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Everything posted by Sensei

  1. In classical physics there is not boundary where force is literally reaching absolute zero. Equations just follow inverse-square law, or inverse-cubic law, etc. and vice versa in the other direction. That is often pointed out argument, by some people on this forum ("antiscience crackpots"), against quantum physics i.e. "why electron does not fall to nucleus". Energy is property of particle. Kinetic energy of particle or molecule, rotational energy of particle or molecule, is "lost" during collision with other particles. "lost" means that other particles will be created, which will carry on that energy away of place where collision happened. i.e. accelerated electron by electron gun, toward e.g. phosphorescent screen, will lose its kinetic energy after collision with the screen, and new photon(s) will be created which will carry on that energy away. Feature which was used in early CRT old TVs. Essential potential energy of particle ("mass-energy") is converted to kinetic energy of newly made particles during annihilation with antimatter (electron and positron). In the case of other particle-antiparticle pair annihilation is much more complicated (part of energy converts to rest-mass of newly created particles e.g. meson PI). Part of mass-energy of nuclei (or nucleus) is converted to kinetic energy of newly made particles during fusion, fission and radioactive decay.
  2. Concrete does not trap much of water *). But in urban areas it causes water to quickly flow to rivers disallowing to be absorbed by soil. Accelerated rate of flow of water might cause flooding even in places hundred kilometers away, as river water level is unnaturally raised up. Simply saying water is too quickly finding path to rivers. In older times the rivers used to meander. But it was taking large of areas of countries, so people started "straightening" rivers, to gain fertile areas around rivers, which used to be muds and swamps, for agricultural production. https://www.google.com/search?q=straightening+rivers "This straightening causes the streams to flow more rapidly, which can, in some instances, vastly increase soil erosion. It can also increase flooding" https://en.wikipedia.org/wiki/River_engineering Read instruction of making concrete (there is mentioned how much of water you have to add to cement), and multiply by worldwide concrete production (search net for both information). https://en.wikipedia.org/wiki/Water–cement_ratio *) ~35% according to the above article.
  3. "Weather satellites have been available to infer sea surface temperature (SST) information since 1967, with the first global composites occurring during 1970.[9] Since 1982,[10] satellites have been increasingly utilized to measure SST and have allowed its spatial and temporal variation to be viewed more fully." https://en.wikipedia.org/wiki/Satellite_temperature_measurements Comparison of temperatures collected from satellites and ground monitoring stations: There is no need for specialized weather satellites to capture photography of Arctic, Greenland, Antarctic etc. etc. and to make timelapse video from forty years: ...or measure the amount of land that has turned into a desert during the last forty years... ... or measure the number of forest fires (and area) during the last forty years.. etc. etc.
  4. @BorisBoris Multimeters, oscilloscopes and electronic/electric devices used by electricians are typically measuring frequency of alternating current (AC) or pulsing DC. This formula tells how much single photon has energy.
  5. Media journalists abuse words like "crisis" to have catchy title for an article, so people will visit and read their article. It is similar to the words "professional", and "intelligent" in advertising materials. Just yet another clickbait. https://en.wikipedia.org/wiki/Clickbait
  6. Therefor scientists (cosmologists with computer programmers together) are making simulations... 1) change code of simulation. 2) change constants and/or variables. 3) rerun simulation on supercomputer cluster . 4) compare results of simulation with results from Hubble and other telescopes. The example of delay of photons travelling from supernova versus neutrinos (which arrive hours or minutes earlier) suggest that similar delay should be from light from distant galaxies. I would start from placing these delays on graph with distance to supernova (measured different methods) to check how delay varies with distance. If data will be consistent later it could be used as method of estimation of distance to supernova just from delay.
  7. Mosquitoes larvae are consumed by e.g. fishes. Adult mosquitoes are consumed by e.g. birds and bats. Extinction of one specie can lead to extinction of other species because natural food chain is interrupted.
  8. In C/C++ there are randomization functions srand() and rand() http://www.cplusplus.com/reference/cstdlib/srand/ rand() gives unsigned integer in range 0 to RAND_MAX. So if you want to receive in different range you have to do e.g. rand() * MAX / RAND_MAX + MIN Python should have equivalent functions of pseudo random number generator (PRNG). https://docs.python.org/3/library/random.html
  9. I have not been invited to your deification.. ps. Anyway, welcome to the "club"..
  10. I think that your thinking requires more rethinking...
  11. @Strange This madness should be stopped once and for all by closing the thread. Done!
  12. Quoting myself: "Notice what would happen with my brute-force algorithm if you would use divisor = 0. You would have infinite never ending loop! Procedure would never exit."...
  13. In multiplication it does not matter, in division it does matter. a*b=c b*a=c but a/b=c b/a=1/c=c^-1 When you multiply you can have a or b equal 0. No big deal. You will just get 0 result. But with division, if dividend is 0, okay. If divisor equals 0 -> illegal operation.. (during computer programming it can rise exception (which must be captured by try {} catch {}), or even crash code, so any division by variable must be checked against being 0 in divisor!) Notice what would happen with my brute-force algorithm if you would use divisor = 0. You would have infinite never ending loop! Procedure would never exit.
