That driver shouldn't have been watching the movie. He should have been watching the trailer.

Boy, those 40-tonne tanker trucks must stir up a crap-ton of particulate pollution. If only there existed a car that didn't require all the gasoline those trucks are toting around.

There are no stupid questions. But there are a LOT of inquisitive idiots.

Third reason: Wind. In the post-launch press conference, Elon mentioned that the wind was significant during landing. (And may reach up to 50mph tomorrow on the way back to port.) So the rocket had to tilt somewhat into the wind to avoid being blown sideways relative to the landing pad, and only went vertical at the last moment. It also explains why the droneship maintains a slight tilt in some of the post-landing footage; this is to cancel out the considerable force of the prevailing wind.

Um, no. I own a vintage 2008 Tesla Roadster, and its range has dropped only about 10% over nearly 8 years. The battery chemistry and durability used by Tesla has only increased since then, so I the Model 3 will do substantially better even than that. Over five years, it might drop 5%. Possibly 10% at the outside, but not anywhere close to 20%.

AlphaGo 'Speechless' after 2nd Win vs Human Go Champion

The subsidence / ground movement effect is dwarfed by the simple thermal expansion of the tube over the day/night cycle, which can grow/shrink up to hundreds of meters over the length of the tube. This effect can be compensated for by allowing the tube to slide smoothly across the pylons to achieve tensile equilibrium. (Perhaps with motorized assist to overcome friction.) The "slack" is taken up at the endpoint stations, through a telescoping system. Each pylon can allow for perhaps a meter of lateral flex to account for local ground shifting, and the pylons themselves can be easily repositioned if they start to get close to their tolerances in a local area.

The complete Alpha-design hyperloop from LA to SF would use about 1 million tons of steel, or about 0.02% of the world's current annual steelmaking output. For scale, this is about 10x more steel than the Birds Nest stadium in Beijing, or about 100 Eiffel Towers' worth.

Presumably every Hyperloop capsule would be instrumented to gather data along its journey to immediately reveal any imperfections or problems. Since the travel surface is a completely controlled environment (no birds pooping on the tracks, etc.), it ought to be far easier to maintain than open highways or exposed railroad tracks. The Hyperloop system will directly generate revenue for its own maintenance and upkeep, whereas bridges really don't. (Toll bridges, maybe.)

Much less than would be if there weren't so much CO2 in the atmosphere trapping the heat. As we inject more CO2 into the atmosphere, less heat escapes to space, and the equilibrium surface temperature rises quickly. This is why the human-caused rise to its current value of >400ppm is so alarming, and where the ultimate 350ppm "safe" limit calculation (to avoid catastrophic temperature increases) comes from.

You are wildly off. A Cat-5 hurricane sustains about 1 petawatt of power output, or ~50x the rate of humanity's fossil fuel consumption. A year's worth of human output could power this hurricane at full strength for about a week. These storms typically last at peak intensity for a couple days. In other words, humans are adding about two or three Cat-5 hurricanes' worth of energy per year to the global environment.

The MacBook product page, in the Graphics and Video Support section, states: "Simultaneously supports full native resolution on the built-in display and up to 3840 by 2160 pixels on an external display, both at millions of colors". However, it looks like this will require either 4k displays with USB-C inputs (passing DisplayPort 1.2), or else USB-C to DisplayPort adapters, neither of which seem to be currently available. The USB-C to HDMI adapters sold by Apple seem to be limited to 1080p.

A person needs at least 20kPa *from the mask to breathe*. Not 20kPa *ambient pressure*. Please learn to read.

The mask pressure must match the ambient pressure, or else the wearer's lungs will rupture (unless they're wearing an enclosed pressure suit). Please learn physics. Again, this is the reason for the 40,000ft flight ceiling for commercial aircraft; oxygen masks rapidly lose their effectiveness with an ambient pressure below 0.2atm, which is why pressure suits are required for pilots flying at higher altitudes. The absolute physical limit for unpressurized flight is known as the Armstrong Limit, which occurs at about 62,000 ft; even wearing an oxygen mask, your bodily fluids will start to boil above that altitude.

The "problematic loading on the capsules" is from the high speed aerodynamics, not the ambient pressure

Aerodynamic loading = pressure. If you have high loadings, you have high pressures. Period.

The high loadings are from high _variations_ in pressure. The average pressure around the capsule is still equal to the ambient pressure. Leaks in the passenger compartment are almost certainly side-facing, so the capsule will equalize to the pressure of the air on the sides of the capsule (which will be close to ambient or likely below, due to the Bernoulli principle), not the higher pressure in front. And note that the variations in pressure don't have to be very high to cause serious buffeting. The Hyperloop capsule masses 15000kg, with a frontal cross-section of about 2 m^2. Applying an extra 1atm to the front of the capsule will decelerate it faster than 1g. If the air beneath the capsule transiently becomes about 0.03atm higher density than the air above (due to turbulence or ground effect), it will lift the entire capsule off the track. This is the worrisome high-speed aerodynamics I was talking about.

