How big is our Galaxy.

Ok, v=cz is only valid for small v wrt c. For larger v, you need the higher order corrections. It's not too hard to get that expansion: square both sides, times top and bottom of rhs by c. Isolate v on lhs and Taylor expand rhs.You are correct, v does not exceed c.

If we're talking about this equation: Then I can do everything you suggest except the Taylor expansion. Let me try reading on and see if I understand anyway.--Percy

From http://www.astro.ucla.edu/~wright/cosmo_02.htm: I think this is an important part of what I'm trying to figure out. How did we come to know this? It looks like the discussion that follows says that we know this because the relativistic Doppler shift law doesn't provide a model that matches the data from cosmological distances. We have to use the "now" distances, which greatly complicates things.I think Iblis said some things earlier that might help, I'll go back and review those.--Percy

Thanks again, I've been having a lot of fun following your clues around I don't know that that's perfectly true, the idea that if gravity is energy it must therefore necessarily dissipate is already a good strong indicator that our formulations about it necessarily require a different view, GR being the best approximation of that different view produced so far; and I'm sure that's only the tip of the iceberg! I do understand your reluctance to step too far outside your field though, I just want to encourage you to continue commenting where you see us touching on aspects relevant to your expertise.For example This is shockingly relevant to our discussion of gravity, especially here at this forum. Let me plug in something about Benard cells so our readers can follow the conversation better Rayleigh—Bnard convection - WikipediaThis shows how self-organizing systems can be seen to develop naturally and asymmetrically (either handedness though) as a direct results of what are intrinsic properties of gravitation. The narrow separation of the planes and the need for the lower plane to grow warmer over time, that is the gravitational distortion of entropy toward the source of gravitation, show that gravity as an energy trap is an essential factor in the development of life "as we know it".Pseudo-panspermia (stellar genesis) might provide the complex chemicals, but in order for them to grow into cells with molecules of a particular handedness and begin the long journey towards greater and greater complexity it seems almost mandatory for them to be at the bottom of a gravity well and thereby attain to variant fluid levels and uneven entropy. The very phrase "uneven entropy" is almost a preliminary definition of life in and of itself.

No, it comes directly from GR. Don't forget that the Big Bang model is not empirical, it is a prediction of GR.

You said,

quote:

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if gravity is energy it must therefore necessarily dissipate is already a good strong indicator that our formulations about it necessarily require a different view, GR being the best approximation of that different view produced so far; and I'm sure that's

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Is this a "different" view than Cavediver's?As for GR I have knowingly kept from THINKING about geodesics when formulating my own thoughts on the object, whether matter or mass or simply the argument of impenetribility (in general)so, whatever I said might be inconsistent relative to the contents of this thread even if it reveals truth in another heading.My concern was a continuum in which an organism body NO MATTER THE DISSIPATION still sustains some heritible causality and correlation across generations within kinematically layered dynamics of motions but I have no idea how this might be related to components of parity deviating entropy in general. It is only through the "infinte" nature of FUTURE lineages that I can even think my use of gravitational forces biologically contributes to the thought process of a physicist in particular. It is true I can think of possible negative or even entropy relative to cell death but I suspect that Gladyshev, haveing giving much more particular thought to the suspected use of dissipation physics than me is more likely correct as to the physical less the biological reality. He might be mistaken in his thought on the relation of thermostat parameters to mitosis but I am not ready to comment on that possibility. Even without a quantification however I DID start to READ Prigogine's original works and I find that he did not clearly seperate as to self-assembly or in the context of population genetics self-fertilization nonequilibrium from non--linear affects(artifacts). That is what confuses me biophysically. Einstein could be mistaken but I am also not in a position to make that reflection determinate.I HAD thought about the possibility that fluctuations in gravity could dissipatively influence the motion of hydrophobic protein side chains within cell membranes such as to influence topobiological flow of SAM molecules where Wright relates DYNAMICS of soma and nucleus but I have NOT related them to particular species and this is necessary. It might be that the thought I am having here has nothing to do with primates at all!! If that is true it can not have the inside influence on the lacking thoughts of physicists. That would not make me sad. I just do not know.In the end I am more interested in testing the existence of Farady derived thermal currents than universal black hole information for a creature of unknown composition, else I prefer to pick out my meat before I eat it. LOL.This message has been edited by Brad McFall, 01-21-2006 05:50 PM

Oh haha, no sir, but as I am looking for models and factoids to help demonstrate why GR is relevant even in the purely ballistical situations SR and Newton were made for I found this insight useful. I am not really up to the task of trying to (effectively) disagree with cavediver yet, even if I had found a reason to, I am still trying to visualize all the implications of simply understanding his argument.I do see your point though as to how shifting the discussion towards the biological implications pushes us even further away from the original topic than Percy has been so kind as to let us stray thus far, your intention not to distract us from the educational process we are still striving through is admirable. And I respect your desire not to distract yourself also, I guess I will just be stuck trying to glean enlightenment from your arguments in other threads where I may have more work to do to find an inroad toward that first glimmer, that's all.As a side comment regarding your potential disagreements with Behe, you do realize the man is a kook right? I mean don't get me wrong, I'm a kook, you're a bit of a kook yourself, but Behe is a whole different scale of kook from us. We may be experimenting from time to time in believing things that may appear to have been demonstrated untrue, as part of what your Goethe links characterized as "exploratory experimentation", but when we discover we have gone wrong we switch off to different tacks. Behe seriously seems to me to be banging his head against the same wall year after year for no good reason other than an obsession with his own fixed ideas. The only value I see coming out of that is a comprehensive list of reasons why he is wrong, surely he should let someone else bear the burden of producing such a list just for his own sanity's sake.

