typodupeerror
Slashdot Deals: Cyber Monday Sale! Courses ranging from coding to project management - all eLearning deals 25% off with coupon code "CYBERMONDAY25". ×

## Comment Re:Hydro = from the sun (Score 1)181

Direct solar may sound nice and work fine in small scale, but collectors would have to cover great areas to be effective

The total world energy consumption is somewhere around 100PWh/year. That's around 274TWh/day. The sunlight hitting the Earth is around 1kW/m^2, so 8kWh/m^2 assuming 8 hours of sunlight. If you assume 100% efficiency in conversion (totally impossible, but we'll start there and refine later), then that means that you need about 3.45E10 m^2 of land devoted to solar power. That's a square about 185km on each side. If you assume 10% efficiency (mass produced photovoltaics are 12-25% these days), then you need an area about 342000km^2, or about the area of Germany, to power the entire world. Now, given the efficiency of power distribution, you probably wouldn't want to put it all in one place, but you could easily fit solar panels enough that, even with transmission losses, you could power all of North America in Utah or Texas without anyone noticing. The difficulty is not the generation, it's the storage.

## Comment Re: Already solved (Score 1)110

I bought a new fridge about 5 years ago. I moved house and worked out that the difference in power consumption between the old fridge I had and the new one that I bought meant that the new fridge paid for itself in 2-3 years. Newer utilities are significantly lower power than ones from even the '80s and '90s. I bet that the next set of low-operating-cost white goods will all have some kind of Internet-related insecurity as standard.

## Comment Re:How about fixing the systems? (Score 1)143

Leap seconds are announced months in advance

i.e. with less warning than the revalidation time for a lot of safety-critical systems.

Anybody who knows about problems with leap days?

Well, aside from the Zune infinite looping...

Leap days (which we call leap years, because consistency is hard) are predictable. Software written 40 years ago will have the extra days at exactly the same times and with exactly the same frequency that the designers thought that they would. You never have problems where some parts of a distributed system got the update and others didn't. Either the code is working, or it's broken. It's also really easy to test.

## Comment Re:This is stupid ... (Score 2)143

You do understand that the navigation is ALSO intrinsically tied to the astronomical positioning of things, right?

Today? Mostly (for anything where accuracy matters to the degree that leap seconds will make a difference in under a few hundred years) it depends on the GPS position, or some equivalent. GPS time, unlike UTC, does not have leap seconds.

## Comment Re:This is stupid ... (Score 2)143

If we don't bother with leap seconds, then the distance that the sun will be off from being directly overhead at the equinox is about the same as it is now from being a couple of hundred miles away from the meridian. A simpler solution to the problem would be to, every couple of thousand years, have a one-hour reset. There is basically nothing that depends on the position of the sun in the sky to that level of accuracy, but there are a huge number of things (including all air-traffic control systems) that depend on keeping time in sync to sub-second accuracy and are safety critical. These things all need some special handling for every adjustment and an extra hour would be no more difficult for them than an extra second, so doing one big correction every couple of thousand years would be far, far cheaper. That's of course assuming that we still care much for a time system that's predicated on a single planet's relationship to its star in 2,000 years. It seems likely that we'll either be sufficiently disbursed that we don't, or that we'll have damaged our civilisation enough that we will have far bigger problems to deal with.

## Comment Re:Um... (Score 2)274

Are those numbers by currency unit or by transaction? I probably do about as many transactions in cash as by card (though contactless is reducing that quickly), but they're all very low value. I'll easily spend more in one card transaction than I will in a couple of weeks of cash transactions (I'm in the UK).

## Comment Re:High Level Waste (Score 4, Informative)330

That's almost as silly as Red Mercury. Do you know why no terrorist plots have actually detonated a dirty bomb? It's not because radioactive materials are hard to get hold of, it's because building an effective dirty bomb is really hard. You have to find something that is sufficiently radioactive to be a problem, that is easy to disburse over a wide area, but which won't disburse so far / quickly that it will simply drop to background radioactivity levels.

## Comment Re:Star wars missile defense (Score 1)330

Well, nothing aside from convincing the USSR to spend so much on defence that their economy collapsed, shortly followed by their political system.

Oh, and those intelligence agencies that are now crying for a greater ability to spy on us so that they can protect us from terrorists? They were completely surprised and thought that the collapse of the USSR was a hoax.

## Comment Re:Sounds like fortran (Score 1)106

It's aimed at the same niche as Fortran, but comes with memory safety, a REPL environment and a JIT, and good interfacing with other languages (including Fortran) to reuse library code. Fortran is probably still a better choice if you're writing a library that lots of people will use.

## Comment Re:jesus thats all it takes? (Score 1)106

Unfortunately it has not chance of dislodging R,

The places I've seen Julia make the most inroads, it's been displacing Fortran, not R. And anything that displaces Fortran makes me happy.

## Comment Re:Do we need another language? (Score 1)106

Your enumeration of requirements omits scientific computing, which is the niche where Fortran is currently dominant and Julia is growing.

## Comment Re:Another day, another language. (Score 1)106

I suspect that most people doing scientific computation have heard of Julia. It's a pretty neat language (and has a lot shallower a learning curve than Fortran, which is the big player in the space. If you're not in a field that uses Fortran a lot, Julia probably isn't too relevant to you). I had a student last year work on hoisting bounds checking out of loops to expose better optimisation opportunities for autovectorisation. In combination with Polly, this got a factor of 4-8 speedup for a lot of workloads and also paves the way for things like GPU offloading for critical loops. There are definitely a lot of places where some of that \$600K could be spent on small improvements that would give huge improvements to end users.

## Comment Re:"just" an implementation of what Android/Google (Score 1)131

To give a simple example: If you want to share a document between two apps on Windows Phone, then one passes it directly to the other. To do the same on Android, one writes it to the (typically emulated) SD card and now that you've completely bypassed the security model, everything else can open it. It would be easy to designate a directory on Windows Phone that would act as the SD card, but only Android apps would be allowed to use it, you wouldn't have the same user model for document sharing between Android and Windows apps as you do between Windows apps. There are lots of other issues with differences in standard widget implementations and so on. Even moving between iOS and Android (whose UIs are a lot more similar to each other than either is to Windows Phone), the difference in behaviour of the back button is confusing.

"Don't worry about people stealing your ideas. If your ideas are any good, you'll have to ram them down people's throats." -- Howard Aiken

Working...