Re: GR space-time motion in the absence of gravity
On Monday, August 3, 2020 at 12:15:23 PM UTC-6, Alan Grayson wrote: > > > > On Monday, August 3, 2020 at 8:55:17 AM UTC-6, Alan Grayson wrote: >> >> >> >> On Sunday, August 2, 2020 at 5:00:22 PM UTC-6, Alan Grayson wrote: >>> >>> >>> >>> On Sunday, August 2, 2020 at 1:55:15 PM UTC-6, Lawrence Crowell wrote: I looked at the precession question, wrote it in WORD and then posted it in the wrong thread. A big line of anti-virus defense is working off-line. I do a lot of work locally and pop on and off the internet. I try to never leave my machines on-line with an open port for anyone or any bot to enter to cause mischief. With this the question is odd. How something moves in free and flat space and spacetime is just determined by its initial conditions. LC >>> >>> If one starts with SR and zero curvature of spacetime, and places a test >>> particle in that spacetime spatially at rest, how will spacetime tell >>> matter how to move if spacetime isn't curved? AG >>> >> >> I think in this situation the direction of motion is ambiguous. AG >> > > No. It doesn't spatially move, but it moves in space-time since the > observer's clock continues to advance. AG > What bothers me about this is that the spatial coordinates generally depend on each other, and time. In this situation will the geodesic equations yield a solution where the spatial coordinates remain fixed? AG > On Sunday, August 2, 2020 at 9:05:57 AM UTC-5 agrays...@gmail.com wrote: > > > On Sunday, August 2, 2020 at 5:30:36 AM UTC-6, Lawrence Crowell wrote: >> >> The periapsis or perihelion advance of Mercury is largely a result of >> classical perturbation theory in classical mechanics. About 10% of the >> perihelion advance could not be accounted for by perturbation methods in >> classical mechanics. >> >> This has to be admired in some ways. Finding the ephemeris of Mercury >> is tough, for the planet makes brief appearances near the sun in >> mornings >> and evenings. Finding an orbital path from its course across the sky is >> not >> easy. The second issue is that perturbation methods in classical >> mechanics >> are difficult. These were developed arduously in the 19th century and Le >> Verrier worked on this to find the planet Neptune from the perturbed >> motion >> of Uranus in 1848. These methods were worked on through the 19th >> century. >> The later work of von Zeipel and Poincare were used to compute the >> periapsis advance of Mercury, but there was this persistent >> 43arc-sec/year >> that resisted these efforts. >> >> It was general relativity that predicted this anomaly in ways that >> are far simpler than the classical perturbation methods. This >> post-diction >> of GR was an initial success in the theory, followed up shortly by the >> Eddington expedition that found the optical effects of GR in a solar >> eclipse in 1919. >> >> LC >> > > I appreciate your grasp of the history, but you haven't answered my > question and don't seem aware of what it is (plus you posted your reply > on > the wrong thread). AG > >> >> On Sunday, August 2, 2020 at 3:49:28 AM UTC-5 agrays...@gmail.com >> wrote: >> >>> >>> >>> On Saturday, August 1, 2020 at 10:35:09 PM UTC-6, Alan Grayson wrote: In flat space, which is tantamount to assuming the absence of gravity, and non-zero curvature, a body placed at spatial coordinates x,y,z, will move because t increments. But if there is zero curvature, in which direction will it move? That is, how is the direction of motion determined? TIA, AG >>> >>> CORRECTION; above, I meant to write, " ... which is tantamount to >>> assuming the absence of gravity and ZERO curvature, ... " AG >>> >> -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/everything-list/1eb6b644-3bcc-444e-a61d-2bf7aabdd10fo%40googlegroups.com.
