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Showing content with the highest reputation on 09/19/19 in all areas

  1. 1 point
    Below the radar ,but with reassurances that steps are being taken to protact the democratic process. To date this reassurance seems to be missing .Can you reassure me?
  2. 1 point
    Probably wind, but who could deny that smile???
  3. 1 point
    Good article on everything we know and don’t know about dark matter here: https://www.forbes.com/sites/startswithabang/2019/09/19/was-dark-matter-really-created-before-the-big-bang/
  4. 1 point
    The thing to keep in mind is unlike say a pressure tank, a battery or a capacitor where energy can be stored and power is transferred at a rate to perform work on some external to the storage device the universe doesn't perform work outside of itself. All the energy is contained within our universe, there is no transfer of heat, energy or mass from outside our universe from inside to outside our universe. Our universe is in essence an isolated system (speaking thermodynamically) an isolated system cannot perform work outside of itself. To put it bluntly in every paper, textbook, article I have ever read on cosmology and the FLRW metric in terms of the universe not once have I ever encountered any usage of power density or even power being involved in any model of the universe I have ever read in 35 years.
  5. 1 point
    I'm not so sure it will end in 2020. If the Democrats can't stop fragmenting and come together behind a viable candidate, we might be stuck with a second term of D Trump. But, say the Chinese have had enough of D Trump's meddling with their economy and exports to their biggest market, and they decide to use Russian strategy and interfere in the election to ensure a Democrat win ( so that things go back to normal ). Would you say the Republicans got what they deserved, or would you want an investigation into possible Democrat 'collusion' ?
  6. 1 point
    I know the following will probably confuse you if you haven't studies thermodynamics but here goes First law of thermodynamics expressed for an adiabatic ( no net inflow or outflow of energy or enthalpy) [math]0=dQ=dU=dU+PdV[/math] Q is total heat assumed to be constant, U is internal energy of matter and radiation in the universe, P is pressure, V is the volume. One finds energy density via [math]u=\frac{U}{V}[/math] and thus [math]du=d(\frac{U}{V})=\frac{dU}{V}-U\frac{dV}{V^2}=-(p+u)\frac{dV}{V}=-3(p+u)\frac{da}{a}[/math] if you divide this equation by [math]d\tau[/math] you get the equations of motion for the FLRW metric [math]u=\rho[/math] now for radiation [math]du=-4u\frac{da}{a}[/math] thus u is proportional to [math]a^{-4}[/math] for matter [math]du=-3\frac{da}{a}[/math] thus u is proportional to [math]a^{-3}[/math] now in both these cases as the universe expands the temperature decreases now for the cosmological constant we need to employ a time derivative [math]\dot{u}=-3(p+u)\frac{\dot{a}}{a}[/math] now a consequence is that the more negative the pressure becomes the less the energy density decreases as the universe expands however energy is created as the universe expands by Lambda so its pressure is minus its energy density p=-u or [math]p=-\rho[/math] the total heat is constant in all the above so there is no power in terms of work/time in terms of the FLRW metric power density is never used as there is no transfer of heat outside of our system defined by adiabatic expansion. https://en.wikipedia.org/wiki/Adiabatic_process this gets complicated in terms of reversibility and a further problem of isentropic processes the work must be performed outside our system which doesn't make sense when discussing the universe when our system is the universe volume. There is no outside of the universe for a transfer of work to occur. So how would you define power in this instance ?
  7. 1 point
    Congrats she is a cutie
  8. 1 point
    First of all, you have to consider what happens when you "bump into" everyday matter. The interaction between you and that matter is all done via electromagnetic fields. The electromagnetic fields in the matter interact with the electromagnetic fields of the matter which you are made of. So the "solidness" any object is just due to this electromagnetic interaction. This electromagnetic interaction is also responsible for the objects interaction with light or any other frequency of the electromagnetic spectrum. They are reason they glow when hot or absorb, reflect, or scatter electromagnetic radiation. Dark matter, by its very nature, does not interact with light in this manner. It is completely lacking in electromagnetic interaction ( like the aforementioned neutrino). Thus it also would not participate in the type of "bumping into" interaction everyday matter does, and thus passes right through you pretty much like you weren't there.
  9. 1 point
    [math]\dot{a}[/math] is velocity of the scale factor [math]\ddot{a}[/math] is acceleration of scale factor An interesting equation using time derivatives [math]\dot{H}=\frac{\ddot{a}}{\dot{a}}[/math] shows that even though the Hubble parameter is decelerating ie slowing down the scale factor is accelerating. On the repulsive gravity (lol a very inaccurate descriptive but some literature uses the term) I personally think it's misleading as one might think anti gravity which is wrong. You can have a force term due to the negative vacuum term w=-1 but you cannot treat it from a centre or an average direction. Every location of spacetime the vector will be in every direction. Ie space expanding. Under that condition the usage of the term Planck force could apply for each discrete quantization of spacetime. The result will be the number of Planck length units will be increasing as space expands.
  10. 1 point
    Well the good news is you can find classical treatments for the equations of state. https://www.google.com/url?sa=t&source=web&rct=j&url=http://www.astronomy.ohio-state.edu/~dhw/A5682/notes4.pdf&ved=2ahUKEwjljPSGl9LkAhVOqp4KHbb8DtwQFjAQegQICRAB&usg=AOvVaw0xjZcR1b8OcNFbrriXGEr2 Here is one that keeps it in a Newtonian fashion By the way I rewarded you some reputation points as your diligent in following proper physics in your modelling and constantly striving to learn as you go. It's a rare pleasure finding a thread in speculations forum where the OP is interested in learning how to properly model as well as expanding his skill set in physics. Your skills have improved immensely since you first joined this forum well done
  11. 1 point
    The warm seeas, above 13c, have thermoclines, which is an intermediate temperature layer that prevents the nutrient-laden deeper water mixing with the upper layer where the photosynthetic marine life is. https://oceanservice.noaa.gov/facts/thermocline.html
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