nhaliday + physics   354

Workshop Abstract | Identifying and Understanding Deep Learning Phenomena
ICML 2019 workshop, June 15th 2019, Long Beach, CA

We solicit contributions that view the behavior of deep nets as natural phenomena, to be investigated with methods inspired from the natural sciences like physics, astronomy, and biology.
unit  workshop  acm  machine-learning  science  empirical  nitty-gritty  atoms  deep-learning  model-class  icml  data-science  rigor  replication  examples  ben-recht  physics 
7 hours ago by nhaliday
Manifold – man·i·fold /ˈmanəˌfōld/ many and various.
Silicon Valley (Big Tech and startups and VC)
Financial Markets
Academia (Good, Bad, and Ugly)
The View from Europe
The View from Asia (Life in PRC? Fear and Loathing of PRC?)
Frontiers of Science (AI, Genomics, Physics, ...)
Frontiers of Rationality
The Billionaire Life
What Millennials think us old folks don't understand
True things that you are not allowed to say
Bubbles that are ready to pop?
Under-appreciated Genius?
Overrated Crap and Frauds?
podcast  audio  stream  hsu  scitariat  science  frontier  interview  physics  genetics  biotech  technology  bio  interdisciplinary  spearhead  multi  genomics  sv  tech  finance  academia  europe  EU  china  asia  wealth  class  fighting  age-generation  westminster  censorship  truth  cycles  economics  people  realness  arbitrage  subculture  ratty  rationality 
7 weeks ago by nhaliday
An adaptability limit to climate change due to heat stress
Despite the uncertainty in future climate-change impacts, it is often assumed that humans would be able to adapt to any possible warming. Here we argue that heat stress imposes a robust upper limit to such adaptation. Peak heat stress, quantified by the wet-bulb temperature TW, is surprisingly similar across diverse climates today. TW never exceeds 31 °C. Any exceedence of 35 °C for extended periods should induce hyperthermia in humans and other mammals, as dissipation of metabolic heat becomes impossible. While this never happens now, it would begin to occur with global-mean warming of about 7 °C, calling the habitability of some regions into question. With 11–12 °C warming, such regions would spread to encompass the majority of the human population as currently distributed. Eventual warmings of 12 °C are possible from fossil fuel burning. One implication is that recent estimates of the costs of unmitigated climate change are too low unless the range of possible warming can somehow be narrowed. Heat stress also may help explain trends in the mammalian fossil record.

Trajectories of the Earth System in the Anthropocene: http://www.pnas.org/content/early/2018/07/31/1810141115
We explore the risk that self-reinforcing feedbacks could push the Earth System toward a planetary threshold that, if crossed, could prevent stabilization of the climate at intermediate temperature rises and cause continued warming on a “Hothouse Earth” pathway even as human emissions are reduced. Crossing the threshold would lead to a much higher global average temperature than any interglacial in the past 1.2 million years and to sea levels significantly higher than at any time in the Holocene. We examine the evidence that such a threshold might exist and where it might be.
study  org:nat  environment  climate-change  humanity  existence  risk  futurism  estimate  physics  thermo  prediction  temperature  nature  walls  civilization  flexibility  rigidity  embodied  multi  manifolds  plots  equilibrium  phase-transition  oscillation  comparison  complex-systems  earth 
august 2018 by nhaliday
Reconsidering epistemological scepticism – Dividuals
I blogged before about how I consider an epistemological scepticism fully compatible with being conservative/reactionary. By epistemological scepticism I mean the worldview where concepts, categories, names, classes aren’t considered real, just useful ways to categorize phenomena, but entirely mental constructs, basically just tools. I think you can call this nominalism as well. The nominalism-realism debate was certainly about this. What follows is the pro-empirical worldview where logic and reasoning is considered highly fallible: hence you don’t think and don’t argue too much, you actually look and check things instead. You rely on experience, not reasoning.


Anyhow, the argument is that there are classes, which are indeed artificial, and there are kinds, which are products of natural forces, products of causality.


And the deeper – Darwinian – argument, unspoken but obvious, is that any being with a model of reality that does not conform to such real clumps, gets eaten by a grue.

This is impressive. It seems I have to extend my one-variable epistemology to a two-variable epistemology.

My former epistemology was that we generally categorize things according to their uses or dangers for us. So “chair” is – very roughly – defined as “anything we can sit on”. Similarly, we can categorize “predator” as “something that eats us or the animals that are useful for us”.

The unspoken argument against this is that the universe or the biosphere exists neither for us nor against us. A fox can eat your rabbits and a lion can eat you, but they don’t exist just for the sake of making your life difficult.

Hence, if you interpret phenomena only from the viewpoint of their uses or dangers for humans, you get only half the picture right. The other half is what it really is and where it came from.

Copying is everything: https://dividuals.wordpress.com/2015/12/14/copying-is-everything/
Philosophy professor Ruth Millikan’s insight that everything that gets copied from an ancestor has a proper function or teleofunction: it is whatever feature or function that made it and its ancestor selected for copying, in competition with all the other similar copiable things. This would mean Aristotelean teleology is correct within the field of copyable things, replicators, i.e. within biology, although in physics still obviously incorrect.

Darwinian Reactionary drew attention to it two years ago and I still don’t understand why didn’t it generate a bigger buzz. It is an extremely important insight.

I mean, this is what we were waiting for, a proper synthesis of science and philosophy, and a proper way to rescue Aristotelean teleology, which leads to so excellent common-sense predictions that intuitively it cannot be very wrong, yet modern philosophy always denied it.

The result from that is the briding of the fact-value gap and burying the naturalistic fallacy: we CAN derive values from facts: a thing is good if it is well suitable for its natural purpose, teleofunction or proper function, which is the purpose it was selected for and copied for, the purpose and the suitability for the purpose that made the ancestors of this thing selected for copying, instead of all the other potential, similar ancestors.


What was humankind selected for? I am afraid, the answer is kind of ugly.

Men were selected to compete between groups, the cooperate within groups largely for coordinating for the sake of this competition, and have a low-key competition inside the groups as well for status and leadership. I am afraid, intelligence is all about organizing elaborate tribal raids: “coalitionary arms races”. The most civilized case, least brutal but still expensive case is arms races in prestige status, not dominance status: when Ancient Athens buildt pretty buildings and modern France built the TGV and America sent a man to the Moon in order to gain “gloire” i.e. the prestige type respect and status amongst the nations, the larger groups of mankind. If you are the type who doesn’t like blood, you should probably focus on these kinds of civilized, prestige-project competitions.

Women were selected for bearing children, for having strong and intelligent sons therefore having these heritable traits themselves (HBD kind of contradicts the more radically anti-woman aspects of RedPillery: marry a weak and stupid but attractive silly-blondie type woman and your son’s won’t be that great either), for pleasuring men and in some rarer but existing cases, to be true companions and helpers of their husbands.

- Matter: a change or movement's material cause, is the aspect of the change or movement which is determined by the material that composes the moving or changing things. For a table, that might be wood; for a statue, that might be bronze or marble.
- Form: a change or movement's formal cause, is a change or movement caused by the arrangement, shape or appearance of the thing changing or moving. Aristotle says for example that the ratio 2:1, and number in general, is the cause of the octave.
- Agent: a change or movement's efficient or moving cause, consists of things apart from the thing being changed or moved, which interact so as to be an agency of the change or movement. For example, the efficient cause of a table is a carpenter, or a person working as one, and according to Aristotle the efficient cause of a boy is a father.
- End or purpose: a change or movement's final cause, is that for the sake of which a thing is what it is. For a seed, it might be an adult plant. For a sailboat, it might be sailing. For a ball at the top of a ramp, it might be coming to rest at the bottom.

A proximate cause is an event which is closest to, or immediately responsible for causing, some observed result. This exists in contrast to a higher-level ultimate cause (or distal cause) which is usually thought of as the "real" reason something occurred.


