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D H

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Everything posted by D H

  1. Wrong. Learn your classical mechanics. Applying a force [math]\mathbf F[/math] to a rigid body with the point at which the force is applied located at a displacement [math]\mathbf r[/math] from the body's center of mass makes the body undergo linear and rotational acceleration according to [math] \aligned \mathbf F &= m\mathbf a \\ \boldsymbol{\tau} &= \mathbf r \times \mathbf F = \boldsymbol I\,\frac{d}{dt} \boldsymbol{\omega} + \boldsymbol{\omega}\times (\boldsymbol I \boldsymbol{\omega}) \endaligned[/math] Here the angular velocity [math]\boldsymbol{\omega}[/math] is the angular velocity of the body with respect to some inertial frame but represented in some frame fixed with respect to the body.
  2. The only glitch is in your understanding of mechanics. You are ignoring that linear momentum contributes to angular momentum via [math]\mathbf r \times \mathbf p[/math]. You need to account for this or you will get nonsensical results (which is exactly what you have obtained).
  3. Stop being silly, Widdekind. Analogies, particularly those presented in elementary texts, are just that: analogies. Take them too far and you end up with nonsense.
  4. As noted earlier, that statement is provably false. However, most useful software products are buggy. A "Hello, world" program isn't very useful. A useful program such as the one that drives this website almost certainly has bugs. The formal methods to which Bascule alluded are not all that useful, either. Employing them is a very expensive process, they can only be used on certain types of software, and the kinds of people who are adept at formal methods are generally clueless at the domain level while people who know the domain are generally clueless regarding the requisite logic behind formal methods. I have seen formal methods deployed once in my thirty years of work, regarding a communications device that works with multi-security level data.
  5. It is the number k+2 that is prime, not the product. If you can find an integer k and some set of non-negative integers a, b, ..., z such that the value of the polynomial is positive then k+2 is a prime number. If k+2 is a prime number, there always exists some set of non-negative integers a, b, ..., z that yield a positive value. In fact, the term in the brackets will be one in this case. The polynomial will evaluate to k+2. In the case that k+2 is not prime, there is no set a, b, ..., z that yields a positive value for the polynomial.
  6. D H

