Summations Only

Whatever this Stenger thing is, it has its own topic.Adminnemooseus

I'd be happy to discuss Barnes comment. But let's first note that the position that you posted here earlier is not consistent with Barnes position. You completely denied that gravity was a fictitious force until you were pressed by Admin with the threat of not getting your thread promoted. In fact, you acted as though calling gravity fictitious was enough to render Stenger a fool. If we review your old post, it is quite obvious that you had no idea what that terminology meant. In fact, you still don't.And what Barnes says is nearly irrelevant. What you need to show here is not that Barnes disagrees with Stenger, but that he agrees with those clearly incorrect statements you made and that I and others called you on.And Barnes is not correct (or at least your summary here is not a correct statement of physics. I attempted to look at Barnes paper, but your link did not work) Gravity in general relativity is always a fictitious force. There is no action at a distance. The problem Barnes describes surrounds a naive application of the equivalence principle. That is, we can distinguish between gravitational fields (generated from spherical or point sources) and motion in accelerated frames because of the gravitational tidal forces which would not be generated using any kind of accelerated frame. Accordingly we cannot replace a gravitational field with an accelerated frame. In other words, Barnes is discussing the limitations of applying the equivalence principle.Yes, Barnes is correct as far as that goes, and indeed that would be enough under Newtonian Mechanics to say that gravity is not fictitious exactly as in centrifugal force. But the fix for that is not to make gravity a non-fictitious force, but to correctly apply Einstein's theory.And in Einstein's theory both the tidal forces and the gravitational force towards the center of mass are generated by the curvature of space-time generated by the mass/energy/stress Tensor. There is no real force 'sometimes' as you state. And in fact is definitely not what Barnes says. Whoa, bro. In your haste to make Stenger wrong, did you see the assumptions underlying Stenger's statement? I'll admit that I have not done the calculation, but did you actually try calculating the dimensionless constant associated with gravitation using the planck mass in place of the proton mass? Do even you know how to do that? If not, then how are you sure that Stenger is incorrect? Your link does not mention gravity at all. I presume the information there is correct. You are quite confused about the direction of Stenger's argument. Stenger's alternate values for the strength of the gravitational force have absolutely nothing whatsoever to do with whether or not gravity is fictitious.Stenger makes comments about the usefulness of calculating the ratio of electric to gravitational strength. He does not dismiss the usefulness other than for the particular purpose of discussing fine tuning. Further, he is not the only scientists to discuss setting G,c, and hbar to 1 by an appropriate choice of units, nor the only scientist to note that the comparison of strengths uses teeny tiny masses. Why should we use a proton mass in the comparison? Again, you are misconstruing this argument completely. The answer to what the strength of gravity should be is calculated by Stenger and others using Newtonian physics. Apparently, Stenger's argument regarding the use of dimensionless constants flew over your head completely. Perhaps you should take another look at that part of the book.ABE:Link to calculation of strength of gravity and comparison to electrostatic strength.http://arxiv.org/ftp/arxiv/papers/0707/0707.0058.pdfSee page 2. for calculation. Edited by NoNukes, : No reason given.Edited by NoNukes, : No reason given.Edited by NoNukes, : No reason given.

Oh dear! That'll give designtheorist an easy way to avoid the obvious point I've made repeatedly on this thread, and fail to reply to Message 361, which explains clearly to him why there is no rational teleological fine tuning argument.Maybe we need another thread on the "lottery fallacy" or the "Texas sharpshooter fallacy" and petitio principiiAssume that Mrs. Life was intended to win the lottery with millions of participants after the draw, and you'll conclude that the draw was fixed.Why the theists who make the fine tuning with intent argument aren't phoning the police to alert them to foul play every time someone wins a lottery I'll never understand.

Your link is comparing the strong force to the electric force.In section 7.2 Stenger is comparing the gravitational force to the electric force, and only for the specific situation of two particles with Planck mass and unit electric change. Stenger may have chosen that particular situation for effect because it produces the same ratio as between the strong and electric forces. He's making the point that gravity is not the weakest force in all situations, that where it is weaker and where it is not varies from situation to situation.--PercyEdited by Percy, : Grammar.

I've upped the thread limit to 500 messages because there's no guarantee that the Commitment to atheism results in bad science - The Victor Stenger Example thread proposal will ever be promoted.