- Ultimate causation explains traits in terms of evolutionary forces acting on them.
- Proximate causation explains biological function in terms of immediate physiological or environmental factors.
gnon  philosophy  ideology  thinking  conceptual-vocab  forms-instances  realness  analytical-holistic  bio  evolution  telos-atelos  distribution  nature  coarse-fine  epistemic  intricacy  is-ought  values  duplication  nihil  the-classics  big-peeps  darwinian  deep-materialism  selection  equilibrium  subjective-objective  models  classification  smoothness  discrete  schelling  optimization  approximation  comparison  multi  peace-violence  war  coalitions  status  s-factor  fashun  reputation  civilization  intelligence  competition  leadership  cooperate-defect  within-without  within-group  group-level  homo-hetero  new-religion  causation  direct-indirect  ends-means  metabuch  physics  axioms  skeleton  wiki  reference  concept  being-becoming  essence-existence  logos  real-nominal 
july 2018 by nhaliday
Why read old philosophy? | Meteuphoric
(This story would suggest that in physics students are maybe missing out on learning the styles of thought that produce progress in physics. My guess is that instead they learn them in grad school when they are doing research themselves, by emulating their supervisors, and that the helpfulness of this might partially explain why Nobel prizewinner advisors beget Nobel prizewinner students.)

The story I hear about philosophy—and I actually don’t know how much it is true—is that as bits of philosophy come to have any methodological tools other than ‘think about it’, they break off and become their own sciences. So this would explain philosophy’s lone status in studying old thinkers rather than impersonal methods—philosophy is the lone ur-discipline without impersonal methods but thinking.

This suggests a research project: try summarizing what Aristotle is doing rather than Aristotle’s views. Then write a nice short textbook about it.
ratty  learning  reading  studying  prioritizing  history  letters  philosophy  science  comparison  the-classics  canon  speculation  reflection  big-peeps  iron-age  mediterranean  roots  lens  core-rats  thinking  methodology  grad-school  academia  physics  giants  problem-solving  meta:research  scholar  the-trenches  explanans  crux  metameta  duplication  sociality  innovation  quixotic 
june 2018 by nhaliday
Dividuals – The soul is not an indivisible unit and has no unified will
Towards A More Mature Atheism: https://dividuals.wordpress.com/2015/09/17/towards-a-more-mature-atheism/
Human intelligence evolved as a social intelligence, for the purposes of social cooperation, social competition and social domination. It evolved to make us efficient at cooperating at removing obstacles, especially the kinds of obstacles that tend to fight back, i.e. at warfare. If you ever studied strategy or tactics, or just played really good board games, you have probably found your brain seems to be strangely well suited for specifically this kind of intellectual activity. It’s not necessarily easier than studying physics, and yet it somehow feels more natural. Physics is like swimming, strategy and tactics is like running. The reason for that is that our brains are truly evolved to be strategic, tactical, diplomatic computers, not physics computers. The question our brains are REALLY good at finding the answer for is “Just what does this guy really want?”


Thus, a very basic failure mode of the human brain is to overdetect agency.

I think this is partially what SSC wrote about in Mysticism And Pattern-Matching too. But instead of mystical experiences, my focus is on our brains claiming to detect agency where there is none. Thus my view is closer to Richard Carrier’s definition of the supernatural: it is the idea that some mental things cannot be reduced to nonmental things.


Meaning actually means will and agency. It took me a while to figure that one out. When we look for the meaning of life, a meaning in life, or a meaningful life, we look for a will or agency generally outside our own.


I am a double oddball – kind of autistic, but still far more interested in human social dynamics, such as history, than in natural sciences or technology. As a result, I do feel a calling to religion – the human world, as opposed to outer space, the human city, the human history, is such a perfect fit for a view like that of Catholicism! The reason for that is that Catholicism is the pinnacle of human intellectual efforts dealing with human agency. Ideas like Augustine’s three failure modes of the human brain: greed, lust and desire for power and status, are just about the closest to forming correct psychological theories far earlier than the scientific method was discovered. Just read your Chesterbelloc and Lewis. And of course because the agency radars of Catholics run at full burst, they overdetect it and thus believe in a god behind the universe. My brain, due to my deep interest in human agency and its consequences, also would like to be religious: wouldn’t it be great if the universe was made by something we could talk to, like, everything else that I am interested in, from field generals to municipal governments are entities I could talk to?


I also dislike that atheists often refuse to propose a falsifiable theory because they claim the burden of proof is not on them. Strictly speaking it can be true, but it is still good form to provide one.

Since I am something like an “nontheistic Catholic” anyway (e.g. I believe in original sin from the practical, political angle, I just think it has natural, not supernatural causes: evolution, the move from hunting-gathering to agriculture etc.), all one would need to do to make me fully so is to plug a God concept in my mind.

If you can convince me that my brain is not actually overdetecting agency when I feel a calling to religion, if you can convince me that my brain and most human brains detect agency just about right, there will be no reason for me to not believe in God. Because if there would any sort of agency behind the universe, the smartest bet would be that this agency would be the God of Thomas Aquinas’ Summa. That guy was plain simply a genius.

How to convince me my brain is not overdetecting agency? The simplest way is to convince me that magic, witchcraft, or superstition in general is real, and real in the supernatural sense (I do know Wiccans who cast spells and claim they are natural, not supernatural: divination spells make the brain more aware of hidden details, healing spells recruit the healing processes of the body etc.) You see, Catholics generally do believe in magic and witchcraft, as in: “These really do something, and they do something bad, so never practice them.”

The Strange Places the “God of the Gaps” Takes You: https://dividuals.wordpress.com/2018/05/25/the-strange-places-the-god-of-the-gaps-takes-you/
I assume people are familiar with the God of the Gaps argument. Well, it is usually just an accusation, but Newton for instance really pulled one.

But natural science is inherently different from humanities, because in natural science you build a predictive model of which you are not part of. You are just a point-like neutral observer.

You cannot do that with other human minds because you just don’t have the computing power to simulate a roughly similarly intelligent mind and have enough left to actually work with your model. So you put yourself into the predictive model, you make yourself a part of the model itself. You use a certain empathic kind of understanding, a “what would I do in that guys shoes?” and generate your predictions that way.


Which means that while natural science is relatively new, and strongly correlates with technological progress, this empathic, self-programming model of the humanities you could do millenia ago as well, you don’t need math or tools for this, and you probably cannot expect anything like straight-line progress. Maybe some wisdoms people figure out this way are really timeless and we just keep on rediscovering them.

So imagine, say, Catholicism as a large set of humanities. Sociology, social psychology, moral philosophy in the pragmatic, scientific sense (“What morality makes a society not collapse and actually prosper?”), life wisdom and all that. Basically just figuring out how people tick, how societies tick and how to make them tick well.


What do? Well, the obvious move is to pull a Newton and inject a God of the Gaps into your humanities. We tick like that because God. We must do so and so to tick well because God.


What I am saying is that we are at some point probably going to prove pretty much all of the this-worldy, pragmatic (moral, sociological, psychological etc.) aspect of Catholicism correct by something like evolutionary psychology.

And I am saying that while it will dramatically increase our respect for religion, this will also be probably a huge blow to theism. I don’t want that to happen, but I think it will. Because eliminating God from the gaps of natural science does not hurt faith much. But eliminating God from the gaps of the humanities and yes, religion itself?

My Kind of Atheist: http://www.overcomingbias.com/2018/08/my-kind-of-athiest.html
I think I’ve mentioned somewhere in public that I’m now an atheist, even though I grew up in a very Christian family, and I even joined a “cult” at a young age (against disapproving parents). The proximate cause of my atheism was learning physics in college. But I don’t think I’ve ever clarified in public what kind of an “atheist” or “agnostic” I am. So here goes.

The universe is vast and most of it is very far away in space and time, making our knowledge of those distant parts very thin. So it isn’t at all crazy to think that very powerful beings exist somewhere far away out there, or far before us or after us in time. In fact, many of us hope that we now can give rise to such powerful beings in the distant future. If those powerful beings count as “gods”, then I’m certainly open to the idea that such gods exist somewhere in space-time.

It also isn’t crazy to imagine powerful beings that are “closer” in space and time, but far away in causal connection. They could be in parallel “planes”, in other dimensions, or in “dark” matter that doesn’t interact much with our matter. Or they might perhaps have little interest in influencing or interacting with our sort of things. Or they might just “like to watch.”

