I would like to strongly reinforce John's comments about boundary conditions. We tend to obsess over the laws and ignore the boundary statements. (Sort of a shell game, IMHO.) If boundary conditions cannot be stated in closed form, the physical problem remains indeterminate! (The aphorism from computer science, "Garbage in, garbage out!" is appropriate to reversible laws as well.)
Then there is the issue of the continuum assumption, which was the work of Euler and Leibniz, not Newton. Newton argued vociferously against it, because it equated cause with effect. The assumption works quite well, however, whenever cause and effect are almost simultaneous, as with a force impacting an object, where the force is transmitted over small distances at the speed of light. It doesn't work as well when large velocities are at play (relativity) or very small distances and times (quantum phenomena) -- whence the need arose to develop the "exceptional" sciences, thermodynamics, relativity and quantum physics. I would suggest it doesn't work well at very large distances, either. Consider galaxies, which are on the order of 100,000 or more light years in diameter. (I was surprised to learn recently that we really don't have decent models for the dynamics of galaxies.) Gravitational effects are relatively slow to traverse those distances, so that cause and effect are not immediate. (Sorry, I don't think quantum entanglement is going to solve this conundrum.) If cause and effect are widely separated, then the continuum assumption becomes questionable and by implication, reversibility as well. Now Noether demonstrated that reversibility and conservation are two sides of the same coin. So I see it as no great mystery that we encounter problems with conservation of matter and energy at galactic scales or higher -- witness "dark" matter and "dark" energy. Of course, I am neither a particle physicist nor an astrophysicist, but merely someone writing from my armchair. So I invite anyone on FIS to put me straight as regards my speculations on these issues. Cheers, Bob U. > Interesting question, Ken. I was not overly impressed with the video > because it didnât explain one of the most crucial points about the use > of information in dealing with quantum gravity, for which we as yet have > no good theory. The issue with both black holes and the origin of the > universe process is that the boundary conditions are dynamical. You can > have as many laws as you could want and still not have a physics if the > boundary conditions are ignored. Usually they are added in as an initial > state, or sometimes ad hoc but when they are changing, especially if they > are mathematically inseparable from the laws, there is a problem with > relying on the laws alone to explain. With black holes there is a question > of whether or not information disappears at their event horizon. There is > a similar issue for the observable portion of the universe at any given > time. It is hard to see how the questions can even be posed without > referring to information. Any boundary in basic physics can be conceived > the same way, and if all masses and energies come from geometry (in a > Unified Theory) then information is all there is in basic physics. > > I have argued for some time now that biological systems are much more > defined by their boundary conditions, which are typically dynamical and > changing, than by their energy flows, so information flows dominate, > though energy flows place limits, so I have talked of the information and > energy budgets being partially decoupled in biological systems. So > information is important to biology because understanding its flow can > answer questions about dynamical boundaries, just like in basic physics. > The energy (and matter) flows I will leave to the biophysicists, but the > paragraph above suggests that these are information flows as well. I like > the potential for unification here. > > Cheers, > John > > From: Fis [mailto:fis-boun...@listas.unizar.es] On Behalf Of Ken Herold > Sent: May 26, 2015 12:30 AM > To: fis > Subject: [Fis] It From Bit video > > Released recently--what about the biological? > > https://www.youtube.com/watch?v=-ATWa2AEvIY > > -- > Ken > _______________________________________________ > Fis mailing list > Fis@listas.unizar.es > http://listas.unizar.es/cgi-bin/mailman/listinfo/fis > _______________________________________________ Fis mailing list Fis@listas.unizar.es http://listas.unizar.es/cgi-bin/mailman/listinfo/fis