    Probability

    Sure it is. Use Bayes' Law. Those prior winning percentages are the prior probabilities you need to apply that law. Wikipedia link: http://en.wikipedia.org/wiki/Bayes'_theorem.
  7. Moved to pseudoscience. The forces involved are not obeying the strong form of Newton's third law, so of course angular momentum is not conserved. Edit In addition, you are not considering the angular momentum due to translation.
  8. Google the term "telescope array". Let me do that for you: http://lmgtfy.com/?q=telescope+array.
  9. Herman, the only solid wall here is you. You have been given ample evidence that we did land on the Moon, including some Russian sites. You have been given ample evidence that the only fraud being committed is that committed by those who claim we did not land on the Moon. Can we lock this thread, please?
  10. The only nonsense and rubbish is that coming from you and dichotomy, hermantc007. You are the one who needs to think and calm down. Think about how massive the conspiracy would need to be, if it were true, in terms of people, technology, and money. Think about why, if the conspiracy were true, NASA added significant risk of exposure by carrying out two manned missions prior to Apollo 11 that went around the Moon but not down to the surface of the Moon and six additional Apollo missions after Apollo 11, all but one of which did go down to the surface of the Moon. Think about the the retroreflectors that were left on the Moon and the rocks that were brought back from the Moon. Think of all of the people outside the US who tracked the missions and listened to the voice loops. In short, THINK.
  11. Your little interior scientist does not know how to do a search for scientific articles. Just a smattering: http://www.sciencemag.org/cgi/content/abstract/171/3968/282 http://www.sciencemag.org/cgi/content/abstract/175/4020/363 http://www.sciencemag.org/cgi/content/citation/182/4113/681 that is bulll shit...............because i think that debates are very useful StringJunky is spot on here. These "debates" are pretty much worthless for the simple reason that there is no debate. We went to the Moon. dichotomy and hemantc007: You are the ones making the elaborate claims. The burden of proof lies on you to prove your claims, not us to disprove them.
  12. You are ignoring inflation.
  13. I am hopeful that your tongue is firmly implanted in your cheek. We don't accept posts 911 wackiness, period, and posts claiming evolution to be false are closed rather quickly. The fact is there is no arguing with kooks who believe the moon landing never happened or that 911 was a government conspiracy. They are immune to logic and evidence.
  14. You are wrong. We went to the Moon. To quote Bascule, ============= Count me in. Almost. I have a slightly more aggressive idea: Anyone who posts a "we didn't go to the moon" type message gets banned immediately.
  15. The latter statement is correct. The first is not. The Russians did have the capability to track the Apollo missions. They needed this capability for their own Lunik (Luna) program. The Russians were the first to place an object on the Moon (Lunik 2, 1959; crash landed); the first to photograph the far side of the Moon (Lunik 3, 1959; the Lunik program is why the craters on the far side of the Moon have Russian names); the first to achieve a soft landing on the Moon (Lunik 9, 1966). Not only did the Russians have the requisite capability, they used it on the Apollo missions. http://www.novosti-kosmonavtiki.ru/content/numbers/271/03.shtml Babelfish translation: http://babelfish.yahoo.com/translate_url?tt=url&intl=1&fr=bf-home&trurl=http%3A%2F%2Fwww.novosti-kosmonavtiki.ru%2Fcontent%2Fnumbers%2F271%2F03.shtml&lp=ru_en&btnTrUrl=Translate Google translation: http://translate.google.com/translate?u=http%3A%2F%2Fwww.novosti-kosmonavtiki.ru%2Fcontent%2Fnumbers%2F271%2F03.shtml&sl=ru&tl=en The directions from on high to build an Apollo monitoring capability (Russian): Советское руководство уделяло большое внимание состоянию дел с реализацией лунной программы как в Советском Союзе, так и в Америке. Для объективного контроля за выполнением американской программы секретарь ЦК КПСС Д.Ф.Устинов, курировавший оборонную промышленность страны, в конце 1967 г. дал поручение главному конструктору РНИИ КП (в то время НИИ-885) М.С.Рязанскому разработать специальный контрольный радиотехнический комплекс, с помощью которого можно было бы принимать сигналы с американских космических кораблей программы «Аполлон», совершавших облет Луны и посадку на ее поверхность. Babelfish translation: Soviet management paid considerable attention to the state of the matters concerning the implementation of lunar program both in the Soviet Union and in America. For the objective control of the execution of American program the secretary of the CC CPSU [D].[F].[ustinov], that treated the defense industry of the country, at the end 1967 g. gave commission to the chief designer of RNII (Scientific Research Institute of Jet Propulsion) KP (at that time NII-885) [M]..[Ryazanskomu] to develop the special control radio-technical complex, with the aid of which it would be possible to assume signals from the American spacecraft of the program “of Apollo”, which accomplished flight around the moon and landing on its surface. When they used this capability (Russian): Слежение велось за космическими кораблями экспедиций «Аполлон-8», «Аполлон-10», «Аполлон-11» и «Аполлон-12» с декабря 1968 г. по ноябрь 1969 г. Со всех этих кораблей принимались с хорошим качеством телефонные переговоры астронавтов с Землей и телеметрическая информация о состоянии бортовых систем. Принимаемый телевизионный сигнал имел низкое качество из-за недостаточного уровня энергетического потенциала радиолинии на базе 32-метровой антенны. Babelfish translation: Tracking was conducted after the spacecraft of expeditions “Apollo-8”, “Apollo-10”, “Apollo-11” and “Apollo-12” since December 1968. until November 1969. From all these ships the telephone negotiations of astronauts with the Earth and telemetry data about the state of onboard systems started with a good quality. TV the signal adopted had low quality because of the insufficient level of the energy potential of radio link on the base of 32- meter antenna.
  16. The same problem appeared for me but then magically disappeared.
  17. Yes. You can only legally wake people up while they are not sleeping. In short, ask a stupid question, get a smartass answer.
  18. D H