But to most religious people, a key emotional appeal of religion is the idea that gods often “answer” prayer by intervening in their world. Sometimes intervening in their head to make them feel different, but also sometimes responding to prayers about their test tomorrow, their friend’s marriage, or their aunt’s hemorrhoids. It is these sort of prayer-answering “gods” in which I just can’t believe. Not that I’m absolutely sure they don’t exist, but I’m sure enough that the term “atheist” fits much better than the term “agnostic.”

These sort of gods supposedly intervene in our world millions of times daily to respond positively to particular prayers, and yet they do not noticeably intervene in world affairs. Not only can we find no physical trace of any machinery or system by which such gods exert their influence, even though we understand the physics of our local world very well, but the history of life and civilization shows no obvious traces of their influence. They know of terrible things that go wrong in our world, but instead of doing much about those things, these gods instead prioritize not leaving any clear evidence of their existence or influence. And yet for some reason they don’t mind people believing in them enough to pray to them, as they often reward such prayers with favorable interventions.
gnon  blog  stream  politics  polisci  ideology  institutions  thinking  religion  christianity  protestant-catholic  history  medieval  individualism-collectivism  n-factor  left-wing  right-wing  tribalism  us-them  cohesion  sociality  ecology  philosophy  buddhism  gavisti  europe  the-great-west-whale  occident  germanic  theos  culture  society  cultural-dynamics  anthropology  volo-avolo  meaningness  coalitions  theory-of-mind  coordination  organizing  psychology  social-psych  fashun  status  nationalism-globalism  models  power  evopsych  EEA  deep-materialism  new-religion  metameta  social-science  sociology  multi  definition  intelligence  science  comparison  letters  social-structure  existence  nihil  ratty  hanson  intricacy  reflection  people  physics  paganism 
june 2018 by nhaliday
Theory of Self-Reproducing Automata - John von Neumann

Comparisons between computing machines and the nervous systems. Estimates of size for computing machines, present and near future.

Estimates for size for the human central nervous system. Excursus about the “mixed” character of living organisms. Analog and digital elements. Observations about the “mixed” character of all componentry, artificial as well as natural. Interpretation of the position to be taken with respect to these.

Evaluation of the discrepancy in size between artificial and natural automata. Interpretation of this discrepancy in terms of physical factors. Nature of the materials used.

The probability of the presence of other intellectual factors. The role of complication and the theoretical penetration that it requires.

Questions of reliability and errors reconsidered. Probability of individual errors and length of procedure. Typical lengths of procedure for computing machines and for living organisms--that is, for artificial and for natural automata. Upper limits on acceptable probability of error in individual operations. Compensation by checking and self-correcting features.

Differences of principle in the way in which errors are dealt with in artificial and in natural automata. The “single error” principle in artificial automata. Crudeness of our approach in this case, due to the lack of adequate theory. More sophisticated treatment of this problem in natural automata: The role of the autonomy of parts. Connections between this autonomy and evolution.

- 10^10 neurons in brain, 10^4 vacuum tubes in largest computer at time
- machines faster: 5 ms from neuron potential to neuron potential, 10^-3 ms for vacuum tubes

pdf  article  papers  essay  nibble  math  cs  computation  bio  neuro  neuro-nitgrit  scale  magnitude  comparison  acm  von-neumann  giants  thermo  phys-energy  speed  performance  time  density  frequency  hardware  ems  efficiency  dirty-hands  street-fighting  fermi  estimate  retention  physics  interdisciplinary  multi  wiki  links  people  🔬  atoms  automata  duplication  iteration-recursion  turing  complexity  measure  nature  technology  complex-systems  bits  information-theory  circuits  robust  structure  composition-decomposition  evolution  mutation  axioms  analogy  thinking  input-output  hi-order-bits  coding-theory  flexibility  rigidity 
april 2018 by nhaliday
Is the human brain analog or digital? - Quora
The brain is neither analog nor digital, but works using a signal processing paradigm that has some properties in common with both.
Unlike a digital computer, the brain does not use binary logic or binary addressable memory, and it does not perform binary arithmetic. Information in the brain is represented in terms of statistical approximations and estimations rather than exact values. The brain is also non-deterministic and cannot replay instruction sequences with error-free precision. So in all these ways, the brain is definitely not "digital".
At the same time, the signals sent around the brain are "either-or" states that are similar to binary. A neuron fires or it does not. These all-or-nothing pulses are the basic language of the brain. So in this sense, the brain is computing using something like binary signals. Instead of 1s and 0s, or "on" and "off", the brain uses "spike" or "no spike" (referring to the firing of a neuron).
q-n-a  qra  expert-experience  neuro  neuro-nitgrit  analogy  deep-learning  nature  discrete  smoothness  IEEE  bits  coding-theory  communication  trivia  bio  volo-avolo  causation  random  order-disorder  ems  models  methodology  abstraction  nitty-gritty  computation  physics  electromag  scale  coarse-fine 
april 2018 by nhaliday
Ultimate fate of the universe - Wikipedia
The fate of the universe is determined by its density. The preponderance of evidence to date, based on measurements of the rate of expansion and the mass density, favors a universe that will continue to expand indefinitely, resulting in the "Big Freeze" scenario below.[8] However, observations are not conclusive, and alternative models are still possible.[9]

Big Freeze or heat death
Main articles: Future of an expanding universe and Heat death of the universe
The Big Freeze is a scenario under which continued expansion results in a universe that asymptotically approaches absolute zero temperature.[10] This scenario, in combination with the Big Rip scenario, is currently gaining ground as the most important hypothesis.[11] It could, in the absence of dark energy, occur only under a flat or hyperbolic geometry. With a positive cosmological constant, it could also occur in a closed universe. In this scenario, stars are expected to form normally for 1012 to 1014 (1–100 trillion) years, but eventually the supply of gas needed for star formation will be exhausted. As existing stars run out of fuel and cease to shine, the universe will slowly and inexorably grow darker. Eventually black holes will dominate the universe, which themselves will disappear over time as they emit Hawking radiation.[12] Over infinite time, there would be a spontaneous entropy decrease by the Poincaré recurrence theorem, thermal fluctuations,[13][14] and the fluctuation theorem.[15][16]

A related scenario is heat death, which states that the universe goes to a state of maximum entropy in which everything is evenly distributed and there are no gradients—which are needed to sustain information processing, one form of which is life. The heat death scenario is compatible with any of the three spatial models, but requires that the universe reach an eventual temperature minimum.[17]
physics  big-picture  world  space  long-short-run  futurism  singularity  wiki  reference  article  nibble  thermo  temperature  entropy-like  order-disorder  death  nihil  bio  complex-systems  cybernetics  increase-decrease  trends  computation  local-global  prediction  time  spatial  spreading  density  distribution  manifolds  geometry  janus 
april 2018 by nhaliday
Eternity in six hours: intergalactic spreading of intelligent life and sharpening the Fermi paradox
We do this by demonstrating that traveling between galaxies – indeed even launching a colonisation project for the entire reachable universe – is a relatively simple task for a star-spanning civilization, requiring modest amounts of energy and resources. We start by demonstrating that humanity itself could likely accomplish such a colonisation project in the foreseeable future, should we want to, and then demonstrate that there are millions of galaxies that could have reached us by now, using similar methods. This results in a considerable sharpening of the Fermi paradox.
pdf  study  article  essay  anthropic  fermi  space  expansionism  bostrom  ratty  philosophy  xenobio  ideas  threat-modeling  intricacy  time  civilization  🔬  futurism  questions  paradox  risk  physics  engineering  interdisciplinary  frontier  technology  volo-avolo  dirty-hands  ai  automation  robotics  duplication  iteration-recursion  von-neumann  data  scale  magnitude  skunkworks  the-world-is-just-atoms  hard-tech  ems  bio  bits  speedometer  nature  model-organism  mechanics  phys-energy  relativity  electromag  analysis  spock  nitty-gritty  spreading  hanson  street-fighting  speed  gedanken  nibble 
march 2018 by nhaliday
Existential Risks: Analyzing Human Extinction Scenarios
Would you endorse choosing policy to max the expected duration of civilization, at least as a good first approximation?
Can anyone suggest a different first approximation that would get more votes?

