watcher Posted March 16, 2009 Report Posted March 16, 2009 But this thread challenges anyone and everyone here to show how and why Euclidean space is discarded it starts with the constancy of lightspeed which led to the conclusion that time like space is also a dimension. and what exactly it is that is 'curved' other than a visual graphic for understanding the effects of gravity. the "curve" is more than a graphic representation, it represents gravity, a real physical phenomenon. the curve represents the connection between a point in 3d space and a point in 4d space. (actually gravity is best explained at 5d ). if the point between dimensions wouldn't take a straight path, what is the point of saying the shortest distance between the two is a straight line? this saying does not represent physical reality and just a whimsical assumption that only exists in your mind. now imagine that you want to straighten this curve so that the point in 3d and 5d is straight. but this must not be done in a whimsical way. to straighten up a longer curve to a straight line, this will create a stress in the line because you shorten it, right? and by doing so, you have succeeded in straightening the curved line but now the space between the two points in not empty anymore, there is stress (force) between them already. do understand what is happening? you cannot separate space any more without screwing up everything. if you do, were back to newton's imaginary strings that connects planets .LOL (and note that the inverse square law is not an explanation of gravity. the formula was derived from actual measurements and therefore just descriptive of gravity behavior) so we discard the "string" and replace it with a curved space. but before you discard this "curve", you must replace it of something else. you just don't discard it outright.what would you replace it? Of course the math of relativity works better for predicting gravitational effects than Newtonian physics. (I take it that is your point... yet again! above.)Yet this doesn't make the metaphor, graphic, (whatever) of "curvature" into an existential entity, an actual medium. You still have no idea that I am challenging the ontological nature of "spacetime" on the grounds that it makes something out of nothing, that it reifies both space (emptiness) and time (an artifact of measuring "event duration.") Ontologically speaking, neither are actual entities in the real cosmos.philosophy 101 - nothing comes from nothing.if you want to prove that spacetime is just a projection of something else, then ontologically speaking, the projection is also the source since all distinction, differentiation, categorization, divisions and separations are done by the mind.reification is what the mind do. LOL Will anyone here examine the transition away from Euclidean geometry with me *without the preconceived absolute belief that the math proves non-Euclidean geometry to be true and Euclidean false?* how do we do that? a mile is always a mile is a good philosophy if you are a surveyor. beyond that i can't see how this can be a sensible ontological idea.you are asking people to revert to a 3dimensinal space, discard time a the 4th dimension.you are dragging science back to Newtonian classical physics.how can that be a good and better departure point for ontology.would you like us to revert to imaginary strings to explain gravity or you have a better alternative explanation for gravity other than a curved space?
jedaisoul Posted March 16, 2009 Report Posted March 16, 2009 Michael, I'd like to investigate how far you have examined this "transcendental, cosmic perspective independent of all local frames of reference". Firstly, I would assume from your comments above that the answer to both the following questions is "yes", but I just want to be sure:1. Do you agree that the velocity of light is finite?Yes. Precisely 299,792,458 meters per second. OK. 2. Do you agree that the velocity of light is fixed?*Yes. Ditto. I've acknowledged SR dozens of times in this thread. Thanks, but the velocity of light being fixed does not necessarily imply SR. However, a velocity is meaningless if it is not with respect TO something. I disagree. Whether your units are meters per second, miles per hour or "earth diameters per" whatever, light travels at constant velocity anywhere in the universe regardless of "frame of reference."*That is simply not sufficient. If you say that "light travels at constant velocity anywhere in the universe", you are taking the universe as your reference. The trouble with that is that the universe (or at least the content of it) is not static. So if you are referring to something other than the content of the universe, you are taking the velocity of light as being fixed with respect to empty space. See below... So we may talk of a car travelling at 50 m.p.h., but that is implicitly with respect to the road (which is taken to be stationary). Similarly, we may talk about an aircraft flying at 500 m.p.h., but in this case it could be 500 m.p.h. with respect to the air around it (the air speed), or with respect to the ground beneath it (the ground speed). Both are legitimate measures of an aircraft's speed, and they can differ by more than 100 m.p.h. I fly an airplane occasionally and am quite familiar with the above. Of course a car or plane has a velocity relative to the center of the galaxy too, but we can take that to be the same as our solar system's velocity rel. to galactic center. But beyond such specific designations of "relative to what", a mile is the same distance