- Larisa: Lava moat!
- Man: Lava moat!
- Woman: Lava moat!
- Larisa: Lava moat!
- Yuna: Lava moat!
- Larisa: Lava moat | Sigh
- Yuna: Lava moat?
- Larisa: Lava moat $$$!
- Yuna: Lava moat…
- Larisa: Lava moat?
- Yuna: Lava moat ¢!
- Larisa: Lava moat!!
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![[1190] Lava Moat 2](/comics/2020-06-29-1190-lava-moat-2.png "[1190] Lava Moat 2")
[1190] Lava Moat 2
└ posted on Monday, 29 June 2020, by Novil
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It’s a good book!
Seems like everyone would lava moat!
Lava mo- ahem…
Great reference, Novil!
(It was also mentioned in the past strip’s comments.)
Well… Larisa now has the power of hypnosis… the world is gonna get burned down.
I swear the little people on the book are a reference to xkcd. It’s something about the hat.
@ Merandil:
It’s a book written by Randall Munroe, who also writes xkcd.
@ Merandil:
Because Larisa is holding a book https://www.goodreads.com/book/show/42086897-how-to by Randall Munroe, the author of XKCD, and both Munroe and XKCD are in the strip tags.
Given Yuna’s been charged with the design of the moat and associated reactor, you can probably bet the reactor’s going to violate several laws of physics (maybe even using the potential energy of a star trapped at the moment of collapse into a black hole [does the Eye of Harmony count as a reactor?]).
Great comic. I love the xkcd reference and how Yuna is just circumventing it with mad science. 😀
While a moat of lava would be cool in theory, sadly it would result in problems. One the problems of building a moat with a layer that can contain, and heat the lava continuously to keep it molten, while not melting the layer that keeps the lava contained. Also given the top of the lava is much cooler and will likely develop a crust, how would you prevent people from just walking across it?
also what material would you use as lava? different materials have different melting points, different combinations will have different properties, densities, and melting points, which will affect what other materials would be required to build such a project.
Common elements in the Crust and mantle, and their melting points include. Carbon [3642 °C], Oxygen [−219 °C], Sodium [98 °C], Magnesium [650 °C], Aluminum [661 °C], Silicon [1414 °C], Phosphorus [45 °C], Sulfur [116 °C], Potassium [64 °C], Calcium [842 °C], Titanium [1668 °C], Manganese [1246 °C], Iron [1538 °C]. Common minerals are Silicon dioxide [1,713 °C], Aluminum oxide [2,044 °C] other possible chemicals could include Mercury [−38 °C], and Gallium [30°C], Zinc [420 °C], Copper [1085 °C]
some combinations would have really high melting points and will make it expensive to keep hot. other combinations can be kept molten while under 1000 °C, and might have the side effect of being horribly toxic.
But certain alloys while they can be molten at lower temperatures might be dense enough that someone could easily walk across with the equivalent of snowshoes.
it would be cheaper and easier, to simply fill a moat with boiling oil and/or Alcohol, light it on fire, and use a pipe to refill the moat from the bottom of the moat. and use electric heaters built into the moat to keep the oil hot and boiling. I’m sure Larisa would much prefer a moat of Fire and boiling oil. as it is harder to cross than a moat of Lava, and includes Fire as part of the design. Also you could use whatever oil is cheapest, or most environmentally friendly, depending on your biggest concerns. you could even bubble propane or methane up through the oil from the bottom of the moat.
@ Kuraimizu:
1: Larisa has a relevant book that has a chapter about exactly that in panel 4.
2: Yuna.
Lava Moat.
@ Kuraimizu:
I feel like you’re being too literal with a comic, here. 🙂
@ Jack:
@ FuryoftheStars:
being literal can be fun, especially when science gets involved.
oh forgot to mention that the moat needs a wall on the inside shore, that over hangs the moat at an angle away from the house. in case the moat explodes, so all the oil and fire is sprayed away from the house. this will happen during two scenarios, during heavy rain fall. Or if you built the moat to have a water line so you can quickly flood the bottom of the moat with water, which will instantly boil in the boiling oil, turn to steam and explode all the oil floating above it up and out. and because the oil was already on fire, it’ll turn into a giant fire ball, or in the case of a moat, a fire wall.
so never let water get into the oil moat, things get very bad very quickly.
Aha… now it is legit… kinda… but not…
Yuna in a Charlie Brown T-shirt does not bode well.
@ Kuraimizu:
As is pointed out in the book, if you chose too low a melting point rock, (It’s got to be rock to be “lava” when melted.) it doesn’t glow nicely, and if it’s not glowing, what’s the point?
It’s actually moderately easy to keep a lava moat molten, if you’re willing to seed it with the right radioisotopes. And what’s better than a lava moat? A radioactive lava moat!
@ Brett P Bellmore:
@ Kuraimizu:
How about using crystalline H20?
