K^2

I do wonder how much work it would be to have the maglev pantograph that doesn't experience wear in the same way... But realistically, unless there are amazing breakthrough in batteries, I suspect the future for the trains is hydrogen. Diesel turbines can be converted into hydrogen turbines relatively readily. Alternatively, hydrogen fuel cells are an option. In either case, the biggest problem is the size and weight of the fuel tanks, and adding an extra car just for hydrogen isn't going to affect the performance of the train all that much. I'm sure there will be safety concerns, but hydrogen EVs in the recent years have demonstrated that this can be done reasonably safely.

While these are a thing, and I don't know the details of all the magic that goes into selecting rebar for concrete, the problem is matching thermal expansion coefficients. Typical value for concrete used in construction is about 10E-6 cm/cm/°C. Steel is usually a touch higher, but very close, and the two can be tuned relatively easily, so you can match rebar to concrete almost perfectly for pretty much every practical need. Glass fibers tend to be closer to 5E-6 cm/cm/°C. There are, apparently, ways to bring down the thermal expansion coefficient of concrete closer to this value, but it's on a threshold and limits the kind of mixes you can use. I'm sure there are use cases where the ability of the rebar to withstand corrosion are drastically more important than being picky with the concrete mix, but it's still important to keep in mind that it is a significant limitation. I have no idea if this is relevant to the railroad ties (sleepers), but if you're asking a question about, "Why are they not using fiberglass for X?" this is often the cause. Cost is the other factor, of course, but less so when you're going for longevity builds, as you normally wouldn't use the cheapest steel rebar for these projects anyways. We are probably going to be seeing a shift away from steel for reinforcement as the time goes on, and we might abandon it entirely at some point in the future, but we're definitely not there yet.

We are learning that methylation has a larger impact on gene expression than was used to be believed, and that environmental factors can impact methylation, which means your lived experience can absolutely impact gene expression in your children, but at the same time, there is a big gap in understanding any of the specifics. While the idea that there can be a beneficial feedback between environment and gene expression in subsequent generations is not entirely implausible, the evidence for it is not there. We both need patterns that cannot be explained by selection, with that later part requiring a lot more evidence than we have now just to have statistical significance, and at least some indication of a mechanism by which a feedback to specific genes can be established. There's an abyss between a claim that, "Your environment can have impact on gene expression of your children," and "There is a mechanism in place to make it more likely for gene expression of your children to be more suited to the environment based on your own exposure to the environment." Getting to the former and claiming that it proves the latter is just stupid. That said, research on the topic is warranted. You just have to be clear about the objectives of a study. You aren't trying to prove that future generations are more fit. We know that already. You have to prove that they are more fit in ways that selection alone does not explain, which is a lot harder.

I've said it elsewhere, but I am going to repeat here that we should insist that pop-sci articles put asterisks next to "habitable," because an eyeball planet is about the worst hellhole imaginable that is technically survivable for some kind of a life form.

That was part of a plan to make it a "free return" mission, in case they had to abort the landing, wasn't it? Allowing them to circumnavigate the moon and get a safe return trajectory with maneuvering thrusters alone if there was engine trouble.

If Take Two sells KSP rights to Valve, it will be the funniest thing ever.

I'm going to assume Real Solar System but with stock KSP physics. The simplest dV-efficient plan is you burn to parking orbit that matches inclination of Lunar orbit. From there, you burn to LTO making any small corrections for inclination at that point. You aim to have the apogee of LTO to just clip the Lunar SoI at a point that crosses Lunar equatorial plane. As soon as you are in the SoI, burn to bring your periapsis down, at the same time aligning the orbit with equatorial plane. At desired periapsis, either establish parking orbit or burn for direct landing. This can be optimized further. For starters, if the Moon axis is pointing towards or away from Earth at the time of capture, you don't need additional corrections - you'll be in equatorial orbit already. But you're still doing a 2-stage capture, which is not the most efficient. The most efficient capture is to bring your LTO apogee higher, so that your nearest approach to the Moon is at your desired periapsis. The problem is that this makes the rest of the math a lot harder. And it's only going to save you, maybe, a few percent on the dV. My sincere advice would be not to attempt this and to go for the two-step capture, with just barely scratching Lunar SoI with your LTO. That gives you very precise points where you can do the adjustments. On that note, since inclination is all about angular momentum, you want to make changes as early as possible. If you realize that your ejection burn to LTO wasn't quite correct, fix it early. If you ended up hitting Lunar SoI at the wrong spot, circularize just inside SoI, then fix your inclination at the next ascending/descending node. You don't want to end up in low Lunar orbit and then start burning fuel to fix this. So long as you start fixing the problem while far enough from the Moon, you aren't going to lose that much fuel. Good planning is just shaving off these last few percent of the total requirements.

