Generating electricity requires generating a potential difference, for which there are not that many methods, barring major advances in physics. Methods such as electromagnetic (the method used for steam power), photovoltaic (solar cells), chemical (batteries, bioelectric), piezoelectric, thermo/pyroelectric, electrostatic. The problem with the latter, more advanced technologies, is that they do not scale easily to the Megawatt scale, required by current centralized generation technologies.

Unless we develop a portable nuclear fusion reactor, the energy available by distributed generation (mostly solar, wind, biomass, maybe using the exotic physics) is low, and would require major changes in current lifestyle to be sustainable.

The principle of conservation of energy still applies – you can not get energy out of nothing. With steam turbine (and solar cell etc.) efficiencies in the >=20% range, there is not much to gain by more efficient generation methods – certainly not an order of magnitude.

On to the second point. Thank you for the pointers to the stories! I thoroughly enjoyed them. I see no contradictions in the stories as long as you are willing to give up determinism and free will. I was trying to put together a more detail description, but then today I bumped into this article: http://discovermagazine.com/2010/mar/02-the-real-rules-for-time-travelers/ which eloquently expresses my point of view.

Secondly, I would be interested to know what contradictions are present in Robert Henlein’s two time travel stories “By his bootstraps” and “All you zombies” neither of which includes a parallel universe.

Therefore door and and c are equal.

With the common system if you choose a and they open door a and it is found to be correct you should still change because you odds are higher with two incorrect choices than the correct.
It goes back to the opening statement. If we have three unknowns. The moment you only have two unknowns this becomes false and you have an entirely new equation.

I was recently thinking the other day that I hate the word “possible”. People love to use that to win any argument. For example, religious people often say, “But don’t you admit that it’s at least POSSIBLE that God exists?” And then I have to respond, “Yes, it’s possible, anything is possible.” What choice do I have? And then the religious person takes my answer as a “win”. It’s so annoying!

The reason this problem is controversial is because it’s TRICKY, and people hate it when they are tricked. Here is another similarly tricky problem: A couple has two children, one of whom is a boy. What is the probability that the other child is also a boy? The answer is a counterintuitive 1/3 because the problem does not state WHICH child is a boy. If the problem had instead stated, “the first child is a boy,” then the answer would be the expected 1/2.

Of course, when you explain that to people, they get mad and say, “Well, you tricked me! It’s an unfair question. You didn’t say which child was the boy, so I assumed it was the first one.” Exactly, you cannot make unfounded assumptions. That’s what the riddle is trying to teach you.

Likewise, the two envelopes problem is a lesson on symmetry. It’s TRICKY because people don’t realize that BOTH envelopes contain either double or half what’s in the other. It’s a symmetrical statement. Even if you reason yourself into switching envelopes, once you’ve switched it then turns out that my envelope STILL contains either double or half what’s in your envelope, so by your reasoning you should switch again. Which is, of course, ridiculous.

People like to complain, “It’s an unfair question. I thought you meant that my envelope was filled first with a constant value of $100, and then yours contains either $200 or $50.” Of course, that’s not what the problem says, and people are making unfounded assumptions.

Also, the incorrect solution that you are talking about, solution 1 on my site, was included on purpose specifically because it’s wrong. I was turning the riddle into one of those, “Here’s a proof that 1 + 1 = 3, where is the error?” type of problems.