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Sensei

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Everything posted by Sensei

  1. http://en.wikipedia.org/wiki/Cross_section_%28physics%29 http://en.wikipedia.org/wiki/Absorption_cross_section
  2. We really don't have to search far for extremities... http://en.wikipedia.org/wiki/Galaxy_rotation_curve Without introducing dark matter it would fail immediately in prediction of Milky Way stars velocity/distance from the center of galaxy: A - predicted by GR B - the real measurement
  3. If somebody would be so (hypothetically) powerful to time travel to the past, he/she would bother writing on FB or Twitter? c'mon..
  4. d = sqrt( ( x1- x0)^2 + ( y1-y0)^2 + ( z1-z0)^2 ) in 3 dimensions. d = sqrt( ( x1- x0)^2 + ( y1-y0)^2 ) in 2 dimensions.
  5. Decay of proton would violate Baryon Number Conservation. On the other hand, in old Universe, the all/most of protons would be converted to heavier elements in fusion process in stars.
  6. It's very simple if you realize what really happens to electrons. In NPN transistor electrons that are on Base, must escape it, to start flowing electrons between Emitter and Collector. That's why you usually connect NPN base to + in battery (through resistor). In PNP it's reversed. Arrow on circuits is always showing opposite direction to flow of electrons (they flow from - to + in battery). ps. you can even make human touch detector with plain NPN transistor. Connect Collector to LED diode with resistor, and Base to some wire. When you will touch wire diode will start shining. ps2. Buy tens of NPN/PNP (f.e. C945), universal circuit board, resistors and LEDs, and start experimenting. Always check in 3+ different specifications whether you have right E/C/B on legs (I have seen specifications that were mutually exclusive for the same model of transistor on the Internet). Connecting Base to + or - without any resistor means usually instant damage of transistor (in such case it's usually permanently conducting). So better use 1k+ ohms resistor in test stage, while checking what are E/C/B on legs. Once you know that f.e. middle leg is Base, you can use smaller/right resistor.
  7. ?? 1 Amper * 1 second is 1 Coulomb. 1 C / e = 1 C / 1.602*10^-19 C = 6.25*10^18 1 C = 6.25*10^18 electrons. so 1 A = 6.25*10^18 electrons per second. It's a matter of Voltage. Dielectric can pass electrons with high enough kinetic energy. Read more here http://en.wikipedia.org/wiki/Electrical_breakdown "Electrical breakdown or dielectric breakdown refers to a rapid reduction in the resistance of an electrical insulator when the voltage applied across it exceeds the breakdown voltage. This results in a portion of the insulator becoming electrically conductive. Electrical breakdown may be a momentary event (as in an electrostatic discharge), or may lead to a continuous arc discharge if protective devices fail to interrupt the current in a high power circuit."
  8. There is also large energy-mass of neutrino. And kinetic energy of emitted electron/positron. You can see it in Cloud Chamber and compare with other radioactive fission of other element to see difference. You mixed beta decay+ with electron capture.. http://en.wikipedia.org/wiki/Electron_capture Beta decay+ is positron emission http://en.wikipedia.org/wiki/Positron_emission When electron is absorbed by nucleus (in electron capture), one of protons change to neutron. So atomic number Z is decreased, and mass number A remain the same. There is no need to import yet another electron, as far as I am aware.
  9. From left: 3rd, 5th, 8th, 10th and 11 are 10 groszy (ten penny), Polish coin, equivalent to 3.333 USA cents current rate (ajb should have them in the pocket). 4rd one is some penny from New York. All of them are 10 penny but from different countries? Are you collecting 10 pennies?
  10. There is no electrons and positrons in photon... Electron and positron have billions time more energy than radiowave photon.