whether measured "down the road" as usual or that same distance in the void of space beyond all cosmic content. Of course this would be strictly theoretical, but when you say miles per hour it does in fact designate an exact and unchanging distance traveled during an exact and unchanging period of time, no matter where the car, plane or photon is doing the traveling or relative to what. Yes, but if you are measuring a distance "in the void of space beyond all cosmic content", your "transcendental, cosmic perspective" turns out to be the same as classical mechanics. What's wrong with that? a) To measure velocities with respect to empty space, you have to be able to, at least in principle, distinguish between one point of space and another. That treats space as a material object, i.e. it reifies it.:evil: The Michelson-Morley experiment (and others like it) showed that the velocity of light does not vary with your velocity with respect to empty space, (which it would if the velocity of light were constant with respect to empty space). So, what, in your "transcendental, cosmic perspective", is the velocity of light fixed with respect to? Again, it travels at a fixed velocity of 299,792,458 meters per second no matter what its source, the direction its heading or what it goes past on the way.... or what any observer sees from whatever perspective.See above. I'm not talking about observers and what they see. I'm talking about what you are measuring the velocity against. Note: This is not an idle, nor a trick, question. I genuinely want to know if you have thought this through. Yes. Time does not slow down. Clocks do. Space does not expand or contract, tho all cosmic "stuff" is expanding outward into space, and, I believe, will eventually implode or contract back to whence it came. Distance between objects varies, of course as they move relative to each other. But a mile is a mile no matter what planet you are on... or in deep empty space. Same for a light minute or year... a universal standard for distance... the same everywhere. I agree that time does not slow down, and space does not contract. I've said so in the web site I linked to. But that does not alter the fact that whenever you, I or a relativist, quote a velocity, it has to be with respect to some datum that is taken to be stationary. P.S. If you have already answered these questions then I apologise, and would be grateful if you could point out where... Actually I've answered these questions many times in many contexts, but I don't mind saying it again. Who knows when I will say it just right for mutual understanding in a given context? MichaelWell, thanks for answering again. I too hope we are approaching a mutual understanding. It seems to me that your "transcendental, cosmic perspective" is nothing more than good old classical mechanics. Now there's nothing wrong in believing in classical mechanics per se, the vast majority of people do so without even knowing that it is classical mechanics; it's also our intuitive view of the universe. But if you put forward such views in a philosophy of science forum, you're going to have a hard time convincing anyone that:a) It's a new idea.:phones: It stands up against the evidence of actual physics experiments that have been conducted and verified many times over. I'd suggest that you need to examine the issues with classical mechanics and the velocity of light. I'm not saying that you should embrace SR. I don't. Nor am I saying that you should accept my model, or the CICS model. You might come up with a different model that fits the evidence. If you do, good luck!
Michael Mooney Posted March 16, 2009 Author Report Posted March 16, 2009 'll start with a reply to last post and work backward (in violation of my usual protocol of first post, first reply. Jedaisoul,You say: Thanks, but the velocity of light being fixed does not necessarily imply SR.I guess we are defining "fixed" differently. I mean that regardless of the velocity or vector of the light source, lightspeed does not change. As you know, tho it's counter-intuitive, the experiments don't lie. I have suggested that the explanation (or how to "make sense of it) is that light can not be "pushed" as in cumulative velocities of mass being "thrown ahead" from a mass (like a spaceship in frequent examples. Different physics applies to massless light.)Me:I disagree. Whether your units are meters per second, miles per hour or "earth diameters per" whatever, light travels at constant velocity anywhere in the universe regardless of "frame of reference."*You:That is simply not sufficient. If you say that "light travels at constant velocity anywhere in the universe", you are taking the universe as your reference. The trouble with that is that the universe (or at least the content of it) is not static. So if you are referring to something other than the content of the universe, you are taking the velocity of light as being fixed with respect to empty space. See below... What you don't get is that I am not "taking" anything as my frame of reference. I know the cosmos is always in dynamic movement, never "static." I also know that lightspeed is independent of all frames of reference, not requiring its velocity to be "with respect" to any reference.j:Yes, but if you are measuring a distance "in the void of space beyond all cosmic content", your "transcendental, cosmic perspective" turns out to be the same as classical mechanics. What's wrong with that?a) To measure velocities with respect to empty space, you have to be able to, at least in principle, distinguish