I'll explain things at a purely classical level, except at one point, since quantum mechanics doesn't really add much to this story.Okay the Strong Nuclear force and the Electromagnetic Force are indeed Forces in Modern physics. This is because they involve particles generating a potential energy field in their vicinity. Nearby particles that can interact with that field will no longer be able to remain stationary without exerting some energy. That is, remaining still is no longer the path of least resistance.Instead the path of least resistance will become some complicated trajectory dictated by the potential energy field. In particular a particle moving inertially (that is with no acceleration) will be forced to accelerate and change its trajectory.Under quantum mechanics these potential energy fields are composed of gluons for the strong nuclear force and photons for the electromagnetic force.So, particles have their trajectories altered by the presence of fields living in spacetime. Without these fields all particles would move on inertial paths, that is paths which involve no acceleration.General Relativity indicates that gravity is entirely different. Instead the shape of spacetime itself is distorted, in the presence of mass. However particles don't have their trajectories altered. They simply move along the usual inertial paths.The confusion of gravity being an actual force comes from the fact that when spacetime is only weakly curved, the inertial paths in the curved spacetime look very similar to non-inertial "force-caused" paths in flat spacetime. So you are able to pretend that gravity is a force living in flat spacetime.However a simple thought experiment reveals the different, "true", nature of gravity.Create a giant sphere the size of the Earth with a large positive electric charge and give yourself a negative electric charge. You will fall toward the sphere, just as you would fall toward the Earth from space under gravity. However you will feel this pull when it begins to accelerate you noticeably. You'll also notice objects heavier than yourself falling more slowly than you, as the same electromagnetic force strength cannot pull these objects quite as fast.Contrast this to gravity. While falling to Earth you feel nothing and more massive objects will fall at the same rate as yourself. This is not the behaviour of a Force tugging on you and the heavier objects, since the heavier objects would be harder to pull down.Instead you and everything else are simply moving on inertial paths in spacetime, you feel nothing, since nothing is actually acting on you. It's simply that spacetime has been distorted around the Earth so that a lot of inertial paths lead to its surface. However this no more a force than the fact that moving north on the Earth leads to the North Pole, which is just a consequence of the shape of the Earth. Falling is just a consequence of the shape of spacetime.Gravity is not a force and there is no gravitational field.

Here's a link to Barnes paper: The Fine-Tuing of the Universe for Intelligent LifeHere's the relevant passage in more complete form, you were right, he was talking about tidal forces: You respond that Barnes is correct that "gravity is not fictitious exactly as in centrifugal force", but isn't it? Isn't Barnes stretching Einstein's elevator analogy by assigning it a second observer who he claims is inside the same inertial frame when in reality two independent observers can never be in the same inertial frame? Isn't the observer in Einstein's elevator really a point observer? And determination of one's presence in a gravity field by observation of other inertial reference frames doesn't mean gravity is not a fictitious force?--Percy

Two observers can indeed be in the same inertial frame. I would suggest that two inertial observers experiencing no relative motion between them, but merely separated in position are actually in the same inertial frame.An observer in an accelerating elevator is in a non-inertial frame. And a single observer looking at two objects in a gravitational field around a spherical body can indeed conduct experiments that distinguish between an accelerating elevator in free space, and an elevator in an inertial frame under the influence of gravity. In the later case, a single well-instrumented observer would see two dropped objects move towards each other as they fell.Now, to answer your question, I think there is some room to argue the meaning of the phrase "gravity is fictitious exactly as is centrifugal force". Centrifugal force and gravity are obviously two different phenomenon produced by different circumstances. But, the phenomenon are alike in that, as is the case for all fictitious forces, the apparent force of gravity and that of centrifugal force are proportional to the mass 'acted on' so that all masses experience the same acceleration in the same circumstances.[1] They differ in that one originates from curved space-time, the other from a change in coordinate systems. So, perhaps 'perfectly analogous' is a better word choice than 'exactly'. But then that depends of the precise definition of 'fictitious'. It is, in my opinion, an error to simply chose a definition that makes Spencer wrong when the conventional description of gravity as a fictitious force is well established. And there is the fact that Spencer's argument is more of an appeal to reason than a proof, anyway.ABE:Or expressed another way, it is perfectly legitimate for Barnes to raise distinctions between gravity and centrifugal force. We can weigh the persuasive force of that distinction and perhaps agree or disagree with Spencer. It is quite another thing entirely to call Spencer a fool for being right.[1] Son Goku covered this in more detail in his post.Edited by NoNukes, : No reason given.Edited by NoNukes, : No reason given.Edited by NoNukes, : No reason given.

