> The hard part is getting up to speed, and slowing down at the destination.

The diffusion method I call "slow interstellar" doesn't require that. If you already live in the Sun's Oort Cloud, and another star gets close enough that the Oort Clouds overlap, you only have to match velocity, which is on the order of 50 km/s. After that you drift along with the other star, spreading to fill their environment, until another close stellar encounter happens. This method requires more patience than humans possess, though.

>English will remain the dominant language because it is so versatile and malleable.

Malleable, this language is

On the other hand, with the rise of real-time voice translation, the need to all speak the same language may go away.

> We know (or can know) which bitcoins were "lost" in MtGox

No, we can't, because those were not block chain transactions. They were funds transactions internal to Mt. Gox's account books. Let's assume Mt. Gox had 500,000 bitcoins in "cold storage" (the private keys printed out and stored in a safety deposit box, where no hacker can get to them). Some of those 500,000 coins belong to Mt.Gox itself, from accumulated trading fees. The rest belong to customers. Who owns what is kept track on their internal database. By fiddling with the database, they can move ownership between accounts without ever touching the coins in cold storage. Being able to trace what shenanigans happened to the database depends entirely on available backups of the database *before* the shenanigans happened.

> So couldn't the top 5 or 10 players in the network, who collectively have something like 75% of the computing power, collude and simply invalidate the transactions out of MtGox?

If by that you mean transactions from a Mt.Gox owned address to one outside Mt. Gox, again no. Blocks from 9 months to 3 years ago (when Mt. Gox was presumably messing around are linked to every block afterwards (that's why it is called a "block chain"). The linkage is by including the hash value of one block as part of the data in the next block (along with new transactions). If you change an old transaction, the hash of that block will change, and no longer match the value stored in the next block. You would have to recalculate new hashes for every block after the one you want to change. This is basically impossible, as it took the whole network's combined power to generate the existing series of block hashes. If 75% of the network gave up working on new blocks, they would lose future income *and* past income, as a different set of people would get the coins generated in each recalculated block. In turn, all the people who spent all those block rewards, or parts thereof, downstream of the miners, would have their balances invalidated.

> "Inherently worthless" is the salient feature of money. When you trade things of intrinsic value you are bartering.

They are not disjoint sets. Money was whatever commodity had the most acceptability and was easiest to trade. Normally that happened to a commodity with features like durability, scarcity, divisibility, etc. The US dollar is backed almost entirely by debt, so it is not true to say it is inherently worthless. Those debts (Treasury bonds, mortgage-backed securities, and bank loans) have value because they pay interest, and you can trade a pile of dollars for any of those debts if you want to hold them directly. Paper money and coin are just convenient size trading units. A home mortgage or Treasury bond are inconvenient for day-to-day purchases.

> VG won't be doing anything special,

Actually "Son of SpaceShip Two", otherwise known as Stratolaunch ( http://www.stratolaunch.com/) , is the special thing. It's the same basic idea, carrier airplane and rocket stages, but much bigger and able to put significant payloads in orbit. Yet another billionaire, Microsoft co-founder Paul Allen, started this up. The same people (Scaled Composites) are building this as SpaceShip Two. But this time they are using parts from *two* 747's to build the world's largest airplane, to maximize launch capacity.

At first, the rocket stages are disposable, and only the airplane comes back, but in the long run I expect them to reuse the rocket stages too, it would save a lot per flight.

> Yeah, I buy it. Hell, I'd work for little more than a pretty meager wage if I could be reasonably sure of ACCOMPLISHING something meaningful in space.

You can, and don't even have to quit your day job. Read up on "self expanding automation" ( http://en.wikibooks.org/wiki/S... ), where a starter kit of machines is used to build parts for more machines, until you have the production capacity you need. In space, instead of sending a whole factory to process asteroids or support a Mars base, you send just the starter kit, and build the rest from local materials. On Earth the same idea of bootstrapping from a starter kit lets you grow your rocket factory or launch site, or any other industrial production you want.

An industrial starter kit will be beyond the average person's finances, but then so is a data center. The way to bring it down to the individual level is (a) to make it distributed - the machines are split up among different people or groups, but they collaborate to make things, or (b) to run a centralized production location on a time share or lease basis. You need a part, you submit the design files and a small payment to have it made. Much of the work becomes designing new or upgraded things to make to expand the system. You can do that at home, because you already have a computer to run the design software.

Once people get the hang of making starter kits and growing them, they can work towards more and more difficult locations. First typical metro areas, then deserts, ice caps, oceans, and finally space. Your first kit, when it is fully grown up, can produce another starter kit for the next location, and so on. You automatically build your supply chain as you go.