How useful would it be to agree on a relatively-simple first-approximation observable-after-the-fact metric for what we want from the future universe, such as total life years experienced, or civilization duration?

We're Underestimating the Risk of Human Extinction: https://www.theatlantic.com/technology/archive/2012/03/were-underestimating-the-risk-of-human-extinction/253821/
An Oxford philosopher argues that we are not adequately accounting for technology's risks—but his solution to the problem is not for Luddites.

Anderson: You have argued that we underrate existential risks because of a particular kind of bias called observation selection effect. Can you explain a bit more about that?

Bostrom: The idea of an observation selection effect is maybe best explained by first considering the simpler concept of a selection effect. Let's say you're trying to estimate how large the largest fish in a given pond is, and you use a net to catch a hundred fish and the biggest fish you find is three inches long. You might be tempted to infer that the biggest fish in this pond is not much bigger than three inches, because you've caught a hundred of them and none of them are bigger than three inches. But if it turns out that your net could only catch fish up to a certain length, then the measuring instrument that you used would introduce a selection effect: it would only select from a subset of the domain you were trying to sample.

Now that's a kind of standard fact of statistics, and there are methods for trying to correct for it and you obviously have to take that into account when considering the fish distribution in your pond. An observation selection effect is a selection effect introduced not by limitations in our measurement instrument, but rather by the fact that all observations require the existence of an observer. This becomes important, for instance, in evolutionary biology. For instance, we know that intelligent life evolved on Earth. Naively, one might think that this piece of evidence suggests that life is likely to evolve on most Earth-like planets. But that would be to overlook an observation selection effect. For no matter how small the proportion of all Earth-like planets that evolve intelligent life, we will find ourselves on a planet that did. Our data point-that intelligent life arose on our planet-is predicted equally well by the hypothesis that intelligent life is very improbable even on Earth-like planets as by the hypothesis that intelligent life is highly probable on Earth-like planets. When it comes to human extinction and existential risk, there are certain controversial ways that observation selection effects might be relevant.
bostrom  ratty  miri-cfar  skunkworks  philosophy  org:junk  list  top-n  frontier  speedometer  risk  futurism  local-global  scale  death  nihil  technology  simulation  anthropic  nuclear  deterrence  environment  climate-change  arms  competition  ai  ai-control  genetics  genomics  biotech  parasites-microbiome  disease  offense-defense  physics  tails  network-structure  epidemiology  space  geoengineering  dysgenics  ems  authoritarianism  government  values  formal-values  moloch  enhancement  property-rights  coordination  cooperate-defect  flux-stasis  ideas  prediction  speculation  humanity  singularity  existence  cybernetics  study  article  letters  eden-heaven  gedanken  multi  twitter  social  discussion  backup  hanson  metrics  optimization  time  long-short-run  janus  telos-atelos  poll  forms-instances  threat-modeling  selection  interview  expert-experience  malthus  volo-avolo  intel  leviathan  drugs  pharma  data  estimate  nature  longevity  expansionism  homo-hetero  utopia-dystopia 
march 2018 by nhaliday
Prisoner's dilemma - Wikipedia
caveat to result below:
An extension of the IPD is an evolutionary stochastic IPD, in which the relative abundance of particular strategies is allowed to change, with more successful strategies relatively increasing. This process may be accomplished by having less successful players imitate the more successful strategies, or by eliminating less successful players from the game, while multiplying the more successful ones. It has been shown that unfair ZD strategies are not evolutionarily stable. The key intuition is that an evolutionarily stable strategy must not only be able to invade another population (which extortionary ZD strategies can do) but must also perform well against other players of the same type (which extortionary ZD players do poorly, because they reduce each other's surplus).[14]

Theory and simulations confirm that beyond a critical population size, ZD extortion loses out in evolutionary competition against more cooperative strategies, and as a result, the average payoff in the population increases when the population is bigger. In addition, there are some cases in which extortioners may even catalyze cooperation by helping to break out of a face-off between uniform defectors and win–stay, lose–switch agents.[8]

Nature boils down to a few simple concepts.

Haters will point out that I oversimplify. The haters are wrong. I am good at saying a lot with few words. Nature indeed boils down to a few simple concepts.

In life, you can either cooperate or defect.

Used to be that defection was the dominant strategy, say in the time when the Roman empire started to crumble. Everybody complained about everybody and in the end nothing got done. Then came Jesus, who told people to be loving and cooperative, and boom: 1800 years later we get the industrial revolution.

Because of Jesus we now find ourselves in a situation where cooperation is the dominant strategy. A normie engages in a ton of cooperation: with the tax collector who wants more and more of his money, with schools who want more and more of his kid’s time, with media who wants him to repeat more and more party lines, with the Zeitgeist of the Collective Spirit of the People’s Progress Towards a New Utopia. Essentially, our normie is cooperating himself into a crumbling Western empire.

Turns out that if everyone blindly cooperates, parasites sprout up like weeds until defection once again becomes the standard.

The point of a post-Christian religion is to once again create conditions for the kind of cooperation that led to the industrial revolution. This necessitates throwing out undead Christianity: you do not blindly cooperate. You cooperate with people that cooperate with you, you defect on people that defect on you. Christianity mixed with Darwinism. God and Gnon meet.

This also means we re-establish spiritual hierarchy, which, like regular hierarchy, is a prerequisite for cooperation. It is this hierarchical cooperation that turns a household into a force to be reckoned with, that allows a group of men to unite as a front against their enemies, that allows a tribe to conquer the world. Remember: Scientology bullied the Cathedral’s tax department into submission.

With a functioning hierarchy, men still gossip, lie and scheme, but they will do so in whispers behind closed doors. In your face they cooperate and contribute to the group’s wellbeing because incentives are thus that contributing to group wellbeing heightens status.

Without a functioning hierarchy, men gossip, lie and scheme, but they do so in your face, and they tell you that you are positively deluded for accusing them of gossiping, lying and scheming. Seeds will not sprout in such ground.

Spiritual dominance is established in the same way any sort of dominance is established: fought for, taken. But the fight is ritualistic. You can’t force spiritual dominance if no one listens, or if you are silenced the ritual is not allowed to happen.

If one of our priests is forbidden from establishing spiritual dominance, that is a sure sign an enemy priest is in better control and has vested interest in preventing you from establishing spiritual dominance..

They defect on you, you defect on them. Let them suffer the consequences of enemy priesthood, among others characterized by the annoying tendency that very little is said with very many words.

To recap, we started with a secular definition of Logos and noted that its telos is existence. Given human nature, game theory and the power of cooperation, the highest expression of that telos is freely chosen universal love, tempered by constant vigilance against defection while maintaining compassion for the defectors and forgiving those who repent. In addition, we must know the telos in order to fulfill it.

In Christian terms, looks like we got over half of the Ten Commandments (know Logos for the First, don’t defect or tempt yourself to defect for the rest), the importance of free will, the indestructibility of evil (group cooperation vs individual defection), loving the sinner and hating the sin (with defection as the sin), forgiveness (with conditions), and love and compassion toward all, assuming only secular knowledge and that it’s good to exist.

Iterated Prisoner's Dilemma is an Ultimatum Game: http://infoproc.blogspot.com/2012/07/iterated-prisoners-dilemma-is-ultimatum.html
The history of IPD shows that bounded cognition prevented the dominant strategies from being discovered for over over 60 years, despite significant attention from game theorists, computer scientists, economists, evolutionary biologists, etc. Press and Dyson have shown that IPD is effectively an ultimatum game, which is very different from the Tit for Tat stories told by generations of people who worked on IPD (Axelrod, Dawkins, etc., etc.).


For evolutionary biologists: Dyson clearly thinks this result has implications for multilevel (group vs individual selection):
... Cooperation loses and defection wins. The ZD strategies confirm this conclusion and make it sharper. ... The system evolved to give cooperative tribes an advantage over non-cooperative tribes, using punishment to give cooperation an evolutionary advantage within the tribe. This double selection of tribes and individuals goes way beyond the Prisoners' Dilemma model.

implications for fractionalized Europe vis-a-vis unified China?

and more broadly does this just imply we're doomed in the long run RE: cooperation, morality, the "good society", so on...? war and group-selection is the only way to get a non-crab bucket civilization?

