nhaliday + electromag   70

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
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
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.
nibble  org:junk  space  sky  visuo  illusion  explanans  physics  electromag  trivia  cocktail  critique  contrarianism  explanation  waves  simulation  experiment  hmm  magnitude  atmosphere  roots  idk 
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
nibble  q-n-a  overflow  space  physics  trivia  cocktail  navigation  sky  visuo  illusion  measure  random  electromag  signal-noise  flux-stasis  explanation  explanans  magnitude  atmosphere  roots 
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).
nibble  q-n-a  overflow  space  measurement  measure  estimate  physics  electromag  visuo  methodology 
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.
nibble  q-n-a  org:junk  org:edu  popsci  space  physics  electromag  measurement  mechanics  gravity  cycles  oscillation  temperature  visuo  plots  correlation  metrics  explanation  measure  methodology 
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.

SPECIAL RELATIVITY WITHOUT ONE-WAY VELOCITY ASSUMPTIONS:
https://sci-hub.bz/https://www.jstor.org/stable/186029
https://sci-hub.bz/https://www.jstor.org/stable/186671
nibble  scitariat  org:bleg  physics  relativity  electromag  speed  invariance  absolute-relative  curiosity  philosophy  direction  gedanken  axioms  definition  models  experiment  space  science  measurement  volo-avolo  synchrony  uniqueness  multi  pdf  piracy  study  article 
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
nibble  preprint  papers  org:mat  physics  electromag  relativity  exposition  history  mostly-modern  pre-ww2  science  the-trenches  discovery  intricacy  classic  explanation  einstein  giants  plots  manifolds  article  multi  liner-notes  org:junk  org:edu  absolute-relative 
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).
nibble  wiki  reference  article  physics  electromag  embodied  curiosity  IEEE  dirty-hands  phys-energy  safety  data  magnitude  scale 
november 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
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
My Old Boss | West Hunter
Back in those days, there was interest in finding better ways to communicate with a submerged submarine.  One method under consideration used an orbiting laser to send pulses of light over the ocean, using a special wavelength, for which there was a very good detector.  Since even the people running the laser might not know the boomer’s exact location, while weather and such might also interfere,  my old boss was trying to figure out methods of reliably transmitting messages when some pulses were randomly lost – which is of course a well-developed subject,  error-correcting codes. But he didn’t know that.  Hadn’t even heard of it.

Around this time, my old boss was flying from LA to Washington, and started talking with his seatmate about this  submarine communication problem.  His seatmate – Irving S. Reed – politely said that he had done a little work on some similar problems.  During this conversation, my informant, a fellow minion sitting behind my old boss, was doggedly choking back hysterical laughter, not wanting to interrupt this very special conversation.
west-hunter  scitariat  stories  reflection  working-stiff  engineering  dirty-hands  electromag  communication  coding-theory  giants  bits  management  signal-noise 
september 2017 by nhaliday
What kills, current or voltage? - Quora
Its an oversimplification to say that voltage kills or current kills and the cause of much misunderstanding.
 
You cannot have one without the other, therefore one could claim that answering one or the other is correct.
 
However, it is the current THROUGH key parts of the body that can be lethal. BUT even a lot of Current in a wire won't harm you if the current is constrained to the wire..
 
Specifically in order for you to be electrocuted, the voltage must be high enough to drive a lethal amount of current through your body over coming body resistance, the voltage must be applied in the right places so that the current path is through your (usually) heart muscle, and it must be long enough duration to stop the heart muscle due to fibrillation.

another good answer:
As I write this note, I’m looking at the textbook Basic Engineering Circuit Analysis by Irwin and Nelms (ISBN 0-471-48728-7). On page 449 the authors reference the work of Dr. John G. Webster who suggests the body resistance values that I have taken the liberty to sketch into this poor character.
nibble  q-n-a  qra  physics  electromag  dirty-hands  embodied  safety  short-circuit  IEEE  data  objektbuch  death 
september 2017 by nhaliday
electricity - Why is AC more "dangerous" than DC? - Physics Stack Exchange
One of the reasons that AC might be considered more dangerous is that it arguably has more ways of getting into your body. Since the voltage alternates, it can cause current to enter and exit your body even without a closed loop, since your body (and what ground it's attached to) has capacitance. DC cannot do that. Also, AC is quite easily stepped up to higher voltages using transformers, while with DC that requires some relatively elaborate electronics. Finally, while your skin has a fairly high resistance to protect you, and the air is also a terrific insulator as long as you're not touching any wires, sometimes the inductance of AC transformers can cause high-voltage sparks that break down the air and I imagine can get through your skin a bit as well.

