I’m not sure I understand how “red sky in morning, sailors take warning” can be both inaccurate and useful. Surely a heuristic for when to prepare for bad weather is useful only insofar as it is accurate?
brendan.furneaux
Karma: 106
These are very cool results. But please, the big cat in the demo image is a leopard, not a tiger. It’s clear that even the SAE feature space knows this, because the images generated are never striped (as tigers always are), and are instead either spotted (as most leopards are) or all black (which is not uncommon in leopards, Wikipedia claims 11% and I expect them to be over-represented in image databases; while even so-called “black” tigers still only have very broad, partially merged black stripes with some light color between).
Minor quibble: Hamilton the musical is based on the biography of Alexander Hamilton by Ron Chernow. So while Lin-Manuel Miranda did arguably know a lot about Alexander Hamilton once he had read the book, I would say that his unique contribution was not (musical theater composition) + (Alexander Hamilton facts), but specifically the idea that a biography of a historical figure most well-known for being killed in a duel with a former vice president was, in fact, material that could be adapted into a musical. (And furthermore that it should be a rap musical.)
Anecdotally, I know a guy who wrote an opera using the transcript of a routine small-town city council meeting as the text, but it didn’t become a hit.
Ergot is toxic and eating contaminated bread has been a historical problem, but the results of ergot poisoning, contrary to pop science/history accounts, don’t seem to be much like the results of LSD, although there is a neurological component. It is plausible that the evolutionary “purpose” of the alkaloids is to poison animals that eat it, but whether the benefit to the fungus comes from decreased predation, improved dispersal, or something else is unclear.
Certainly there exist fungi which produce psychoactive compounds in order to alter the behavior of an animal, such as the charming Massospora cicadina, aka the cicada sex zombie fungus.
Also: Did Albert Hoffman hit the most powerful variant on the first try? No, he was systematically investigating similar compounds for pharmacological properties (not psychedelic properties, just regular drug discovery). LSD is just the one that had significant novel effects at low doses, and so it is the one which became famous.
The extreme potency of LSD is indeed a critical part of the story; synthesizing it is difficult in part because it’s very hard to produce it in any large quantity without incidentally ingesting active doses through the air. According to Wikipedia, the threshold dose to feel effects is about 25µg. Not milligrams, like the active dose of most medicines, _micro_grams. I am sure chemists over the years have gotten accidental doses of 25µg of many tens of thousands of chemicals without ever noticing it. Albert Hoffman’s original accidental dose was consistent with a ~threshold effect, so it doesn’t seem to be especially serendipitous. He just happened to be the lucky chemist who was working with a chemical which is psychoactive in such trace amounts. (He then intentionally tested a dose of 250µg, which he thought was very small but which is in fact a solid dose.)
LSD as such does not occur in nature, so it has no evolved biological role. It is a semi-synthetic chemical, meaning that it is synthesized in a lab by chemical reactions, but that the usual starting material is biological (typically ergotamine, which is, as you allude, found in ergot).
Regarding the effect of longitude, rather than fiddling with the offset, I think you want two terms, sin(lon) and cos(lon). Together they model a sinusoid with any offset.
Ok, now I understand the type of maneuver you are talking about. That definitely does make sense. I wonder if our hypothetical probe has knowledge early enough about the orbital trajectories of the stars close to the black hole, such that it can adjust its approach to pull off something like that without too much fuel cost. Of course it’s a long trip and there is plenty of time to plan, but it seems that any forward-pointing telescope would tend to be at significant risk while traveling at 0.8c into a galaxy, let alone 0.99c before the primary burn. However, “not likely to survive if deployed for the whole trip” is not the same as “can be deployed for long enough to make the necessary observations.” One advantage to a “simple” powered flyby of the black hole is that at least you know well ahead of time where it’s going to be, and have a reasonably good estimate of its mass.
Alternatively, could it get that information prior to launch, and if so are the trajectories of those stars stable enough that they would be where they need to be after millions of years of travel? My guess is no.
In the typical case, there are (at least) two meaningful bodies other than the spacecraft doing the maneuver; in real-world use cases so far, typically the sun and a planet. An (unpowered) slingshot maneuver doesn’t change the speed of the spacecraft from the frame of the planet, which is the object that the spacecraft approaches more closely, but it does change the speed in the center-of-mass frame, and it works by transferring orbital energy between the planet-sun system and the spacecraft. But the key is that in order to change your speed as much as possible relative to the center of mass, the object which you approach closer (i.e., “slingshot around”) should be the object which is smaller, and thus has higher speed relative to the center of mass. Of course it still needs to be much larger than your spacecraft. In no case would that object be the central black hole of a galaxy, unless your goal is to reduce your speed relative to an even bigger nearby galaxy, or perhaps just to change direction.
Are you talking about some other type of situation? My orbital intuition is that if you are going to trade orbital energy with a system, you have to get close to it relative to the separation of the bodies in the system, so it will generally make sense to talk about slingshotting around one of the bodies in particular. This is especially true when you are approaching with much higher than escape velocity, so that an extended dance with more than one close approach is not possible unless the first approach already did almost all the work.
