I'm going to look at that YouTube video since you make it sound interesting Please Register or Log in to view the hidden image!. Which one is it or who posted it? Or is it in the Wiki links you posted?
Yes, if you interpret the diagram as space-propertime, where all worldlines have the same length. Then at larger radius you advance less trough proper-time (you age less). See the diagrams linked in the video description (first and last link).
A mathematical construct. Yes, I can see that. So it doesn't cause gravity any more than a crime wave causes crime. I don't understand. What are some phase changes of matter resulting from presures generated by gravity ? And what IS gravity ? With respect, I have omitted the rest of your post because it was beyond me (although no doubt very meaningful) and I need to get my mind around the above first.
Yes, I think it's well worth reading. Definitely more philosophy than science, but that's no bad thing. Still highly interesting IMO. PS - re your edit, no wrong taken. Had you in fact meant the latter, it wouldn't have been a problem, becuse it would have been quite true to say I am more (such as it is) capable at philosophy than science. I have absolutely NO science background.
I can't agree with your first sentence above, if you say that it is anything more than a mathematical abstaction. As to the rest of your post, I don't think I am able to commnet on it and hope others here can.
I would agree if you would allow me to refer to it as ingenious mathematical abstraction. In the absence of a mechanism for gravity, he proposed that the best explanation for the observed motion of objects stems from the fact that the "form and structure" of space and time are not fixed or absolute, but are determined by how matter and energy somehow affect them as if they were curving space. The curvature of spacetime caused by the presence of matter and energy would then determine how objects move. Can you agree that the "as if" effect of gravity is pretty well quantified by the math that describes that motion? It does come pretty close, much closer than classical Newtonian mathematical quantification. The lack of a mechanism though seems obvious and over the years I have noticed that some science enthusiasts don't see that there is a missing mechanism. Fortunately, I rarely see someone who says they have professional physics credentials say that the geometry of spacetime is itself a real physical mechanism, so maybe we agree to that extent. The rest is unremarkable pseudoscience if you believe, like Aqueous Id implied, that gravity is somehow electromagnetic. Others believe that the mechanism is the physical curvature of spacetime caused by the geometry that supports Einstein's main statements of general relativity. Those who have quit looking for some other mechanism are not the vast majority of the dedicated scientific community still looking for "gravity". If you agree that the mechanism is still unknown, then you begin to brainstorm what the nature of matter and energy might be; what is it that physically makes objects move the way they do. My mention of the aether, or a foundational medium as I have come to call it, that fills space, is not scientific and so Aqueous Id is safe to call it pseudoscience despite the fact that some of the quantum studies sure sound like they are describing something unseen that exists in the space between objects. But that is just a layman perspective. I started this thread to simply confirm that the scientific community is not saying that there is a generally accepted mechanism, because when I pursue my hobby out in the "Fringe Forums", I always want to be sure that my supposed model has not been falsified, even though I cleary state that it is not science. (2302)
I see what you are saying and appreciate your description relating to the topologies. I understand what you were referring to; the Newtonian cylinder turns into the spacetime cone and the motion of the apple is described in the two geometries. That brings me to: When you say that the distortions of space and time explain time dilation and the bending of light, I take that to mean that within the Theory of General Relativity, they explain those observations, but in addition, you would acknowledge that there is no mechanism described within the theory that explains them.
It means that the model predicts those observed effects quantitatively. This is the implied meaning of "explain" in the context of physics. Depends on what "mechanism" means.
I agree with you in regards to the distinction between "explains" in the context of a layman's discussion and in the usage of the word "explains" in physics. Are you saying that the same distinction holds true in the usage of the word "mechanism"?
Quite frankly, I have no idea what people want to hear, when they ask about a "mechanism". And I'm not sure if they really know what they want.
That's fine, I will not try to imply I know what people mean by any particular word usage either. No argument on that from me.
Oops, I see you beat me to it. I should have let the describe vs. explain issue be put to rest with your post, but I got distracted by Lakon's reference to A.T.'s posted video, and then by A.T.'s post that led to my objection to "explains" as opposed to "describes". I hereby retract my subsequent response to A.T. which fell short, compared to your clarification.
