Measuring the even-numbered electron 'affects' the result of measuring an odd-numbered one (or another even numbered one) because they are entangled, not because they are coherent, though I suppose in a sense coherence would be what makes the result predictable. Please provide an example of coherence (in terms of spin only) where the particles are not entangled. I don't think it's possible, because I don't think coherence means anything useful in terms of spin only. Any two electrons would trivially be coherent (in terms of spin) because they differ by a fixed phase angle, unless in this case coherent also means in-phase (i.e. having the same spin).

You do need coherence in the double-slit experiment in order to observe a distribution of points where the electrons hit over time that match the same interference pattern they would have if they were all interfering with each other as a classical wave. If you vary the direction or energy of the electrons, for example, you would not see such a pattern.

That's entanglement, not coherence.

In your first example, they are entangled and coherent. In the second example, they are entangled and the odd-numbered electrons are coherent, as are the even ones, but they are not coherent with each other. Though I'm not sure coherence means much when only looking at a single discrete attribute like spin. I think you want either a continuous attribute, or multiple discrete ones.

The double-slit experiment (e.g. with electrons) is a better example of coherence. You shoot an electron through a double-slit. The electron-wave goes through both slits, interferes with itself, and has a higher probability of hitting in the points with constructive interference (when measured by contact with the target), and a lower probability of hitting the points with destructive interference. Shoot more electrons the same way, and they land according to the same probability distribution. The electrons are coherent because they have the same wavefunction after passing through the slits and interfering with themselves, whether they go one at a time or they are in a beam. However, they do not all hit at the same location because their trajectories are not entangled.

In the context of photosynthesis, I'm guessing this means that the electrons that are moved by the energy from the photons follow paths that are more limited than you might expect from classical physics, because the of interference in the wavefunction among the different paths. (I am also not a physicist).

Well-to-tank efficiency for gasoline is around 80%. Mine-to-power plant for coal is around 90%.

That's only relevant if the ownership or operation of the solar panels is dependent on the use of the EV. If they'd have the solar panels anyway, then the decision to use an EV mostly affects the electricity markets in the use of marginal power plants (which tend to be fossil-fuel powered), and the system-wide decisions on deploying other power sources (where the use of EVs is likely to encourage more renewables). It doesn't matter much whether the owner has solar panels themselves.

No, an EV is at most 80% efficient (plug to wheel) with current technology. It does allow more flexibility in energy sources, though you can potentially have non-fossil liquid fuels too. Gasoline cars are only limited to something like 25% efficiency (tank to wheel) if the gasoline is converted to useful energy using combustion. If you use a fuel cell, it can be much higher, which is the point of the article, using a FC instead of an ICE for extending the range of an EV.

They did include generation. Burning gas in an ICE is equivalent to burning another fuel at the power plant. They did not include fuel production in either case (you also have to dig up and process coal and natural gas). The only thing unfairly left out was transportation of gas from the refinery to the pump, which is a small energy expenditure compared to the ranges given for everything else. Given that it's just a ballpark estimate, it's not bad. The ICE efficiency and transmission losses both look a bit high, but not enough to make a huge difference.

What this shows is that BEVs are more efficient than ICEs even if you get all of your electricity from coal (and hopefully, you don't). But fuel cells are more efficient at converting their fuel source to electricity than any process involving combustion, which isn't really surprising. Of course it's best if you can power your FCEV on something other than fossil fuels, and the same goes for BEVs.

Sure I can, with 2 additional lines of code: one outer loop that iterates through all possible seeds, and another that iterates through all known pseudo-random number generator algorithms.

...and none of those sequences are actually random.

It's a perfectly cromulent word.

Yeah, those are effectively the same. But a $500K salary with a potential $5M bonus for exceptional success, or a potential $5M penalty for failure is different. A major screw-up means you owe $4.5M.

...by about 1.3% due to the recession. Over the last 3 years, they increased on average 2.2% per year, which is a bit less than both the average in recent times and the IPCC prediction. So all this really says is that in terms of how much stuff we burn, the world has mostly "recovered" from the recession. 6% is a big increase for one year, but it's an increase from a point below the trend. And climate trends are meant to be measured over decades, not years.