I suspect another issue is that it’s too dangerous to fly at 0.99c as you are entering a galaxy. There’s too much gas and dust.
If I understand correctly, the Penrose process as such (i.e., actually extracting energy from the black hole’s rotation) only works if your exhaust is expelled fast enough, relative to you, that is is put on a negative energy orbit, which necessarily falls into the black hole. I’m not sure how you could perform a retrograde burn in which your exhaust somehow enters the black hole but you don’t, since in a retrograde burn your exhaust is getting extra orbital velocity.
I am still really curious whether it helps to execute the retrograde Oberth maneuver within the ergosphere of a Kerr black hole, and if so whether it is better or worse, or even possible, if you approach on an initially retrograde orbit. Of course the approach orbit is probably steeply inclined because you don’t want to spend any longer than necessary flying at 0.8c through the galactic disc.
Ahh, that makes more sense.
I don’t understand how a slingshot maneuver off of a central black hole would work. My understanding was that a slingshot never slows you down in the frame of the object you are slingshotting around, it only changes your direction. Since the central black hole is presumably stationary with respect to the rest of the galaxy, this wouldn’t help you in slowing down. Slingshotting around an intermediate mass black hole (if such things exist) out in the galactic disc seems like it would be more useful.
Or maybe there is something about general relativity that changes things?
It seems implausible that everyone who grew up in Britain in the 1960s would have genetic variants that no one else has. Their parents and children would have grown up in different decades, whether in Britain or elsewhere, and they would also have those variants.
I hate to make a comment just to be pedantic with a definition, but it honestly confused me the first time you used the word “dichotomy” in this post to refer to a division into three, rather than two, categories, and then disturbed me every subsequent time. It’s possible that this is informed by my training in biological taxonomy, where we also use the contrasting word “polytomy”, meaning a division into more than two parts. In this case, you could use the less common “trichotomy”, meaning division in exactly three, including the same nuance as “dichotomy” that the division is absolute and idealized. Alternatively, “taxonomy”, “classification”, “categorization”.
Despite those three moments of confusion, I really enjoyed the post; more so because I had not previously seen the original.
I have also found this with Bohnanza; although the rules say that the most points win, my group has always made it a faux pas to actually count points before the end of the game. Everyone plays to maximize their own score, rather than to beat the opponents, and it is definitely the case that people who accept “bad” trades tend to do better than people who walk away from the negotiating table. (At the same time, people who can instead negotiate the “bad” trade into something better do the best of all.)
I would say that Agricola (by the same author) and its spinoff Caverna, also have the opportunity for positive-sum trades if you play to maximize your own score rather than to beat the other players; I expect the same is true for many/most other worker placement games. In those games, resources accrue to the board at a fixed rate until someone spends one of their limited actions to harvest them. There are a fixed number of turns, so there is a fixed amount of each resource which is produced by this mechanism. For instance, the 4-wood space in Agricola accrues 4 wood each round for the 14 rounds of the game, for a total of 56 wood. In a game where players are hotly contesting the wood, the space gets harvested by someone every round, so the action efficiency is 4 wood/action. In a game where players let the wood build up and harvest it every other round, the action efficiency is 8 wood/action. Everyone may get the same total wood in the game, but with less opportunity cost.
I believe there are also single-celled eukaryotes which have more than two mating types.
I think the key is that you have to have a system where a third mating type makes sense. Having fallen into the basin of attraction of anisogamy, and then later sexual differentiation of reproductive anatomy, it’s much harder to develop a new sex that could reproduce with existing males and females (but not itself).
The way the fungal system that leads to the claim of over 20,000 mating types for Schizophyllum commune is similar to how our pheremones (purportedly?) work; you just want to find someone who smells different (i.e., has a different set of MHC) from you, and there are many ways to have different MHC combinations. If someone develops a new one—good! They smell different than everyone (except their own children) and so they never end up stuck with a distantly related potential mate who nevertheless smells too much like them, and this improves their reproductive success until the new MHC is widespread in the genepool. Additionally (in the case of MHC but not mating types) there is purportedly actual immune benefits which drive this, in addition to the generally beneficial encouragement of “out-crossing”.
I came here to say this; there are many species of Eukaryotes that seem to reproduce exclusively asexually. I know Malmesbury said not to mention Fungi, but I’m a mycologist so it’s what I do. The lesson there seems to be the asexuality evolves fairly easily from sexuality, and is adaptive when you have a good genome which is well adapted to a relatively stable environment. But it’s also kind of a dead end; you don’t usually see large groups of related species which are all asexual (with the possible exception of Glomeromycota, although their genomes suggest they are in fact getting some action). Instead, the closest relatives of asexual species are often sexual species. I believe the same is also observed in plants.
Maybe I am missing some previous rationalist discourse about the red sky saying. I remember reading it in books as a child, and do not know (except that it is listed here as a useful heuristic) whether it is actually true, or what the bundled incorrect causal story is. I have always interpreted it as “a red sunrise is correlated with a higher chance of storms at sea.” That claim does not entail any particular causal mechanism, and it still seems to me that it must be either accurate and therefore useful, or inaccurate and therefore not useful, but it’s hard to imagine how it could be inaccurate and useful.