Yeah, if we have a hypothetical super-hero that doesn't mind a bit of vacuum exposure, but otherwise have a human-like anatomy, bone-conducting headphones should be fine. Microphones are a bit of a problem, though. Laryngophone would pick up vibrations from your throat, but the vibrations are normally produced by air passing through your vocal chords, and even if your super-hero can hold their breath in a vacuum, this is going to be a very limited resource.

I use bone conduction headphones as my daily driver, because I don't like earbuds that sit in my ear canal, and over-the-heads tend to have somewhat uncomfortable (for me) bands. Bone conductors are light, weather proof, and don't get in the way of me having a conversation with somebody at the same time as wearing them. Sound's a little different, but unless you're very particular about something like music, it's more than good enough. In theory, yeah, they should work even in vacuum, but I'm not sure if they'd do me much good if my ears are exposed to the vacuum. I can't think of any scenario where I don't lose consciousness within 15 seconds at the very best.

Great point. We should bring back lead in gasoline and water pipes too. There is absolutely no way whatsoever to tell if it has any negative impact, and what if it does something good for you? After all, so many generations in the past had to live with lead pois... I mean, with lead in their diet. Fortunately, we do have pretty good research, and thanks to that, have gotten rid of many pesticides that were particularly dangerous. DDT comes to mind. In addition, a lot of genetic modification has been used to increase our crops' pest resistances, greatly reducing the need for pesticides in a lot of cases. All in all, we're actually doing pretty well on that front. The pesticides we are still using are far less harmful, many crops require less pesticide use, or even none at all, and we've even used sterilized releases of certain pest insects to curb populations instead of relying on chemicals.

Ignoring any mutually induced magnetization (which we can fold into the permeability), the magnetic field of two magnets is the sum of individual magnets' contributions. So while the net field seems to flow around the magnets, the rate of change of the magnetic field (which is what drives the eddy currents) is the same as if the second object wasn't a magnet. Another way you can think of is that the density of the fields of the original magnetic field is fluctuating within the magnet as you move the magnets closer or let them move further apart. If this didn't happen, the magnets would not be able to do work against each other, and that means they wouldn't be able to apply a force on each other. But to answer the more direct question, no, there would be no heat produced by a changing magnetic field in perfect vacuum. There would still be a loss to electromagnetic radiation, but that can be mitigated by changing the field more slowly. And if you have any sort of a gas, there would almost certainly be some amount of conductivity due to ionized particles, and that would result in a very, very tiny heat loss. But for any practical purpose, your losses are going to be in anything electrically conductive, which is the magnets themselves, any metal frameworks, and any circuitry you might be using (if this is meant for energy storage.)

Heat comes from energy losses as work is being done against the system. When you move magnets around, that's usually in form of induced currents in anything conductive. Typically, even a superconductive magnet will have parts to it that are conventionally conductive, and moving magnets around will result in currents flowing through these, generating heat. That said, you can make magnets ridiculously efficient even when ordinary conductors are involved, which is a big part of why electric vehicles can get so many wins.

Magnets, generally, don't like existing. Magnetic field has a lot of energy stored in it. The problem making stronger magnets is similar to trying to make a stronger pressure tank, but with additional challenges. Just like a pressure tank, a magnet can fail mechanically, literally tearing itself apart, but it can also fail on a phase-transition level, causing it to become something far less magnetic in an instant, dumping all that energy. And you basically only have the energy of chemical bonds to balance it, putting an upper limit on how high the stored energy can go.