Also, like you mentioned, the heart is controlled by electric pulses and repeated pulses of electricity can throw this off quite a bit and cause a heart attack. However, I don't think that this is unique to alternating current. I read once about an unfortunate young man that was learning about electricity and wanted to measure the resistance of his own body. He took a multimeter and set a lead to each thumb. By accident or by stupidity, he punctured both thumbs with the leads, and the small (I imagine it to be 9 V) battery in the multimeter caused a current in his bloodstream, and he died on the spot. So maybe ignorance is more dangerous than either AC or DC.
nibble  q-n-a  overflow  physics  electromag  dirty-hands  embodied  safety  short-circuit  IEEE  death 
september 2017 by nhaliday
Drude model - Wikipedia
The Drude model of electrical conduction was proposed in 1900[1][2] by Paul Drude to explain the transport properties of electrons in materials (especially metals). The model, which is an application of kinetic theory, assumes that the microscopic behavior of electrons in a solid may be treated classically and looks much like _a pinball machine_, with a sea of constantly jittering electrons bouncing and re-bouncing off heavier, relatively immobile positive ions.

The two most significant results of the Drude model are an electronic equation of motion,

d<p(t)>/dt = q(E + 1/m <p(t)> x B) - <p(t)>/τ

and a linear relationship between current density J and electric field E,

J = (nq^2τ/m) E

latter is Ohm's law
nibble  physics  electromag  models  local-global  stat-mech  identity  atoms  wiki  reference  ground-up  cartoons 
september 2017 by nhaliday
Constitutive equation - Wikipedia
In physics and engineering, a constitutive equation or constitutive relation is a relation between two physical quantities (especially kinetic quantities as related to kinematic quantities) that is specific to a material or substance, and approximates the response of that material to external stimuli, usually as applied fields or forces. They are combined with other equations governing physical laws to solve physical problems; for example in fluid mechanics the flow of a fluid in a pipe, in solid state physics the response of a crystal to an electric field, or in structural analysis, the connection between applied stresses or forces to strains or deformations.

Some constitutive equations are simply phenomenological; others are derived from first principles. A common approximate constitutive equation frequently is expressed as a simple proportionality using a parameter taken to be a property of the material, such as electrical conductivity or a spring constant. However, it is often necessary to account for the directional dependence of the material, and the scalar parameter is generalized to a tensor. Constitutive relations are also modified to account for the rate of response of materials and their non-linear behavior.[1] See the article Linear response function.
nibble  wiki  reference  article  physics  mechanics  electromag  identity  estimate  approximation  empirical  stylized-facts  list  dirty-hands  fluid  logos 
august 2017 by nhaliday
Lecture 3: Global Energy Cycle
solar flux, albedo, greenhouse effect, energy balance, vertical distribution of energy, tilt and seasons
pdf  slides  nibble  physics  electromag  space  earth  sky  atmosphere  environment  temperature  stock-flow  data  magnitude  scale  phys-energy  distribution  oscillation  cycles  lectures  geography 
august 2017 by nhaliday
On the measuring and mis-measuring of Chinese growth | VOX, CEPR’s Policy Portal
Unofficial indicators of Chinese GDP often suggest that Beijing’s growth figures are exaggerated. This column uses nighttime light as a proxy to estimate Chinese GDP growth. Since 2012, the authors’ estimate is never appreciably lower, and is in many years higher, than the GDP growth rate reported in the official statistics. While not ruling out the risk of future turmoil, the analysis presents few immediate indications that Chinese growth is being systematically overestimated.

