J.C.MacSwell

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About J.C.MacSwell

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  1. Rotation - is it absolute?

    I am getting at " can any inertial frame rotate with respect to any other inertial frame?". If the answer is no, then I would say (under the right set of assumptions, those I think implied in the OP) that rotation is absolute. But if any inertial frames can rotate wrt any other inertial frames then it is less clear, unless there is a set of inertial frames that is preferred (with respect to rotation, not absolute motion)
  2. Rotation - is it absolute?

    Here is my thinking: If something is rotating it is rotating with respect to an inertial frame. If something somewhere else is rotating it is also rotating with respect to an inertial frame. These frames may be moving with respect to each other, but if they are also rotating with respect to each other then at least one of those rotations can not be considered absolute...but which one? ...so if ("if" is the key to the question, if this is known to be impossible the point is moot) any inertial frames can rotate with respect to each other then (perhaps?, obviously based on some assumptions, but similar in some respects to those for no absolute motion) there can be no absolute rotation.
  3. Vertical Farms: Ethanol Fuel

    If you are farming where nothing would otherwise farm, with no external energy inputs, the net carbon effect would be 0% after being put to use. If pulling fossil fuels it is 100 %.
  4. Rotation - is it absolute?

    A closely related question would be "can any inertial frame rotate with respect to any other?" I believe it may be possible, but am not certain. If it can then perhaps the answer to the PO might be no. (though I am not absolutely certain of that either)
  5. I have difficulties understanding relativity

    It's always the 90 percent of Lawyers that give the rest a bad rep... (I kid of course...please don't sue me)
  6. Oh boy... falling into a black hole

    The only thing from it left at the event horizon is the radiation it gave off before it entered. That rapidly gets redshifted into oblivion...theoretically there forever but decreasing (quantum effects aside... in any event (pun intended), at some point it will be indistinguishable from the Hawking Radiation or if the black hole grows in size it (the "signature") is gone. But in any case the object is no more at the event horizon than you are a light year from earth (in every direction) due to any unencumbered radiation you sent off last year.
  7. Squat Physics

    Assuming the weight and body move in the same manner the force on the legs is the same. If the speed of the movement varied the forces would vary as well.
  8. How much Power do I need to levitate 1 kg?

    If you "get" to assume no losses then choose an infinitely large blade diameter. The power required to hover will be zero, equivalent to sitting on the ground (pushing against a large mass) Practically, you can optimize based on assumptions of the real losses... From Wiki (actuator disc theory or momentum theory) Where: T is the thrust {\displaystyle \rho } is the density of air (or other medium) A is the area of the rotor disc in fluid dynamics, the momentum theory or disk actuator theory is a theory describing a mathematical model of an ideal actuator disk, such as a propeller or helicopter rotor, by W.J.M. Rankine (1865), Alfred George Greenhill (1888) and Robert Edmund Froude (1889).
  9. Energy of a Light Wave Question

    Or what frame it is 10 micron's in...so taking it further it really is not aware of how much energy it has...just out there blissfully playing the field.
  10. Good points. I will now put my personal space program on hold... Seriously, I guess it is all about the assumptions we make, and how we compute the odds based on them. From what we know, or think we know, intelligent life may not be reachable by ourselves or ourselves by "them", but the more we learn the better our assumptions can potentially become. Finding hints of any life as we know it within reach, coupled with our understanding of evolution would surely make intelligent life out there seem more plausible, given that "out there" is pretty vast and diversified.
  11. Human origins pushed back to 500,000 YAG

    I think we are genetically indebted to more than one., though quite possibly mostly to one (plus of course the ones who stayed behind).
  12. Human origins pushed back to 500,000 YAG

    +1...but only because I laughed...
  13. Human origins pushed back to 500,000 YAG

    Thanks. If we assume that is correct, almost 200,000 years old, why does it reflect back to 500,000 years?
  14. Human origins pushed back to 500,000 YAG

    Any thoughts on why a 177,000 to 194,000 year old find outside of Africa, of apparently Sapiens teeth, would push things back that much? At a glance that seems a stretch.
  15. Question about Rotation

    Using a frame with fixed axes in space, you remain spinning on the same axis the whole time. Using your example with the aeroplane (which has a commonly defined frame that is not generally inertial) say you had something massive inside that could contort like a cat, and you were isolated in space. You could realign the plane so that the axis of spin was along any alignment wrt the aeroplane. Most alignments would not be stable and they would tend to misalign, but at all times the axis of spin would remain fixed in space (it might not seem it at times, and the massive "cat" on board would have to be included) I hope that makes sense. Doesn't seem as clear as I hoped it would sound.