between one point of space and another. That treats space as a material object, i.e. it reifies it. Again, beyond the relativity paradigm as the absolute "yardstick" for reality, lightspeed is the same everywhere without the need for the constant reference, "with respect to..." The last thing I would do is to "treats space as a material object." (Quite the opposite. "It's is no-thing... emptiness... in which "things" exist.) "In principle," light can travel from one locus in space to another with no-thing existing at either designated "point." :hihi: The Michelson-Morley experiment (and others like it) showed that the velocity of light does not vary with your velocity with respect to empty space, (which it would if the velocity of light were constant with respect to empty space). See my SR comment above... no required "with respect to"... same speed everywhere, even through empty space with *no reference points." See above. I'm not talking about observers and what they see. I'm talking about what you are measuring the velocity against. See above. The velocity of light is constant regardless of "what you are measuring (it) against.) It would still be the same of there were "no intelligent life in the universe" measuring anything! Do you see what I mean? I agree that time does not slow down, and space does not contract. I've said so in the web site I linked to. But that does not alter the fact that whenever you, I or a relativist, quote a velocity, it has to be with respect to some datum that is taken to be stationary. I am glad to hear your first statement above. So you don't "buy" "time dilation" or "space expansion/contraction" either? I think your use of the word "fact" above is inaccurate, as I've argued above. Even if you isolate the source of light from the rest of the cosmos (or say the universe consisted of just one star ;)...) the velocity of light traveling out into empty space is the same, relative to its star/source only! That's the only "relative to what?" required... its speed relative to its source...... It seems to me that your "transcendental, cosmic perspective" is nothing more than good old classical mechanics. Now there's nothing wrong in believing in classical mechanics per se, the vast majority of people do so without even knowing that it is classical mechanics; it's also our intuitive view of the universe. But if you put forward such views in a philosophy of science forum, you're going to have a hard time convincing anyone that: Maybe from the above you can see how it goes beyond classical mechanics, especially with respect to SR and the recognized accuracy of the math of GR, but without the reified "curvature" of space or malleability of time. a) It's a new idea. I have no interest in claiming novelty/originality. But when space and time "became" "things"... I objected, from my earliest studies of Einstein and Minkowski... which was quite a long time ago!;) :singer: It stands up against the evidence of actual physics experiments that have been conducted and verified many times over. Maybe you missed the way I distinguish the experimental results and the math from the ontology of "spacetime" which is usually taken for granted as a verified "real medium" by same. I'd suggest that you need to examine the issues with classical mechanics and the velocity of light. I'm not saying that you should embrace SR.As above... I do already! This only highlights the extent to which you misunderstand me.I don't. Nor am I saying that you should accept my model, or the CICS model. You might come up with a different model that fits the evidence. If you do, good luck! Thanks, but I already have. The evidence is that reifiying "spacetime" is superfluous to relativity. and its vastly improved math describing the *effects of gravity.*And until someone can show that space is "something" with curvature, I'll stick to what I have "seen" all my life as cosmos expanding out into "good ol'" Euclidean space (by whatever controversial dynamic of "the Bang"... and eventually reversing the expansion via gravity (Yes, the "critical cosmic mass" for such a "gravitational net" is being found in various forms, in various ways!) commencing the implosion half-cycle back into a ball of "all there is"... or many consecutive implosions into smaller "balls" and explosions... supernova-wise... So, Maybe you have judged "my cosmology" without fully understanding it.Anyway, thanks for your sincere efforts here, even if their intent has been to set me straight on the "facts." (I'm not too serious on the word "facts", but you get my drift.)Michael
Pyrotex Posted March 16, 2009 Report Posted March 16, 2009 Pyrotex:Guess you missed how the difference is ultimately an illusion. Again... :doh:OK... Back to basics. Is the ...distance between earth and sun ...93 million miles, ...or does it vary with ...relativistic effects? ...Michael me boy,I was trying above to use a little humor. I was in no way trying to be rude or trying to bait you. I felt that a bit of levity might releave the stress and make it easier for all of us to listen to each other. As many folks on this website will attest, I am a rather levitous fellow at times. :) Levitous? Is that a word? Levitary? Levitational? Leviticus? oh well... To answer your question quoted above: [ahem] The distance between Earth and Sun is 93 million miles.As measured from the Earth. Specifically, from the Palomar Observatory's 200-inch Hale Telescope. There. I hope that settles any remaining confusion that we may have. 93 million. Yup. Now, I really must insist that you ignore that spaceship coming from Epsilon Eridani, the one that is zooming through our Solar System at 95% of the speed of light. Just ignore it. It's not relevant at all. And especially ignore the telescope on that ship, the one that appears to be measuring the distance between the Earth and the Sun. Just ignore it. Why any idiot alien would want to do his/her/its surveying at that speed in the first place is beyond reason. And if its fool telescope even works, the idiot is gonna measure the Earth-Sun distance as... [woops] I'm sorry about that Michael. I got distracted. 