Re: GR space-time motion in the absence of gravity
On Monday, August 3, 2020 at 8:55:17 AM UTC-6, Alan Grayson wrote: > > > > On Sunday, August 2, 2020 at 5:00:22 PM UTC-6, Alan Grayson wrote: >> >> >> >> On Sunday, August 2, 2020 at 1:55:15 PM UTC-6, Lawrence Crowell wrote: >>> >>> I looked at the precession question, wrote it in WORD and then posted it >>> in the wrong thread. A big line of anti-virus defense is working off-line. >>> I do a lot of work locally and pop on and off the internet. I try to never >>> leave my machines on-line with an open port for anyone or any bot to enter >>> to cause mischief. >>> >>> With this the question is odd. How something moves in free and flat >>> space and spacetime is just determined by its initial conditions. >>> >>> LC >>> >> >> If one starts with SR and zero curvature of spacetime, and places a test >> particle in that spacetime spatially at rest, how will spacetime tell >> matter how to move if spacetime isn't curved? AG >> > > I think in this situation the direction of motion is ambiguous. AG > No. It doesn't spatially move, but it moves in space-time since the observer's clock continues to advance. AG > >>> >>> >>> >>> On Sunday, August 2, 2020 at 9:05:57 AM UTC-5 agrays...@gmail.com wrote: >>> On Sunday, August 2, 2020 at 5:30:36 AM UTC-6, Lawrence Crowell wrote: > > The periapsis or perihelion advance of Mercury is largely a result of > classical perturbation theory in classical mechanics. About 10% of the > perihelion advance could not be accounted for by perturbation methods in > classical mechanics. > > This has to be admired in some ways. Finding the ephemeris of Mercury > is tough, for the planet makes brief appearances near the sun in mornings > and evenings. Finding an orbital path from its course across the sky is > not > easy. The second issue is that perturbation methods in classical > mechanics > are difficult. These were developed arduously in the 19th century and Le > Verrier worked on this to find the planet Neptune from the perturbed > motion > of Uranus in 1848. These methods were worked on through the 19th century. > The later work of von Zeipel and Poincare were used to compute the > periapsis advance of Mercury, but there was this persistent > 43arc-sec/year > that resisted these efforts. > > It was general relativity that predicted this anomaly in ways that are > far simpler than the classical perturbation methods. This post-diction of > GR was an initial success in the theory, followed up shortly by the > Eddington expedition that found the optical effects of GR in a solar > eclipse in 1919. > > LC > I appreciate your grasp of the history, but you haven't answered my question and don't seem aware of what it is (plus you posted your reply on the wrong thread). AG > > On Sunday, August 2, 2020 at 3:49:28 AM UTC-5 agrays...@gmail.com > wrote: > >> >> >> On Saturday, August 1, 2020 at 10:35:09 PM UTC-6, Alan Grayson wrote: >>> >>> In flat space, which is tantamount to assuming the absence of >>> gravity, and non-zero curvature, a body placed at spatial coordinates >>> x,y,z, will move because t increments. But if there is zero curvature, >>> in >>> which direction will it move? That is, how is the direction of motion >>> determined? TIA, AG >>> >> >> CORRECTION; above, I meant to write, " ... which is tantamount to >> assuming the absence of gravity and ZERO curvature, ... " AG >> > -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/everything-list/66c5bf45-f1ef-4104-92f5-611a9af14cb1o%40googlegroups.com.
Re: GR space-time motion in the absence of gravity
On Sunday, August 2, 2020 at 5:00:22 PM UTC-6, Alan Grayson wrote: > > > > On Sunday, August 2, 2020 at 1:55:15 PM UTC-6, Lawrence Crowell wrote: >> >> I looked at the precession question, wrote it in WORD and then posted it >> in the wrong thread. A big line of anti-virus defense is working off-line. >> I do a lot of work locally and pop on and off the internet. I try to never >> leave my machines on-line with an open port for anyone or any bot to enter >> to cause mischief. >> >> With this the question is odd. How something moves in free and flat space >> and spacetime is just determined by its initial conditions. >> >> LC >> > > If one starts with SR and zero curvature of spacetime, and places a test > particle in that spacetime spatially at rest, how will spacetime tell > matter how to move if spacetime isn't curved? AG > I think in this situation the direction of motion is ambiguous. AG > >> >> >> >> On Sunday, August 2, 2020 at 9:05:57 AM UTC-5 agrays...@gmail.com wrote: >> >>> >>> >>> On Sunday, August 2, 2020 at 5:30:36 AM UTC-6, Lawrence Crowell wrote: The periapsis or perihelion advance of Mercury is largely a result of classical perturbation theory in classical mechanics. About 10% of the perihelion advance could not be accounted for by perturbation methods in classical mechanics. This has to be admired in some ways. Finding the ephemeris of Mercury is tough, for the planet makes brief appearances near the sun in mornings and evenings. Finding an orbital path from its course across the sky is not easy. The second issue is that perturbation methods in classical mechanics are difficult. These were developed arduously in the 19th century and Le Verrier worked on this to find the planet Neptune from the perturbed motion of Uranus in 1848. These methods were worked on through the 19th century. The later work of von Zeipel and Poincare were used to compute the periapsis advance of Mercury, but there was this persistent 43arc-sec/year that resisted these efforts. It was general relativity that predicted this anomaly in ways that are far simpler than the classical perturbation methods. This post-diction of GR was an initial success in the theory, followed up shortly by the Eddington expedition that found the optical effects of GR in a solar eclipse in 1919. LC >>> >>> I appreciate your grasp of the history, but you haven't answered my >>> question and don't seem aware of what it is (plus you posted your reply on >>> the wrong thread). AG >>> On Sunday, August 2, 2020 at 3:49:28 AM UTC-5 agrays...@gmail.com wrote: > > > On Saturday, August 1, 2020 at 10:35:09 PM UTC-6, Alan Grayson wrote: >> >> In flat space, which is tantamount to assuming the absence of >> gravity, and non-zero curvature, a body placed at spatial coordinates >> x,y,z, will move because t increments. But if there is zero curvature, >> in >> which direction will it move? That is, how is the direction of motion >> determined? TIA, AG >> > > CORRECTION; above, I meant to write, " ... which is tantamount to > assuming the absence of gravity and ZERO curvature, ... " AG > -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/everything-list/dddfe57e-d619-446b-949a-90d2b23e4576o%40googlegroups.com.
