I really, REALLY wish that were true.

The ground-preparation benefits of raised roadways have been known for decades, nothing special there. The problems are (1) making a system that interfaces smoothly with ground-level transportation, and (2) minimizing the amount of construction necessary for the spans. The Russians(?) even did some interesting work way back on a system of paired concrete-encased cables that tireless cars could drive along - far cheaper than roadways per mile, and wonderfully suited to rough terrain. But who wants to drive along such a contraption?

You're thinking build-in-place costs, which is always much higher. You would build both pylons and tubes in factories designed specifically to build such things - lengths of double-sided spiral-weld, pressure-tested, heavily lined pipe are already available in suitable diameters and arbitrary lengths for urban waterworks. It's just a matter of dropping them in to place with sufficiently flexible airtight strain relief joints and throwing in an occasional vacuum pump to compensate for the inevitable leaks. Make the proper pylon-riding transportation and deployment rigs and you could be dropping them into place at an astounding rate without having to deal with ground-level delays.

As for transportation energy - that's part of the beauty: any point where you want serious acceleration in one direction, you also want serious deceleration in the other, and thanks to the external linear motors in use you can recycle all that energy (minus inefficiencies), using the energy generate by slowing one car to accelerate the one going the opposite direction.

As for what happens when a major leak develops - well that entire leg of that tubeline, whatever's between the closest isolation valves (the nearest two stations if nothing else) will have all the cars rapidly slow down as air pressure in the tube climbs, eventually coming to a rest on their wheels. Then, ideally, all the cars fire up their back-up motors and trundle down to the next station where they can get back into a properly depressurized line (separate "tug cars" are another option, but have multiple issues) It's a major inconvenience for passengers, but not nearly so bad as a failed railway - the route still works, it just gets suddenly slow until the leak is fixed.

As for the "failure" of rail in the US, perhaps you're not aware but there are essentially *no* major passenger rail lines in the US - it's all owned by cargo-moving companies, and passenger trains just rent access in between the cargo trains. And if you've spent much time riding Amtrack, you know they *suck* - the line is always pretty much the same, but they are chronically incapable of keeping a schedule, and any time there's a rail conflict *they* are the ones who have to sit interminably on the sidelines while the cargo trains that actually know how to keep to a schedule pass.

Plus there's the "minor" issue that virtually all the rail systems in the US are *old*, and can't support high-speed trains - so you're dealing with trains that aren't notably faster than your car, even at the top speeds they rarely reach. And then there's commuter lines which, for the most part, are an even greater embarrassment. Hyperloop on the other hand could be considerably faster than airlines for short-to-medium hops (long hops too, but that's getting ambitious) for potentially cheaper than rail, and the functioning of the system would rely on it being almost fully automated, so no idiots at the helm screwing things up for everyone with their inability to keep to a schedule. Plus no issues with weather. I suspect there would actually be quite a demand.

There might be issues to be discovered, but then that's why they're making a test track, now isn't it?

Well, there's .goo - they do seem to ooze into everything...

Well, it eats, excretes, and reproduces, all that's missing is some form of self-organization.

Rail needs an extremely expensive foundation, and right-of-ways. Hyperloop requires occasional pylons, radically reducing the ground-level expense. And it's not like the tubes themselves are high-tech, it's just a bunch of sturdy, reasonably airtight tubes - size large urban water pipe would probably do the job fine with a little cable suspension to support the lengths between pylons.

For any given leg of the journey you probably want all the trains traveling at the same speed, as set by the long-haul trains - there's no passing lane in the tubes after all, and a train going 800+mph covers an awful lot of ground in 30s. If you want to make a 15 minute trip by 200mph train, you've just backed up the 800mph trains for an hour. So any switching would have to be at roughly full speed - once on a side loop you could then do whatever you want of course. And the linear accelerators are likely to be a significant fraction of the total cost - it takes many miles to get a train up to 800mph, the rebooster stations just give them a little speed bump, and every station would need it's own quad of zero-to-full-speed accelerators (one each braking and accelerating for both directions)

There is however the possibility of putting more than 2 tubes on the pylons - once the right-of-way has been acquired and the pylons erected there no reason you couldn't have both a 2-way pair of high-speed tubes, and a second pair of low-speed tubes all suspended from the same pylons. The tubes themselves are after all probably only a fraction of the total cost, and having a second pair of tubes would also offer redundancy when inevitable downtime is necessary for one of the others.

Then if you wanted to get really fancy you could periodically have multi-mile "switching stations" to accelerate cars from one tube to the other

Well, construction costs should be lower than rail thanks to pylon's dramatic reduction in necessary ground preparation per mile, and the technical simplicity (it's just a big, airtight pipe after all), and it should be dramatically faster than commercial planes, as well as being much cheaper to operate. Bigger up-front costs, but only minor operating costs, and the operating costs are the vast majority of the expense of airplanes.

