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Prometheus

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Everything posted by Prometheus

  1. We really know nothing about the effect of low gravity on the body. What research we have regards the micro-gravity environments of LEO. It would be folly to interpolate between these 1G and 0G environment data points. Another reason to go to the moon first, and get intermediate data points.
  2. That was from the 2015 study I gave. They didn't get those number themselves but provide these references to justify it: Seifritz W. Mirrors to halt global warming? Nature. 1989;340(6235):603. 10.Early JT. Space-based solar shield to offset greenhouse effect. Journal of British Interplanetary Society. 1989;42(567–569). 11.McInnes CR. Minimum mass solar shield for terrestrial climate control. JBIS. 2002;55(9–10):307–11.
  3. But it would threaten to knock the structure off the L1 point and so require a significant amount of fuel to keep it in place.
  4. Why the equator? I thought the Earth's tilt took it out of the ecliptic plane?
  5. Additionally geostationary orbit wouldn't work. This orbit means an object is always above the same point on Earth which means at night time its pointing away from the sun.
  6. I remember seeing a back of the envelope calculation that estimated the amount of mass needed for such a shade to be effective at cooling would require an orbital infrastructure of epic sci-fi proportions (and didn't even attempt to calculate the warming caused by building a launching all those rockets). I think it was a science communicator called Scott Manley if you want to have a google around to find it. Can't find it, but i have an envelope handy. Found this study that estimated the mass of a sun shield needs to be 10^7–10^8 tonnes. Let's take 10^7. That's 10^10 kg. The current cheapest vehicle per kilo is currently the Falcon 9 at $1400 per kilo. The cost of just launching this structure would be $14 trillion. Pretty expensive but economically possible i guess, if we ignore politics. A Falcon 9 can launch 22,800 kg per launch, which would require ~ 440000 launches. Space X have one of the best launch cadences in the world but only managed 31 last year. If we started now we might get it done in 30 years if we can increase the launches to 15000 a year. Apparently a Falcon 9 produces 360,000 kg of C02 per launch. So we'd be adding 10^11 kilos, or 10^8 tonnes, of C02 into the atmosphere by the end of the project. All this is based on costs to launch to LEO. L1, the most feasible place it could sit, would be far more expensive (both $ and C02) - but those numbers aren't so easy to get. I conclude that it's not feasible with current tech, and by the time it does become feasible it would be too late to significantly contribute i.e. the damage would be done. But feel free to check these numbers because i haven't.
  7. I heard that its lifespan, if all goes well, will be determined by the amount of fuel it has to keep it in its L2 orbit - because the Ariane 5 rocket did such a good job on its infection burn that is anticipated to be 10 years.
  8. By convention, in the fields i'm familiar with - medicine, biology and computer science - the first author will have contributed the most and the last author will be the most senior academic, usually the head of a lab. The middle authors will have contributed the least. I've been on papers where the squabbling of who goes where on the author list gets pretty intense and petty. Many publications require that the contribution each author makes is explicitly stated, unfortunately PLOS biology doesn't seem to be one. Karl Friston is a pretty reputable name though, I can't believe he would have tolerated too much jockeying.
  9. Accuracy is a terrible metric to assess these things: fine for classifying dog and cat images, but for law and health it misses so many nuances. There's also no mention of how well the AI generalises to data not in the original train/test distribution. I can't find the original publication, if it has been published in a peer reviewed journal, so can't dig into any details. Until then I wouldn't believe these numbers any more than my claim that i just developed an AI with 99.56% accuracy for predicting a bull's bowel habits.
  10. Ghana were awarded a penalty, which they missed. The game then went to penalties and Suarez, who was one of their main penalty takers, couldn't take one, so there were plenty of downsides, Ghana were just unable to capitalise on them. Additionally, Suarez was banned from the semi-final against the Dutch, which Uruguay lost. As to whether it's right - i can see both sides, but seeing Suarez celebrate the penalty miss was pretty galling.
  11. I've not the foggiest. Check out the lecture - The Royal Institution has a good reputation so i presume he's not talking total quack. As i remember he just mentions it near the end without many details.
  12. There are perhaps lessons we can learn from cellular automata - take rule 30 for instance. The generating process is perfectly known and simple, yet the manifestations of it are anything but. The central column the rule produces can only be modelled as a stochastic process (currently - £10k prize if you prove otherwise), so much so it is used as the random number generator in Mathematica. We could say that, in this case, the randomness is emergent from the rule. There was an interesting Royal Institute lecture on time - the lecturer ended by speculating that time was an emergent property based on our psychology - or something close to that effect..
  13. Putting aside that i know no physics - perhaps we can think of it in terms of how we model phenomena. Taking the Mexican wave as an example, each person could be understood in terms of simple up and down motions, but to capture the wave we might want to use sinusoids (ignoring that we might use sinusoids to understand the initial up and down motion). So a property is emergent when we decide, for whatever reason, to apply a new model to understand it. Emergence then isn't a property of the universe, but a property of how we understand it.