Iterated Prisoner’s Dilemma contains strategies that dominate any evolutionary opponent:


analogy for ultimatum game: the state gives the demos a bargain take-it-or-leave-it, and...if the demos refuses...violence?

The nature of human altruism: http://sci-hub.tw/https://www.nature.com/articles/nature02043
- Ernst Fehr & Urs Fischbacher

Some of the most fundamental questions concerning our evolutionary origins, our social relations, and the organization of society are centred around issues of altruism and selfishness. Experimental evidence indicates that human altruism is a powerful force and is unique in the animal world. However, there is much individual heterogeneity and the interaction between altruists and selfish individuals is vital to human cooperation. Depending on the environment, a minority of altruists can force a majority of selfish individuals to cooperate or, conversely, a few egoists can induce a large number of altruists to defect. Current gene-based evolutionary theories cannot explain important patterns of human altruism, pointing towards the importance of both theories of cultural evolution as well as gene–culture co-evolution.


Why are humans so unusual among animals in this respect? We propose that quantitatively, and probably even qualitatively, unique patterns of human altruism provide the answer to this question. Human altruism goes far beyond that which has been observed in the animal world. Among animals, fitness-reducing acts that confer fitness benefits on other individuals are largely restricted to kin groups; despite several decades of research, evidence for reciprocal altruism in pair-wise repeated encounters4,5 remains scarce6–8. Likewise, there is little evidence so far that individual reputation building affects cooperation in animals, which contrasts strongly with what we find in humans. If we randomly pick two human strangers from a modern society and give them the chance to engage in repeated anonymous exchanges in a laboratory experiment, there is a high probability that reciprocally altruistic behaviour will emerge spontaneously9,10.

However, human altruism extends far beyond reciprocal altruism and reputation-based cooperation, taking the form of strong reciprocity11,12. Strong reciprocity is a combination of altruistic rewarding, which is a predisposition to reward others for cooperative, norm-abiding behaviours, and altruistic punishment, which is a propensity to impose sanctions on others for norm violations. Strong reciprocators bear the cost of rewarding or punishing even if they gain no individual economic benefit whatsoever from their acts. In contrast, reciprocal altruists, as they have been defined in the biological literature4,5, reward and punish only if this is in their long-term self-interest. Strong reciprocity thus constitutes a powerful incentive for cooperation even in non-repeated interactions and when reputation gains are absent, because strong reciprocators will reward those who cooperate and punish those who defect.


We will show that the interaction between selfish and strongly reciprocal … [more]
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march 2018 by nhaliday
The Space Trilogy - Wikipedia
Out of the Silent Planet:

Weston makes a long speech justifying his proposed invasion of Malacandra on "progressive" and evolutionary grounds, which Ransom attempts to translate into Malacandrian, thus laying bare the brutality and crudity of Weston's ambitions.

Oyarsa listens carefully to Weston's speech and acknowledges that the scientist is acting out of a sense of duty to his species, and not mere greed. This renders him more mercifully disposed towards the scientist, who accepts that he may die while giving Man the means to continue. However, on closer examination Oyarsa points out that Weston's loyalty is not to Man's mind – or he would equally value the intelligent alien minds already inhabiting Malacandra, instead of seeking to displace them in favour of humanity; nor to Man's body – since, as Weston is well aware of and at ease with, Man's physical form will alter over time, and indeed would have to in order to adapt to Weston's programme of space exploration and colonisation. It seems then that Weston is loyal only to "the seed" – Man's genome – which he seeks to propagate. When Oyarsa questions why this is an intelligible motivation for action, Weston's eloquence fails him and he can only articulate that if Oyarsa does not understand Man's basic loyalty to Man then he, Weston, cannot possibly instruct him.



The rafts or floating islands are indeed Paradise, not only in the sense that they provide a pleasant and care-free life (until the arrival of Weston) but also in the sense that Ransom is for weeks and months naked in the presence of a beautiful naked woman without once lusting after her or being tempted to seduce her. This is because of the perfection in that world.

The plot thickens when Professor Weston arrives in a spaceship and lands in a part of the ocean quite close to the Fixed Land. He at first announces to Ransom that he is a reformed man, but appears to still be in search of power. Instead of the strictly materialist attitude he displayed when first meeting Ransom, he asserts he had become aware of the existence of spiritual beings and pledges allegiance to what he calls the "Life-Force." Ransom, however, disagrees with Weston's position that the spiritual is inherently good, and indeed Weston soon shows signs of demonic possession.

In this state, the possessed Weston finds the Queen and tries to tempt her into defying Maleldil's orders by spending a night on the Fixed Land. Ransom, perceiving this, believes that he must act as a counter-tempter. Well versed in the Bible and Christian theology, Ransom realises that if the pristine Queen, who has never heard of Evil, succumbs to the tempter's arguments, the Fall of Man will be re-enacted on Perelandra. He struggles through day after day of lengthy arguments illustrating various approaches to temptation, but the demonic Weston shows super-human brilliance in debate (though when "off-duty" he displays moronic, asinine behaviour and small-minded viciousness) and moreover appears never to need sleep.

With the demonic Weston on the verge of winning, the desperate Ransom hears in the night what he gradually realises is a Divine voice, commanding him to physically attack the Tempter. Ransom is reluctant, and debates with the divine (inner) voice for the entire duration of the night. A curious twist is introduced here; whereas the name "Ransom" is said to be derived from the title "Ranolf's Son", it can also refer to a reward given in exchange for a treasured life. Recalling this, and recalling that his God would (and has) sacrificed Himself in a similar situation, Ransom decides to confront the Tempter outright.

Ransom attacks his opponent bare-handed, using only physical force. Weston's body is unable to withstand this despite the Tempter's superior abilities of rhetoric, and so the Tempter flees. Ultimately Ransom chases him over the ocean, Weston fleeing and Ransom chasing on the backs of giant and friendly fish. During a fleeting truce, the "real" Weston appears to momentarily re-inhabit his body, and recount his experience of Hell, wherein the damned soul is not consigned to pain or fire, as supposed by popular eschatology, but is absorbed into the Devil, losing all independent existence.
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january 2018 by nhaliday
Fermi paradox - Wikipedia
Rare Earth hypothesis: https://en.wikipedia.org/wiki/Rare_Earth_hypothesis
Fine-tuned Universe: https://en.wikipedia.org/wiki/Fine-tuned_Universe
something to keep in mind:
Puddle theory is a term coined by Douglas Adams to satirize arguments that the universe is made for man.[54][55] As stated in Adams' book The Salmon of Doubt:[56]
Imagine a puddle waking up one morning and thinking, “This is an interesting world I find myself in, an interesting hole I find myself in, fits me rather neatly, doesn't it? In fact, it fits me staggeringly well, must have been made to have me in it!” This is such a powerful idea that as the sun rises in the sky and the air heats up and as, gradually, the puddle gets smaller and smaller, it's still frantically hanging on to the notion that everything's going to be all right, because this World was meant to have him in it, was built to have him in it; so the moment he disappears catches him rather by surprise. I think this may be something we need to be on the watch out for.
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january 2018 by nhaliday
Why do stars twinkle?
According to many astronomers and educators, twinkle (stellar scintillation) is caused by atmospheric structure that works like ordinary lenses and prisms. Pockets of variable temperature - and hence index of refraction - randomly shift and focus starlight, perceived by eye as changes in brightness. Pockets also disperse colors like prisms, explaining the flashes of color often seen in bright stars. Stars appear to twinkle more than planets because they are points of light, whereas the twinkling points on planetary disks are averaged to a uniform appearance. Below, figure 1 is a simulation in glass of the kind of turbulence structure posited in the lens-and-prism theory of stellar scintillation, shown over the Penrose tile floor to demonstrate the random lensing effects.

However appealing and ubiquitous on the internet, this popular explanation is wrong, and my aim is to debunk the myth. This research is mostly about showing that the lens-and-prism theory just doesn't work, but I also have a stellar list of references that explain the actual cause of scintillation, starting with two classic papers by C.G. Little and S. Chandrasekhar.
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december 2017 by nhaliday
light - Why doesn't the moon twinkle? - Astronomy Stack Exchange
As you mention, when light enters our atmosphere, it goes through several parcels of gas with varying density, temperature, pressure, and humidity. These differences make the refractive index of the parcels different, and since they move around (the scientific term for air moving around is "wind"), the light rays take slightly different paths through the atmosphere.

