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swansont last won the day on January 17

swansont had the most liked content!

About swansont

  • Birthday May 12

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    Washington DC region
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    Geocaching, cartooning
  • College Major/Degree
    PhD Atomic Physics Oregon State University
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  • Evil Liar (or so I'm told)

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  1. ! Moderator Note Further, you posted something similar before and the thread was closed. You don't get to dump it on us again
  2. Light definitely has a velocity (we can measure the propagation time over some distance) and can impart an impulse since it has momentum. So saying no force is involved is incorrect.
  3. There are a number of videos that show if you toss a ball vertically on a moving platform, it comes back down to the point of origin on the cart. such as So insisting that the ball would come straight down when the cart is moving is a non-starter; we can see that the ball doesn’t do this. The ball travels a greater distance in the lab frame than in the cart’s frame. The wrinkle for the light clock is the restriction that the speed of light is the same in both frames. d = ct. Since d is greater and c is the same, t must be greater
  4. I’m not agreeing. Are you agreeing that the path lengths are different?
  5. The speed along the vertical axis is the same in both frames. The analogy is meant to show the difference in path that you are denying.
  6. Another method us to use light (from a flash lamp or LEDs) to excite atoms from the ground state (0) to some state (3), which then decays to another state (2), which then has a population inversion with respect to a lower state (1) E3>E2>E1>E0 incoming light has energy E3-E0, laser transition has energy E2-E1 The transition from 3 to 2 can be non-radiative The transition from 1 to 0 (or some other intermediate state) is usually strong, so the in little population in 1, allowing N2>N1, which is what an inversion is (N is the population of the state)
  7. The engine’s energy source is the hot reservoir. How you get it to be hot is not included in the analysis. The hot reservoir heats up the gas. That’s the QH. The gas heats up the cold reservoir. Qc
  8. No. We can all agree on the speed. Your error was in the duration A better analogy would be tossing/dropping a ball while on a train. To someone on the train it goes straight down. To someone on the ground, it does not.
  9. It’s an energy analysis, not a force analysis. You can do this in mechanics, too. You use the tools that get you to the answer. An object falls; you can say it’s because of a force, but also say it’s because things go to their lowest potential energy. Heat is the flow of energy. No, it doesn’t. QH is not equal to Qc Nobody is claiming it’s an outside force. The gas at the end is colder than the gas before the piston moves. The cold reservoir heats up. If you disagree, then where does the energy come from that appears as mechanical work? All of it has been removed? The gas is at absolute zero?
  10. The neutrons would have to be from fission, which isn’t happening very often, and there isn’t much heavy water.
  11. I’m not sure how tritium would be formed from fuel rods in a cooling pool. I think the concern would be damage to the control rods and contamination by fission products.
  12. Why is this the expected amount? Citation? Looks to me like it’s just over 100 ppm https://www.co2levels.org Citation? My understanding is that it’s a logarithmic dependence, and you get a certain increase for each doubling of concentration. Can you explain why you think this is a valid test?
  13. No, they aren’t. They tend to be in the ground state. And you can’t use photons of the laser’s wavelength to get the excess atoms in the excited state (the population inversion), because of the stimulated emission. So you have to use some other method. In a HeNe laser, an electric discharge excites the He, and collisions with Ne causes Ne excitations. You have more atoms in an excited state than a lower state, so stimulated emission can give you amplification. In diode lasers, there is an electronic excitation of the electrons to a higher band.
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