Of course any increase is large compared to what should be happening...

Now you're making things up. According to NREL, back in 2004, the time needed to generate the amount of energy used to produce solar panels was about 3-5 years or less, depending on the type of panels ( http://www.nrel.gov/docs/fy04osti/35489.pdf ). The financial payback time (time to recover the dollar cost through savings on your bill) without subsidies is longer because you're paying for more than manufacturing energy, and because the competing technologies are both subsidized and are also larger, more established industries.

According to Murphy & Hall ( http://dx.doi.org/10.1111%2Fj.1749-6632.2009.05282.x ), the EROI for PV is 6.8. That means it takes one unit of energy from somewhere else to result in 6.8 units of electricity from the panels. Compare that to natural gas, which has an EROI of 10, which means it takes 1 unit of energy from other sources to get enough gas out of the ground to burn for 10 units of energy. This comparison doesn't take into account that the "energy returned" is in the form of a finite resource you have to burn in the case of gas. In other words, with 1 unit of natural gas, you can generate 6.8 units of electricity by using it to build PV, or you can get around 0.4 units of electricity by burning it in a turbine, after deducting the amount needed to get another unit of gas out of the ground. For comparison, the same source says that nuclear power has an EROI of 5-15, and coal is higher at 80. Again, this doesn't take into account that you're using the fuel itself.

In terms of environmental impact, grid-tied solar power makes sense with today's technology (or 10-year old technology for that matter). In terms of dollar cost for putting it on residential roofs, maybe you don't save money without the subsidies. For the window film, who knows.

Solar panels are not carbon-neutral, but they generate about 90% less greenhouse gas emissions than the conventional plants they displace, which are primarily coal- and gas-fired.

And what about the subsidies that make conventional electricity feel artificially cheap?

Solar production tends to match up pretty well with peak demand. Better than, say, regular power plants.

You're right, it's only fair to subsidize energy from fossil fuel sources. You know, real energy.

It's different because you can still change your password thus restricting access again, and also everyone else's passwords to the same system are still effective. You have a problem if everything shares the same password and it can't be changed- that is security by obscurity. Or if you have a system where everyone's password is their birthday, and then it leaks that this is your obscurity system.

If a password is used directly to grant access to you system, then yes, that is security by obscurity and is bad security. In a more sufficient security system, you might use a password as a shared secret to authenticate someone's identity, and use that identity to grant access. This is a completely different security architecture, and is better. It's different because authentication and authorization are treated as separate issues.

Certainly obscurity can add to security, but you really want a security system that is sufficient without it.

This is completely different from grid-connected solar.

Most likely this will not be deployed until the utility implements real-time pricing (or at least hourly pricing, rather than the monthly pricing we have now), where electricity prices vary during the day based on the exact system conditions. They will have to pay you at the price when they draw power from your battery (or more likely, you will just use the power in your house, and pay that much less), and you will pay a lower rate to charge at night (or whenever it is cheapest if the electricity supply changes drastically). This is a net savings for you, even if there is a small loss of electricity in the process. In this case, the utility wouldn't even have to ask- your charging system would probably do it automatically just to save you money through arbitrage in the electricity market.

If there is no instantaneous pricing, they will have to pay you a fee just for being available, plus pay you back for whatever power they draw. This fee would exceed any loss. In this case, the utility would have to control your battery because you would have no incentive to discharge otherwise. This is similar to load-shedding agreements utilities have now with large customers.

There are two obvious ways you can maintain availability of power for the car owner.

1) Let the owner say the next time they need to have a full or partial charge- when they leave for work, when they finish work, when they get back from vacation in 2 weeks, etc. You want to do this anyway so the system can decide the best time to charge the battery. And a "don't discharge" option would be very simple if you expect emergency trips. Most people don't.

2) Make sure they have enough power to get to the nearest battery swapping station if they happen to need to drive somewhere right after the battery is discharged.

Nope. Either they will be paying you far more than your net loss in charge for the availability, or they will be paying you at far higher retail prices when they buy the power from you than when you are charging the battery. Either way, you're going to make money on it. And the utility will save money by keeping less reserves available, and avoiding use of more expensive generators.