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Showing content with the highest reputation on 08/20/19 in all areas

  1. Unless you are a stage magician!
    1 point
  2. The numbers may work in this case but consider this. The Hubble constant is only constant at a point in time. In the past it is much higher. Where as the zero point energy calculations don't vary. So although you see similarities for Hubble parameter value today you may not get the same relations at an earlier time period. I would recommend you try a few different time periods and see...
    1 point
  3. I recall from many years ago similar projects being discussed. My recollection is that there were no structural issues-- but there were efficiency issues. Solar power already evaporates water for the entire surface of the ocean and delivers it to land in the form of precipitation. This, of course, is of limited efficiency because some of the precipitations falls on the oceans, or in places it cannot be efficiently used. However, since floating desalination systems detract from the natural evaporation, they would have to be correspondingly more efficient to make a net benefit. The challenge is in making the floating system, and the energy required to retrieve the water thus produced, sufficiently efficient to make it financially superior to capturing the natural precipitation.
    1 point
  4. Simple - Yes and no. I think. We know its got an arrow, we know it „bends” along with space under conditions which implies its got „interactive features” which further might imply that time is a thing. But that does not have to be true... just like space is volume, time might just be analogous to volume. On the other hand, we don’t even know if time had a beginning and it might not be a valid question whether there was a beginning to the Universe because conditions at t=0 were so much different from what we see now. Most theorerical physicists agree that GR has to be eventually complemented by a fuller theory and not just because we need to marry gravity under QM and GR but more fundamentally, we don’t know what gravity and spacetime fundametally is. It is pretty obvious (at least to my lame, amateur mind) that what we define as gravity is just a „leak” of something more fundamental, maybe time and the concepts of beginning/before/after are a part of something larger too on the cosmic scales. One thing we can be sure of, our gut is a bad adviser due to our evolutionary handicap of living is our small Earth bubble. There hasnt been a revolution in my lifetime in physics, I hope the next ~30 years will erect one so I can witness it
    1 point
  5. I developed one such machine, but it was a quarter century ago, so they can have evolved in a completely different direction meanwhile. This automatic cashier could read a barcode, let the customer pay with a bank card, and deactivate the anti-theft stripe, optionally reactivate it. The anti-theft stripe is covered with permanent magnets which, after they're made, deactivate the stripe by saturating it, so the detectors at the store's exit don't notice the stripe. The magnets are chosen weak, but it still takes a good magnetic field to make them, and at some distance through the air. This demands a strong current in the deactivating coils, which I obtained over a short time by capacitor discharge. The combination of significant field, strong current and short time creates a mechanical shock that is noisy. It could be reduced by making the coils stiffer and suspending them separately from all surfaces. I didn't care at that time, possibly nobody did meanwhile. In a different experiment, I had 350V and 20kA in several turns that created 7T, and this one was much more noisy. Even the feed cables had to be hold on the table or they would jump away from the other. The friend how did that regularly told me that once a connection screw wasn't tied, it just vaporized when the current passed, and he stays deaf for a day.
    1 point
  6. No, scientists remain unsure whether gravity can be quantised or not.
    1 point
  7. They haven't yet been able to work out how to quantify gravity into a discrete unit, like photons, which is necessary to define it as a particle. That's why gravitons are still theoretical.
    1 point
  8. For a brick, the unequivocal answer is NO! [math]{a_{c1}} = \frac{{\left[ {{m_1}{{\ddot r}_1}} \right]}}{{{m_1}}} = {{\ddot r}_1} = 0[/math] if [math]{{\vec F}^e} = 0[/math] For the CM system of bodies, the answer is YES! Acceleration of the Center of Mass is not a function of "external force." [math]{a_c} = \frac{{{d^2}{R_c}}}{{d{t^2}}} = \frac{{\sum {{m_i}{{\ddot r}_i}} }}{{\sum {{m_i}} }} + \frac{{\sum {{{\dot m}_i}{{\dot r}_i}} }}{{\sum {{m_i}} }} = ?[/math] if [math]{{\vec F}^e} = 0[/math] The acceleration of the CM of the system of bodies is the result of both external and internal forces. But the most interesting is another! The CM of a system of bodies can change without acceleration at all! You talk about CM, having in your head the concepts of "force", "acceleration", "velocity" [math]{{\vec R}_c}(t) = {{\vec R}_c}(0) + {{\vec V}_c}(t)t + \frac{1}{2}\frac{{{{\vec F}^e}}}{M}{t^2}[/math] But the CM "moves" like this: [math]{{\vec R}_c}(t) = \frac{{\sum {{m_i}(t){r_i}(t)} }}{{\sum {{m_i}} (t)}}[/math] The CM cannot move! CM is not a material object! A CM can only CHANGE how the result of a function of 2 (two) variables changes. I also have the right to ask you questions. Do you see the CM of this system? Do you see how he moves? === The Varipend task is not mathematically complicated and has a very accessible explanation from a physical point of view, which does not go beyond the school textbook. but this task is extremely difficult in terms of psychology. Therefore, I must ask you questions so that you LEARN to answer them YOURSELF.
    -1 points
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