"Now that I think about it, a ballista that doesn’t have skeins, but a bending bow, is in fact a giant crossbow. Kindly ignore those scare-quotes around the term; it’s fine. "

"That ‘giant crossbow’ is a ballista, an ancient weapon widely used by the Romans among others. They came in different sizes, and usually fired a wooden missile with a metal head—metal being far too costly to use for the entire shaft. The one in the show seems to use bending in the arms to store energy, though—the Roman ones had stiff, straight arms that didn’t bend much, embedded in vertical skeins of fibre that twisted and stretched to store energy. The Legions used to choose musically talented men for ballista crews—they balanced the two skeins by twanging them and matching the notes, as though tuning a guitar. The fibre in the skeins was usually animal tendon, though there’s a story that at one siege, the women of the town volunteered to cut off their hair to be woven into torsion springs for the ballistae—probably apocryphal, as human hair has lousy strain-energy storage.I suppose it may encourage Cersei to find that the weapon can penetrate a dragon’s skull…a dried-up skeletal one, rotting for centuries in a cellar…fired at point-blank range, with no scaly hide protecting it, and of course neither moving (much less flying) nor breathing fire at the operators. I’m not so sure it’ll do as well in actual combat against a magical monster the size of a bus. A bit like shooting at an elephant, say. You really want that first shot to do the job, because your target won’t give you much leisure for a second one. Old time elephant hunters used double rifles for exactly this reason—I wonder if that’s why the ballista seems to have two bows?"

"I’ve once or twice wanted to become Captain Kerning, and run around fixing signs with horrible spacing errors. This one, though, I’d be content to leave alone. The combination of bombast and ineptitude is pitch-perfect.https://pricetags.wordpress.com/2016/12/02/kickstart-the-greatest-security-threat-in-vancouver/"

"I can’t help thinking that this is solving the wrong problem. Most of the heaviest parts of the frame are still in metal—the bamboo only replaces the straight, simple tubes, which are relatively low in weight anyway. Plus, the weight of a bike is really not that important for anyone except racing cyclists. I’d be far more interested in a system for recovering energy lost in braking, to reduce the total effort required in start-stop urban cycling. That would actually add to the weight of the bike, but would increase the cyclists average speed and improve comfort. I like the idea of replacing mined materials with grown materials, but when most people are still getting around in two-tonne masses of steel, making already-spare machines a tiny bit less metal-intensive seems like a lot of effort for small gain. Cutting the weight of car wheels by even 10% would save way more total metal mining and refining. Kudos to the designer, and I’d love to see that woven bamboo in lots of other applications—I just think the same ingenuity and effort could have far more impact elsewhere."

"The Pantheon is perhaps not an ideal example. It has several substantial cracks, and would have a lot more if they hadn’t added massive step-rings to the outside to counter the spreading force of the dome. It’s not that the concrete is so excellent; more that the Romans were willing to use massive quantities of it, and eschew windows, to create a stable dome.The thing I’d like to see us take away from the Pantheon would be its use of varying aggregates, of differing density and strength, at different heights in the structure. We tend to use high-strength concrete for everything, when a lot of lower buildings could use low-density, insulating aggregates, for better thermal performance and strength adequate for the task. The materials used by the Romans are not especially rare, and we understand their chemistry a lot better than the ancients did. I suspect it’s a combination of habit, customer expectations, and narrowly-written safety regulations, that keep us using the kind of concrete we do. Considering the very large (though sometimes overstated) contribution of concrete manufacture to global warming, it’s past time we looked at making concrete out of naturally-occurring materials, rather than using energy-intensive Portland cement in everything."

"Thanks for this piece, Rain—clever and fun. The toilets, by the way, are clearly based on Roman models. The buckets in the middle of the space, with the handled objects sticking out of them? That’s the Roman equivalent of toilet paper—a sponge on a stick, kept in a bucket of vinegar by way of rendering it slightly less disgusting to SHARE a backside-wiping tool. The slots at the front of the toilet openings are to let you reach in with the stick. https://www.youtube.com/watch?v=W5CESP6JZDkAccording to Christian legend, Jesus begged for water on the cross, and was given to drink from a sponge soaked in vinegar. That sounds cruel to us, of course, but it was a LOT nastier to the earliest readers of the story, who knew about Roman toilets. "

"It’s a clever concept, but there’s no way it will run a lightbulb for 20 hours. That 1,000 mAh is not an amount of energy, it’s an amount of current for an amount of time. If it’s like a lot of portable power banks, its battery operates at about 3.7 V. 1,000 mAh is one Amp-hour, times 3.7 volts yields 3.7 watt-hours, which would run a 60W lightbulb for 3.7 minutes. A smartphone uses way, way less power than a lightbulb, and nowhere near 180 watts. I’d be surprised if I could find a laptop that used that much power, even at peak; most of them around in the low tens of watts."