93 million miles. The distance. Between Earth and Sun. That's it. No kidding. I wouldn't lie to you. [stupid goddam alien] :hihi: :singer: ;) ;) All levity aside. The Earth-Sun distance is 93 million miles. Seriously. We know this because we have measured it. We even measured it from a Frame of Reference on the Earth, so we wouldn't have to made any Relativistic corrections. Now, that stupid goddam alien is going to measure an entirely different Earth-Sun distance. Seriously. Does that "change" the distance? Absolutely not. He just gets a different value. If he/she/it has any brains, he/she/it will make the appropriate Relativistic correction to counteract the effect of the spaceship's speed. When the corrections are made, the result will be---93 million miles. Measuring is a form of observation. Observation is a fancy term for what is seen.When Frames of Reference are whizzing around near the speed of light, this changes or "distorts" what is seen. Like looking through the bottom of a Coke bottle. Like looking at the bottom of a pool through six feet of water. There is distortion in what one sees. This distortion has no effect on the actual distances or sizes. But we may not always be able to directly measure the actual distance or size. All we can count on is our ability to observe. There is no mystical god's-eye view of the cosmos that we can avail ourselves of. Not to get measurements, anyway. And if that stupid alien doesn't know any better than to correct for Relativity, then f**k him/her/it. :lol: :lol: :lol: :lol: :lol:
Michael Mooney Posted March 16, 2009 Author Report Posted March 16, 2009 Erasmus:Michael, put try to examine things from another perspective. Imagine someone shows up, claims repeatedly to have studied arithmetic, but then makes the claim 2+2=5. Try to open yourself to the idea that you have misunderstood something in your studies.Again and again I have said that I am not arguing with the math of relativity, which in fact turns out to be a well recognized advance in describing the effects of gravity, for instance, or the invariability of lightspeed. My challenge here is and has been, for all these pages, an ontological challenge of the reification of space, time, and "spacetime" which results in a non-Euclidean model of "curved space" etc... which, to me is nonsense. (Note: Gravity makes mass trajectories curve, and relativity describes those trajectories way better than Newtonian physics... its "strings between masses", etc. So you open with a strawman argument against me. No contest. ... math shows that non-Euclidean geometry COULD be true. So could Euclidean geometry. Glad to hear you say the latter. Still open to what exactly it is that is said to be "curved" in non-Euclidean space... or what the nature of, say "the fifth dimension" might be... let alone the 11 to 26 "dimensions" in string.M-theory... but that's another can of worms!( I understand, as does everyone, 3-d space and "time" as part of velocity for moving things.) The key word in your next two paragraphs is "Imagine."If your "big triangle" with more than 180 degrees of angles is presented as a real possibility (on curved space and all)... we *must* start with what, exactly such a curved space is, in reality, ontologically speaking. Obviously a globe or a bubble... a sphere has a curved surface. Maybe your triangle is "drawn" from the north pole at apex to an arc on the equator as base. By definition, this is no longer a "triangle", which is based on a plane and always has 180, no matter its size.So we know that spheres have curved surfaces. How does this show that "space is curved" as per non-euclidean geometry? Obviously Euclidean geometry recognizes all geometric shapes, including spheres. Now, lets extend this parable to three dimensions. We cannot picture a 3 dimensional curved space (though we can picture a 2d one, which is why I used the ants on a beach ball example). We must never make the unfounded assumption that what we can visualize is all that can exist. To be clear: Space has three known dimensions, and time is usually considered a fourth. When we use the word "dimension" we had best know what it is we intend to denote. I'll grant "time" as event duration. The cosmos is not static, and elapsed time for whatever to "happen" can be called the fourth dimension. (The line, the plane, and volume are the the three spacial dimensions, and the latter need not be described by geometric shapes, but can be "infinite space."To use your phrase, "We must never make the unfounded assumption that"... what we call "another dimension" is an actual reality unless we know what it is... and can explain it upon request. I hereby make that request for all supposed "dimensions" beyond the four I have just described. Maybe your next statements offer such a description:Now, imagine what that clever student might say. "How do we really know until we make a really big triangle and measure some angles?" So the question of what kind of geometry (Euclidean, non-Euclidean) is an experimental question. One that can be determined by measuring (for instance) the angles of a very large triangle. Surely my big triangle surveyed on Earth's surface above can be so measured for angle totlal. Still doesn't make earth's surface into "curvature of space." Modern science cannot actually do this experiment, but there are equivalent experiments, and they have been done.Please specify and elaborate in detail how they serve as evidence for "curved space"... which is *not the same* as the curved surface of a sphere!Michael, you defined distance via parallax determination in your posts on the Earth, Sun distance. I can calculate for you (if you like) or you can take my word that parallax gives different answers depending on where you are, and how you are moving. Imagine sending out three groups to measure the distance between the Earth and the Sun using parallax. One group goes to Mercury and does the measurement. One group stays on Earth and does the measurement. One goes and lands on Halley's comet and does the measurement. All three come back with different numbers. Which group gives your correct distance? I have bored everyone to death with my agreement that relativity provides correction for observer perceptual error due to lightspeed delay. No thanks on the calculations. The Mercury anomaly is one of the three most famous examples of the vindication of relativity theory. (Am I repeating myself? Yes, over and over!)MM:What is the shortest distance between the dots? Would a total consensus on the obvious straight line be considered "proof." Maybe not, but.... E:Consensus doesn't equal truth. There are probably hundreds of questions both qualitative and quantitative on which the consensus will indicate the wrong answer. Ok, I knew this was coming. So, say my line on flat paper is 10 inches long. (The shortest distance between the dots is a ruler-straight line between them, undoubtedly.) Then, after I bend the paper into an arch and stick a long needle through the dots, the distance between the dots along the straight needle is now, say 8 inches. Now the line on the paper's surface is the long way around, specifically 1.25 longer than the "shortest distance" along the needle. Maybe this example will come closer to the required "proof." I know the math is accurate!Thanks for your time. Gotta go.Michael
Michael Mooney Posted March 16, 2009 Author Report Posted March 16, 2009 Pyrotex,I appreciate your sense of humor. As you can see from my other posts today, I am not arguing (never have!) with the advance of relativity in correcting "observer error" due to lightspeed delay during the process of measurement. How this squares with Modest's constant use of "for observer A" the distance is... whatever... while "for observer B" at different relative velocity, etc, the distance is... (different)... no one has yet answered. He refuses to acknowledge that the "actual distances" are not changing due to these relativistic effects... or even that there is such a thing as "actual distance."Still waithing for an answer. Nuff said on that, I reckon.... until I hear from Modest or an apologist for his argument. Michael
Erasmus00 Posted March 16, 2009 Report Posted March 16, 2009 For (hopefully) clarity, I am going to reply to things out of order, I hope this helps. On the distances, I think you have again missed my point. I really am trying to be clear. Let me lay out some reasoning and tell me where you disagree. 1. If "distance" is an objective quantity independent of reference frame, then a. there should be a way to define "distance" so that everyone can measure and agree on a number. i.e. every person, any where in the universe, should be able to measure the distance between the Earth and the Sun and get the same answer. Its a question of definitions, "what do we mean when we say distance?" b. no such method exists. Conclusion: distance is not independent of reference frame. Where do you disagree? Now, on to curavture: To be clear: Space has three known dimensions, and time is usually considered a fourth. When we use the word "dimension" we had best know what it is we intend to denote. My example was designed in the three spatial dimensions. We do not need to include time or any other dimension. Now, does this make sense: if I supposed the surface of the Earth was flat, I could check this by going out to my driveway, drawing a large triangle, and measuring its angles. In fact, they will be slightly greater then 180, so I can say "aha, the Earth (or at least my driveway) is not a flat surface." This is (as you have said) because THE SURFACE OF THE EARTH IS CURVED. The 2 dimensional surface of the Earth is a curved surface. Even though it LOOKS flat locally everywhere (my driveway for instance) if we connect three points on the surface with lines that on the surface, the resulting shape has angles that add up to something other than 180. All of this makes sense right? So now, lets go to 3 dimensional space. What does it mean to say this 3d space is curved? (because we cannot visualize a curved 3d space) It means that if I draw a triangle, its angles don't add up to 180. So lets define a curved space as "a space where angles in a triangle don't add up to 180." This is what we mean by a curved space. Does this make sense? So, would you agree that if I went and drew a triangle between Earth, Alpha Centari, and Barnard's star and measured the angles of that triangle, and there weren't 180 degrees, then it would be fair to say the 3d geometry of space is a curved geometry?