  14. The simplest brute-force dividing algorithm in C/C++ would look like: int quotient = 0; while( dividend >= divisor ) { dividend -= divisor; quotient++; } int reminder = dividend; // subtraction failed "subtract divisor from dividend until dividend is greater than or equal to divisor". The number of repetitions on the loop will be O(quotient) The more sophisticated version could left-shift divisor prior subtraction from dividend. Each binary left-shift operation is multiplication by 2. At the same time value added to quotient should be multiplied by 2. (In binary numeral system left-shift is equivalent of multiplication by 2, move the all bits one position to the left and make room for 0 at the end for the least significant bit) So e.g. division of 1000 by 50 will look like: temporary_quotient = 1; 1000 > 50 (true) 50*2 = 100, temporary_quotient*2 =2 1000 > 100 (true) 100*2=200, temporary_quotient*2=4 1000>200 (true) 200*2=400, temporary_quotient*2 =8 1000>400 (true) 400*2=800, temporary_quotient*2=16 1000>800 (true) 800*2=1600, temporary_quotient*2=32 1000>1600 (false! We are using previous values and subtract it from 1000! i.e. 800 and 16) 1000-800=200, quotient += temporary_quotient (16) Repetition of entire procedure once again: temporary_quotient = 1; 200 > 50 (true) 50*2 = 100, temporary_quotient*2=2 200 > 100 (true) 100*2=200, temporary_quotient*2=4 200 == 200 (they are equal, end of the loop) 200-200=0, quotient += temporary_quotient (16+4=20) 50 * 20 = 1000 That reminds me that the single division operation in machine code of Motorola 68000 (Amiga 500, Atari ST) was talking over 150-170 cycles of cpu (running at 7.16 MHz) (unsigned integer div faster, signed integer div slower). So at max it could do just 7,160,000 / 150 = ~47,000 divisions per second.
  15. Kinetic energy of electrons change as they fly through wire and are colliding with atoms giving them part of their energy, thus heating medium they pass through. I already gave example of it in Joule heating article to read by you.. Measurement how much power/energy was dissipated on electric or electronic element is done by measurement of voltage drop, and multiplication by current passing through it. Car burning fuel during travel is pretty good analogy of electron losing kinetic energy during travel through circuit.
  16. Did you read this forum Homework Help rules? https://www.scienceforums.net/forum/35-homework-help/
  17. To get projected coordinate, 3D world original coordinate must be multiplied by projection matrix. https://en.wikipedia.org/wiki/3D_projection In orthogonal projection matrix, one 3D axis is simply cleared (multiplied by 0). What you need to do is construction of inverse of projection matrix. https://www.google.com/search?q=inverse+projection+matrix (in some cases it is not possible to reverse projection, to get original coordinate, like in orthogonal projection were you lost certain axis data) Axonometric projection that you gave is similar to isometric projection. https://en.wikipedia.org/wiki/Isometric_projection In the above article there are showed matrices which can be used to get such projection. In your case it's simple as you know that [math]\alpha[/math] used to be originally 90 degrees, [math]\beta =\frac{360-2*\alpha}{2}[/math] was also 90 degrees, and length of each Rhombus edge used to be (prior projection) the same value (projection of square, not rectangle).
  18. I think that the same results as "gravitational waves" (bending of spacetime curvature) would have burst of electric neutral particles, extremely weakly (or none) interacting with ordinary matter, interacting only gravitationally..
  19. Photons are practically the only thing that you, and scientists, see and are able to measure their properties and quantities. Have you been on the Moon, Mars or Sun? No. You just saw photons from them emitted or reflected. Measurement of mass of the Moon, Mars, or Sun, is done by observation how other cosmic objects in neighborhood reacts, and reversing Newton's law of universal gravitation. Apart from photons there is very little amount of neutrinos (they are used as indicators of supernova explosions). Apart from photons and neutrinos, there are cosmic rays. So, you (and scientists) learn what material is by observation of photons emitted by that material (spectral emission and absorption lines).