Stars are point sources
…the Moon is not
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december 2017 by nhaliday
galaxy - How do astronomers estimate the total mass of dust in clouds and galaxies? - Astronomy Stack Exchange
Dust absorbs stellar light (primarily in the ultraviolet), and is heated up. Subsequently it cools by emitting infrared, "thermal" radiation. Assuming a dust composition and grain size distribution, the amount of emitted IR light per unit dust mass can be calculated as a function of temperature. Observing the object at several different IR wavelengths, a Planck curve can be fitted to the data points, yielding the dust temperature. The more UV light incident on the dust, the higher the temperature.

The result is somewhat sensitive to the assumptions, and thus the uncertainties are sometimes quite large. The more IR data points obtained, the better. If only one IR point is available, the temperature cannot be calculated. Then there's a degeneracy between incident UV light and the amount of dust, and the mass can only be estimated to within some orders of magnitude (I think).
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december 2017 by nhaliday
How do you measure the mass of a star? (Beginner) - Curious About Astronomy? Ask an Astronomer
Measuring the mass of stars in binary systems is easy. Binary systems are sets of two or more stars in orbit about each other. By measuring the size of the orbit, the stars' orbital speeds, and their orbital periods, we can determine exactly what the masses of the stars are. We can take that knowledge and then apply it to similar stars not in multiple systems.

We also can easily measure the luminosity and temperature of any star. A plot of luminocity versus temperature for a set of stars is called a Hertsprung-Russel (H-R) diagram, and it turns out that most stars lie along a thin band in this diagram known as the main Sequence. Stars arrange themselves by mass on the Main Sequence, with massive stars being hotter and brighter than their small-mass bretheren. If a star falls on the Main Sequence, we therefore immediately know its mass.

In addition to these methods, we also have an excellent understanding of how stars work. Our models of stellar structure are excellent predictors of the properties and evolution of stars. As it turns out, the mass of a star determines its life history from day 1, for all times thereafter, not only when the star is on the Main Sequence. So actually, the position of a star on the H-R diagram is a good indicator of its mass, regardless of whether it's on the Main Sequence or not.
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december 2017 by nhaliday
Is the speed of light really constant?
So what if the speed of light isn’t the same when moving toward or away from us? Are there any observable consequences? Not to the limits of observation so far. We know, for example, that any one-way speed of light is independent of the motion of the light source to 2 parts in a billion. We know it has no effect on the color of the light emitted to a few parts in 1020. Aspects such as polarization and interference are also indistinguishable from standard relativity. But that’s not surprising, because you don’t need to assume isotropy for relativity to work. In the 1970s, John Winnie and others showed that all the results of relativity could be modeled with anisotropic light so long as the two-way speed was a constant. The “extra” assumption that the speed of light is a uniform constant doesn’t change the physics, but it does make the mathematics much simpler. Since Einstein’s relativity is the simpler of two equivalent models, it’s the model we use. You could argue that it’s the right one citing Occam’s razor, or you could take Newton’s position that anything untestable isn’t worth arguing over.

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november 2017 by nhaliday
Equilibrium thermodynamics - Wikipedia
Equilibrium Thermodynamics is the systematic study of transformations of matter and energy in systems in terms of a concept called thermodynamic equilibrium. The word equilibrium implies a state of balance. Equilibrium thermodynamics, in origins, derives from analysis of the Carnot cycle. Here, typically a system, as cylinder of gas, initially in its own state of internal thermodynamic equilibrium, is set out of balance via heat input from a combustion reaction. Then, through a series of steps, as the system settles into its final equilibrium state, work is extracted.

In an equilibrium state the potentials, or driving forces, within the system, are in exact balance. A central aim in equilibrium thermodynamics is: given a system in a well-defined initial state of thermodynamic equilibrium, subject to accurately specified constraints, to calculate, when the constraints are changed by an externally imposed intervention, what the state of the system will be once it has reached a new equilibrium. An equilibrium state is mathematically ascertained by seeking the extrema of a thermodynamic potential function, whose nature depends on the constraints imposed on the system. For example, a chemical reaction at constant temperature and pressure will reach equilibrium at a minimum of its components' Gibbs free energy and a maximum of their entropy.

Equilibrium thermodynamics differs from non-equilibrium thermodynamics, in that, with the latter, the state of the system under investigation will typically not be uniform but will vary locally in those as energy, entropy, and temperature distributions as gradients are imposed by dissipative thermodynamic fluxes. In equilibrium thermodynamics, by contrast, the state of the system will be considered uniform throughout, defined macroscopically by such quantities as temperature, pressure, or volume. Systems are studied in terms of change from one equilibrium state to another; such a change is called a thermodynamic process.
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november 2017 by nhaliday
[1509.02504] Electric charge in hyperbolic motion: The early history and other geometrical aspects
We revisit the early work of Minkowski and Sommerfeld concerning hyperbolic motion, and we describe some geometrical aspects of the electrodynamic interaction. We discuss the advantages of a time symmetric formulation in which the material points are replaced by infinitesimal length elements.

SPACE AND TIME: An annotated, illustrated edition of Hermann Minkowski's revolutionary essay: http://web.mit.edu/redingtn/www/netadv/SP20130311.html
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november 2017 by nhaliday
Autoignition temperature - Wikipedia
The autoignition temperature or kindling point of a substance is the lowest temperature at which it spontaneously ignites in normal atmosphere without an external source of ignition, such as a flame or spark. This temperature is required to supply the activation energy needed for combustion. The temperature at which a chemical ignites decreases as the pressure or oxygen concentration increases. It is usually applied to a combustible fuel mixture.

The time {\displaystyle t_{\text{ig}}} {\displaystyle t_{\text{ig}}} it takes for a material to reach its autoignition temperature {\displaystyle T_{\text{ig}}} {\displaystyle T_{\text{ig}}} when exposed to a heat flux {\displaystyle q''} {\displaystyle q''} is given by the following equation:
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november 2017 by nhaliday
Static electricity - Wikipedia
Electrons can be exchanged between materials on contact; materials with weakly bound electrons tend to lose them while materials with sparsely filled outer shells tend to gain them. This is known as the triboelectric effect and results in one material becoming positively charged and the other negatively charged. The polarity and strength of the charge on a material once they are separated depends on their relative positions in the triboelectric series. The triboelectric effect is the main cause of static electricity as observed in everyday life, and in common high-school science demonstrations involving rubbing different materials together (e.g., fur against an acrylic rod). Contact-induced charge separation causes your hair to stand up and causes "static cling" (for example, a balloon rubbed against the hair becomes negatively charged; when near a wall, the charged balloon is attracted to positively charged particles in the wall, and can "cling" to it, appearing to be suspended against gravity).
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november 2017 by nhaliday
Hyperbolic angle - Wikipedia
A unit circle {\displaystyle x^{2}+y^{2}=1} x^2 + y^2 = 1 has a circular sector with an area half of the circular angle in radians. Analogously, a unit hyperbola {\displaystyle x^{2}-y^{2}=1} {\displaystyle x^{2}-y^{2}=1} has a hyperbolic sector with an area half of the hyperbolic angle.
nibble  math  trivia  wiki  reference  physics  relativity  concept  atoms  geometry  ground-up  characterization  measure  definition  plots  calculation  nitty-gritty  direction  metrics  manifolds 
november 2017 by nhaliday
general relativity - What if the universe is rotating as a whole? - Physics Stack Exchange
To find out whether the universe is rotating, in principle the most straightforward test is to watch the motion of a gyroscope relative to the distant galaxies. If it rotates at an angular velocity -ω relative to them, then the universe is rotating at angular velocity ω. In practice, we do not have mechanical gyroscopes with small enough random and systematic errors to put a very low limit on ω. However, we can use the entire solar system as a kind of gyroscope. Solar-system observations put a model-independent upper limit of 10^-7 radians/year on the rotation,[Clemence 1957] which is an order of magnitude too lax to rule out the Gödel metric.
nibble  q-n-a  overflow  physics  relativity  gedanken  direction  absolute-relative  big-picture  space  experiment  measurement  volo-avolo 
november 2017 by nhaliday
What is the connection between special and general relativity? - Physics Stack Exchange
Special relativity is the "special case" of general relativity where spacetime is flat. The speed of light is essential to both.
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november 2017 by nhaliday
What is the difference between general and special relativity? - Quora
General Relativity is, quite simply, needed to explain gravity.