    logic problem

    That is the question. There are four cases: The hamburger is poisoned or safe to eat; you ask the liar or truth teller. 1. Poison, liar. The other guard tells the truth: the hamburger is poisoned. The one you asked will say it is safe. 2. Poison, truth teller. The other guard will lie, saying the hamburger is safe. The one you asked will report this honestly (safe). 3. Safe, liar. The other guard will say it is safe. The one you asked will say it is poisoned. 4. Safe, truth teller. The other guard will say it is poisoned. The one you asked will say it is poisoned. So, ask a guard whether the other guard will say the hamburger is safe or poisoned. Eat the hamburger if the answer is poisoned. Do not touch it if the answer is safe.
  19. D H

    logic problem

    There's only one hamburger, but you are on the right track. Edit dr432, he didn't answer your original question!
  20. By way of analogy, think of a busy, but not overcrowded, freeway. Suppose some car changes lanes where it shouldn't. Drivers of the immediately adjacent cars will have to brake hard to avoid a collision. Drivers of nearby cars will have to brake because of the actions of those adjacent cars. The traffic slows down in the vicinity of this near accident. These slowdowns can persist for a long time if the freeway is busy. Many other factors such as busy interchanges, curves in the road, and changes in the number of lanes also cause areas where traffic slows down. The car density, the number of cars per unit freeway length, will be higher than average at these areas of congested traffic. In other words, congestion spots are density waves. Density waves caused by obstructions are stationary. Those caused by near-collisions can move, but at a different rate than the traffic. Regardless of whether these density waves are stationary or moving, the cars move through them. Now think of the galaxy as a rather large freeway. The stars are cars moving on this big freeway. The spiral arms are congestion areas, or density waves. Google "density wave theory" to read more on this topic.
  21. What edge of the universe?
  22. The human eye has a limited dynamic range. The iris adjusts to let in enough light to see but not so much that it is blinding. (This doesn't work when you walk from bright sunlight to a dark room, or vice-versa.) The rods and cones also adapt, and rather slowly. When you step outside to look at the stars, your need twenty minutes or so to fully adapt to the darkness. From the Apollo 17 post-landing debrief, http://history.nasa.gov/alsj/a17/a17.postland.html Cernan - "When you were in the lunar module, looking out the window, you certainly couldn't see stars. Using the telescope was sort of like being in a deep well; it cut out all the reflected light and let you see the stars. It was also generally true that, when you were on the surface in the LM's shadow, there were too many bright things in your field-of-view for the stars to be visible. But I remember that I wanted to see whether I could see stars, and there were times out on the surface when I found that, if you allowed yourself to just focus and maybe even just shielded your eyes to some degree, even outside the LM shadow you could see stars in the sky. And, quite frankly, under the right conditions here on Earth on a bright sunlit day, you can do the same thing. I could see stars through my helmet visor; not easily, but it can be done."
  23. The speed of light is finite. The light we see now coming from Proxima Centauri was emitted 4.2 years ago. The light we see now from the Andromeda galaxy was emitted 2.5 million years ago. We are seeing further and further into the past as our telescopes gaze ever further into the universe.
  24. Is it possible to get an advanced degree that is not directly related to your Bachelor's? Sure. http://en.wikipedia.org/wiki/Michael_D._Griffin#Education As a MechE you may well have a better understanding of Newtonian mechanics than do those physics grads. That's because education in physics is more concerned with quantum physics than Newtonian mechanics. To switch from mechanical engineering to physics you will need to take some upper level undergraduate physics classes to meet the requirements for admission into a graduate level physics program.
  25. I changed Sisyphus' emphasis. Neither solar sails nor ion drives are anywhere close to being in our "current stable of technologies", particularly with respect to accelerating a massive vehicle at a constant acceleration of 0.1g for several weeks. The Wiki article on Mars colonization has undergone a lot of editing since Sisyphus' post. The article currently reads "Both of these are currently feasible" rather than "Both of these are in our current stable of techniques". Solar sails remain purely in the realm of science fiction. Ion propulsion has been used on small vehicles. SMART-1, which massed all of 367 kg, used a Hall effect thruster to accelerate at just under 0.00002 g. SMART-1 was launched on September 27, 2003 and achieved lunar orbit on November 15, 2004. Not exactly speedy.
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