The stuff liquefies at a reasonably low 273K, which can be reached with conventional heat exchangers, but in its solid form, covers quite a bit of landmass, especially in the southern hemisphere, as well as the peaks of many famous mountains. It ranges from perfectly clear to brilliant white, although it is nearly always clear in its molten state.
The only downside is you can’t work with it in the absence of dihydrogen monoxide, which is a potent and highly dangerous industrial solvent, and one that readily gets into the food and water supply with even the slightest containment breech.
Ah, I see where the problems will come from for Sandra.
I also read that book! Really glad you somewhat addressed the logistical problems of having a lava moat.
I see. She can heat the molten rock with a local black hole (aka Wally) like a Romulan engine core.
Ah, glad that the technical issues are sorted! 🙂
This reminds me of the “Chicken chicken chicken” conference: https://www.youtube.com/watch?v=yL_-1d9OSdk
Don’t get any on the patio, or Alice will kill you.
@ Brett P Bellmore:
Metal, glass, crystal, and various other minerals and chemicals are all derived from rocks, and are just a refined form of rock, after all rock is basically just stuff that has been melted and/or crushed into a solid mass. One can easily claim that molten metal is a form of lava. And molten metal has some of the best glow, as long as it’s hot enough. As long as you can get it over 500°C most things start to glow pretty nicely.
LAVA MOAT!?
@Kuraimizu
“While a moat of lava would be cool in theory” Actually I’d rather expect it to be quite hot.
Keeping it molten won’t be too much of an issue. A double layer of graphite with air insulation between would be quite effective at keeping heat loss to a minimum but melting the rock in the first place requires a massive amount of energy.
@ Merandil:
Maybe because the book was written by the same guy who writes XKCD?
Ack! Literally the only two webcomics I follow are Sandra and woo and XKCD! This mini “crossover” is too perfect!
Never thought I’d see an XKCD reference here
I’m starting to believe the foreseer didn’t foresaw his prediction’s influence on the future.
The prediction is quickly fulfilling itself.
@ MaxArt:
Reference to what?
I’m actually curious now.
@ Scythe-Nova:
There’s a well-hidden reference to another webcomic (or, at least, something the author of that other webcomic produced). None of the other commenters have noticed it yet, so I’m not gonna spoil it. /s
Circumvented by ‘What? You think this is Earth-temperature lava?’
@SeanR@ SeanR:
Just start with a glacier.
Hehehehehe.
This is what I first thought of when I heard “lava moat” as well. Love the reference.
I think Sandra’s dream is now a parallel of greek prophecy, just like Oedipus, Perseus’ granddaddy, and any greek mythos involving prophecy being fulfilled by trying to prevent it.
Lava moat
@ Brett P Bellmore:
“Moderately easy” does a lot of work here. To keep a thing in molten state with radioactivity, you need at least a few megawatts energy. Assuming you are using Co-60 as your isotope, which has the sharpest gamma photon among the “usual” isotopes, you’ll get 6 MeV from each nuclear reaction. That is roughly 100 pW. To get 10 MW of power, you’ll need 1000 TBq of Co-60. That is a terrible amount of radioactivity. It is about the same as was released in the Chernobyl disaster. And it would not come cheap.
Naturally, only some of that energy would be kept in the moat, and an appreciable amount of photons would escape it. The energy flux above the moat would be such that anyone within a few hundred meters would be killed in minutes. Above and near the moat, nobody could survive even seconds.
Droggelbecher.
Lava moat is so last year. Magma cannon is where it’s at. https://dwarffortresswiki.org/index.php/DF2014:Stupid_dwarf_trick#Magma_cannon
Haven’t read the book but did Randall really propose a lava moat there and why it’s expensive since Yuna designed a cheaper lava moat in the end here? If not, then thanks as anyways.
♪Laav moat…♪ (mondegreen, sung to the tune of “Love Boat”)
I am not sure if my memory is correct, but I think this comic used to be funny with situational comedy, for example subverting of expectations in 0017, but nowadays it’s just substituting funny with absurdity.
@ tofei:
Yes, this was part of the book – it was prohibitively expensive, and dangerous, and it does look like there is some cartoon physics involved in Yuna’s approach.
@ KaxTax formerly known as KayJay:
It’s possible if she’s using a thorium salt reactor.
@ Kuraimizu: Which is why it’s pointless to list. Just look up the stones…
Fun fact: Dwarf Fortress wiki used to be named “Magma Wiki”.
@ masterwre:
Minecart-based systems require less magma-proof materials than pump stacks. Also, they naturally ensure magma comes in manageable doses and allow better horizontal reach without flooding (in that velocity limitation due to inherent viscosity of magma is circumvented by throwing).
@ Kuraimizu:
“You’re being pedantic”
https://www.youtube.com/watch?v=VPOa72dsrGw