These are the search results for: rifle shots in alyeska pipeline http://preview.tinyurl.com/mtu...

Fortunately, a vacuum spill is much easier to clean up than an oil spill.

Wait, meaning that while it's technically possible, but it'd be really tricky to accomplish? Gee, I wish I had written something like "Branching would be really tricky, but there's no physical barriers" at the top of my post ;)

Well, there are physical barriers to a static design that allows branching. Actively moving an entire section of tube to reconnect it to a new one is sort of a brute-force approach, and highly unlikely that it would be worth the complexity and risk, in my opinion at least.

Drag is reduced in the first place by using hydrogen even at a given pressure. And you can use 1/4th the pressure and still maintain lift because you're moving four times as fast. And given how few reboosts are needed from LA to SF in the base case, a few more per unit distance hardly seems limiting.

1/4th the pressure is still problematic, because what do you do while you're accelerating up to speed? You'd have to use pressurized onboard gas to levitate with, which would then require more vacuum pumping with every run. The Alpha design uses wheels for "taxiing" at low speeds; it's unclear at what speed the compressor is able to provide all of the needed lift.

If you consider that the steel Hyperloop pipe draped across 30m-spaced pylons will approximate a vertical sine wave, then at 700mph the allowable sag is only about 5cm

Irrelevant because earthquakes impose far more deflection that you have to be able to counter (and that the proposal calls for countering) than a craft moving past.

Relevant because the problem is the frequency, not the amplitude. Large earthquakes tend to cause much lower-frequency deflections, which are far easier to deal with, even if the amplitude is higher. The problem I described has to do with the static height profile of the tube, not the effect of the passing capsule distorting it (which is negligible). Even if the skis (on springs) can accelerate at 10g's to maintain contact with the tube surface, then a 5cm oscillation with 30m wavelength is sufficient to cause the skis to completely lift off the surface of the tube after each pylon, causing a very jarring ride. A low-frequency earthquake deflection on the other hand, say with 200m wavelength, could not realistically have high enough amplitude to cause the skis to skip like this. Of course, if you have the bad luck to be riding the hyperloop straight over the epicenter when the earthquake lets loose, then there will be high-amplitude earthquake waves of all frequencies and all bets are off.

Mechanical braking from 1500mph in the event of an emergency is also a non-starter

What, you're picturing drum brakes or something? You're moving at high speeds in a giant steel tube. Magnetic braking couldn't possibly be easier.

The Alpha proposal calls for a "mechanical braking system"; I agree that magnetic brakes would be preferable in principle, though at Hyperloop speeds there's enough kinetic energy involved that the capsule component of the brakes would likely melt from the induced current. Permanent magnets on the capsule would probably be too heavy. And magnets/electromagnets on 350 linear miles of tube would likely be too costly/complicated. So unless there's a way to have the electromagnet component on the capsule, but make sure that nearly all the heat is dissipated in the steel tube and not the capsule, I'm not sure it would be workable. I have similar concerns about the aluminum capsule rotor, and whether it might become problematically hot during the linear acceleration/deceleration phase. A solid aluminum rotor could absorb the electromagnetically induced waste heat from 0-700mph acceleration without melting (by a factor of about 2), but the Alpha design calls for it to be hollow. And accelerating to 1500mph involves >4x the energy of 700mph.

a 700mph capsule will incur about 2g's of aerobraking deceleration

Where are you getting this from? Even if the tube was instantly full pressure (which it wouldn't be), a streamlined shape will not experience 2Gs at 700mph, any more than a passenger jet losing full engine power does. And anyway, 10g horizontal is not fatal even if that was the case. The average untrained individual, properly restrained, can tolerate 10g for a minute without even loss of cognitive function.

According to High-G training, untrained individuals tend to black out between 4 and 6 g's. (Then a few sentences later it says that one minute at 15g's could be deadly, then a few sentences after that says that several minutes at 17g's is ok. Go figure.) In any case, streamlined passenger jets are not traveling 700mph in 1atm; more like 550mph in 0.2atm. And the Hyperloop capsule is emphatically NOT streamlined; it has a honking circular front cross-section with a giant compressor on it, designed for very low-pressure input, which would immediately stop working if the pressure spikes up. Subjecting the entire Hyperloop capsule shape suddenly to 1atm, in a tube not much bigger than it is, would result in tremendous aerodynamic drag.

Clever, but probably unworkable given the large cross-section of the capsule relative to the tube. Even on a perfectly straight track (no banking), taking the upper branch would require the skis to "split" wide enough that the entire capsule width would fit between them. Given the Alpha design numbers (ski width 0.9m, tube diameter 2.23m, capsule width 1.34m), the skis would have to split nearly horizontal to avoid the lower-branch "gap", and it's unlikely they could function at such a steep angle. Maintaining the precise shape of a non-circular tube against vacuum pressure is also a very difficult problem.