html). It is not a replacement for a standard graphics program but it lets kids be creative in a different way (composing images from erady made components.) I think it has some cool things like fractal-based generation of trees, letting the child "draw" a forest with each tree a randomly generated fractal. (I haven't followed Tux paint too much. Does it have these things? Tux paint have a problem of "too many penguins". It makes a child's drawing look like a Windows desktop after an ISP instalation disk has been run, assuming the ISP's logo is a penguin ;-) ).

At Utrecht University I did a course exactly like this, and it was called Software Project. Students form teams and work on projects submitted by Dutch companies. It works both ways: the students learn how software development works in real life (instead of in a 'safe' environment like university), and the companies get to test their ideas, see how they work out, and get at least a beginning of the implementation. They usually don't submit business-critical projects.

Our team worked on a project called Cheetah, and we worked with SVN for version control/concurrent access, a development wiki for sharing and working out ideas, a bug tracking system, and agile software development (pair programming, big visible charts, user stories). Some of us had more technical insight and had experience running servers, building websites, etc. while others had knowledge of diabetes (which the project was about), or access to medical information because their mother worked in a hospital, and so on. All in all a very enjoyable course where I learnt a lot.

One of the problems we ran into was that agile software development doesn't work very smoothly if the team meets only one or two days a week; most of us did other courses or had part-time jobs.

There still seems to be a popular belief that PV systems cannot 'pay back' their energy investment. The data from recent studies show however that although for present-day systems the EPBT can still be high, it is generally well below the expected life time of a PV system

Aside from "all my life, you've got a good point, and it appears that I might be low in that number - the first is recent and from a "non-lefty biased" source, the others vary in source quality and recent (the last is 1977).

13.8% http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd= Retrieve&db=PubMed&list_uids=6664484&dopt=Abstract
12-15% http://www.anythingleft-handed.co.uk/faq.html#perc entage
13% http://www.cs.uu.nl/wais/html/na-dir/lefty-faq.htm l
11% http://www.righthandlefthand.com/
8-15% (Wikipedia really, but I've confirmed the original source through my University's access to the online copy Hardyck, C., & Petrinovich, L. F. (1977). "Left-handedness," Psychological Bulletin, 84, 385-404. - You have to read the article itself to get the range, the abstract lists only 10%)

Personally, I like monadic parser combinators, like those provided by the Parsec library for Haskell. You can parse arbitrary context free grammars, and even many sensible context-sensitive ones with little difficulty, you get to write your parsers in the language (Haskell) and you get meaningful parse error reports for free.

A major downside to the approach is that Parsec itself lacks a symmetric choice combinator, having only left-biased conjunction, together with a combinator which causes a parser not to consume input when it fails. Though other libraries, like Koen Claessen's ReadP rectify this, the associated performance costs tend to be higher.

I tend to use Parsec even for some tasks where many people would use regular expressions. It might not be quite as fast as statically building your parser, but it's possible to get really quite decent performance out of it, and the convenience level is quite high.

Another interesting thing to look at are arrow-based parser combinators, like PArrows -- these allow for a greater level of optimisation at runtime, so you can get really good performance while allowing for things like symmetric choice. They also can allow for cool features like the ability to inspect the parser and emit code in various languages for that parser. (The one I linked to has the ability to compile parsers to JavaScript code in fact.) The downside is that arrows tend to be a little more inconvenient to program with than monads.

Personally, I like monadic parser combinators, like those provided by the Parsec library for Haskell. You can parse arbitrary context free grammars, and even many sensible context-sensitive ones with little difficulty, you get to write your parsers in the language (Haskell) and you get meaningful parse error reports for free.

A major downside to the approach is that Parsec itself lacks a symmetric choice combinator, having only left-biased conjunction, together with a combinator which causes a parser not to consume input when it fails. Though other libraries, like Koen Claessen's ReadP rectify this, the associated performance costs tend to be higher.

I tend to use Parsec even for some tasks where many people would use regular expressions. It might not be quite as fast as statically building your parser, but it's possible to get really quite decent performance out of it, and the convenience level is quite high.

Another interesting thing to look at are arrow-based parser combinators, like PArrows -- these allow for a greater level of optimisation at runtime, so you can get really good performance while allowing for things like symmetric choice. They also can allow for cool features like the ability to inspect the parser and emit code in various languages for that parser. (The one I linked to has the ability to compile parsers to JavaScript code in fact.) The downside is that arrows tend to be a little more inconvenient to program with than monads.