Special Relativity is the special case of GR, when the metric is flat — which means no gravity.

You need General Relativity when the metric gets all curvy, and when things start to experience gravitation.
nibble  q-n-a  qra  explanation  physics  relativity  synthesis  hi-order-bits  ground-up  gravity  summary  aphorism  differential  geometry 
november 2017 by nhaliday
GPS and Relativity
The nominal GPS configuration consists of a network of 24 satellites in high orbits around the Earth, but up to 30 or so satellites may be on station at any given time. Each satellite in the GPS constellation orbits at an altitude of about 20,000 km from the ground, and has an orbital speed of about 14,000 km/hour (the orbital period is roughly 12 hours - contrary to popular belief, GPS satellites are not in geosynchronous or geostationary orbits). The satellite orbits are distributed so that at least 4 satellites are always visible from any point on the Earth at any given instant (with up to 12 visible at one time). Each satellite carries with it an atomic clock that "ticks" with a nominal accuracy of 1 nanosecond (1 billionth of a second). A GPS receiver in an airplane determines its current position and course by comparing the time signals it receives from the currently visible GPS satellites (usually 6 to 12) and trilaterating on the known positions of each satellite[1]. The precision achieved is remarkable: even a simple hand-held GPS receiver can determine your absolute position on the surface of the Earth to within 5 to 10 meters in only a few seconds. A GPS receiver in a car can give accurate readings of position, speed, and course in real-time!

More sophisticated techniques, like Differential GPS (DGPS) and Real-Time Kinematic (RTK) methods, deliver centimeter-level positions with a few minutes of measurement. Such methods allow use of GPS and related satellite navigation system data to be used for high-precision surveying, autonomous driving, and other applications requiring greater real-time position accuracy than can be achieved with standard GPS receivers.

To achieve this level of precision, the clock ticks from the GPS satellites must be known to an accuracy of 20-30 nanoseconds. However, because the satellites are constantly moving relative to observers on the Earth, effects predicted by the Special and General theories of Relativity must be taken into account to achieve the desired 20-30 nanosecond accuracy.

Because an observer on the ground sees the satellites in motion relative to them, Special Relativity predicts that we should see their clocks ticking more slowly (see the Special Relativity lecture). Special Relativity predicts that the on-board atomic clocks on the satellites should fall behind clocks on the ground by about 7 microseconds per day because of the slower ticking rate due to the time dilation effect of their relative motion [2].

Further, the satellites are in orbits high above the Earth, where the curvature of spacetime due to the Earth's mass is less than it is at the Earth's surface. A prediction of General Relativity is that clocks closer to a massive object will seem to tick more slowly than those located further away (see the Black Holes lecture). As such, when viewed from the surface of the Earth, the clocks on the satellites appear to be ticking faster than identical clocks on the ground. A calculation using General Relativity predicts that the clocks in each GPS satellite should get ahead of ground-based clocks by 45 microseconds per day.

The combination of these two relativitic effects means that the clocks on-board each satellite should tick faster than identical clocks on the ground by about 38 microseconds per day (45-7=38)! This sounds small, but the high-precision required of the GPS system requires nanosecond accuracy, and 38 microseconds is 38,000 nanoseconds. If these effects were not properly taken into account, a navigational fix based on the GPS constellation would be false after only 2 minutes, and errors in global positions would continue to accumulate at a rate of about 10 kilometers each day! The whole system would be utterly worthless for navigation in a very short time.
nibble  org:junk  org:edu  explanation  trivia  cocktail  physics  gravity  relativity  applications  time  synchrony  speed  space  navigation  technology 
november 2017 by nhaliday
The Moon And Tides
Why does the Moon produce TWO water tides on the Earth and not just one?
"It is intuitively easy to understand why the gravitational pull of the Moon should produce a water tide on the Earth in the part of the ocean closest to the moon along the line connecting the center of the Moon with the center of the Earth. But in fact not one but TWO water tides are produced under which the Earth rotates every day to produce about two high tides and two low tides every day. How come?

It is not the gravitational force that is doing it, but the change in the gravitational force across the body of the Earth. If you were to plot the pattern of the Moon's 'tidal' gravitational force added to the Earth's own gravitational force, at the Earth's surface, you would be able to resolve the force vectors at different latitudes and longitudes into a radial component directed towards the Earth's center, and a component tangential to the Earth's surface. On the side nearest the moon, the 'differential' gravitational force is directed toward the Moon showing that for particles on the Earth's surface, they are being tugged slightly towards the Moon because the force of the Moon is slightly stronger at the Earth's surface than at the Earth's center which is an additional 6300 kilometers from the Moon. On the far side of the Earth, the Moon is tugging on the center of the Earth slightly stronger than it is on the far surface, so the resultant force vector is directed away from the Earth's center.

The net result of this is that the Earth gets deformed into a slightly squashed, ellipsoidal shape due to these tidal forces. This happens because if we resolve the tidal forces at each point on the Earth into a local vertical and horizontal component, the horizontal components are not zero, and are directed towards the two points along the line connecting the Earth and the Moon's centers. These horizontal forces cause rock and water to feel a gravitational force which results in the flow of rock and water into the 'tidal bulges'. There will be exactly two of these bulges. At exactly the positions of the tidal bulges where the Moon is at the zenith and at the nadir positions, there are no horizontal tidal forces and the flow stops. The water gets piled up, and the only effect is to slightly lower the weight of the water along the vertical direction.

Another way of thinking about this is that the gravitational force of the Moon causes the Earth to accelerate slightly towards the Moon causing the water to get pulled towards the Moon faster than the solid rock on the side nearest the Moon. On the far side, the solid Earth 'leaves behind' some of the water which is not as strongly accelerated towards the Moon as the Earth is. This produces the bulge on the 'back side' of the Earth."- Dr. Odenwald's ASK THE ASTRONOMER
org:junk  nibble  space  physics  mechanics  cycles  navigation  gravity  marginal  oceans  explanation  faq  objektbuch  rhythm 
november 2017 by nhaliday
Stability of the Solar System - Wikipedia
The stability of the Solar System is a subject of much inquiry in astronomy. Though the planets have been stable when historically observed, and will be in the short term, their weak gravitational effects on one another can add up in unpredictable ways. For this reason (among others) the Solar System is chaotic,[1] and even the most precise long-term models for the orbital motion of the Solar System are not valid over more than a few tens of millions of years.[2]

The Solar System is stable in human terms, and far beyond, given that it is unlikely any of the planets will collide with each other or be ejected from the system in the next few billion years,[3] and the Earth's orbit will be relatively stable.[4]

Since Newton's law of gravitation (1687), mathematicians and astronomers (such as Laplace, Lagrange, Gauss, Poincaré, Kolmogorov, Vladimir Arnold and Jürgen Moser) have searched for evidence for the stability of the planetary motions, and this quest led to many mathematical developments, and several successive 'proofs' of stability of the Solar System.[5]


The planets' orbits are chaotic over longer timescales, such that the whole Solar System possesses a Lyapunov time in the range of 2–230 million years.[3] In all cases this means that the position of a planet along its orbit ultimately becomes impossible to predict with any certainty (so, for example, the timing of winter and summer become uncertain), but in some cases the orbits themselves may change dramatically. Such chaos manifests most strongly as changes in eccentricity, with some planets' orbits becoming significantly more—or less—elliptical.[7]

Is the Solar System Stable?: https://www.ias.edu/ideas/2011/tremaine-solar-system

Is the Solar System Stable?: https://arxiv.org/abs/1209.5996
nibble  wiki  reference  article  physics  mechanics  space  gravity  flux-stasis  uncertainty  robust  perturbation  math  dynamical  math.DS  volo-avolo  multi  org:edu  org:inst  papers  preprint  time  data  org:mat 
november 2017 by nhaliday
New Theory Cracks Open the Black Box of Deep Learning | Quanta Magazine
A new idea called the “information bottleneck” is helping to explain the puzzling success of today’s artificial-intelligence algorithms — and might also explain how human brains learn.