https://asia.nikkei.com/magazine/20170831/Politics-Economy/Chinese-provinces-heed-Xi-s-calls-for-accurate-GDP-data
org:ngo  econotariat  study  summary  economics  growth-econ  econometrics  econ-metrics  measurement  broad-econ  china  asia  sinosphere  the-world-is-just-atoms  energy-resources  trends  correlation  wonkish  realness  article  multi  news  org:foreign  n-factor  corruption  crooked  wealth  visuo  electromag  sky  space 
july 2017 by nhaliday
List of Chinese inventions - Wikipedia
China has been the source of many innovations, scientific discoveries and inventions.[1] This includes the Four Great Inventions: papermaking, the compass, gunpowder, and printing (both woodblock and movable type). The list below contains these and other inventions in China attested by archaeology or history.
china  asia  sinosphere  technology  innovation  discovery  list  top-n  wiki  reference  article  history  iron-age  medieval  arms  summary  frontier  agriculture  dirty-hands  civilization  the-trenches  electromag  communication  writing  publishing  archaeology  navigation 
june 2017 by nhaliday
Edge.org: 2017 : WHAT SCIENTIFIC TERM OR CONCEPT OUGHT TO BE MORE WIDELY KNOWN?
highlights:
- the genetic book of the dead [Dawkins]
- complementarity [Frank Wilczek]
- relative information
- effective theory [Lisa Randall]
- affordances [Dennett]
- spontaneous symmetry breaking
- relatedly, equipoise [Nicholas Christakis]
- case-based reasoning
- population reasoning (eg, common law)
- criticality [Cesar Hidalgo]
- Haldan's law of the right size (!SCALE!)
- polygenic scores
- non-ergodic
- ansatz
- state [Aaronson]: http://www.scottaaronson.com/blog/?p=3075
- transfer learning
- effect size
- satisficing
- scaling
- the breeder's equation [Greg Cochran]
- impedance matching

soft:
- reciprocal altruism
- life history [Plomin]
- intellectual honesty [Sam Harris]
- coalitional instinct (interesting claim: building coalitions around "rationality" actually makes it more difficult to update on new evidence as it makes you look like a bad person, eg, the Cathedral)
basically same: https://twitter.com/ortoiseortoise/status/903682354367143936

more: https://www.edge.org/conversation/john_tooby-coalitional-instincts

interesting timing. how woke is this dude?
org:edge  2017  technology  discussion  trends  list  expert  science  top-n  frontier  multi  big-picture  links  the-world-is-just-atoms  metameta  🔬  scitariat  conceptual-vocab  coalitions  q-n-a  psychology  social-psych  anthropology  instinct  coordination  duty  power  status  info-dynamics  cultural-dynamics  being-right  realness  cooperate-defect  westminster  chart  zeitgeist  rot  roots  epistemic  rationality  meta:science  analogy  physics  electromag  geoengineering  environment  atmosphere  climate-change  waves  information-theory  bits  marginal  quantum  metabuch  homo-hetero  thinking  sapiens  genetics  genomics  evolution  bio  GT-101  low-hanging  minimum-viable  dennett  philosophy  cog-psych  neurons  symmetry  humility  life-history  social-structure  GWAS  behavioral-gen  biodet  missing-heritability  ergodic  machine-learning  generalization  west-hunter  population-genetics  methodology  blowhards  spearhead  group-level  scale  magnitude  business  scaling-tech  tech  business-models  optimization  effect-size  aaronson  state  bare-hands  problem-solving  politics 
may 2017 by nhaliday
The Issue that Time Forgot | West Hunter
Human population genetics in the 1960s was obsessed with the question of genetic load. Much of the motivation was concern about health consequences of radiation and nuclear weapons. We now know that radiation does bad things to organisms but that the mutation rate in mammals is nearly insensitive to the effects of ionizing radiation. No one knew that then. Popular concern about the issue was also pumped up by monster movies, which were everywhere on late night television. Does anyone remember Godzilla?

...