Pyrotex Posted March 16, 2009 Report Posted March 16, 2009 Pyrotex,I would very much appreciate your clarification of this exchange:You: Me: We make observations. That's all they are, just observations. All else being equal, if You and Me are in the same Frame of Reference, we will make the same observations (and get the same distance value).If we are in different Frames of Reference (traveling at huge speed relative to one another), our observations may be significantly different (and get significantly different values). THIS IN NO WAY ALTERS THE ACTUAL DISTANCE. There is no acceptable interpretation that would have the actual distance change from one value to the other. Relativity doesn't claim otherwise.Nobody on this thread claims otherwise. If YOU are claiming that the CORRECT INTERPRETATION IS THAT THIS ALTERS THE ACTUAL DISTANCE, then you really need to disabuse yourself of that silly notion. :) :) :) No rudeness intended. It is possible for two people in different Frames of Reference to measure the same things and get different distances. However, if they ALSO measure their relative velocities, and make the appropriate corrections for Relativity, they should get the same distance. There is nothing extraordinarily complicated about this. Observing while traveling at high speeds introduces "distortion" in your observations.Observing something that is traveling at high speeds introduces "distortion" in your observations.
watcher Posted March 17, 2009 Report Posted March 17, 2009 Measuring is a form of observation. Observation is a fancy term for what is seen. science is mostly based on what is seen. its a called experiment. When Frames of Reference are whizzing around near the speed of light, this changes or "distorts" what is seen. Like looking through the bottom of a Coke bottle. Like looking at the bottom of a pool through six feet of water. There is distortion in what one sees. the distortion is based on the fact that everything in motion undergo lorentz transformation. it is not only what is seen that is distorted, but even our instruments and all our organs of perception are distorted. (i.e. all that are made of electrons) This distortion has no effect on the actual distances or sizes. But we may not always be able to directly measure the actual distance or size. All we can count on is our ability to observe. if all we can count on is our distorted ability to observe, what's the point of saying there is an actual distance? isn't it obvious that distances are distorted along with observations? if everything is distorted, who is the absolute final arbiter to say that behold this is the actual distance?( my answer is at the bottom ). assuming an actual distance exists outside a frame of reference is the same as saying space is absolute and not subject to distortions. There is no mystical god's-eye view of the cosmos that we can avail ourselves of. Not to get measurements, anyway. michael must be using his third eye. hehe THIS IN NO WAY ALTERS THE ACTUAL DISTANCE. again, the actual distance you are saying is only your imagination. if all points in space do not agree in measurement, who would be the keeper of this actual distance you are talking about? It is possible for two people in different Frames of Reference to measure the same things and get different distances. However, if they ALSO measure their relative velocities, and make the appropriate corrections for Relativity, they should get the same distance. comparing and correcting two measured distances of 2 different frames of reference is not the same as getting the actual distance. it only means finding another frame of reference common to them. the word actual is a subjective adjective that still rely from a point of view of another frame of reference. so getting an actual distance means stop using a frame of reference at all. which is unfeasible. there is no actual distancethere is no actual time. there is only actual "C". it is the only thing that is not distorted and is constant in all frames of reference. spacetime interval is the relationship of space and time arbitrated by "c" (lightspeed)space is a thing. time is a thing. they are subject to distortions. otherwise how can they enter into a relationship if they are absolute and/or imaginary and just a pigment of einstein imagination? the question is what kind of things are they. or better yet, determine the nature of C
jedaisoul Posted March 17, 2009 Report Posted March 17, 2009 The velocity of light is constant regardless of "what you are measuring (it) against.) It would still be the same of there were "no intelligent life in the universe" measuring anything! Do you see what I mean?I see what you mean, but you are still misinterpreting what I said. When I say all velocities are with respect to what you measure them against, I do NOT suggest that the act of measurement is changing what is measured. I agree that the velocity woul be the same even if there were no intelligent life to measure it. That does not alter the fact that a velocity is a measure of one thing moving with respect to another in a given period of time. That is the definition of a velocity. That "other" thing that the motion may be with respect to may be an abstract entity (like a reference frame), or a material entity (like another object), but either way, you cannot have a velocity that is not with respect to something which is taken as your stationary reference. I am glad to hear your first statement above. So you don't "buy" "time dilation" or "space expansion/contraction" either?That's right. There are a number of people who do not accept SR as an accurate description of the universe. Even if you isolate the source of light from the rest of the cosmos (or say the universe consisted of just one star ...) the velocity of light traveling out into empty space is the same, relative to its star/source only! That's the only "relative to what?" required... its speed relative to its source.That's pure classical mechanics (without a light medium). Let me explain:Lets take an A10 tank buster. Say it flies at about 350 mph, and fires shells that leave the cannon at a muzzle velocity of about 700 mph. Because the cannon fires in the direction of flight, these two velocities add, and the shells hit the tank at 1,050 mph (or thereabouts). So about a third of the punch that enables the shell to pierce the tank's armour actually comes from the velocity of the plane. Light is different. One thing we know for certain is that it's velocity is NOT fixed with respect to the source. Beyond that, opinions vary: 1) SR is based on the assumption that the strange effects of the way light moves is due to its velocity. So if a material object could move at that velocity, it would experience the universe the way that light does. Hence there is a gradation of effect with velocity. This is not noticeable at normal velocities because it is so small, but never-the-less it is still present. SR is, of course, the dominant intrpretation, and is the only one that is widely accepted in the scientific community. 2) An alternative is to say that light (and all electromagnetic phenomena) is fundamentlly different from material objects. So physical entities are divided into (at least) two sorts:a. Material objects, that have mass, and cannot travel at the velocity of light.b. Electromagnetic phenomena, that do not have mass, and can travel at the velocity of light. In this interpretation, material objects experience space and time classically, but electromagnetic phenomena do not. There is no gradation between the two. (This raises problems of how differnt classes of physical entities can experience the universe in different ways, but that is not relevant here). 3) Classically, it was thought that there was a light medium (the aether) and that light moves at a fixed velocity with respect to that medium. I think that Steve Bryant's CICS is a variation on that idea, but I'm not absolutely sure that is so. (My apologies to Steve if that is a misrepresentation). Anyway, I'm glad that you have taken my comments in the friendly way they are intended. I hope I've given you an insight into the complexity of the issues.