Re: Wolfram Physics Summer School report
To get up to speed on his "summer school" requires first reading the tech ref: https://www.wolframphysics.org/technical-introduction/ to learn the *"Wolfram" hypergraph rewriting* vocabulary. Graph/Hypergraph rewriting has been around a long time, now migrating from computer science to physics. Remains to be seen whether Wofram's project gets traction. *The algebras of graph rewriting* https://www.researchgate.net/publication/311737035_The_algebras_of_graph_rewriting Graph rewriting is Turing-complete, hence sufficiently expressive to encode any other model of computation. It is applied with considerable success in modeling of biological systems (especially protein interaction networks, see [13]). In fact, many models in statistical physics, theoretical chemistry and combinatorics can be seen as particular cases of graph rewriting systems. Most notably, the Heisenberg-Weyl algebra, the combinatorial algebra underlying chemical reaction systems and the theory of the harmonic oscillator, is a particularly simple case of a graph rewriting algebra. ... More abstractly, the physical concept of worldlines of particles is reflected to a certain extent in the syntax of the rule diagrams through causality constraints bearing on vertices and edges. A given rule diagram represents the “time evolution” of vertices and edges through the course of sequential applications of rewriting steps. In this way, one might indeed interpret rule diagrams as some form of analogues of Feynman diagrams for modeling interactions in particle physics. @philipthrift On Sunday, August 2, 2020 at 3:09:09 PM UTC-5 Lawrence Crowell wrote: > I probably need to look at Wolfram’s ideas here a bit. He is making > references to these graphs as entanglements. I am a bit unclear on what is > meant here. An bipartite entanglement is represented as *---* and a > tripartite entanglement is a three-way thing, a bit like the bolos the > Argentine gauchos throw, where each node is entangled with the other two, > but not all three individually. To talk about geodesics is where things get > a bit strange. A general relativity = quantum mechanics perspective, which > has been something I have worked on since 1988, where spacetime is > constructed from large N-tangles, may reference some sort of such > correspondence. There are topological obstructions between a bipartite and > tripartite entanglement transforming into each other Yet if quantum > entanglements and spacetime topological connection in ER bridges or > wormholes are fungible with each other it is then possible to think of an > N-tangle or constructed tensor network of entanglements as equivalent to N > entangled black holes that contain a common interior. > > LC > > On Sunday, August 2, 2020 at 6:27:06 AM UTC-5 cloud...@gmail.com wrote: > >> Stephen Wolfram @stephen_wolfram >> https://twitter.com/stephen_wolfram/status/1289381082165633026 >> >> *So exciting to see how quickly things are moving with >> #WolframPhysics... Makes me think of quantum mechanics circa 1925. It's >> taken me 2 weeks just to summarize part of what got done at our Summer >> School ...* >> >> tech ref: https://www.wolframphysics.org/technical-introduction/ >> >> >> https://writings.stephenwolfram.com/2020/07/a-burst-of-physics-progress-at-the-2020-wolfram-summer-school/ >> >> [excerpt] >> ... >> >> The starting point for any discussion of quantum mechanics in our models >> is the notion of multiway systems, and the concept that there can be many >> possible paths of evolution, represented by a multiway graph. The nodes in >> the multiway graph represent quantum (eigen)states. Common ancestry among >> these states defines entanglements between them. The branchial graph then >> in effect gives a map of the entanglements of quantum states—and in the >> large-scale limit one can think of this as corresponding to a “branchial >> space” ... >> >> The full picture of multiway systems for transformations between >> hypergraphs is quite complicated. But a key point that has become >> increasingly clear is that many of the core phenomena of quantum mechanics >> are actually quite generic to multiway systems, independent of the details >> of the underlying rules for transitions between states. And as a result, >> it’s possible to study quantum formalism just by looking at string >> substitution systems, without the full complexity of hypergraph >> transformations. >> >> A quantum state corresponds to a collection of nodes in the multiway >> graph. Transitions between states through time can be studied by looking at >> the paths of bundles of geodesics through the multiway graph from the nodes >> of one state to another. >> >> In traditional quantum formalism different states are assigned quantum >> amplitudes that are specified by complex numbers. One of our realizations >> has been that this “packaging” of amplitudes into complex numbers is quite >>
