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I think the math is fine, but a perfectly rigid rod cannot exist in our universe, so there's no paradox, even though it would let you send messages faster than light. It's like calculating how strong of a hydraulic press you'd need to compress matter into neutronium in your garage, or claiming that if a spaceship could travel at 2x light speed, then it could fly its way back out of a black hole.

One challenge I've heard of is: If you carry 100 tons of cargo from point A to point B in an airship, for the airship to return to point A, it needs to take on another 100 tons of new cargo (or ballast), or it needs to vent (or compress) lifting gas, in order to maintain the correct buoyancy. I wonder what the best approach is here, & how it affects the economics? Is water ballast safe & cheap enough, or is there a better way?

Compressed hydrogen has low enough density that even at dangerously high pressures it would take up most of the luggage & passenger areas of a car, just to get mediocre range. Liquid hydrogen has better density (roughly 2x), but it's still not great, & you're dealing with a cryogenic propellant that's constantly venting explosive gas (so it runs out of gas when parked for ~3 days, can't be parked in an enclosed space, & still doesn't deliver impressive range). I'm all for using hydrogen for things in general, but as I understand it there are hard physical limits that make it a poor choice for personal motor vehicles as we understand them today (size, safety & range in particular).

Methanol or renewable synthetic gasoline seem like they'll always outperform hydrogen for ICE cars.

Hydrogen airships would be cool though & we could make them safe with modern technology (both preventing fires & making the passenger compartment an under-slung survival cell with parachutes & giant airbags so a catastrophic loss is survivable)

> You can exercise without changing your diet, but you won't loose (much) weight.

Exercising without changing your diet is seriously nontrivial for most people, due to compensatory eating - if you burn an extra 400 kCal, you will likely experience commensurate increase in appetite & eat an extra 400 kCal. It takes a lot of vigilance & discipline to avoid that.

IMO that's the 'real' reason diet is a more effective lever for weight loss than exercise. In theory, burning those extra 400 kCal thru exercise is just as effective for creating a caloric deficit as reducing daily consumption by 400 kCal, but in practice it still requires you to eat less than what feels normal/adequate.

Supersonic rounds make a distinctive noise that machines could reliably distinguish from fireworks (humans can learn to do this too). But distinguishing arbitrary subsonic ammo vs. arbitrary fireworks seems like it would be at least an order of magnitude harder & I don't think it could be made 100% reliable

Tragic as it would be, that worst case global warming scenario is still more of a "set human population levels & quality of life back 200 years" situation, rather than a literal extinction event though. I see a lot of hyperbole & doomerism around these topics online & I think pushback is fair.

We should be doing more to prevent the worse global warming outcomes. The stakes are billions dying or having miserable lives, which should be motivating enough. I don't think it helps to spin a dark fantasy about it being too late & humans actually going extinct. In the long run, an 8x reduction in human population & a few centuries of bad weather isn't really even a close call, let alone a legitimate extinction risk.

The first generation or two of Vipers were very raw & unrefined, with ~400 horsepower, no stability control, no anti-lock brakes, minimal safety features, cheap & janky looking interiors, etc. It sounds great to me (aside from the lack of a/c & nice ergonomic interior), but it would be extremely easy to have a bad time if you're an average driver.

I'm not sure about the analogy though, they might have been thinking of later Viper versions where the complaints would be more about cost, gas mileage, or general impracticality for daily use.

I think I first heard about it in a Scott Manley video - maybe this one, https://m.youtube.com/watch?v=JNT28WKAxgs - & read more on Wikipedia & possibly elsewhere

Reminds me of my favorite story from the Manhattan project: The project needed massive amounts of wire for all the equipment, but copper was in short supply for the war effort. They ended up working out a deal with the Treasury Department to use silver instead, since it was an even better conductor & apparently more available at the time. Part of the deal involved making sure not to lose any silver & IIRC they managed to not only return all the borrowed silver, they even found some extra to return by tearing up the floors in all the mints, warehouses & workshops, to incinerate & reclaim the precious metal, just like in the article!

I used to have a lot of trouble with insomnia, but a few years ago I discovered Drachinifel's YouTube channel about naval history https://m.youtube.com/@Drachinifel

Now I fall asleep listening to his 'drydock' Q&A episodes or lectures on historical campaigns, technologies, etc. & it's not really a problem at all anymore. It's been amazingly helpful.

I find the content interesting enough that I don't feel bored & restless, but not so urgent or exciting that it keeps me up. And I get multiple nights out of each episode by falling asleep fairly quickly

Just thought I'd share in case it works for anyone else

I thought the big concern around falling down on the moon is the risk of sharp rocks & abrasive dust damaging your spacesuit, not that it's hard to get up. Still, these 'SuperLimbs' sound like a cool technology that will probably be useful for something

This YouTube channel has a lot of good info about different historical swords https://www.youtube.com/@scholagladiatoria - pretty sure he covers the difference in metallurgy between Japanese & European swords

The main thing I've heard is that in Europe all the best swords used spring steel, which is hard enough to cut really well while also being able to flex without getting chipped, broken or bent. Japanese smiths couldn't make spring steel for various reasons, so as a workaround they used differential hardening, etc. to make the cutting edge super hard, while the back & sides ended up more ductile. It works pretty well, but the cutting face is still a little bit brittle & the sword as a whole ends up heavier & vulnerable to getting bent b/c it doesn't snap back into shape like spring steel would

If atmospheric nitrogen dropped by half, I'd imagine the effects would be pretty significant for aircraft, birds & internal combustion engines. Rocket launches would become more efficient (less drag), but reentry would be more challenging, w/ less overall drag & proportionally more oxidizing effect when aero-braking

Most engines would probably run hotter & weaker w/out as much nitrogen to use as a working fluid (maybe we'd compensate for this w/ water injection & get even better performance though?)