Cells will fail and will need replacing from time to time, and will be expensive to do.

Most manufacturers Guarantee their panels for 20-30 years, so that is minimum life. Of course on average they will last longer. Longer than most power plants, and yes, virtually maintenance free.

home energy usage is pretty much the exact inverse of when the most solar radiation is available

In fact, the average electricity demand on the grid typically follows the sun cycles, especially in summer when electricity use peaks. The peak grid loads are typically ~40% higher at midday than the nighttime minimum. Even in the winter, when the day peaking is less pronounced (and shifted towards morning/evening), solar could address as much as 35-40% the national electricity demand even without storage. See http://currentenergy.lbl.gov/pjm/index.php for an example of demand curves.

Of course storage on the grid is important, and needs work, but we could address a HUGE amount of US electrical need without it.

However, for serious microgeneration, at the current time the only halfway practical and affordable renewable energy source is wind, which is vastly cheaper

Wind is very cheap, not halfway practical cheap, but cheap as coal cheap. Hydro is very cheap as in cheaper than coal cheap, and photovoltaics are the cheapest thing going when you don't have a 100 year old subsidized grid infrastructure. Because of that, photovoltaics is the only option in many places in the developing world, because the cost of the lines is 10 times more expensive than the coal plant that make the power. But more importantly, PV is getting exponentially cheaper to manufacture by the decade, and new low cost technologies are just starting to leak out of the lab into a marketplace near you. (However, note that demand has outstripped supply by 30% with 40%/year growth in the market for several years, even if the manufacturing is getting cheaper, it is not currently seen in the market because of high demand).

Bottom line, renewables are the cheapest things going, even without addressing the huge subsidy imbalance going to traditional fuel sources (oil, coal, nuclear, etc)

The energy to make a typical wind turbine is generated by the turbine over a period of six months - it's more like 6 years for solar.

Photovoltaics cells have an energy pay-back period ranging from 3 months for newer technologies (e.g. CIS, CdTe) to 3 years for traditional crystalline silicon. Even mainstream multi-crystal silicon has a payback period of 0.8 years. And these numbers don't even address the newer, and lower embodied energy low cost multi-junction concentrators or low temp printable cells.

So when you look at a 30 year life span, that gives PV an Energy return on investment of 10:1 for Crystal Si, 37:1 for multi-Crystal Si, and 100:1 with CIS. Compare that to typical fuels: Coal (9:1), nuclear (4:1), US oil (3:1), Mid-east oil (10:1-30:1).

Unless photo voltaic solar becomes vastly cheaper, it's simply a non-contender except for novelty value, even if you live in the desert.

A desert is not needed as solar insolation is relatively uniform throughout the US (and world). The best location in Arizona is only twice as good as the worst place in the Washington rainforest, with the majority of the US within 80% insolation of the best location in Arizona!

Even with today's "high" PV prices, PV is unique in that it is deployable on any rooftop, parking lot, or yard at the point of use. With net-metering or battery storage that means PV competes with retail energy not w

With a space, that is. His name is 't Hooft, not 'tHooft. The guy even has a webpage about it, so this means people are getting his name wrong all of the time...

  - webpage how to spell his name: http://www.phys.uu.nl/~thooft/ap.html

Mark

Hand-picking two years, and doing a linear fit between them is not science. It is better to fit the entire curve and then see if you see any trends. The result still depends on the amount of smoothing you do, but at least you're not aiming for a certain trend to come out.

Using a fitting segments of cubic polynomials, the result that comes out is this: http://www.phys.uu.nl/~romans/temp.png

Instead of telling people who matter, you're just posting it on Slashdot.

Noted. I have tried explaining this stuff to my hippie non-geek (but still somewhat-suspicious-of-government) girlfriend, and it's harder than I thought it would be. I don't have a clue how to get the message out to Joe Sixpack.

In any case, how do you know about somebody's key before they've called you first?

Web of Trust. There are tens of thousands of nerds whom I have never met or communicated with in any way, whose PGP keys I am able to look up and verify to some degree. Granted, that whole "to some degree" thing is open to abuse, but if one of them does start acting out-of-character (i.e. someone at mit.edu starts sending me signed Viagra spam) then I can start looking at the chain of introducers.

The cool thing about the global WoT is that not everyone needs to meet everyone; you just have to meet a few people.

Of course, you could use BIND or any other full-blown nameserver, but pdnsd is pretty low-overhead to setup and administer.