It is still very much a "point to point" transportation system, which does limit it's usefulness, but high speed rail pales in comparison, in terms of both speed and construction cost. If you assume a decent bus/monorail/commuter train/etc. system ties in to the same down-town transportation hub as the Hyperloop, it should be extremely feasible - might even provide endpoint cities the incentive they need to build public transportation systems that are worth a damn. Or perhaps it just hosts a thriving Zipcar station.

The problem with maglev is it's *expensive* - every mile of rail needs not only a better-than-normal-rail foundation to survive the stresses of high-speed transit (maglev only eliminates the high-frequency vibrations), but also a "track" of either extremely powerful permanent magnets, or an active maglev system. And reliabilty must be *extremely* high, since losing power for even a second means your high-speed train is going to cease to levitate and tear up a goodly length of expensive track, in addition to probably destroying itself and its passengers.

Hyperloop on the other hand is basically just a length of vacuum tubing on stilts, with occasional vacuum pumps along its length to compensate for leakage, and magnetic "mass drivers" wherever there's need for a speed change - all the rest of the cleverness is in the cars themselves, which float on a cushion of air like an air-hockey puck. And anything but the most catastophic of failures will result in the cars coasting to a stop as the air density in the tube gets too high to support their speed. Between the technical simplicity of the tubes, and the long stretches between pylons where the ground doesn't need to be prepared at all, Hyperloop track is potentially cheaper per mile to construct than rail, even in rural areas, and in urban areas rail can't begin to compete.

Tunnels? I thought the Hyperloop concept was to suspend the tubes between pylons so that it would cost only a fraction of even normal rail to construct, with comparatively minimal required ground preparation or interference with ground-level construction.

And unicorns *may* suddenly leap out of my bum, but without some form of supporting evidence for that claim I'm not going to take it seriously. All life we know of depends on cell walls to maintain a sufficient density of organic chemistry, and now we know that cell walls functionally much like our own could exist on Titan, using compounds we already know exist in the atmosphere. That's a big boost for the argument that there might be life on Titan.

As for porous materials - life might well start there, but it's not likely to get very far unless its chemistry is either all bound to a single macro-molecule, or is contained within some sort of semi-permeable envelope. The very porosity which contained the chemistry would also severely restrict the flow of energy and nutrients, so that probably only a very thin layer of pores could support life, and the first bit of life that found a way to leave its prison would have a bounty of resources at its disposal beyond anything its ancestors could have "dreamed" of.

Slashdot summaries are confused, when not outright inaccurate - news at 11. If you actually want to know details, you're pretty much required to RTFA.

As for your question, humans (/mammals/animals/multicellular organisms) are a recent addition, not typical of Earth-based life.

Earth life is water-based (well, suspended anyway), with lipid(hydrocarbon)-based cell walls to keep vital chemistry sufficiently concentrated to continue. Eventually blue-green algae evolved their ability to photosynthesize and poisoned the planet with toxic oxygen byproducts, which some of the survivors later managed to harness as a fuel. But that's really an incidental development so far as life itself is concerned. Before that life was all chemovores - likely consuming complex organic molecules from either hydrothermal vents and/or their fellows for both nutrients and energy.

In this case researchers have found some other hydrocarbons that can form "cell walls" with properties very similar to those in our own cells, except that they operate in a liquid methane suspension instead of water, at temperatures that would render our own cell walls solid. One of those hydrocarbons is acrylonitrile, a compound found in Titan's atmosphere, so the building blocks for cell walls at least are already present there.

What's the difference?

They're probably misrembering slightly - the moon has a two-week day, followed by a two-week night, for a full diurnal cycle almost exactly the same as it's orbital period around the Earth (it's tidally locked after all). The discrepancy is of course due to the fact that the Earth completes about 1/12th of an orbit around the sun per one rotation of the moon, so the length of a lunar sol is slightly different than the rotational period - just like with the Earth itself, but more dramatic since a lunar month/day is a lot longer.

That's what I remember as well - and I seem to remember another study suggesting that humans had a much more difficult time adapting to day lengths outside the range of about 22-26 hours (+/- 2 hours), or was it +/- 1 hour? I forget.

You're talking catch, not quantity of available fish - catch naturally increases with better technology, but as available fish reserves are depleted that only makes the problem worse. Both total mass of fish, and individual specimen size have been declining for a *very* long time. But hey, maybe we can learn to eat jellyfish, they seem to be thriving in the warmer, less predator-rich waters.