Recent content by bobob

  1. B

    Physics forums and anonymity

    Yes and it's quite annoying that the government cannot manage to secure that information.
  2. B

    Physics forums and anonymity

    That's true, but we don't live in a perfect world, so there is no perfect solution. However, given that connecting the dots can lead to people being denied health insurance, jobs, housing, etc., one has to decide what is a priority. Also, just because a name looks like a real name does not mean...
  3. B

    B Why is it assumed communication through entanglement would be FTL?

    Define a "preferred frame" that is consistent with relativity. The only definition of "preferred" that makes sense is one in which the measured values are some "true values" to which other frames can be referenced and not lead to contradictions.
  4. B

    B Why is it assumed communication through entanglement would be FTL?

    I disagree. There is no sensible definition of "preferred" that would be self-consistent.
  5. B

    B Why is it assumed communication through entanglement would be FTL?

    But that cannot be correct. The measurements are spacelike separated, so they are made simultaneously. Neither measurement can occur "before" the other and create a cause and effect relationship because they cannot be time ordered. You would have to reject relativity. Apparently, what people...
  6. B

    B Why is it assumed communication through entanglement would be FTL?

    Relativity tells you that the events (sender and receiver) are spacelike seperated and therefore cannot be time ordered. That means there are some frames in which the assumed receiver gets the message before it is sent.
  7. B

    Light testing for leaks in a thin metallic membrane

    The op did not ask about locating the holes or cracks. The op only asked about finding out whether or not there was one.
  8. B

    Physics forums and anonymity

    Another argument for annonymity is that if you use your real name ANYWHERE, you may unintentionally end up with no privacy more places than just here. It's not so much that using one's real name here is a problem if it happened in isolation, but the possibility of using that information to play...
  9. B

    Light testing for leaks in a thin metallic membrane

    Well, since a phototube can count photons at the single photon level. I'm not sure how much more accurate you could get. Those are used in spectrophotometers. They are sensitive enough that if there is enough light for you to see, it's way to bright for a photoutbe. Light through a pinhole...
  10. B

    7.2 cubic metres of Nitrogen compressed, will last 30mins-1hr of usage

    If you are going to fill lots of tires, you would be better off using a liquid nitrogen dewer. Those have gas phase valves that allow you to take warm gas out. Since nitrogen goes from liquid to vapor at an expansion ratio of a little over 600:1, you can pack a lot of gas into an LM2 dewer...
  11. B

    Light testing for leaks in a thin metallic membrane

    A photomultiplier tube is off the shelf and you can count photons with it. There are also avalanche photodiodes available off the shelf. You don't need complicated intruments to look for light leaks. All that's required is the phototube (or avalanche photodiode), a power supply and an oscilloscope.
  12. B

    Light testing for leaks in a thin metallic membrane

    You might try a photomultiplier tube.
  13. B

    A Interpretation of Bi-207 decay spectrum

    Gammas from the decay of the 207Pb excited states. Look up the level schemes.
  14. B

    High current power supply for servos? 40+ amps

    Find used sorenson power supply. They make lots of supplies that will fit your needs. Try ebay, but watch out for shipping costs.
Top