-MIT's Open Courseware at: http://ocw.mit.edu/index.html

-Textbook revolution at http://textbookrevolution.org/

-Physiscs texts at: http://www.phys.uu.nl/~thooft/theorist.html#langua ges

-The assayer at http://www.theassayer.org/

-Open content at http://www.hewlett.org/Programs/Education/Technolo gy/OpenContent/opencontent.htm

I also know a number of econometric and statistics texts that are also available as free Ebooks, but they are of interest only to specialists.

No, it was Indiana, and it really did happen.

As I said when I went over the high-end and the entry Unix server markets earlier this year, without any doubt, IBM has been an increasingly dominant factor in the Unix server business, across all form factors and SMP scalability, since the Power4 processors debuted four years ago. IBM is, in fact, arguably the main reason that the Unix server business has seen any growth at all.

http://www.phys.uu.nl/~bassa/eclipses/20051003.htm l

Why don't you tell us about the DSL service in the Yukon, Nunavut, or Northwest Territories?

With ad blocking becoming ever more popular among users, why do you block ads?

Because they are f***ing annoying. They play loud music, they steal focus and interrupt what I am doing. Some nasty flash and/or JavaScript ads consume my poor laptop's CPU and memory resources and make things run slow. Overall, they slow things down and get in my way.

They leave cookies and trackers and attempt to invade my privacy.

Now, I don't mind embedded jpg or gif ads too much, especially when they are unanimated. I've even clicked on one or two, and I don't go out of my way to block them. Though if they leave a cookie from the ad server, they are gone.

And with what?

I use pdsnd. I look through my cookie file and examine the source host of any obnoxious/popup ads. I then negative cache their domains.

Do you view internet ads as different from say, TV ads?

Yes, if they are loud (audio-compresed), flashy, popup crap. I block TV ads, too, via my DVR.

What about in a magazine? Do you not buy a magazine because it has too many?

Magazine ads don't flash, suddenly spring up in front of the page, or make noise. I don't have to actively do something in order to ignore them. They are a completely different thing.

Of course, smelly cologne ads will keep my from buying a magazine.

I'm specifically talking about the ads in a webpage, but even popup blockers can cause problems with me using a site.

If I can't use a site because it doesn't work without the ads, then it's probably not a site worth visiting, anyway.

As an example of good internet advertising, Google ads.

As an example of relatively good advertising, Slashdot's ads.

As an example of completly aweful, wish-I-could-nuke-the-server's-building kind of ads, see x10.com or just about any pr0n site.

Pluto is 2274 km in diameter. You can get the estimate of the diameter of 2003 UB313 by:

• Getting the distances from Earth and the Sun.
• Getting the magnitudes from the discoverer's paper.
• Using these equations.

Or, you could just look on the discoverer's page and get 97%.

You already know the brown marble is bigger by .1 inch, yet you claim since the polished white marble is brighter it is bigger?

No, I claim that by knowing the distance, albedo, and brightness of the marbles, we can calculate their size. When we measure these quantities and run them through the equations, the brown marble will be shown to be bigger.

Furthermore, if I move that polished white marble up next to the brown one, it gets brighter, right?

Yes, due to the inverse square law.

So by your definition, that polished marble will GROW bigger in diameter.

No, it appears brighter due to the fact that it's closer.

What I'm trying to convey to you is that there is NOT a 1:1 relation between reflectivity and size.

I didn't make that claim.

Maybe if you could provide a link to how these guys actually measure these distances and sizes WITHOUT actually being able to take a tape measure to them (or send a probe)

OMG, are you for real? Did you even try to Google it?

That's about the same age my younger son Jonatan started using the computer intensively. The older one (Daniel) started a bit later (about 4 1/2). But we had a laptop with only a touchpad back then so it was more difficult for him. Last year the children's demand for the computer became so high that I set them up with their own computers (photo of their room, that my wife would never have allowed me to publish if she could prevent it...).

Whatever they play, on the computer or not on the computer, the most important thing is that it should be a tool to aid their creativity, not to limit it. In "Hardware toys" it means things like Lego basic constrution sets (and other manufacturers. Both quality and quantity are mportant factors here: lack of each limits the child's creativity).

With Daniel we started with some cheap commercial games from Office Depot clearance. I don't think it's the right way. These quite limit the child to following instructions.