Seems like a good place to thank the moderation team, with @Vanamonde and @Gargamel in particular, but everyone's been great, really. If it all gets demolished in the interest of profit, goodbye, and thanks for all the fish.

I don't think we have any radio data on it. Just visual spectrum magnitude estimates. That's part of why everyone's so excited. We're going to have every instrument watching this time. We're going to get full radio data, IR and UV observations from a number of ground and space observatories, and people will be checking gravitational interferometers and neutrino detectors to see if we pick up anything in the noise that might be correlated. I don't know if we'll get the signal on the latter two that is actually measurable, but I know that neutrino fluxes from supernovas with lower apparent magnitude have been picked up. So if neutrino flux and visual brightness are anything at all close to proportional, I think we'll get something. Gravitational I'm much less optimistic about, but maybe there's clever filtering people can do based on timing correlations? It'll be interesting to see what we get either way. At a minimum, I suspect we'll have a much refined estimate on the star's mass based on what we measure. And that might give us a better model for estimating the period of these events based on composition and proximity of the binary, letting us extend that measurement to more distant novas and possibly use them as a yet another candle. Since measuring intergalactic distances is still a pain, this might be useful to correlate with at least some nearby galaxies, and that could have ripples to the rest of the ladder.

Zvezda, Poisk, and Rassvet have docking ports compatible with Soyuz and Progress craft. Pirs used to have one too, but has been decommissioned. While Chinese spacecraft started out heavily based on Soyuz, I don't know if they would have kept up with any modifications related to ISS and/or went off on their own path for their own station. Keep in mind that it's not just whether or not the ports themselves fit, but everything involved in aligning the two craft together for the docking to happen safely. If the ports themselves are identical, but the alignment guides are installed differently, you're not going to be able to dock. And even if the two systems are completely identical, and you want to take on the risk of manual docking, it's still something entirely untested with any number of potential problems arising. Honestly, if things were that dire, a better option might be a space walk.

I mean, even if the Starliner was completely DOA, it's not like there is no way to get the crew home. They might be stuck on ISS longer than planned, but you could always work the rotation of the future launches in a way that gets them home soon enough, and lets the normal schedule resume shortly thereafter. Back when the Soyuz was having issues, people were even talking about adding extra seats to the dragon, which it's been designed to handle at least on paper, so something like that would be an option in a genuine emergency. It's just fun to poke fun at Boeing, and how they're trying to be nonchalant about the whole thing a little too hard, given all the RP disasters they're in the middle of. If it weren't for all the other problems the company has been having, we probably wouldn't even be discussing this beyond the, "Oh, they're going to take a closer look at what's up before heading home." And yeah, I don't think anyone currently aboard the ISS minds the mission extension. It's not like there's nothing to do or the crew is stuck alone without resources.

Hypothetically speaking, if you were able to make a mirror that reflects any wavelength with near enough to 100% efficiency, you could build a tiny star that sits comfortably in an enclosure that fits in your pocket and can power your car, yes. The reason you can't has to do with how electrons in matter interact with electromagnetic radiation at such short wavelengths. I can see some kind of hypothetical superconducting degenerate matter being able to do that without flatly breaking known physics, but the kinds of pressures that involves already require being in a core of a star, so that seems entirely moot for any practical purpose.

I don't think there was ever a Vandenberg launch that my area wasn't overcast for. I'll keep an eye out, but I'm pretty sure I'll only see clouds.

I saw this dig by Futurism, and couldn't scroll past that title. Nothing new of substance, but sharing for the title anyways. https://futurism.com/the-byte/boeing-starliner-astronauts-stranded

We all know that cats can survive a fall from an arbitrary height. Things they land on, however, aren't as lucky. This cat, evidently, fell from pretty high up. Possibly an airplane.

