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Comment: Re:Anti-math and anti-science ... (Score 1) 981

by roca (#47933545) Attached to: ISIS Bans Math and Social Studies For Children

Christians throughout history have understood that the laws God prescribed for Israel in the Old Testament are not mandatory outside that context, and in particular are not to be applied wholesale to gentiles (i.e. almost everybody). This isn't some modern opportunistic innovation, it's explicit in the New Testament (e.g. Acts 10-11,15).

Comment: Re:Anti-math and anti-science ... (Score 1) 981

by roca (#47933519) Attached to: ISIS Bans Math and Social Studies For Children

The Protestant reformers would have objected violently to your characterization. To them, rejecting the human authority of the Pope in favour of 'sola scriptura' was a move *away* from secularism. You're right that ironically it provided room for true secularism to grow.

But the grandparent post is right nevertheless. The Christianity of the New Testament is fundamentally compatible with secularism and pluralism because it grew up as a minority faith in the Roman Empire and took hold through mostly-peaceful implementation of the teachings of Jesus. There have been a lot of deviations from that course but those deviations can be corrected/stripped away without doing violence to the core, and in the modern era have been.

Comment: Re:Rockets suck (Score 2) 211

by db48x (#47795507) Attached to: Battle of the Heavy Lift Rockets

A rocket is a mass driver, and all of the "scifi" types of propulsion break the laws of physics one way or another. Space elevators would be pretty nice, but we still haven't found a material strong enough. Carbon nanotubes are the current hope, but we can't make them long enough yet; they'd have to be very long indeed to make a strong enough elevator. Short nanotubes have to be glued together and then you're down to the strength of the glue.

Comment: Re:Why does it take so long? (Score 5, Informative) 211

by db48x (#47795361) Attached to: Battle of the Heavy Lift Rockets

For the most part it's a difference in magnitude. The speeds the rockets achieve are much higher than any airplane, let alone car, ever manages. The thrust of the engines is stupendous, the liquid H2 and O2 fuels are cryogenic, the flame temperatures in the engine are extreme. In fact, they're so extreme that the engines use precise control over the flow fuel and oxidizer entering the engine to create a layer of cooler gasses around the inside of the engine nozzle, so that it doesn't melt or ablate entirely away. Everything has to work in vacuum and at ambient air pressure and at max Q during flight.

All of this and more adds up to a much harder design problem, much more stringent test requirements, much tighter manufacturing tolerances, etc. The principle is the same, however; any change to one component of a system may require changes to every other component.

The one thing that all forms of engineering from (whether software, civil, aerospace, or other) have in common is the management of complexity. The automotive engineer designs the engine mounts in your car to accept a wide range of engines, so that they can manufacture several variants of the same car with different engines without having to redesign every component. Similarly, SpaceX has greatly reduced their cost and risk by reducing the complexity of their rockets; one way they did this was to use the same engine for both the first and second stages of their rockets (the first stage simply uses more of them). Another way was to avoid cryogenic fuels; they have a lower specific impulse (fuel efficiency), but a much greater space efficiency (liquid H2 is very light; that orange tank is huge, and 80% of it is for the H2 tank) plus you avoid having to deal with cryogenic fuels, and the complicated materials engineering that goes into designing the tanks to hold them.

If you want to know more, MIT has some great lectures on the subject, even ones suitable for non-engineers. A good one is An Electrical Engineering View of a Mechanical Watch . The description of this lecture only touches on superficial matters; Sussman's real point is that the means of abstraction present in an engineered system can be applied to any other engineered system, and that it's only by designing the right abstractions that engineers make continual progress in designing newer and better systems. He states this directly in the first two minutes, which is quite handy. You might also check out the video lectures for the Structure and Interpretation of Computer Programs , the first lecture of which goes into much the same topics in the realm of software engineering.

Comment: Re:Why does it take so long? (Score 5, Insightful) 211

by db48x (#47795103) Attached to: Battle of the Heavy Lift Rockets

Unlike in Kerbal Space Program, when you stack rocket components on top of each other you have to reengineer the bottom one to hold up the top one; they say that they're reusing the main tank, but that might be true in a narrow sense if they reuse the H2 tank inside the orange Space Shuttle External Tank. Then you have to engineer the manufacturing processes and factories for producing any new components (and there will be lots of those), plus the modified one (easier, but still plenty to go around), plus you have to engineer the test facilities for all the components, and you have to test the test facilities, and then test the components, and then test-launch the vehicle, etc. Don't forget to document everything, and to design training procedures so that you can hire new people to build these things, and test them, etc, etc. It actually is rocket science.

The first Rotarian was the first man to call John the Baptist "Jack." -- H.L. Mencken

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