What was the value of the Nevada desert before we built Las Vegas? What's it worth now? Musk is the equivalent of the Connestoga wagon builders for the first settlers. Real estate developers will do the bulk of the work, like they do on Earth. Remember that Mars has the same land area as the Earth (minus oceans), and none of it is claimed yet.

It will if you do it right. Self-expaning factories and mining everywhere would bring the cost down to that range.

* Self-expanding production is where you deliver a "starter kit" of machines. Those machines make parts for more machines out of local materials. An example is using CNC machine tools to make metal parts out of Metallic type asteroid rock. The expanding collection of machines then can make more and more items.

* Sourcing your raw materials locally, in every orbit, turns the exponential rocket equation into a linear problem.

The combination of the two has the potential to reduce the cost of supporting a human on Mars by a factor of 2500 over today's cost. You won't get that reduction all at once, but it brings the cost of a colony (mostly self-supporting, lots of people) within reach.

> . Asteroid mining isn't going to do anything, directly, for people on Earth.

This is incorrect. Space is already a $300 billion/year industry, of which NASA only represents 6%. Most of it is in the thousand or so satellites in Earth orbit, doing communications, navigation, weather, mapping, etc. Today, when a satellite breaks a part or runs out of fuel, there is no way to fix or refuel it. So you have to launch a whole new satellite at great expense. An "orbital service station" with the capacity to do those things is worth billions a year. Since Near Earth Asteroids can supply 30-50 times more fuel, plus the potential for other supplies, it makes that service station cheaper to operate. That's enough of a "first market" to bootstrap the development. Once you are up and operating, other activities become economic besides satellite servicing.

> We've spent the last half century turning into a knowledge society

And all of those billions of computers run on energy, as does the rest of civilization. Modern civilization is based on replacing human and animal labor with mechanical and electrical power. The amount of solar energy passing closer than the Moon is equal to the whole world's fossil fuel reserves *every minute*. We just have to learn how to exploit it. Leveraging resources already on location is part of that equation.

> while space travel is largely a money pit.

Space industry worldwide is $300 billion a year, of which NASA is about 6%. Most of the money, and most of the recent technology improvements, are from satellite communications. High efficiency solar arrays and ion propulsion have been used on satellites for about 15 years now. The Dawn asteroid mission (which has electric thrusters) was 7 years later and 1/4 the mass.

The Rocket Equation gives us guidance on how to get around it. Increase exhaust velocity or reduce velocity increments. For lots more detail, see my book ( http://en.wikibooks.org/wiki/S... ), but here are a few ideas:

* Replace some of the bottom part of reaching orbit with higher efficiency engines. That can be anything from subsonic jets (Stratolaunch) to ramjets, to ground accelerators. Replace some of the top part of reaching orbit with electric thrusters transferring momentum to a fractional space elevator (only reaches part way to the ground. By reducing the velocity provided by chemical engines, and more by other methods, you lower the mass ratio.

* Mine for fuel everywhere: scoop mine our atmosphere from orbit, process asteroid rock in high orbit, mine Phobos for fuel, etc. By repeatedly fueling at each location, you reduce fuel needed to a series of linear steps, instead of an exponential. If fuel extraction has a large mass return on your capital equipment, how much you need to launch from Earth drops dramatically.

> Whereas most people in slashdot are brainwashed and gullible morons that would rather invest in the most useless and most expensive form of energy generation: photovoltaics.

I guess you think Warren Buffet is a moronic investor too:

http://www.bloomberg.com/news/...

> It reminds me of that old joke about why the Space Shuttle (and now SLS) design is influenced by the width of a horses ass.

Two horse's asses. Wagons were sized according to the width of two horses, and roads were in turn sized to fit the wagons. When underground mining got serious, the mining wagons were just converted outdoor wagons, still pulled by two horses. Then they started putting rails under the wagons, to allow moving heavier loads with less friction. Rail lines began to be used outdoors, pulled by horses at first, so the rail spacing continued to be suitable to the width of two horses. One engines replaced horses, the rails stayed the same width. Go look at train tracks today, you will see they are the right size for two horses to fit.

The Solid rocket boosters for the Space Shuttle were shipped by rail from Utah to Florida, and thus had to fit on railcars on the standard rail spacing. In turn, the size of the boosters set the lift capacity of the rocket, and thus how big the Shuttle Orbiters could be. Finally, the Space Station modules had to fit in the Orbiter, so the Space Station's design is dictated by the width of two horse's asses.

I may have been responsible for this analysis about 30 years ago at Boeing. I was both designing launch vehicles, and had a hobby interest in the history of technology. It is also possible it came up in a USENET discussion on sci.space back then. I don't remember any more.

Since this was the post office calling, the answer would be to go to the local machine shop and borrow one for a minute. Since they deliver to everyone in town anyway, just assign whichever letter carrier has that shop on their route to do it.