"Causality" or "determinism"?
in [Relativity]
|
Prev: ARINDAM BANERJEE, THE greatest cuckoo of all time
Next: How is SR this probability problem explained?
From: Tue Sorensen on 6 Mar 2010 18:37 On 6 Mar., 04:19, thro...(a)sheol.org (Wayne Throop) wrote: > :: There are certain things that are not affected by your frame of > :: reference. These are invariants, and you can use them to good > :: effect in many circumstances. This seems to be what Wayne was > :: talking about. > > : Tue Sorensen <sorenson...(a)gmail.com> > : Yes, that does smack of a universal frame of reference... > > His point is that it does NOT smack of a universal frame of reference. > I'm not sure why you think it does. > > Consider a long, thin rod in arbitrary x,y coordinate systems. Say you > have one coordinate system in which one end of the rod is at x=0,y=0 > and is at a 30 degree angle wrt the x axis. At the same time, another > coordinate system x',y', in which the same rod has one end at x'=0,y'=0 > and is at a 60 degree angle wrt the x' axis. > > Now consider the x vs x' coordinate of the other end of that rod. > Note that x *does* *not* *equal* x'. The displacement along x is not > invariant to rotation. However, the other end of the rod is still the > same distance from the origin, so x^2+y^2 = x'^2+y'^2. > > In short, x-extent and y-extent is not invariant to rotation. > But distance *is* invariant to rotation. > > In relativity, distance and duration are not invariant to changes > in velocity. But space-time intervals between any two events *are* > invariant. The spacetime interval being x^2-t^2; much significance > is tied to that change from "+" in the pythogorean theorem to "-" in > space-time intervals. > > And none of this implies in any way an absolute frame of reference. > In fact, it pretty much denies it. Because you may note that you can > use whatever coordinates (aka "whatever frame") you want, and you still > get the same spacetime intervals. But what if the laws of the universe are more like spacegravity and activitytime, and not, as in relativity, spacetime at all? - Tue
From: Tue Sorensen on 6 Mar 2010 18:43 On 6 Mar., 04:59, thro...(a)sheol.org (Wayne Throop) wrote: > :: Yes, though it's always best to keep in mind that the *amount* of > :: energy "contained" in a particle is observer (that is, coordinate > :: system) dependent, not invariant. =A0Which always makes me less than > :: sanguine to say that particles "contain" energy. > > : Tue Sorensen <sorenson...(a)gmail.com> > : Hm, can you make me understand this better? > > Probably not. I'm beginning to conclude. I could be wrong, of course. > > The basic problem seems to be an issue of the implications of the > laws of nature being the same for all "observers" (by which is meant, > coordinate systems), when combined with the fact that the speed of light > is a law of nature. This means that many of the things you think > are objective (in the sense of being the same to all observers), like > distance, duration, and simultaneity, are not. > > And neither is energy or momentum. There are things that *are* the same > to all observers; they just aren't what you are expecting, and you are > extremely reluctant to give up the things you are expecting to go > with what the universe is actually doing rather than what you > think it should be doing. > > I'm only guessing, but that's how it seems to me. Fair points. But actually I have no strong opinion about a universal frame of reference. That was just somehting I threw out there as a kind of feeler, to adjust some of my impressions. By and large I agree with much of what relativity says (though I'm not crazy about it treating time as a dimension), and my own ideas are certainly based off of relativity to a great degree. - Tue
From: nuny on 6 Mar 2010 18:49 On Mar 5, 5:53 pm, Tue Sorensen <sorenson...(a)gmail.com> wrote: > On 5 Mar., 23:35, Erik Max Francis <m...(a)alcyone.com> wrote: > > > > > Tue Sorensen wrote: > > > Isn't that exactly what EMR is, though? Superpositional lightspeed > > > waves that only rarely, under certain circumstances, act as particles? > > > Um, no. Presuming by "EMR" you mean electromagnetic radiation, it just > > consists of photons, which are elementary particles which always travel > > at c. > > > > I think EMR qualifies as "energy" too. I know it's difficult to put > > > into equations, but essentially I think we have to operate with such a > > > thing as free-floating energy, and electromagnetic radiation is the > > > main form of it. After all, perhaps the most cental process in all the > > > universe - stellar fusion - concerns vast quantities of matter being > > > transformed into energy (and hence comprises a major illustration of E > > > = mc2). I think the proper way of comprehending the universe is to > > > understand how matter and energy behave in relation to each other, not > > > just in Einstein's equation but concretely in the physical universe. > > > It's not clear what you're confused about here, but it's clearly something. > > I doubt not that! :-) > > > Photons contain energy, yes. (They're very simple particles; they don't > > contain much else.) Other particles also contain energy, and > > arrangements of particles, given certain fields, can also contain energy > > within them. This is all well-known; you're acting like we don't > > understand how fusion works. > > What I guess I am getting at is that, since matter is something > concrete Um, well, it isn't though, is it? Matter diffracts through gratings just like light: http://en.wikipedia.org/wiki/Diffraction#Particle_diffraction It even amplifies just like light: http://cua.mit.edu/ketterle_group/Projects_1997/atomlaser_97/atomlaser_comm..html > energy