  20. Telescopes, like Hubble, record photography of cosmic objects, and distant galaxies. To get good quality picture from distant object, telescope must be recording object with very long exposure. https://en.wikipedia.org/wiki/Astrophotography "This is done by long time exposure since both film and digital cameras can accumulate and sum light photons over these long periods of time. " Long-time exposure photography https://en.wikipedia.org/wiki/Long-exposure_photography Photons are emitted with inverse-square law, so their quantity per area drops with distance. Read inverse-square law wikipedia article if you are not familiar with it. So, if you know that object should emit specific amount of energy, you can estimate distance to it, by reversing inverse-square law. This method is called "Standard candles". https://en.wikipedia.org/wiki/Cosmic_distance_ladder Scientists found that distant objects are redshifted. Some of them extremely redshifted. This is article you must read: https://en.wikipedia.org/wiki/Redshift The older galaxy you see, the more distant it is, and the higher redshift. It leaded to conclusion of that Universe is expanding. https://en.wikipedia.org/wiki/Expansion_of_the_universe List of galaxies with some very high redshift (z value): https://en.wikipedia.org/wiki/List_of_galaxies For example this galaxy found in 2016: https://en.wikipedia.org/wiki/GN-z11 "GN-z11 is a high-redshift galaxy found in the constellation Ursa Major. GN-z11 is currently the oldest and most distant known galaxy in the observable universe.[4] GN-z11 has a spectroscopic redshift of z = 11.09, which corresponds to a proper distance of approximately 32 billion light-years (9.8 billion parsecs).[5][note 1]" To measure redshift, scientists are measuring shift of spectral lines emitted by well-known elements like Hydrogen or Helium, with assumption that they never changed in the past history of the Universe. Again, if you're not familiar with it, you must read articles about spectral lines, emission spectrum, blackbody radiation etc. ps. Yes, in computer games and simulations, programmers are constructing them in such way, that entities living inside are reaching internal "wall" which is impossible to be transcended..
  21. It depends on specie. Take for example bees. "The queen–worker developmental divide is controlled epigenetically by differential feeding with royal jelly; this appears to be due specifically to the protein royalactin." https://en.m.wikipedia.org/wiki/Royal_jelly (epigenetics effects section) (worker-bee and queen-to-be larvae are usually sisters)
  22. Sensei


    Conclusion? Don't forget your cat! Just in case you would get lost in the middle of the galaxy.. ps. Love goes to Ripley.. 😙 (and Jonesy obviously too)
  23. Decimal is just one of infinite number of numeral systems. It is used in computers just to show result to user. Computers don't compute in decimal system. Irrational number never ends. Rational number, if it has no repeating fraction, will end. You can find algorithm for finding repeating fraction in this article: https://en.m.wikipedia.org/wiki/Repeating_decimal (different numeral system have different repeating fraction) But from computer programming point of view, you should start from making rational number class (i. e. taking p/q as arguments), or download 3rd party from net. Override ToString() (e.g. Java or C#) or << operator (C++) or method used to convert to decimal string to support repeating fraction.
  24. To talk about numbers we would have to pick up specific materials to compare their exact properties. Here we have resistivity table of some example materials, conductors and insulators: Air has at least 7.74*10^23 higher resistivity than Copper. My words still applies: Unclear for uneducated / improperly educated.. P = I * U E=Q * U Power dissipated by electrons passing through medium depends on current and voltage (voltage drop on element). Energy dissipated (...) depends on charges and voltage (drop). Charge Q divided by elementary charge e = 1.6021766*10^-19 C is quantity of electrons. In static electricity discharge, quantity of electrons (therefor Q and I as well) could be millions or billions times smaller than in typical electric or electronic device. e.g. P = 20,000 V * 10^-10 A = 0.00002 W Actually, in early XIX century, there was used technique to measure how much energy wire dissipated by placing it in water, and measuring temperature increase of water. Therefor calorie unit (1 calorie = energy needed to increase temperature of 1 gram of water by 1 C) has been introduced. https://en.wikipedia.org/wiki/Joule_heating "James Prescott Joule first published in December 1840, an abstract in the Proceedings of the Royal Society, suggesting that heat could be generated by an electrical current. Joule immersed a length of wire in a fixed mass of water and measured the temperature rise due to a known current flowing through the wire for a 30 minute period. By varying the current and the length of the wire he deduced that the heat produced was proportional to the square of the current multiplied by the electrical resistance of the immersed wire.[2]" As a result of very low power, very low energy, dissipated in very short time, on such wire with 20 kV, it does not melts, as melting temperature of metal is not reached fast enough. Give it constant 20,000 V, for seconds or minutes, and it will melt and break apart, disconnecting circuit.. That's how fuses work. https://en.wikipedia.org/wiki/Fuse_(electrical)#Thermal_fuses "In electronics and electrical engineering, a fuse is an electrical safety device that operates to provide overcurrent protection of an electrical circuit. Its essential component is a metal wire or strip that melts when too much current flows through it, thereby stopping or interrupting the current." (notice words on Wikipedia: metal wire melts)
  25. What states of matter do you know from physics lessons? Solid, liquid, gaseous and plasma. Wire is solid. But after heating it (by too large current) it melts. Heat it more and it will change state to gaseous. Heat it considerably more and it will change state to plasma. Sometimes, just sometimes, under special conditions of the environment (temperature and pressure), some state is skipped (e.g. sublimation). I don't know where you get idea that solid metallic wire turns immediately to plasma skipping two states of matter. Breakage happens in the weakest point of wire and immediately shutdowns current. Applying large current to melt metal is widely used method in metalurgy.
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