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  1. I had previously asked the question "Is there gravity at the center of a sphere?" and the sum of the answers was "no." I.e., in a sphere of uniform density there is some point "X" within the sphere where the sum of the mass in the region [X to the surface of the sphere] exceeds the sum of the mass in the region [X to the center of the sphere] and the "gravitational pull" should invert and become directed to the outer surface of the sphere. From some of the replies that were posted it seems the fundamental question (is there gravity at the center of a sphere?) is actually quite old and rath
  2. Pincho - thanks for the observation. That is precisely the point of the question. Gravitrons are a quantum consideration and space-time is the centerpiece of general relativity. We all know the 2 theories have not yet been integrated into a single unified theory. However, where I have seen other answers to the question of gravitrons escaping the event horizon, the responses are generally framed in the context of general relativity and space-time. That begs the point of the question since it is trying to use one theory to explain the other. Gravitrons require a quantum explanation. Rega
  3. Assumptions 1. Gravitrons are the hypothetical particle that carries "gravity" as a force. The particles (if they exist) would be massless spin 2 bosons. 2. Black holes are defined by their ability to prevent the escape of anything that falls below the event horizon including massless particles (e.g., photons). 3. Because of #2, no information escapes from the black hole (this is a good thing given that we would otherwise need to deal with the physics of singularities). 4. The ability of a black hole to prevent information transfer is generally explained in relativist terms as "a
  4. Suggest a read of Hawkins "Grand Design." To very crudely and somewhat presumptuously reduce his argument to a few sentences, the universe we see is as it is because we are here to observe it. Borrowing from quantum mechanics, Hawkins argues that the universe we see is only one of an infinite number of universes that were created during the big bang. Using an analogy from the "two slit" experiment, a particle will travel all possible pathways to the target beyond the slits. Likewise, the big bang, which was a quantum event, will produce all possible universes. Like the particles pat
  5. I'm notorious for making "order of magnitude" mistakes, so it is highly likely I am wrong and your are right. My calculations are below. Regardless :rolleyes: to explore what happens, you don't really need a disc. 48 kilometers of 1/4 inch copper pipe would do the trick (although that would not be rigid enough to survive). It is less a matter of whether it is technically feasible right now in time, as opposed to what would be the experimental prediction "if you could build it." ++++++++++++++++++++++++++++++ I calculated things this way using as a model the example given at the e
  6. That's interest. OK at 10e6 rpm (16666 rps) you only need a disc that is 3 kilometers radius for the linear velocity to exceed C. To build that is within the realm of today's technology since the disc does not need to be solid. In fact, I'd envision not a disc but a rigid rod (akin to a steel pipe) fixed at its rotational center. Think about a carbon nanotube 6.5 kilometers in length and then start it spinning.
  7. Yes - the maximum speed on my router is 58,000 rpm. It is a seriously dangerous piece of hardware that requires a great deal of respect. Reason I seldom use it freehand and generally keep it firmly mounted to the router table :D
  8. I've always wondered how fast a disc of a given size could spin. The question actually isn't all that absurd. Though experiment - Consider a disc with a radius of "X" meters with a rotational velocity of "Y" revolutions/sec. The absolute maximum spin rate would occur when the linear velocity at the edge of the disc gets close to C (299792458 m/sec). For a disc rotating at 1000 rps (my carpentry router rotates at about this speed)the radius would only need to be 4.8 kilometers to achieve a linear velocity slightly greater than C at the edge of the disc. For a disc rotating at 100E6 r
  9. Thanks much for the response(s). I don't feel so bad now that I know Newton considered the question in the 1700's. I'm a tad behind on my reading of the literature :P Cheers, jkref
  10. I ask the question as a thought experiment about black holes.Because they are "infinity dense" they could be considered homogeneous. Hence, at the center of the BH (and I am not talking about the event horizon, rather the black hole itself), you would carry the arguement to its extreme and there would be no gravitational field at the core of the BH.
  11. Thought experiment - Consider a hypothetical object which is a perfect sphere of some radius "X" and some gravitational field "Y" when measured at the surface of the sphere. For the simpliest case, let's assume the matter contained in the sphere is homogeneously distributed throughout the sphere and there is no density differential as you proceed from the surface to the center of the sphere.The gravitational field at any point on the surface of the sphere will always be "Y" since the mass producing the field will be the same relative to the observer regardless of where the observer locates
  12. Thanks folks. If I understand the responses correctly, it boils down to the idea that it is a singularity with a non-zero radius. That leads into a further question - are all BHs the same size (note - I am not referring to the Schwarzschild radius which varies according to the mass of the B). I am referring to the entity that exists at the center of the BH which is the BH itself. One commonly reads that a BH has "infinite" density. My understanding (non sequitur) of "infinite" is that one "infinite" is identical to any other "infinite." If that is true, a micro BH generated in the LH C
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