The key paper about load was published in 19582. Morton, Crow, and Muller showed that, under some simplifying assumptions, the regression of mortality (and on other traits like IQ) on the inbreeding coefficient could reveal the nature of our burden of mutations. In particular the negative logarithm of the rate, for example the infant mortality rate, should be linear in the inbreeding coefficient:

-ln(q) = A + Bf

where q is the mortality rate and f the inbreeding coefficient. Their important insight was the if our load is mostly deleterious recessives then the rate should increase rapidly with inbreeding. If, on the other hand, our load reflects a lot of balanced polymorphisms then the load should not increase very much with inbreeding. In particular the load ratio, B/A, ought to be something like 10 if there are a lot of deleterious recessives while something like 2 if there are a lot of balanced polymorphisms. A clear explanation of the the theory and the results availabe by the early 1970s can be found in the classic Cavalli and Bodmer text3.

The bottom line was that load ratios from human populations did not give a clear signal either way. A typical B/A ratio was something like 4. The interest in and optimism about load theory in 1960 had fizzled by 1970.

Today all those issues are back on the table in a big way. What is our burden of mutation? How many of our aches and pains and premature deaths are costs of balanced polymorphism? Unfortunately the whole toolkit of 50 years ago has been mostly forgotten by the current generation of human population geneticists. A shame.

- Harpending
west-hunter  scitariat  discussion  history  mostly-modern  electromag  bio  sapiens  genetics  population-genetics  genetic-load  mutation  kinship  reflection  stylized-facts  methodology  🌞 
april 2017 by nhaliday
Overview of current development in electrical energy storage technologies and the application potential in power system operation
- An overview of the state-of-the-art in Electrical Energy Storage (EES) is provided.
- A comprehensive analysis of various EES technologies is carried out.
- An application potential analysis of the reviewed EES technologies is presented.
- The presented synthesis to EES technologies can be used to support future R&D and deployment.

Prospects and Limits of Energy Storage in Batteries: http://pubs.acs.org/doi/abs/10.1021/jz5026273
study  survey  state-of-art  energy-resources  heavy-industry  chemistry  applications  electromag  stock-flow  wonkish  frontier  technology  biophysical-econ  the-world-is-just-atoms  🔬  phys-energy  ideas  speedometer  dirty-hands  multi 
april 2017 by nhaliday
George Green (mathematician) - Wikipedia
It is unclear to historians exactly where Green obtained information on current developments in mathematics, as Nottingham had little in the way of intellectual resources. What is even more mysterious is that Green had used "the Mathematical Analysis," a form of calculus derived from Leibniz that was virtually unheard of, or even actively discouraged, in England at the time (due to Leibniz being a contemporary of Newton who had his own methods that were championed in England). This form of calculus, and the developments of mathematicians such as Laplace, Lacroix and Poisson were not taught even at Cambridge, let alone Nottingham, and yet Green had not only heard of these developments, but also improved upon them.

It is speculated that only one person educated in mathematics, John Toplis, headmaster of Nottingham High School 1806–1819, graduate from Cambridge and an enthusiast of French mathematics, is known to have lived in Nottingham at the time.
people  history  early-modern  britain  math  science  physics  electromag  stories  frontier  giants  wiki  discovery  old-anglo  pre-ww2  the-trenches  the-great-west-whale  allodium 
march 2017 by nhaliday
Which one would be easier to terraform: Venus or Mars? - Quora
what Greg Cochran was suggesting:
First, alternatives to terraforming. It would be possible to live on Venus in the high atmosphere, in giant floating cities. Using a standard space-station atmospheric mix at about half an earth atmosphere, a pressurized geodesic sphere would float naturally somewhere above the bulk of the clouds of sulfuric acid. Atmospheric motions would likely lead to some rotation about the polar areas, where inhabitants would experience a near-perpetual sunset. Floating cities could be mechanically rotated to provide a day-night cycle for on-board agriculture. The Venusian atmosphere is rich in carbon, oxygen, sulfur, and has trace quantities of water. These could be mined for building materials, while rarer elements could be mined from the surface with long scoops or imported from other places with space-plane shuttles.
q-n-a  qra  physics  space  geoengineering  caltech  phys-energy  magnitude  fermi  analysis  data  the-world-is-just-atoms  new-religion  technology  comparison  sky  atmosphere  thermo  gravity  electromag  applications  frontier  west-hunter  wild-ideas  🔬  scitariat  definite-planning  ideas  expansionism 
february 2017 by nhaliday
Orthogonal — Greg Egan
In Yalda’s universe, light has no universal speed and its creation generates energy.

