tag:blogger.com,1999:blog-8967515.post116612426098255688..comments2023-05-08T06:58:26.907-07:00Comments on Dialogos of Eide: Against SymmetryPlatoHagelhttp://www.blogger.com/profile/00849253658526056393noreply@blogger.comBlogger2125tag:blogger.com,1999:blog-8967515.post-42018591902399710742008-04-15T09:32:00.000-07:002008-04-15T09:32:00.000-07:00Neil:It seems to me as well, that implications of ...<B>Neil</B>:<I>It seems to me as well, that implications of symmetry are indeed connected to questions of emergence (emergence from symmetry?)</I><BR/><BR/>This a point of contention between opposing views. While Lee Smolin tries to dismiss it away by explaining it the way he does?<BR/><BR/><I>Time translation symmetry gives conservation of energy; space translation symmetry gives conservation of momentum; rotation symmetry gives conservation of angular momentum, and so on.<B>John Baez</B></I><BR/><BR/>I refer you back to Bee's answer and just add "<A HREF="http://math.ucr.edu/home/baez/noether.html" REL="nofollow" TITLE="Noether's Theorem in a Nutshell-by John Baez-March 12, 2002">John Baez's comment section</A>" for consideration. I am not about to fool with the complexities of those things I do not understand completely.:)<BR/><BR/>Just that positions are recognized on the basis of their determination.PlatoHagelhttps://www.blogger.com/profile/00849253658526056393noreply@blogger.comtag:blogger.com,1999:blog-8967515.post-12891365030852403332008-04-14T17:22:00.000-07:002008-04-14T17:22:00.000-07:00OK, here's my own problem with presumed implicatio...OK, here's my own problem with presumed implications of symmetry in physics (as I posted also to Backreaction): I wonder how it is that mere space-time symmetries {per Noether theorem] can prove conservation laws regardless (IIUC) of the particulars of the physical laws involved. For example, the following exercise shows the danger of simplistically interpreting e.g. “Homogeneity in space implies conservation of momentum, and homogeneity in time implies conservation of energy.” Let’s assign different values of G; G1 and G2, to two otherwise physically normal masses m1 and m2. (Hence, we keep the standard, non-gravitational definition of “mass” for inertia and kinetic energy.) We connect them with a rod. The forces between them will be unbalanced, because we have: f12 = G1m1m2[r]12/r^2 but f21 = G2m1m2[r]21/r^2. (The forces on the masses are a function only of mg, since we are by fiat just adjusting G and not inertial mass.) Hence the closed system will accelerate - “reactionless drive.”<BR/><BR/>Energy and momentum are not conserved unless perhaps we make awkward demands on general relativity etc. Note that although different G were assigned to the masses, those values of G are attached to the masses and are not characteristic of regions of space as such.<BR/><BR/>Aren't there hidden or not so hidden assumptions that go into Noether type claims, making their “proof” of conservations laws more dependent on particulars than the usual description seems to imply?Neil Bateshttps://www.blogger.com/profile/04564859009749481136noreply@blogger.com