I'm going to have to bow out of this discussion. Thanks, Cavediver and Iblis, for your help. I'll return to trying to better understand GR when I have more time.--Percy

see also extra alia:http://EvC Forum: Can't ID be tested AT ALL? -->EvC Forum: Can't ID be tested AT ALL?http://EvC Forum: Can't ID be tested AT ALL? -->EvC Forum: Can't ID be tested AT ALL?

Ok here is where I see the problem, we less-experienced physics fans are going to have trouble reconciling this statement with this one It seems like we are wrong no matter what we try to believe, do you see that?Now based on the more recent statement and all our careful disclaimers about "relative to the observer", I will venture to guess that we are right in imagining that our clocks are going at the same speed, but for the wrong reasons?Considering that when I talk out the points of space and so on you seem to approve my logic, I may not be as wrong as when we try to juice up the rubber-band model.But when I do imagine it in terms of contraction and expansion of the points, I end up thinking time slows down for the distant galaxies for the same reason it slows down for the astronaut who wanders too near a black hole (disregarding the way his feet get ripped off by the gravity differential of course.)That is to say, it proceeds normally for him but slows down relative to us. But when he wanders away again, this has been a real effect, he is much younger than us. This doesn't seem to correspond to what happens with the distant galaxies the way I would like it to, if our clocks are actually proceeding at the same rate due to our common state of being at rest in respect to our individual comoving frames.From this viewpoint I feel Percy would be right in trying to emphasize that the "doppler effect" relativity is not the same as the "actually moving through space" relativity, in that the one doesn't really affect our relative aging and the other does. In other words, contrary to what I have been trying to think, there is a real solid difference between the time-dilation effects of contraction of space like black holes versus expansion of space like the Hubble-Einstein universe.Why would that be?* No rush, whenever you get the chance, thanks for all your help thus far; thanks also Percy for all your input, I think I have gotten a couple of times smarter just trying to research your pointy questions (though not smart enough to understand Lorentz yet lol)

I belive the universe is infinite.

OK, you're right... I've been confusing and have presented mixed messages... no wonder Percy fled I will try to do better, but I have to take a step back.Time is simply the length of a path through space-time. We all take different paths, so time is completely individualistic. If the path is a geodesic, it follows the straightest path through the curved space-time. What this means in practical terms is we just go with gravitation, we do not fight it, we do not experience or apply a force to accelerate ourselves away from the path that we would otherwise follow. If we do accelerate, the path becomes shorter in the following sense: if two observers start at the same point in space-time and finish at the same point, then the one who has experienced the greater acceleration during the path from start to finish will have expereienced less time. In other words, that observer will be younger. This is the Twin's Paradox. It has NOTHING to do with Lorentz time-dilation as such (which is concerned with OBSERVATIONS of observers travelling at some relative velocity), but is certainly just as much part of SR as it is GR. In SR there is no gravity, so the geodesic through space-time is just much more simple.So, two observers in two cosmologically separated galaxies are not accelerating significantly to deviate much from their geodesic and thus they experience the maximum possible time along their respective time-lines. For one observer to visit the other will require acceleration which will shorten the travelling observer's time-line. Thus when he arrives, he will give less time since the big bang than the stationary observer.The time-dilation we see occurring in a distant galaxy is purely an observational effect. And this is identical to seeing an astronaut slow down as he heads into a black hole... an observational effect. The astronaut will happily (assuming low tidal forces!) approach the event horizon and enter the black hole, whilst an external observer will see the astronaut slow and red-shift out of existence as he approaches the event horizon. Purely observational effect.Now, if the astronaut rather sensibly chooses not to fall through the event horizon, he must accelerate away from the black hole. This acceleration will be substantial, and his time-line will shorten dramatically. When he gets back to the external observer, the time difference will be considerable.So in all cases - SR, cosmology and black holes - we have two completely separate effects: observational effects caused by Lorentz and doppler, and then we have shortening of the time-line caused by acceleration. In all cases - Twin's Paradox, cosmology and black holes - these two separate effects are totally confused, and leads to all sorts of misunderstandings.Does this make sense?

No problem, Percy. I more than understand time constraints. You may just want to have a glance over the above post I've just written to Iblis. I think you will find it useful. Far too often I try to reply to questions rather than doing the right thing which is to step back a bit, and lay some foundation. I think I managed this in that post, but see what you think.

Thanks cavediver, you cleared up the whole confusion in one fell swoop.This puts an end to all my "calculable-but-never-observable" language of course, seeing as how the doppler portion is all about observation there isn't any point where things that cross horizons then experience a reversed duration in any sense at all, relative or otherwise.The time-dilation we see with things moving away has no real relation of any kind to the time-dilation actually experienced in things moving in any direction, they are just confounded together because people want to think that what we observe bears some relation to what actually happens.The triplets paradox doesn't mean anything at all because we have no reason to assume that we can take what we observe, subtract the distance, and call that the time of the event at all in such a case. The aging that is observed differently by the two inertial frames is just a difference in observation, not in the actual procession of time for the observed object. The third "twin" is really experiencing more time-dilation than people traveling slower than him and less than people traveling faster than him, regardless of direction.Thanks for all your assistance!

Cool Sorry it took so long to get a decent explanation out... I think that's it in a nutshell. I would say "undergoing more/less acceleration" just to avoid the confusions we have been talking around these last few posts.