On Yalda’s world, plants make food by emitting their own light into the dark night sky.
greg-egan  fiction  gedanken  physics  electromag  differential  geometry  thermo  space  cool  curiosity  reading  exposition  init  stat-mech  waves  relativity  positivity  unit  wild-ideas  speed  gravity  big-picture  🔬  xenobio  ideas  scifi-fantasy  signum 
february 2017 by nhaliday
Einstein's Most Famous Thought Experiment
When Einstein abandoned an emission theory of light, he had also to abandon the hope that electrodynamics could be made to conform to the principle of relativity by the normal sorts of modifications to electrodynamic theory that occupied the theorists of the second half of the 19th century. Instead Einstein knew he must resort to extraordinary measures. He was willing to seek realization of his goal in a re-examination of our basic notions of space and time. Einstein concluded his report on his youthful thought experiment:

"One sees that in this paradox the germ of the special relativity theory is already contained. Today everyone knows, of course, that all attempts to clarify this paradox satisfactorily were condemned to failure as long as the axiom of the absolute character of time, or of simultaneity, was rooted unrecognized in the unconscious. To recognize clearly this axiom and its arbitrary character already implies the essentials of the solution of the problem."
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february 2017 by nhaliday
electromagnetism - Is Biot-Savart law obtained empirically or can it be derived? - Physics Stack Exchange
Addendum: In mathematics and science it is important to keep in mind the distinction between the historical and the logical development of a subject. Knowing the history of a subject can be useful to get a sense of the personalities involved and sometimes to develop an intuition about the subject. The logical presentation of the subject is the way practitioners think about it. It encapsulates the main ideas in the most complete and simple fashion. From this standpoint, electromagnetism is the study of Maxwell's equations and the Lorentz force law. Everything else is secondary, including the Biot-Savart law.
q-n-a  overflow  physics  electromag  synthesis  proofs  nibble 
february 2017 by nhaliday
The Secret Histories | West Hunter
WW2 and the Civil War: https://westhunt.wordpress.com/2016/12/30/the-secret-histories/#comment-86474
the great divergence:
https://westhunt.wordpress.com/2016/12/30/the-secret-histories/#comment-86588
Untrue. Drastically wrong. Who has made a greater contribution to human knowledge – James Clerk Maxwell [ one guy !] , or East Asia over the past five hundred years?
https://westhunt.wordpress.com/2016/12/30/the-secret-histories/#comment-86527
When people talk about the “Great Divergence”, they don’t seem to place much emphasis on the fact that at the very top, Western Europe was enormously more intellectually sophisticated than China. Europeans were using Jupiter’s moons as a clock in 1800 and directly measuring the gravitational force of a 12-inch lead ball. European physics & mathematics were far advanced over China’s at that point. Indeed, you could argue that Hellenistic science and mathematics were far advanced over those of China in 1800.
Cavendish experiment: https://en.wikipedia.org/wiki/Cavendish_experiment
Torsion balance: https://en.wikipedia.org/wiki/Torsion_spring#Torsion_balance
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january 2017 by nhaliday
Talkin’ ’bout their generations | West Hunter
According to the Decode results, mothers contribute 15 mutations, regardless of age, while men contribute 25 + 2*(g-20) mutations, when g is the average paternal age. As I pointed out earlier, if g is the same in both sexes, the average number of mutations is just 2g, which makes for 2 mutations per calendar year. I’ve been checking out average maternal age: it doesn’t vary much. The lowest I’ve seen was 26, the highest 30, so 28 is a reasonable number. So far, in the data we’ve gathered, the population with the highest paternal age was in Gambia, with an average paternal age of 47. If we assume that the average maternal age is 28 (which look about right from the graph: I haven’t digitized it yet) then the average kid would receive 94 new mutations (15 maternal, 79 paternal). With an average generation length of 37.5 years (the average of 28 and 47), that makes for 2.5 mutations per calendar year: about 15% higher than you would see in most populations, where the gap between average maternal and paternal age is not nearly as large.

A Gambia-sized gap would result in a noticeably higher rate of neutral genetic divergence. If it had existed long enough you might be able to notice it, but I think there’s a better chance of seeing this effect in Australian Aborigines, who had high average paternal age and might have had it for a long time. Other than the Australians, I would guess that all the old-dad societies are relatively recent.

