Jump to content


Senior Members
  • Posts

  • Joined

  • Last visited

  • Days Won


Everything posted by Carrock

  1. 'which way the conventional current flows through the capacitor' As (ideal) capacitors don't pass direct direct current the answer is ( at different times ) left to right, right to left and there is no current at all. 'ie which direction is the direction of conventional current around loopABCD' As current (and its direction and phase) varies around the loop (it may or may not change direction through CD) I can't answer this question or understand how it is the same as asking 'which way the conventional current flows through the capacitor' 'Now reverse the power supply to the resistor chain, as in fig2 and answer the same question.' After transients have become negligible the answer is as above. Was this a trick question?
  2. from http://www.mi.mun.ca/users/cchaulk/eltk1100/ivse/ivse.htm etc Where the charge carriers are electrons, this is only true if the electrons are defined as having negative charge ie the conventions aren't independent.
  3. from http://en.wikipedia.org/wiki/Landauer's_principle: Perhaps the EU is concerned more with improving efficiency rather than reducing computer speed. My current computer is only only able to consume twice as power as my first one but it runs about 1000 times faster....
  4. Carrock


    This argument is often used by the nuclear industry. In any other context, body repair mechanisms are regarded as a means of minimizing and sometimes preventing long term damage. In other words, if low level radiation causes no harm, why do repair mechanisms try to minimize its effects?
  5. Something wrong here. If ( as he can ) David can determine the pH then there are 3 answers to the question, not just B. (posted before I saw studiot's Response.)
  6. All that's really needed for a counterargument is the title..... The End of Pascal's Wager: Only Nontheists Go to Heaven at http://infidels.org/library/modern/richard_carrier/heaven.html
  7. I recall reading a long time ago that beekeepers rarely get arthritis. There are a lot of dubious claims but this seems pretty definitive: ( ref http://www.ncbi.nlm.nih.gov/pubmed/18807725 )
  8. So failing to see something unexpected once somehow virtually guarantees that person will in future see any repetition?
  9. First claim I've ever seen that a "a suite of scientific instruments powered by a warm battery containing 8.5lb of pure plutonium" in the LM descent stage helped the astronauts. Not up to the BBC's usual standard.
  10. In jaydnul's post of 4 September 2014 - 10:29 PM he attempted to refute a double slit experiment referred to by IM Egdall on 04 Sept 2014 - 9:32 PM by referring to ( I presume ) Feynman's comments on a single slit experiment. As there was no reference in jaydnul's post to either single slit or double slit or Feynman, I assumed he was referring only to the double slit experiment. In this experiment, it's only possible to know the momentum and position if you know which slit the electron passed through etc and according to Feynman et al you can do that or have the two slit interference pattern. As he only referred to 'the experiment' in this post, I think it is unreasonable for jaydnul to criticise me for not having guessed 'the experiment' referred to two different experiments. It would be helpful in this topic if posters made clear which experiment(s) they're referring to.
  11. You can't find the position and the momentum the electron needed to get there. ( eg you would break time symmetry ) An alternative rather simplistic view, without doing the maths.... If you want to find the position of the electron very accurately, detect it with a very short wavelength photon ( gamma ray ). The accuracy, and the energy of the photon, increases as you shorten the wavelength. As you've hit the electron very hard, you don't have much idea of the electron's momentum before the detection event. If you want to know the electron's momentum accurately, detect it with a very long wavelength low energy photon. You can't measure its position to much better than a wavelength. An example of a minimal observation:- in double slit diffraction set up minimally interacting detectors to see which slit each electron goes through without stopping them. Whether or not you look at the detectors' output, you will find the interference pattern has disappeared. There are lots of apparent getouts, many of them suggested by Einstein in thought experiments. They all failed. His nearest success was the EPR paradox; if QM is valid then eg a photon leaving the sun 'knows' what angle your polaroid sunglasses will be at when it hits them eight minutes later. Photons always get it right.
  12. My first thought .... Seems like a Wankel engine to me. In http://www.gizmag.com/duke-engines-axial/33631/
  13. The ESA paper does not describe that or alternative optical focussing. As there is a laser at each star power from each laser is only required for half the distance. Any calculation of power etc would require an enormous number of assumptions and a few billion/trillion dollars to verify them. There may be a few billion dollars' worth of relevant classified "Star Wars" research. Which part of "With a lot of work ....." did you not understand? This is my last post in this topic.
  14. One of the things I've always liked about U.S. patent law it that it doesn't refuse to accept perpetual motion machine patents. A working machine is required though. I generally accept authoritative pronouncements on the laws of physics until someone more impressive comes along.
  15. A lot of proof of concept work has been done on this eg http://www.esa.int/gsp/ACT/doc/POW/ACT-RPR-NRG-2009-SPS-ICSOS-concepts-for-laser-WPT.pdf and http://www.academia.edu/4135938/Laser_Starways_light_bridges_to_the_closest_stars
  16. With a lot of work ..... The power would depend on how much acceleration the passengers wanted. And of course I'd have to guess the minimum practical mass per unit area of the sail to see how big it could be. It couldn't usefully mass more than about half the payload. With onboard fuel, you first have to accelerate all the deceleration fuel up to maximum speed.
  17. High energy lasers focussed over interstellar distances on a spacecraft's light sail to accelerate it are a reasonable extrapolation of current technology. With one at each end of the journey efficiency would be much better than any onboard fuel.
  18. I wasn't really demanding evidence, just trying to make a point about the limitations of knowledge without getting too serious. I've thought better of claiming that there is no evidence that anyone in government has ever committed an undetected crime.
  19. Indeed. There is no evidence that any government has ever succeeded in keeping anything completely secret.
  20. Your post explains everything except why they bothered to come. Perhaps they are much like juveniles throwing stones at a hornets nest. If we succeed in stinging them their parents will come along and humanely destroy the nest.
  21. Sorry - I meant to say isospin monatomic hydrogen, where the atoms don't combine into dihydrogen unless a few atoms' spins are flipped. The energy of reaction is enough to flip more spins for a runaway reaction. I believe there is at least a 0.01% probabilty of this fuel being used in the next hundred years.
  22. It's possible that most ETs have calculated that sending out, say, a terawatt of 'I am here' signals for a million years would give them a 50% chance of contacting one other ET civilisation. They may not be advanced enough to take the long view.
  23. Spin polarized monatomic hydrogen has been the rocket fuel of the future since at least the 1950s. I don't know the specific impulse but it is pretty high. It's nowhere near as easy to handle as nitroglycerine and it requires a liquid helium plated fuel tank as it reacts explosively with anything else. There are a few more similarly trivial problems to overcome before it comes into use.
  24. There's actually a lot of practical value on the moon. There's water that can be electrolysed for rocket fuel and at least most of what you'd need to manufacture spacecraft. Only about 3% or less of the energy required to launch an interplanetary spacecraft from earth is required to launch it from the moon. You could even build a linear accelerator to launch spacecraft using only electric power from ( a large number of ) solar panels. Of course all this would require an enormous investment before there was any payback. Science fiction would be pretty dull if authors ran their ideas past an economist.....
  25. It's not at all clear how long inflation continued ( perhaps far longer than the minimum required to fit observations ), but at the end of inflation the (now) observable universe was certainly very small. However it seems likely a much larger volume at that time was very similar to what we can see - no edge effects have been detected. It could easily have been more than 30 billion light years in diameter back then. Enough to qualify as a big bang?
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.