This is a silly objection. That isn't how payback times are used.

Payback time is a quick indication of return on investment. You then compare that return on investment with the other options available to you, such as leaving the money in the bank.

If you included interest rates in payback time, you'd need to be constantly adjusting it as rates changed, and it would differ for different entities depending on their access to finance. Instead you keep it simple, and each entity has its own idea (based on circumstances and current interest rates) of what the effective payback time is of leaving the money in the bank (or not borrowing it, or investing it in other opportunities.) (For example, a start-up is likely to require a very short payback time - they're strapped for cash and are trying to get their Big New Idea to market where they hope it will make a fortune. Up-front money is then very expensive compared to down-the-road money. For them, it may make sense to lease a supercomputer even if buying it would have a two year payback time.)

What is missing from this analysis is depreciation of assets. After 6.4 years, money in the bank will have depreciated much less than the solar cells. Payback time is a rough guide - it tells you whether it is worth your while doing a more detailed analysis including finance cost, depreciation, tax implications etc.

They aren't. They're using an established term "energy payback". The authors wrote an analysis which will be useful to many people but used the word "payback" in a way which does not match your preconceived notion of how it should be used. For this, you label them "charlatans".

So all the people interested in energy payback times should not be able to publish or read about it because you've claimed ownership of the word "payback" and won't license them to use it? They should use a less clear term to express their meaning because otherwise some random idiot who reads technical papers might make the leap "payback = money", despite the term "energy payback" being self explanatory?

Had you argued that because this is "energy payback" rather than financial payback, it isn't worthy of being reported on Slashdot, I could respect your argument. Instead you label people charlatans because what they discuss is not what you're interested it.

Oh good, I'll just print up a bunch of fliers saying you torture kittens and set fire to orphanages and post them around your home town. Because nobody has heard of you and I'm not a publicly listed company, it will be 'opinion' rather than 'libel'.

I have no idea whether this guy's claims are justified, but neither do you. My liking Wikipedia does not therefore mean that the facts or the law are on the side of Wikipedia.

When El Nino leads to a new record high temperature by a large margin (for argument's sake, in 2015), the denialists will quietly adopt this as their new standard for 'normal' and in 2025 they'll be saying "warming is a hoax because temperatures haven't risen on average since 2015."

http://xkcd.com/1321/

I believe you've just taken what was intended as reductio ad absurdam seriously.

No, as you would have seen if you'd read the article. By their numbers, about 60% of the energy cost of streaming is in the data center.

Whoosh

How about a detachable luggage compartment (boot/trunk)? You don't own the car, but you have your own luggage compartment in which you keep your miscellaneous crud. Call a car, attach your compartment, drive to the mall, detach compartment, shop and fill compartment, call another car, go home, detach, unpack at your leisure while the car goes on its next mission.

Me too - as soon as it is affordable, convenient and drives better than I do. They've got one out of three already.

If you drive on the same streets that I do, you trust me with your safety. As my driving skills are below median, this should be a lot more worrying to you then the prospect of being in a computer-driven car. (Fortunately for you, surveys show that below-median drivers are rare.)

You seem to be under the impression that Eratosthenes measured the size of the Earth more accurately than the 18th century scientists on whose work the metre was based. If so, you are wrong.

We don't know for sure how accurate Eratosthenes measurement was, because we don't know for sure how big the 'stadia' he measured in were, but probably he was out by 16%. His method had systematic errors in it which would prevent a highly accurate measurement.

By contrast, scientists had been able to measure the non-sphericity of the Earth prior to the definition of the metre, which is a 0.5% effect.

From Wikipedia: "The circumference of the Earth through the poles is therefore slightly more than forty million metres (40,007,863 m)"
which indicates a 0.02% error in the original definition of the metre.

If you're in the right part of the world, the word also means "traffic light".

If your interface allows DMA, does that not mean that a malicious device can own your computer as soon as it gets plugged in?

Also, I thought I'd read that USB had DMA and hence this security problem.

Could someone who actually knows what they're talking about comment on this please?

Guns don't kill people. Gun-obsessed people kill people.

(I suspect the high velocity lumps of lead may play a part too.)

TFA was points to a 2012 press release, but it contains not much more information. They must need to supply energy to this reaction, but whether this energy is as heat, electricity or something else is unclear.

I see two uses from the point of view of the U.S. navy. One is to put one of these chemical plants in an aircraft carrier, power it with the carrier's reactor, and generate fuel for the aircraft on board. The other is to put the chemical plant on a nuclear powered supply ship, which will then transfer the fuel to non-nuclear surface ships.

From a world energy point of view, this is a way to turn non-fossil fuel power (nuclear, hydro, wind) into hydrocarbon fuel, with the overall process being carbon neutral. Burning fossil fuels to provide the energy for this process would certainly be counter productive in terms of CO2 emission and very likely economically counter productive as you'd be better chemically processing your fossil fuel instead.

By the time you're going to all of this trouble to turn electricity into fuel, it is unlikely that you'd want to run a car on it - you'd rather just have an electric car. For aircraft we really have no good alternative to hydrocarbon fuels, so it could be used here. However, on the road to a low-carbon future, we have decades worth of lower hanging fruit (notably coal power stations) before we really need to care about whether our aircraft fuels are carbon neutral.

Conspicuously missing from the articles is the energy efficiency of this process. Given the $3-$6 per gallon projected jet fuel cost, presumably the efficiency is not too bad. (I notice this number hasn't changed since 2012 which makes me suspicious that it is more guesswork than calculation.)