The higher mutational load is not just a consequence of the higher per-year mutation rate in these old-dad societies – since generations are longer, there is less selection per calendar year (considering that most selection acts early in life). The number of mutations per generation is probably the most important number. I found some numbers for Polar Eskimos, hunter-gatherers (they gather snow) in a tough environment: average maternal age was 27, average paternal age was 32, for an average generation length of 29.5. They’d have 64 mutations a generation: the per-generation rate in Gambia is 47% higher.

There are also qualitative differences in selection: selection is weaker in childhood and stronger in midlife in an old-dad society, as Henry pointed out. So that situation should select for longer life, except that’s hard to manage in the presence of higher-than-usual genetic load.

https://westhunt.wordpress.com/2012/10/19/base-substitutions-and-deletions/
According to Jim Crow”s 2006 article, base substitutions are mostly (overwhelmingly) from males and increase with paternal age, but small deletions are contributed about equally by males and females, with no noticeable age effect. Probably the deletions happen during meiosis.

So, with a huge gene like those involved in Duchenne’s muscular dystrophy or neurofibromatosis I, which have many exons (79 for dystrophin), many of the mutations are caused by deletions. The paternal age effect is weaker for those syndromes (since less than half of the causal mutations are base substitutions)

https://westhunt.wordpress.com/2012/08/26/gerontocratic-polygyny/
https://westhunt.wordpress.com/2012/09/05/obvious-yessss-it-was-obvious/
https://westhunt.wordpress.com/2012/08/22/paternal-age/
https://westhunt.wordpress.com/2012/09/17/gambia/
https://westhunt.wordpress.com/2012/09/16/paternal-age-and-the-force-of-mortality/
No surprises here save one. While selection for survival should extend male lifespans by 10 to 20 years in the case of old fathers, selection for survival before the age of reproduction is much weaker in the the case of older fathers. A prediction is that adolescent and young male death rates should be higher in old father societies because selection is weaker. I never realized that.

Hamilton’s theory does not describe human life history very well, as Rogers shows in his Figure 16.1 and discusses in the text. Human female fertility ceases long before the theory predicts that it should and humans live much longer. The reconciliation certainly has to do with kin selection or indirect selection. For example Kris Hawkes pushes the “grandmother hypothesis” according to which females cease reproduction and instead work for their daughters’ children. If she is right this grandmother effect selected for the prolonged human lifespan, and the long lifespan of males is a side-effect of selection for long life in females.
west-hunter  objektbuch  genetics  genetic-load  developmental  paternal-age  epidemiology  science-anxiety  scitariat  multi  social-structure  life-history  mutation  🌞  effect-size  data  ideas  speculation  methodology  gender  gender-diff  sex  africa  recent-selection  pop-diff  kinship  selection  population-genetics  electromag  longevity  aging  iq  intelligence  neuro  eden  explanans  age-generation 
november 2016 by nhaliday
Thick and thin | West Hunter
There is a spectrum of problem-solving, ranging from, at one extreme, simplicity and clear chains of logical reasoning (sometimes long chains) and, at the other, building a picture by sifting through a vast mass of evidence of varying quality. I will give some examples. Just the other day, when I was conferring, conversing and otherwise hobnobbing with my fellow physicists, I mentioned high-altitude lighting, sprites and elves and blue jets. I said that you could think of a thundercloud as a vertical dipole, with an electric field that decreased as the cube of altitude, while the breakdown voltage varied with air pressure, which declines exponentially with altitude. At which point the prof I was talking to said ” and so the curves must cross!”. That’s how physicists think, and it can be very effective. The amount of information required to solve the problem is not very large. I call this a ‘thin’ problem’.

...

In another example at the messy end of the spectrum, Joe Rochefort, running Hypo in the spring of 1942, needed to figure out Japanese plans. He had an an ever-growing mass of Japanese radio intercepts, some of which were partially decrypted – say, one word of five, with luck. He had data from radio direction-finding; his people were beginning to be able to recognize particular Japanese radio operators by their ‘fist’. He’d studied in Japan, knew the Japanese well. He had plenty of Navy experience – knew what was possible. I would call this a classic ‘thick’ problem, one in which an analyst needs to deal with an enormous amount of data of varying quality. Being smart is necessary but not sufficient: you also need to know lots of stuff.