sounds like he's just talking about autoencoders?
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september 2017 by nhaliday
I can throw a baseball a lot further than a ping pong ball. I cannot throw a bowling ball nearly as far as a baseball. Is there an "optimal" weight for a ball to throw it as far as possible? : answers
If there are two balls with the same size, they will have the same drag force when traveling at the same speed.
Smaller balls will have less wetted area, and therefore less drag force acting on them
A ball with more mass will decelerate less given the same amount of drag.
The human hand has difficulty holding objects that are too large or too small.
I think that a human's throw is limited by the speed of the hand at the moment of release -- the object can't move faster than your hand when it's released.
A ball with more mass will also be more difficult for a human to throw. Thier arm will rotate slower and the object will have less velocity.
As such, you want the smallest ball that a human can comfortably hold, that is heavy for its size but still light with respect to a human's perspective. Bonus points for drag reduction tech.
Golf balls are surprisingly heavy given their size, and the dimples are designed to convert a laminar boundary layer into a turbulent one. Turbulent boundary layers grip the surface better, delaying flow separation, which is likely the most significant contribution to parasitic drag.
TL; DR: probably a golf ball.
nibble  reddit  social  discussion  q-n-a  physics  mechanics  fluid  street-fighting  biomechanics  extrema  optimization  atmosphere  curiosity  explanation 
september 2017 by nhaliday
Early History of Electricity and Magnetism
The ancient Greeks also knew about magnets. They noted that on rare occasions "lodestones" were found in nature, chunks of iron-rich ore with the puzzling ability to attract iron. Some were discovered near the city of Magnesia (now in Turkey), and from there the words "magnetism" and "magnet" entered the language. The ancient Chinese discovered lodestones independently, and in addition found that after a piece of steel was "touched to a lodestone" it became a magnet itself.'


One signpost of the new era was the book "De Magnete" (Latin for "On the Magnet") published in London in 1600 by William Gilbert, a prominent medical doctor and (after 1601) personal physician to Queen Elizabeth I. Gilbert's great interest was in magnets and the strange directional properties of the compass needle, always pointing close to north-south. He correctly traced the reason to the globe of the Earth being itself a giant magnet, and demonstrated his explanation by moving a small compass over the surface of a lodestone trimmed to a sphere (or supplemented to spherical shape by iron attachments?)--a scale model he named "terrella" or "little Earth," on which he was able to duplicate all the directional properties of the compass. (here and here)
nibble  org:edu  org:junk  lecture-notes  history  iron-age  mediterranean  the-classics  physics  electromag  science  the-trenches  the-great-west-whale  discovery  medieval  earth 
september 2017 by nhaliday
Ptolemy's Model of the Solar System
It follows, from the above discussion, that the geocentric model of Ptolemy is equivalent to a heliocentric model in which the various planetary orbits are represented as eccentric circles, and in which the radius vector connecting a given planet to its corresponding equant revolves at a uniform rate. In fact, Ptolemy's model of planetary motion can be thought of as a version of Kepler's model which is accurate to first-order in the planetary eccentricities--see Cha. 4. According to the Ptolemaic scheme, from the point of view of the earth, the orbit of the sun is described by a single circular motion, whereas that of a planet is described by a combination of two circular motions. In reality, the single circular motion of the sun represents the (approximately) circular motion of the earth around the sun, whereas the two circular motions of a typical planet represent a combination of the planet's (approximately) circular motion around the sun, and the earth's motion around the sun. Incidentally, the popular myth that Ptolemy's scheme requires an absurdly large number of circles in order to fit the observational data to any degree of accuracy has no basis in fact. Actually, Ptolemy's model of the sun and the planets, which fits the data very well, only contains 12 circles (i.e., 6 deferents and 6 epicycles).
org:junk  org:edu  nibble  physics  space  mechanics  history  iron-age  mediterranean  the-classics  science  the-trenches  the-great-west-whale  giants  models  intricacy  parsimony 
september 2017 by nhaliday
Lecture 14: When's that meteor arriving
- Meteors as a random process
- Limiting approximations
- Derivation of the Exponential distribution
- Derivation of the Poisson distribution
- A "Poisson process"
nibble  org:junk  org:edu  exposition  lecture-notes  physics  mechanics  space  earth  probability  stats  distribution  stochastic-processes  closure  additive  limits  approximation  tidbits  acm  binomial  multiplicative 
september 2017 by nhaliday
Resonance in a Pendulum - YouTube
The vibration of any given washer is able to transmit its energy only to another washer with exactly the same frequency. Since the length of a pendulum determines its frequency of vibration, each pendulum can only set another pendulum vibrating if it has the same length.
nibble  video  social  physics  mechanics  waves  oscillation  synchrony  flux-stasis  increase-decrease  concrete  ground-up  dirty-hands  phys-energy  frequency  spreading 
september 2017 by nhaliday
Resonance - Wikipedia
Resonance occurs when a system is able to store and easily transfer energy between two or more different storage modes (such as kinetic energy and potential energy in the case of a simple pendulum). However, there are some losses from cycle to cycle, called damping. When damping is small, the resonant frequency is approximately equal to the natural frequency of the system, which is a frequency of unforced vibrations. Some systems have multiple, distinct, resonant frequencies.
nibble  physics  mechanics  waves  oscillation  synchrony  wiki  reference  article  flux-stasis  increase-decrease  frequency  spreading 
september 2017 by nhaliday
Reynolds number - Wikipedia
The Reynolds number is the ratio of inertial forces to viscous forces within a fluid which is subjected to relative internal movement due to different fluid velocities, in what is known as a boundary layer in the case of a bounding surface such as the interior of a pipe. A similar effect is created by the introduction of a stream of higher velocity fluid, such as the hot gases from a flame in air. This relative movement generates fluid friction, which is a factor in developing turbulent flow. Counteracting this effect is the viscosity of the fluid, which as it increases, progressively inhibits turbulence, as more kinetic energy is absorbed by a more viscous fluid. The Reynolds number quantifies the relative importance of these two types of forces for given flow conditions, and is a guide to when turbulent flow will occur in a particular situation.[6]

Re = ρuL/μ

(inertial forces)/(viscous forces)
= (mass)(acceleration) / (dynamic viscosity)(velocity/distance)(area)
= (ρL^3)(v/t) / μ(v/L)L^2
= Re

NB: viscous force/area ~ μ du/dy is definition of viscosity
nibble  concept  metrics  definition  physics  mechanics  fluid  street-fighting  wiki  reference  atoms  history  early-modern  europe  the-great-west-whale  britain  science  the-trenches  experiment 
september 2017 by nhaliday
Fermat's Library | Cassini, Rømer and the velocity of light annotated/explained version.
Abstract: The discovery of the finite nature of the velocity of light is usually attributed to Rømer. However, a text at the Paris Observatory confirms the minority opinion according to which Cassini was first to propose the ‘successive motion’ of light, while giving a rather correct order of magnitude for the duration of its propagation from the Sun to the Earth. We examine this question, and discuss why, in spite of the criticisms of Halley, Cassini abandoned this hypothesis while leaving Rømer free to publish it.
liner-notes  papers  essay  history  early-modern  europe  the-great-west-whale  giants  the-trenches  mediterranean  nordic  science  innovation  discovery  physics  electromag  space  speed  nibble  org:sci  org:mat 
september 2017 by nhaliday
Europa, Enceladus, Moon Miranda | West Hunter
A lot of ice moons seem to have interior oceans, warmed by tidal flexing and possibly radioactivity.  But they’re lousy candidates for life, because you need free energy; and there’s very little in the interior oceans of such system.

It is possible that NASA is institutionally poor at pointing this out.
west-hunter  scitariat  discussion  ideas  rant  speculation  prediction  government  dirty-hands  space  xenobio  oceans  fluid  thermo  phys-energy  temperature  no-go  volo-avolo  physics  equilibrium  street-fighting  nibble  error  track-record  usa  bio  eden  cybernetics  complex-systems 
september 2017 by nhaliday
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