modest Posted March 17, 2009 Report Posted March 17, 2009 How this squares with Modest's constant use of "for observer A" the distance is... whatever... while "for observer B" at different relative velocity, etc, the distance is... (different)... no one has yet answered. He refuses to acknowledge that the "actual distances" are not changing due to these relativistic effects... or even that there is such a thing as "actual distance."Still waithing for an answer. Nuff said on that, I reckon.... until I hear from Modest or an apologist for his argument. Who, me? I’m honestly, at this point, not even sure where our contention lies. I think there might be a pretty large difference between how you and I are using similar terms which might be part of the problem. For me personally there is no difference between “distance”, “actual distance” or “objective distance”. Those all mean the same thing to me. Distance is what gets measured with a ruler. I could define that more specifically and with more examples, but the "with a ruler / measuring tape" sums it up nicely. Now we could, were we sufficiently clever, define “actual distance” to mean “distance according to frame A”. You could then get away with saying “the actual distance does not change with velocity”. I would actually be ok with that. I’d be freakin’ ecstatic if we defined a kind of “invariant distance” to mean the distance between two events in space and time which would then be fixed, absolute, universal, not frame dependent, etc. But, if “actual distance” is defined to mean: “what I ‘actually’ measure with my ruler” then it most certainly does change with velocity. If you change your velocity even a bit then it must change. We can differ philosophically about why that happens, but the fact will remain—it does happen. It must happen for our description of the universe to be consistent. How else am I going to get myself from the earth to the sun in less than a minute accelerating less than c? Think it out... do the math. The person making the trip needs to think the distance gets shorter for the universe to work correctly. With a change in velocity came a change in distance between the objects. As far as my personal philosophy... I don’t understand the distinction between what is measured and what is considered physically real. To me they seem to go pretty well hand-in-hand. There’s also no reason I can conjure which compels two people to agree on the “real” distance between objects. Or, put another way, why distance needs a single “actual” value. A person riding in a car would say the car had no momentum while a person sitting on the street would say the car had a good deal of momentum. We don’t demand one of those values of momentum be “real” or “absolute” while the other is not. They are both actual and real relative to some velocity. As long as we keep straight which we’re talking about then both are mutually consistent. So, let’s define some terms. If you, Michael, want to say “actual distances don’t change with velocity” then you should define “actual distance”. ~modest
jedaisoul Posted March 17, 2009 Report Posted March 17, 2009 We make observations. That's all they are, just observations. All else being equal, if You and Me are in the same Frame of Reference, we will make the same observations (and get the same distance value).If we are in different Frames of Reference (traveling at huge speed relative to one another), our observations may be significantly different (and get significantly different values). THIS IN NO WAY ALTERS THE ACTUAL DISTANCE. There is no acceptable interpretation that would have the actual distance change from one value to the other. Relativity doesn't claim otherwise. Nobody on this thread claims otherwise. [snip] Observing while traveling at high speeds introduces "distortion" in your observations.Observing something that is traveling at high speeds introduces "distortion" in your observations.It is my understanding that this is not strictly true. SR (and GR) says that the ACTUAL DISTANCES and TIME elapsed CHANGES with the different frames of reference. It's not just a "distortion in the observations". That is why in the Twin Paradox more time ACTUALLY elapses for the twin that stays on the Earth than for his twin who travels at near-light velocity to an from a distant star. Which leads me to Watcher's comment: science is mostly based on what is seen. its a called experiment.there is no actual distancethere is no actual time. there is only actual "C". it is the only thing that is not distorted and is constant in all frames of reference.It is my understanding that this is not strictly correct. The PROPER time interval or distance between two events (which is the same thing in spacetime) is the same irrespective of the frame of reference. The proper time elapsed betwen two events is measured in the frame of reference in which the two events are co-located (i.e. a timelike interval). The proper distance is measured in the frame of reference in which the two events are simultaneous (i.e. a spacelike interval). See http://en.wikipedia.org/wiki/Proper_distance:Proper length is analogous to proper time. The difference is that proper length is the invariant interval of a spacelike path while proper time is the invariant interval of a timelike path.