Yes, I agree with the 'as if' effect. The sun too, behaves every morning 'as if' it is actually rising in the east, and I would assume that for millenia, mankind had well quantified math and geometry to describe that motion. Agree. I don't believe that gravity is electromagnetic anymore than I believe it is caused by geometry. I have NO idea what gravity and / or it's physical mechanism is. Call it psuedoscience, or whatever, I too tend to lean toward the aether concept. This is also as a consequence of reading much cosmology, mysticism, philosophy, etc, although not necessarily believing everything that I read - just taking it all in and seeing what views percolate to the surface. I appreciate that. I enjoy your occassional 'out of the envelope' thinking, and also your humility.
Not at all. It's a statement of disambiguation. Electromagnetic waves are "made of" oscillating electric (E) and magnetic (B or H) fields. Maxwell's equations are the collection of basic laws of electromagnetics. Space. Yes, free space designates space that is not occupied by any propagating medium. They're not in it. They're properties. No. It means that understanding electromagnetics is essential to understanding propagation. I'm saying aether is based in the belief that all waves propagate like acoustic waves do, which is a belief of the 19th c. (and ealier) scientific community. Retreading the dead belief in purported science is quintessential pseudoscience. Avoiding the fact of static field propagation devoid of any medium is part of that. It has nothing to do with me. The only sampling that comes to mind is standardized testing, such as the college admissions tests given to science majors. Yes, it's a fact that folks who believe in aether cast electromagnetic propagation as "acoustic" (i.e. mechanical) propagation. And it's a fact that the original belief in this was been replaced by discoveries in electromagnetics, special relativity and quantum mechanics. But the 1881 publication by Michelson in the American Journal of Science was the seminal work that killed 19th c physicists' belief in aether. That's problematic. If you'd had physics, you wouldn't be asking. But without physics, it's not likely you'd find closure from reading physics. But if you were going to take a science entrance exam, you might be expected to know facts such as those in the link below. To get the big picture, you'd need to trace the state of science from Maxwell to Michelson-Moreley to Lorentz-Poincare to Einstein. http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/mmhist.html#c2
Some more about that first youtube vid: When both the Newtonian and Einsteinian spacetimes are unrolled (like they are initially), obviously two dimensions of space are 'suppressed'. When they are rolled up, there is a map from one curve to the other such that points on each curve 'match up' horizontally. Now obviously spacetime doesn't "roll up" into a cylinder or truncated cone; the point is that a map exists between both versions of spacetime. If the truncated cone (which unrolls to a section of an annulus) is the 'real' version, then something has to happen to the first, Newtonian one. What that is is the appearance of a 'downward' force. Another view is that, although the curves are horizontally equivalent, they're different in a vertical projection: on the left, the Newtonian curve projects vertically onto a circle, on the right the Einsteinian curve doesn't, it projects onto a spiral. Also note that the rolling up procedure makes the time axis a closed curve (but this is strictly mathematical, time doesn't loop around itself in the real universe). That is, it distinguishes time from distance (in one dimension). In that sense it's "ok", because that's what we as observers do. It's an abstraction, therefore (and I hope it isn't doing your head in too much).
It's just that a radial 2D slice through spacetime around a spherical mass (radial space + time dimension) has a metric that can be most easily mapped to a surface of revolution. So they are used for embedding diagrams of this particular spacetime slice. That is a wrong idea one could easily get looking at the rolled version. Therefore it is important to point out that circularity of time is not mean to be implied. If you need more than one "circumnavigation", you arrive on a new layer of the diagram, not at an old time coordinate.
I think that if I pursue your response here I will be taking the thread to places that I didn't intend, and places I wouldn't want to go in this forum. Please feel free to pick up discussion of your points on how EM propagates and how the luminiferous ether has been falsified and superseded, on my "Alternative Theories" thread where I can discuss your points without venturing into forbidden territory in a hard science forum.
But it is mathematically true. The rolling up procedure is just another way to describe parallel transport. Unrolling a truncated cone gives you a section of an annulus. The two radii of this annulus correspond to the curvature along the time dimension at different potentials (they're fixed by the gradient). Rolling it back up makes this curvature vanish, instead you have two 'flat' circles with different radii which both depend on how big the spacetime slice is.