  11. Computers don't compute at speed of light. Single thread is doing at maximum 3 billion simple math operations or so per second. Multiple it by number of threads, in quad-core it's 8 HT threads, so it's like 24 billion operations per second. This number is often limited because of slow access to memory and hardware. Regular algorithm of chess game is checking the all possible positions of figures, either side, rate how good or bad is move, and repeating it over and over again. After some time chess engine is returning the best for it move and figure moves to new position on screen. The faster computer, or cluster of computers, the more possible to check positions in human the same time. Human doesn't play chess this way. You don't need f.e. to (virtually) move pawn from a2 to a3 to know it's bad senseless move (most the time). We know from past experiences which moves are "good", which are "bad". So amount of moves to rate is quite small for human. We think and judge "why somebody did that move?" "what was purpose of it?", and seeing that figure will be used in future to some kind of attack, we do something to prevent it.
  12. I found higher resolution label http://www.groceries-express.com/WebPages/3680091718%20Top%20Care.html So it appears to be pharmacy product. I would buy IPA in electronic shop and try distilling it to see whether it's giving the same result as the one that you already used. Verify products from various sources and compare whether result is always the same. Did you use ceramic/glass balls/pieces inside of bulb during distillation? Did you make sure that you're not exceeding 83 C temperature too much?
  13. Wow. Well said. You're such good person. From now on it'll be mine the favorite quote from this website.
  14. Change "bro" to "Sir" or "Madame" and people will start liking you..
  15. Java has JIT. http://en.wikipedia.org/wiki/Just-in-time_compilation
  16. Distillation of pure methanol, ethanol, isopropyl, or with mixture with pure water should give you just initial alcohol. They will be first flowing because they have lower boiling point than water (methanol first 65 C b.p, ethanol second 78 C b.p., isopropyl last with 83 C b.p.). That's why we have to flush away the initial result of distillation of home made moon shine, because it's methanol. We don't know what source of isopropyl you used. You should check out label to learn what it contains. We don't know in how clean environment you were doing distillation... Did you use glass or metal bulbs and pipes? What metal(s)? Take photo of setup, it'll be easier for you and us to tell.. Bought in chemical equipment shop? These tend to be made of heat resistant glass, with small capacity, but chance to contaminate is minimized. Bought in shop with alcohol distillers, etc stuff.. ? These tend to be made of copper or special steel, and aimed to distillate just moon shine ethanol, not general purpose distill. Or built by yourself?
  17. The same is with any macroscopic object - you have to stop it from moving to tell exactly where it is (with great precision f.e. 1 mm or better), and then we know that its momentum is 0 and position is exact.
  18. "Thanks for registering Your account has been successfully created, although it is not yet active. In order to activate it please check your email in a few minutes for our welcome message and follow the instructions in it. Please notice that we only allow one membership account per email address. This pre-registration email confirmation step will expire in 48 hours. If you do not confirm your email within that time, both your username and the specified email will become again available for new registrations." This is message I received..
  19. Where did you get such idea? When electron annihilate with positron gamma photons are produced. Then gamma photons can be absorbed by some charged particles and new bunch of photons emitted with lower energy, lower frequency.. And after a while energy that was in electron and positron is spread in millions or billions of other particles.. Susskind proposed multi universe idea as explanation of why physical constants have values, as they have, in our universe. Who is believing in it, won't be searching for sense in why physical constant have value as we measure.
  20. Elite Engineer, EdCarl, where did you get isopropyl that is not pure, so you have to distill it?! In any electronic shop you can always get 99.9% pure C3H8O... http://en.wikipedia.org/wiki/Isopropyl_alcohol It's essential thing to run cloud chamber. I have liters of it: It costs 5$ for 1 L.
  21. If you have star with initial mass m, after burning out all fuel and collapse it's mass is smaller than initial m. During lifetime star is ejecting clouds of gas/plasma in eruptions.
  22. Distance between Earth and Sun is ~150 mln km..
  23. If teachers are learning just theory, make electrostatic machine by yourself, and show class.. You can get better grade. See video http://www.youtube.com/watch?v=Zilvl9tS0Og
  24. Electrostatic experiments are boring? Cut paper to pieces 1x1 mm, 100 pieces. Then rub some glass tube on fabric, and touch paper pieces. They will stick to glass tube.
  25. I think many depends on teacher. If I would be learning in school, I would be showing cloud chamber, electron gun, Crookes tube. Showing what happens when there is electric and magnetic field around them etc. etc. Showing how to create high voltage, electric arc, vacuum arc. Nothing stops you making them by yourself.
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