With Jonatan, we didn't make the effort to look for things to buy. He's a second child... So it was more like finding whatever we have that can occupy him so he doesn't bother us, and it worked better. M$ Paint turned out to be really great for him. It was simple enough to use, and he was very creative with it. Then he discovered Google: he uses Google images to look for pictures, then he cpopies and pastes them into his own works (He got a bit addicted to Google, and when we went on a 3 weeks vacation and he didn't have acess to the computer he was drawing pictures of the Google logo with his crayons... A few months ago when he wanted to find something his granfather told him it cannot be found on Google. So he said to his Grandpa: "Grandpa, anything can be found on Google if you know how to look for it!". Even searching Google requires creativity).

Another good piece of Children's software that encourages creativity is Drape (Drawing Programming Environment). It is a sort of programming environment similar to to Logo in some respect, but not exactly the same. One advantage is that it allows for very easy mouse interaction, so a child can create things that "work" quite easily (i.e., with just a bit of adult intervention). Form the same source, Game Maker is more suitable for older children. It is a programming environment to create games, either by using drag and drop or a builtin programming language. I've seen nice cooperation between the younger and older brother here: the young one chooses the objects and graphics, and drwas the levels of the games. The older one completes the game by adding the more abstract parts: actions and interactions. Logo is of course a very good thing for children. For the smaller ones the online r-logo is very easy and fun to use. For more serious Logo programming MSWlogo is a much more powerful implementation (including 3-dimensionality and multi-tasking). There's no need to "choose one". My son Daniel first thinks of an idea he wants to implement, then chooses the most appropriate tool, just like a programmer choosing the most appropriate programming languge for the job (he has several flavors of Logo and choses the one that has what he needs for a project. He also uses Visual Basic that he learned at school).

What else?
For several months my kids were addicted to Enigma. It's "just a game", but actually it involved loads of creativity in solving an entirely different puzzle in each level, and has the right balance between sing the brain and coordinating mo

Game Maker is actually a programming environment. It is free as in beer (or milk if it is for kids) unless you want the extras. It is used by Prof.dr. M.H. Overmars of Universiteit Utrecht as the basis of course on game design. The students think they are learning how to make games but what they are actually learning is event driven programming. It might be more fun to learn to program in this environment, especially for kids, and not just for boys. My kids are right now quite addicted to GameMaker. Even 5 years old Jonatan can design a bit with the help of 11 years old Daniel. Daniel is just making games most of the time this summer, and learning programming on the way (last year he learned Logo, and also VB at school, but Game Maker is much more fun...).

Game Maker is actually a programming environment. It is free as in beer (or milk if it is for kids) unless you want the extras. It is used by Prof.dr. M.H. Overmars of Universiteit Utrecht as the basis of course on game design. The students think they are learning how to make games but what they are actually learning is event driven programming. It might be more fun to learn to program in this environment, especially for kids, and not just for boys. My kids are right now quite addicted to GameMaker. Even 5 years old Jonatan can design a bit with the help of 11 years old Daniel. Daniel is just making games most of the time this summer, and learning programming on the way (last year he learned Logo, and also VB at school, but Game Maker is much more fun...).

At work, a competition was formed. If you're interested, I can look up the rules we used.

Yes, it wouldn't do any harm to brush up on your C++ skills. If you don't have a C++ compiler yet, get Dev-C++ http://www.bloodshed.net/devcpp.html

Then try to finish at least one game. It doesn't matter how simple it is. If you then want to concentrate on design, instead of the nitty-gritty details, you might want to try http://www.cs.uu.nl/people/markov/gmaker/

For 3D, 3DGamestudio http://www.conitec.net/a4info.htm is a cheap, decent, all-around game authoring system. You can cobble together a quick FPS and if you put more time into it, a good RPG.

The two I just mentioned are for the windows platform, btw.

If you really want to start with a good (cross-platform) 3D engine, Irrlicht http://irrlicht.sourceforge.net/ is a good open-source one. It works with Dev-C++.

The important thing is to get one game out.

A common formula for approximating the evolution of delta-T over time is 31 * Cy^2, where Cy is expressed in centuries.

The formulae are to some extent empirical as well as being approximations. The evolution of delta-t is also extremely 'noisy', and is far from a good fit with any of the formulae.

For the last few years it's been at around 64 seconds (see data in here), which comes to about 3 or 4 seconds less for the present time than some recent formulae were predicting even only a few years ago, and last time I checked nobody had a really good explanation. So it's a bit optimistic to extrapolate over 1000 years!

-wb-

• Be published
• Have discussed percentage of various software being pirated.
• Have weighed total cost of ownership versus economic means