should be, too, rather than just being potential, > kinetic, momentum, Joules, etc. I am searching for an "energy medium" > of sorts - a carrier medium of pure energy. And I think we have it in > EM waves. So electromagnetic energy is somehow the "fundamental" form of energy, and that everything else is just it, in disguise. That's... how shall I put it... wrong. Example; do you believe that you are attracted to the Earth via the electromagnetic interaction? Do you really think that gravitation is just electromagnetism in disguise? > I realize that "pure energy" Where did you get the concept of "pure energy"? > in the spatial universe as we > know it will most often turn into particles, and that the quantum/ > superpositionality properties of energy prevents it from being > concrete like matter, but I will still claim that electromagnetic > radiation in itself, in its wave form, when the wave function is > maintained/uncollapsed, must correspond to "energy" (and only after > the collapse of the wave function do we get particles, because that's > when the given quantum of energy "shrinks"/collapses into material > definition). > After all, going by E = mc2, what takes place in stars is > the fusion of hydrogen into helium (etc.), leading to a massive > release of energy, i.e. EMR; light in diverse wavelengths being > emitted from the star, i.e. matter having turned into energy. Correct? Partly. What about the kinetic energy and spin of the neutrinos? There's a LOT of energy tied up in them. Are you claiming that neutrinos are somehow photons in disguise? > I think there is a reluctance in current science to define energy > properly, and acknowledge its nature in the form of EMR. It is as if > we refuse to accept "energy" as an extant and real phenomenon in > itself (the way we see matter), preferring to look at it only as > particles or kinetic momentum. And this seems to be because of the way > energy is treated in the equations and the math. To me, this way of > treating energy is obsolescent. We need a better way of talking about > and defining energy, also in the math. That is my impression, at > least. That's consistent with your use of the phrase "pure energy". I still want to know where you got it, and what you think it describes. Energy isn't a "thing in itself", it's a property of matter and of spacetime. Mark L. Fergerson
From: Luke Campbell on 6 Mar 2010 18:52 On Mar 5, 7:26 pm, Peter Knutsen <pe...(a)sagatafl.invalid> wrote: > On 05/03/2010 21:20, Luke Campbell wrote: > > > On Mar 4, 5:37 pm, Tue Sorensen<sorenson...(a)gmail.com> wrote: > > >> 2. > >> Isn't it obvious to anybody that mammals are more complex than, say, > >> amphibians? > > > No. Not obvious at all. > > > This is an example of species chauvinism with no biological support. > > In fact, the biochemistry of amphibians tends to be more complex than > > that of mammals, if for no other reason than they need proteins which > > work over a wide temperature range, whereas we mammals can hyper- > > specialize to a very narrow temperature range at which to carry on our > > bio-chemical processes necessary to life. > > I wondered too, about that one. I believe I know that mammalian lungs > are more sophisticated, and also mammalian brains, but beyond that, I > don't know of any great difference, although of course I should have > thought of the protein thing. > > Are there any examples, other than lung structure and brains, where > mammals are more complex than amphibians? Mammalian lungs are more highly subdivided, a useful thing for oxygen junkies like ourselves, since it increases the overall surface area to absorb oxygen. The additional level of complexity seems small to me, but that's my personal bias - it is relatively easy to grow new folds and subdivisions. Now, birds, they have an amazing respiratory system, much more efficient than that of us mammals, but birds are neither amphibians nor mammals so I'll not go down that route. We have a somewhat more complex heart, with four chambers. Again, a useful adaptation for oxygen junkies - it allows us to pump blood with high pressure to our tissues, ensuring rapid delivery of oxygen, without blowing out the more delicate lung tissue. It also prevents mixing of oxygenated and unoxygenated blood, for a bit higher efficiency of oxygen distribution. As you note, our brains are much more complicated than those of amphibians. Again, this comes down to being oxygen junkies - brains are fantastically expensive organs, requiring a high metabolic load whether in use or not. As warm blooded animals, we need to burn large quantities of fuel just to keep our temperatures up, so the extra expense is not too much overhead. For a frog, with a much lower energy budget, a complex brain would be prohibitive. Mammalian kidneys are quite remarkable, able to concentrate nitrogenous waste against an osmotic gradient. Frogs don't need this - they can dump the waste directly into water (with notable exceptions, such as the so called monkey frogs). That's about all I can think of where we are obviously more complex than a frog. Luke
From: Luke Campbell on 6 Mar 2010 18:55
On Mar 6, 12:34 pm, Greg Goss <go...(a)gossg.org> wrote: > How far down the tree do antibody based immune systems run? I think > that antibodies are only in mammals, too, but it's not my field. Antibody systems essentially like ours in all relevant aspects are present in chondrichthyes (sharks and rays), ray finned fish, and lobe finned fish (including all tetrapods - mammals, reptiles, avians, and amphibians). Lampreys and hagfish show evidence of antibody-like immune systems that apparently diverged from a common ancestor of ours back before our ancestors were vertebrates. Luke |