That is wildly exaggerated, TBH. Your typical interplanetary transfer is in tens of km/s. A 2RPM rotation involves a rotation around a point 250m from the center of mass (this can be more or less than 500m of cable, depending on your counterweight, naturally) and has velocity w.r.t. combined CoM of only 50m/s. This is well within the mid-course correction burns you'll be doing anyways. Likewise, loss of gravity, while disorienting, is about as dangerous as riding on a drop tower at an amusement park. You do still have the spin of the rocket itself, but it's likely to be a fairly stable rotation and the resulting centrifugal effects will be minor enough for this to be at worst comparable to a slip-and fall on flat ground. You can never exclude a risk of injury in any sort of a fall, but you can also slam your hand closing a hatch, so you know. What is a real risk is the cable snap-back. Back of an envelope estimate, a lot of materials you'd consider for a cable would stretch by about ~10% before failing. You want a good safety margin, so you're probably going to be looking at a little less than 5%. Call it a 10m stretch from CoM, where the cable's most likely to snap. A fully-fueled Starship is 5kT, which means you're looking at 1/2 * 50MN * 10m = 250MJ of energy stored in the cables. It's not a LOT, but it's enough to get the tip of the cable flying at you at a decent speed. (Yes, I know the energy is split between multiple cables, but so is the mass of the cable you have to get moving...) With a very rough estimate of 20T of cables in there, you'd get something like 50m/s average speed, but the tip is likely to be traveling closer to the speed of a bullet. The odds of that tip hitting the ship are not zero, and it will absolutely slice clean through. There are safety measures you can take. The tension wave will propagate at the speed of sound through steel, which is on the order of a few km/s. That technically gives you enough delay for emergency severing of the cable. If you put accelerometers everywhere along the length of the cable, you can cut all the cables from the ship, causing both ends to snap together instead, resulting in very low chance of any part of the cable hitting the ship with significant velocity. You obviously want this system to be rock solid, but what emergency system isn't? And we are looking after a catastrophic failure, which is very unlikely to begin with. We build suspension bridges using essentially the same tech. All of that said, when people talk about testing a centrifuge on ISS, people do talk about small radius centrifuge. As mentioned earlier in this thread, we do now have strong evidence that even a sub-5m radius centrifuge is viable for artificial gravity with a trained crew. Especially if you don't mind ramping up the speed over a few days when the trip starts, and winding it down on arrival. And that is an entirely different structure. Something with a revolution period of about 4 seconds and compact enough to fit in the inner hull of the Starship. If we're going to see artificial gravity on a trip to Mars, that is far more viable than any tethered design. And it's also something we can comfortably test on the ISS with very reasonable expense. I mean, it's still a full sized module requiring some amount of orbital assembly with current launchers, but again, if we're looking at testing this for interior of a Starship, the best way to test it would be to assemble one within the Starship, dock it to ISS, and just keep it docked for a few months. What better proof of Starship's capability to take a crew to Mars could you possibly ask for?

Our water never gets warm enough for a swim without a wetsuit. Otherwise, I'd probably be doing a lot of the same. There are a few bays not far from here that do heat up by end of July-August, but they all involve a bit of driving. And when the weather's good, also lots of standing in traffic to get to them. For anyone who doesn't mind a wetsuit and into surfing, though, these are some of the best locations. (Though, I suspect, same can be said about your area.)

I really want a rogue planet Easter egg. Something that looks like a once habitable (or even industrialized?) world that got flung out of its ancestral home eons ago and has been floating through the void of space ever since, its atmosphere having condensed and subsequently frozen as vast "oceans" between the elevated areas that were once its continents. Because it would be far enough out from Kerbol, it would make sense for it to be uncharted and nearly undetectable, but it can also stay entirely fixed. Though, I do recall some speculation sparked by the discussion of the stellar movement being a factor Intercept is considering, potentially indicating Kerbol being part of a binary with a nearby star. That would both be a great excuse to bring in the nearby star system closer to Kerbol, as 0.1ly or even smaller distances aren't unusual for such configurations, and would allow the formerly rogue planet to be a Kerbol capture, still being absurdly far away and entirely uncharted until you put an effort into it, but nonetheless, being on orbital rails, making it a little easier to plan transfers to it. Again, not a bad way to bring all of the concepts and planet work already done by the authors of this thread into KSP1. (Edit: Though, I'll be honest. I'm growing more and more tempted to build an engine in Unreal as a proof of concept.)