Jump to content

Lorentz Jr

Senior Members
  • Posts

    515
  • Joined

  • Days Won

    6

Everything posted by Lorentz Jr

  1. Articles on space.com: December 09, 2022 November 17, 2022
  2. Short answer: because it's math. As long as you can specify a limit of a range, you can define a range that's "open" at that end, meaning the number is excluded. Longer answer: because the density of real numbers is infinite. There's nothing special about 2. You can use any real number to terminate a range of real numbers, and you can make the limits of the range any combination you like of open (excluded) or closed (included), but there is no "next" number immediately before or after the limits. You can also exclude a number between the limits of the range, but that breaks the range into two ranges, because there's always an infinite number of other reals between any two given reals. Not much of a gap between them, of course, but that doesn't always matter in mathematics.
  3. If you study macroeconomics for a while, you'll learn that there's no reason for wages to be coupled to productivity. Just the opposite, in fact. When all workers become more productive, the result is a productivity glut, which inevitably leads to layoffs and downward pressure on (real) wages. The whole argument for wages increasing with productivity is a combination of political moralizing and a naïve application of microeconomic reasoning.
  4. Okay, that's great. Except Genady suggested the exact opposite of that: Get it? He sees a problem with a geologist believing that Earth is 5 thousand years old. That means he agrees with you: scientifically, it's not rational for a geologist to believe the earth that old.
  5. This is all WAY over my head, but have you ever tried using geometric algebra? It's supposed to be simpler and more versatile. Geometric Algebra Techniques for General Relativity GRAVITY, GAUGE THEORIES AND GEOMETRIC ALGEBRA Geometric Calculus in Gravity Theory Geometric Algebra, Spacetime Physics and Gravitation
  6. Atmospheric forces on the exhaust gasses can get complicated. https://www.brainkart.com/article/Back-pressure-and-optimal-expansion-at-the-end-of-the-Rocket-nozzle_5114/
  7. Fext is the external force on the rocket, including unburnt fuel. Exhaust gasses aren't part of the system. Yep. [math]\displaystyle{ \Delta v = -v_e \ln\left(1 - \frac{r_m}{m_0}\Delta t\right) = v_e \ln\left( \frac{m_0}{m_0 - r_m\Delta t}\right) }[/math] For constant [math]r_m \equiv -dm/dt[/math] in a vacuum.
  8. If the rocket ejects a mass dm at speed ve in a time dt, the acceleration of the mass is a = ve/dt. So the force acting on it is F = ma = dm(ve/dt) = ve(dm/dt). In the rocket's reference frame, that's also dpgas/dt.
  9. Okay. So you're another one of those senior posters I need to avoid getting into arguments with or I'll get into trouble. Thanks for clearing that up. 🙂
  10. I feel like I'm scraping the barrel just by getting into this conversation.
  11. I don't think Genady can time travel. You posted your comment "why would a geologist believe the Earth is 5 thousand years old?" after his comment, so it doesn't count as context. There's also the problem that "why would a geologist believe the Earth is 5 thousand years old?" doesn't count as disagreement with the comment "I see a problem with a geologist believing that Earth is 5 thousand years old."
  12. I'm sorry, could you please explain the logic behind your comments here? I'm having trouble following it.
  13. Explaining relativity: 8 pages. Explaining Newtonian mechanics: 9 pages and counting. 😂
  14. Or they could just make a robot that disassembles itself mechanically and then reassembles the parts. I guess they like T2 more than Iron Man. 🙄
  15. The photo caption calls the species "elusive" and "critically endangered". "an unusual kind of fish ... The spotted handfish" "the spotted handfish, and its even more critically endangered relatives, the red handfish and Ziebell’s handfish" The article says the species is rare, and it says those two other handfish species are even rarer, but it doesn't explicitly say anything about handfishes in general.
  16. Blaise Pascal rejected math and physics in favor of religion later in his career. Georges Lemaître was a physicist and a Catholic priest. John Polkinghorne was a physicist and an Anglican priest.
  17. It doesn't need to be sold elsewhere. Loss of support for public debt is the best thing that could happen to American workers. A little competitive devaluation, more exports, fewer imports, more jobs. The only real question is why the trade and currency imbalances have been normalized for so long that people think restoring the balance would be a problem.
  18. Noisy inputs are what we were discussing earlier: input signals with too much noise in them. Noisy outputs are neural output signals with noise in them, i.e. what you would get from the neuron with not enough averaging. Apparently, noisy neurons create their own noise and this is necessary for learning: https://news.stanford.edu/2015/03/18/decisions-noisy-neurons-031815/
  19. The state of a neuron is its output value, and the state of the network is the set of all its neurons' states.
  20. It means something like "out of sync with". Meaning the time isn't synchronized with the Sun in the usual way, with AM in the morning and PM in the evening.
×
×
  • 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.