jedaisoul Posted March 17, 2009 Report Posted March 17, 2009 So, let’s define some terms. If you, Michael, want to say “actual distances don’t change with velocity” then you should define “actual distance”. ~modestHi Modest. Please see my comments above about PROPER distances (and time intervals). These ARE invariant with respect to the (inertial) frame of reference in which they are calculated. The difference is that a proper time is measured in the frame of reference in which the events are co-located. A proper distance is measured in the frame of reference in which the events are simultaneous. However, the ACTUAL distance and time intervals measured in other frames of reference WILL be different. This is not just an illusion (or distortion of the measurements). In any given inertial frame of reference:(time interval) squared - (spatial distance) squared = (spacetime interval) squared. Hence if spatial distance = 0, time interval = spacetime interval,and if time interval = 0, spatial distance = spacetime interval.
modest Posted March 17, 2009 Report Posted March 17, 2009 Hi Modest. Please see my comments above about PROPER distances (and time intervals). These ARE invariant... I couldn't agree more, but I'm quite sure you're not going to get Michael to discuss the distance between events, only objects. The idea that there's a spactime distance between an event tomorrow on the moon and yesterday on earth... well, I don't see that working with the philosophy being proposed. But, I'd be ever too happy to be proven wrong ~modest
jedaisoul Posted March 17, 2009 Report Posted March 17, 2009 I couldn't agree more, but I'm quite sure you're not going to get Michael to discuss the distance between events, only objects. The idea that there's a spactime distance between an event tomorrow on the moon and yesterday on earth... well, I don't see that working with the philosophy being proposed. But, I'd be ever too happy to be proven wrong ~modestPoint taken
Pyrotex Posted March 17, 2009 Report Posted March 17, 2009 ...the distortion is based on the fact that everything in motion undergo lorentz transformation. Yes, I know. :) I was trying for an explanation that did not rely on an understanding of physics -- which I have a degree in. :)...assuming an actual distance exists outside a frame of reference is the same as saying space is absolute and not subject to distortions. If one is being picky, then you are correct. Again, I was trying for more of a simplified, even cartoonish, explanation that Michael might find paletable. Philosophically, it doesn't do any "damage" to speak of an "actual distance" -- it's just that you can never know what it is. :) :) :)...there is no actual distancethere is no actual time...Yes, if by "actual" you mean "absolute". It all boils down to this: 1. To know a distance, you must make a measurement.2. To make a measurement, you must make it FROM somewhere.----[like the old punchline, "Everybody has to be somewhere!"]3. The place from which you do the measuring is YOUR frame of reference. It is either the "beginning" or the "end" of the line of distance you are measuring.4. The object or event that defines the other end of the distance you are measuring has its own frame of reference. [and Everything has to be somewhere.]5. A measurement can only be made by the observation of a transfer of information.----[the "information" can take the form of photons, particles, waves, sound...]----[However, across the vaccuum of space, we are limited to photons, traveling at C.]6. No frame of reference can be held to be the "correct" or the "absolute" frame of reference.7. If the two frames of reference are traveling at high enough speed relative to each other, then the measurement will be affected or "distorted" in a certain way. It matters not WHICH frame of reference you are in; the "distortion" is the same either way.8. This "distortion" is non-intuitive. If you are relying on common experience and common sense to understand this, then you won't.9. The constancy of the speed of light in a vaccuum -- as observed from ALL frames of reference -- was assumed by Einstein, not proven. :eek:10. This constancy of C, as well as its finite value, means that ALL measurements suffer Lorentz-Fitgerald "distortions". No exceptions.11. ALL experiments between frames of reference, with one traveling at near-C speeds relative to the other -- have confirmed that Einstein's assumption, and his conclusion, predict exactly the values we measure in those experiments.12. Measurements of a distance made from two unique frames of reference, not at rest with respect to each other, will yield different values.
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