...

Nimitz believed Rochefort – who was correct. Because of that, we managed to prevail at Midway, losing one carrier and one destroyer while the the Japanese lost four carriers and a heavy cruiser*. As so often happens, OP-20-G won the bureaucratic war: Rochefort embarrassed them by proving them wrong, and they kicked him out of Hawaii, assigning him to a floating drydock.

The usual explanation of Joe Rochefort’s fall argues that John Redman’s ( head of OP-20-G, the Navy’s main signals intelligence and cryptanalysis group) geographical proximity to Navy headquarters was a key factor in winning the bureaucratic struggle, along with his brother’s influence (Rear Admiral Joseph Redman). That and being a shameless liar.

Personally, I wonder if part of the problem is the great difficulty of explaining the analysis of a thick problem to someone without a similar depth of knowledge. At best, they believe you because you’ve been right in the past. Or, sometimes, once you have developed the answer, there is a ‘thin’ way of confirming your answer – as when Rochefort took Jasper Holmes’s suggestion and had Midway broadcast an uncoded complaint about the failure of their distillation system – soon followed by a Japanese report that ‘AF’ was short of water.

Most problems in the social sciences are ‘thick’, and unfortunately, almost all of the researchers are as well. There are a lot more Redmans than Rocheforts.
west-hunter  thinking  things  science  social-science  rant  problem-solving  innovation  pre-2013  metabuch  frontier  thick-thin  stories  intel  mostly-modern  history  flexibility  rigidity  complex-systems  metameta  s:*  noise-structure  discovery  applications  scitariat  info-dynamics  world-war  analytical-holistic  the-trenches  creative  theory-practice  being-right  management  track-record  alien-character  darwinian  old-anglo  giants  magnitude  intersection-connectedness  knowledge  alt-inst  sky  physics  electromag  oceans  military  statesmen  big-peeps  organizing  communication  fire  inference  apollonian-dionysian  consilience  bio  evolution 
november 2016 by nhaliday
Son of low-hanging fruit | West Hunter
You see, you can think of the thunderstorm, after a ground discharge, as a vertical dipole. Its electrical field drops as the cube of altitude. The threshold voltage for atmospheric breakdown is proportional to pressure, while pressure drops exponentially with altitude: and as everyone knows, a negative exponential drops faster than any power.

The curves must cross. Electrical breakdown occurs. Weird lightning, way above the clouds.

As I said, people reported sprites at least a hundred years ago, and they have probably been observed occasionally since the dawn of time. However, they’re far easier to see if you’re above the clouds – pilots often do.

Pilots also learned not to talk about it, because nobody listened. Military and commercial pilots have to pass periodic medical exams known as ‘flight physicals’, and there was a suspicion that reporting glowing red cephalopods in the sky might interfere with that. Generally, you had to see the things that were officially real (whether they were really real or not), and only those things.

Sprites became real when someone recorded one by accident on a fast camera in 1989. Since then it’s turned into a real subject, full of strangeness: turns out that thunderstorms sometimes generate gamma-rays and even antimatter.
west-hunter  physics  cocktail  stories  history  thick-thin  low-hanging  applications  bounded-cognition  error  epistemic  management  scitariat  info-dynamics  ideas  discovery  the-trenches  alt-inst  trivia  theory-practice  is-ought  being-right  magnitude  intersection-connectedness  sky  electromag  fire  inference  apollonian-dionysian  consilience 
november 2016 by nhaliday
Why Information Grows – Paul Romer
thinking like a physicist:

The key element in thinking like a physicist is being willing to push simultaneously to extreme levels of abstraction and specificity. This sounds paradoxical until you see it in action. Then it seems obvious. Abstraction means that you strip away inessential detail. Specificity means that you take very seriously the things that remain.

Abstraction vs. Radical Specificity: https://paulromer.net/abstraction-vs-radical-specificity/
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september 2016 by nhaliday
Cyborg Nest
north sense implant to give you an internal compass
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june 2016 by nhaliday

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