But by definition, isn't an inertial reference frame restricted to a region of space small enough to have a negligible curvature? Wasn't that the intent of the Einstein thought experiment, that the person in the closed room couldn't tell whether he was in a gravity field or experiencing acceleration? That if you start giving him the means to detect the difference by extending his room (his frame) in size so that he can measure variance in acceleration then wouldn't that be a different thought experiment?--Percy

Not so sure about that. Some retellings I have seen do suggest that, but not all. I've never seen a description of the original thought experiment using Einstein's own words.There is nothing scientifically wrong with your approach. But I think Einstein's thought experiment instead considered a uniform gravitational region in which the tidal forces did not exist. He understood this picture would not represent real situations, and working out how to accommodate those situations mathematically was the bulk of 8 years work.I don't believe Einstein defined 'inertial frame' differently from the way he did in special relativity. But I also don't see any difference that would result from the approach you suggest.Added by edit. I think even a uniform gravitational region requires curvature of space-time. Without that curvature, how would we explain the trajectory of a bullet without introducing real forces? Edited by NoNukes, : No reason given.

You appear to be right. I couldn't find Einstein's original wording, but I think I found a fair description of it in a chapter in book by John Norton titled Thought Experiments in Science and Philosophy (Thought Experiments in Einstein's Work). On page 137 he has Einstein referring to a "homogenous gravitational field."So doesn't that render Barnes comments about tidal forces moot?Anyway, according to Norton (if you read on from page 137), Barnes' objections are not original. They were raised way back when Einstein first proposed the general theory almost a hundred years ago. But aren't these objections also beside the point? What does it matter if gravity manifests itself in the real (rather than ideal) world in a way that allows us to tell the difference between gravity and acceleration. When you simplify the issue down to the core, the two types of forces cannot be distinguished. That is what is important for a mathematical theory, and that is why gravity is legitimately indistinguishable from a fictitious force. That relativity has passed so many tests gives us great confidence in this interpretation.--Percy

Some of them at least.At some point we have to move beyond the thought experiment to deal with non-homogeneous fields. So I don't think we can dismiss everything Barnes says on the basis of the specific wording of the thought experiment.But I think his comment that those real non-homogeneous situations require real forces is not just moot; its wrong. Exactly. Nicely said. Edited by NoNukes, : No reason given.

Hi, DT.I apologize for the delay: I'm in the middle of a move across the country. The college-level variant of an old wives' tale always starts with "There have been studies done that show..."Would you have accepted that from me? What level of fine-tuning, eh? Let's go with 7.84. Does that sound good to you? Your answer to #4 contradicts your answer to #1. You methodology is to take your sample size of 1 (Earth), assume that all possible forms of life must require the same conditions as we observe for that one data point, then choose universe parameters based on how they might lead to those conditions. Clearly, you're just assuming that parameter values close to our universe's parameter values are required for life.

Thanks. Your link is a keeper!!!

The assumption that a particular value or range of values of parameter is "rare" is an undemonstrated premise. And simply telling us that people have written papers based on constants having different values does not answer the question of whether those parameters can actually be varied, and independently varied, over any range. Are those answers to be found in those papers? I doubt that, and I've asked designtheorist to provide evidence from the papers he relies on.Well, designtheorist refuses to discuss any of those papers giving the excuse that he'd have to review/discuss all of them. Well how about picking one or two papers and answering the question?Without being able to convert paramater ranges into probabilities, we cannot even get to the point of saying that one parameter or a combination of parameters is 'rare', and thus we cannot even get to the point of accusing designtheorist of making the Texas Sharpshooter error, which would surely be a possible next step.So what level of fine tuning would move me to the point of accusing designtheorist of making the sharp shooter fallacy or to the point of bringing out other possible explanations for why fine tuning does not imply design?My answer:No level of fine tuning that is not tied to probabilities instead of merely comparing ranges of potential variability, when the potential for varying the parameters independently is itself is not assessed, should grab my attention.