The speed of sound would decease slightly, while the speed needed to generate lift at a given altitude would increase. This would definitely affect airplanes, e.g. a plane that can cruise at 15k feet but not 30k feet might not be able to reach 15k feet anymore

Although we can't directly measure the one way speed, can't we at least demonstrate that the speed of light is the same for various arbitrary directions? I'm imagining sending a very brief & well columnated laser pulse aimed at e.g. Pluto, such that we have to "lead" the shot based on light travel time. If the outward bound light pulse travels slower/faster than expected, it will arrive at the wrong time & miss the planet, won't it?

You could repeat the experiment at different times of the Plutonian year to verify other directions, etc..

I think there may be practical problems with this method in terms of creating such a well columnated laser pulse, but in principle couldn't we use it to rule out anisotropic light speeds in several (perhaps most/all) directions?

NASA has actually looked into this & found the ideal method for safely vandalizing tires https://www.thedrive.com/news/nasa-built-a-tire-assault-vehi... (it's an RC robot w/ a drill, for testing how space shuttle tires perform when damaged)

As long as it doesn't end up in a flatspin an airliner should be able to pull up from a dive. For an extreme example where this was tested in practice, in the https://en.m.wikipedia.org/wiki/China_Airlines_Flight_006 incident, a pilot lost control of a 747 & ended up diving 30k feet at speeds approaching/potentially exceeding mach 1, then pulled 5 Gs leveling off at 10k feet once he regained situational awareness, & they were still able to land safely, although there was some damage

IMO the bigger problem would be needing multiple helicopters pulling together - wind or the jet's engines might pull the helicopters enough that they'd crash into each other, & you'd definitely want to start the engines before freefall..

It would be nice to see someone get rid of Putin for high-minded ideals like peace, justice, democracy, or the welfare of Russians & Ukrainians. But I'm not too optimistic on it happening that way.

I worry that anyone w/ the will & the means to assassinate Putin would likely be a power hungry would-be dictator making an aggressive play to replace him. Things could shake out better in the chaos, but they could just as likely go worse

If it's not legal to drive drunk, why would it be legal to drive up to 5 cars at once through a computer, where latency & limited views would likely create similar impairment?

Sure, 95% automation w/ remote drivers can work most of the time. If there's an obstacle blocking the road an automated car can stop for a remote driver to carefully pass by. But it would be a huge liability in any situation where "stop & wait for a remote driver" isn't a safe option.

I do think there will be a significant market for this kind of thing, but it will be more of a premium subscription for L4 vehicles, mostly sold to older folks & less confident drivers. Using it to approximate L5 directly seems dubious

For that I'd purpose a "taxi Turing test" - a vehicular automation engineer rides in the back wearing augmented goggles that block out where a driver may or may not be sitting & distort all voice audio to sound robotic. The engineer requests navigation thru various routes & environments or whatever testing they'd do for normal L5 evaluation. Not sure I see the point, but doable

It's not cost effective. (Same reason we don't encase it in giant synthetic diamonds or bury it in the earth's mantle)

Plus the material is valuable & space launches are dangerous. Launching to space probably introduces more contamination risk than any other option short of intentionally making dirty bombs out of it

No, the ignition here is small - on the order of a stick of dynamite. There's no reasonable way to scale it up to the size of a hydrogen bomb. Even if the lasers could just be scaled up larger & still work, which they can't b/c the lasers would make too dense of plasma & block their own beams, the number you'd need & the geometry of trying to use it on a full scale bomb would be totally impractical even for a single test. Also, a city sized laser ignition source w/ a bomb at the middle wouldn't be a useful weapon even if it were possible

I like your thinking & I wish this was a thing, but even if it were legal to sell new cars w/out ABS, traction control, backup cameras, etc., it seems like anyone who would actually follow thru w/ buying a car like that could just buy a used car - or buy a car w/ a salvage title & replace everything to their exact preferences - for way less than a new car costs anyway

the rounded symbols for 'database' icons are based on some ancient storage medium used in early mainframes - magnetic drum memory I think

We invented farming, so we had the opportunity. Other animals never figured out how to get milk unless humans or their mothers give it to them.

I use pycharm and as long as I set the virtualenv I'm using as the Project Interpreter in Preferences it lets me "drill down" to the library code as well

I remember watching a TV ad where Michael Jordan around the age he was when he retired played 1-on-1 against himself as a college player. This was 15-20 years ago & I wrote an essay for high school English class on how that ad shows we can't believe our eyes when it comes to what we see on TV. It was visually much more convincing than the examples I see here, so I can't help but think deepfakes haven't quite caught up with professional editing, at least not yet.

I read that at least one shuttle commander thought the ejector seats would've been useless anyway b/c if you used them while the solid rocket boosters were still running you'd get burned up & lose your parachutes from the SRB exhaust - and your altitude & velocity would be too high to eject by the time you'd be safe from the SRBs

I think it's time we develop chemical agnostic impairment tests. I don't really care whether someone is impaired because of alcohol, research chemicals, or just emotions & extreme sleep deprivation; I care whether they have their wits, judgment & reflexes up to par to safely drive a car. And we should be able to test for that directly.

IME .bashrc already doesn't work the same on OS X, though, so that's still a weird reason.

thank you. this really validates my decision to work as a backend Python engineer at a well-established startup.