  14. Thanks for the suggestions, but it seems @TheVat is right - there doesn't seem to be any science fiction that documents the experience of entering a black hole. If anyone does come across something, i'd be grateful to know.
  15. Related to points one and two is to what metrics are any algorithms optimising? Is it simply ad revenue for something like facebook, is it view time or click rate for something like youtube. And, perhaps more important, are the metrics transparent?
  16. Can anyone recommend some sci-fi books involving black holes. In particular I'm looking for stories that involve someone, or something, going into a black hole and what they experience. I've looked around and found plenty of books, but usually they feature black holes as navigational obstacles, or power sources, or weapons, or even as sentient beings - but i'm only interested if it explores the experience of being in (or even around) a black hole. Also, not interested in films/TV shows - unless based on books.
  17. I got the numbers from Sabine Hossenfelder's blog - not verified the numbers myself but she seems like a trustworthy source (a theoretical physicist).
  18. My understanding is that Q is a poor metric of performance as it doesn't take account of the energy put into the entire reactor, just that used to create the plasma. Apparently things like confining that plasma with powerful electromagnets takes an awful lot of energy which are not taken into account with Q. If you use Q_total (i.e all the energy used by the reactor) as a metric then the value for JET is more like 0.01.
  19. Where America has Manifest Destiny, China has the Mandate of Heaven- they have a fundamentally different attitude to government than America, a more trusting one based on Confucian principles. Similar to evolved systems, neither is 'correct' but has benefits/risks. One more prone dictatorships, but also easier to harmonise to a purpose: if Covid 19 had been more virulent the benefits of the latter would be more clear. The Chinese people have been rebelling against governments at least a thousand years before the country that established America even existed, so I wouldn't worry about them being passive - as long as the government is fulfilling its end of the Mandate, the Chinese people are content, and why wouldn't they be? We might disagree with their position but we don't get to impose our view on them and to mistake it as docility is just to misunderstand their mindset. China's military aggression in and around the South China Sea needs to be understood in its historical context - China still remembers its utter humiliation by numerous Western powers and Japan. The Chinese people generally support their government in establishing a strong military presence around its territory to ensure that never happens again. If the West wants to limit China's influence they should stop bullying nations and start helping them. For instance, Australia has been harassing East Timor for decades in order to force access to oil fields, even pulling out of the UN convention on the Law of the Sea to avoid a binding ruling at the international court of justice. Now East Timor has invited China to help build up their infrastructure, giving China a presence right on Australia's coast. Taiwan has about a quarter of the semiconductor market. China would control over a third if it swallowed Taiwan.
  20. It's a risk/benefit calculation. A chest x-ray for a cough, say, is quite different to one for a penetrating chest injury. It's not uncommon to see push back against a doctor referring a patient for a CT scan if the radiologist (sometimes after being flagged by the radiographer) feels the risk may be too great - particularly for young people and abdominal scans.
  21. This falls firmly under 'all models are wrong, some are useful'. BMI is used as a rough marker in certain settings, no professional is (or at least should be) using this single metric to make any clinical decisions. If fat distribution is particularly important a more thorough method would be used. Bioimpedance is common in nutritional studies. First you should decide what you actually want to measure, then decide if BMI is good enough to that end. In some cases it is.
  22. True, but it's not unreasonable to ask. How unsatisfactory would it be to a end a discussion about whether, or at what age, abortion should be legal, or the legal status of various drugs with 'whatever a court says'. AGI is irrelevant to this particular discussion. DABUS is far from AGI yet its legal personhood is still being discussed, and apparently granted, in some courts. With the development of narrow AI like AlphaFold, which vastly improves previous attempts to model protein folding with implications in drug discovery, these legal discussions will likely (and rightly in my opinion) become more frequent regardless of AGI development. Given the glacial speed of politics and law, starting the discussion before it becomes a pressing matter seems prudent. Regarding AGI, that blog was a bit vague. Here, about 350 ML researchers were surveyed regarding the estimated timeline of human level machine intelligence development. Granted, it might be something like fusion power (another 20 years right?), but it's the most thorough guess i've seen kicking around. I found it incredibly hard to find out anything about the actual architecture of this model. This is the closest i could find - short on detail. I very much doubt it's anywhere near GPT-3, AlphaFold or Tesla's self-driving architecture. Sounds more like a gimmick to start a discussion.
  23. You underestimate how seriously people take Star Wars. Trying to apply any physics to Star Wars is not going to go well, it's all space magic. You'd get more mileage out of something like The Expanse, but being more realistic that doesn't have llight sabres either.
  24. To reinforce MigL's point that history isn't always written by the victors we can look to the Arthurian myth which demonises the victorious Anglo-Saxons (and later used by the Normans to frame themselves as liberators of the native population), and the Three Kingdoms period of China in which the Han empire was overturned by the Jin dynasty, yet it's the former who come out smelling like roses. And of course, the Romans conquering Greece - but i'm not aware of any Epics written by the conquered peoples in that instance. I once heard that the US government is in some part influenced by Iroquois governance - is there any truth to that?
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