Cap'n Refsmmat Posted October 6, 2011 Posted October 6, 2011 Yes, thanks. How are the "end points" measured in the accelerator? And how do those measuremets confirm that the distance between them has been shortened by their respective high velocities? In other words, how does going faster make the distance traveled, or length between them shorter or contracted? Er. That's not how length contraction is measured in a particle accelerator at all. Here's a few resources you can look over: http://www.physicsforums.com/showthread.php?t=299618 http://www2.slac.stanford.edu/vvc/theory/relativity.html http://books.google.com/books?id=o4dc_zcnl1cC&pg=PA296&lpg=PA296&dq=feynman+pancake+particle&source=bl&ots=zF5thdnWqZ&sig=eCMAhKbn6Cv__5RnIIlcPPulAWU&hl=en&ei=FvaMTrqtG5CKsAKvzOjeBA&sa=X&oi=book_result&ct=result&resnum=2&sqi=2&ved=0CB8Q6AEwAQ#v=onepage&q=feynman%20pancake%20particle&f=false On the other hand, how "logically consistent" is the assumption that solid objects either change shape or their shape can not be known because of the great mystery of c and how things look from different frames of reference. Same for the natural/objective/intrinsic distance between objects in the real cosmos. Very consistent, when you include it in the set of ideas that constitute modern physics, such as 4D Minkowski space. Clearly inconsistent when you contrast it with the beliefs you personally hold.
tar Posted October 6, 2011 Posted October 6, 2011 (edited) Owl, OK, I don't understand SR completely. I just have the main drift. And as we have established, the NOW of SR counts all points that are not moving relative to us as being in our now simultaneously, regardless of their distance from us. This NOW is contrived, imaginary with no way to check on what is really happening NOW at distant points. We are doing it in our minds, with communication between the observers at these points happening at the speed of thought. But we know from experience that stuff happening NOW a lightyear away, will arrive here in a year. So what we have going on in our imaginations is REALLY happening now. It proves out later, to have been the case. Same operation is going on when you imagine the Sun an AU away and run a mind experiment and calculate when the light will leave a spot and arrive at another, and when something moving with a velocity relative to both the Earth and the Sun will be at various points, and what they will see. You are contriving the whole thing. Imagining the whole thing based upon the measurements you hear have been made, operating in this environment, from the perspective of the Sun and the Earth being stationary relative to each other, always a constant (give or take) distance away, and light always taking the appropriate time to make the trip. Then you have to switch back and forth from a Sun observer to a laser guy, to the other laser guy, to the Earth observer, and make everything add up in terms of who will see what when, and all you have to use is your "one" perspective, counting the Sun and the Earth as both in the same stationary frame. YOU have to contrive this imaginary NOW to make these calculations, and state how far the Sun REALLY is based on how long light will take to make the trip. But take a laser fighter guy/gal by himself/herself. All the points in his/her NOW are stationary in reference to him/her. He/She is not moving. The Sun and the Earth and the other laser fighter are. His/her calculation of the distance light travels in a second, is based on how long it takes light to go from a point that is stationary, one light second away from him/her. This point, that he/she is measuring to, is stationary to him/her, but moving at the same velocity as she/he is, according to us and our Sun/Earth FOR. You, Owl, try to pick apart SR, by saying that the whole universe has to be interpreted as having only one distance and time measurement possibility, and that is the one taken from the Earth/Sun FOR. SR on the other hand says, that the measurements of time and distance along the direction of the difference in velocity between two frames will nescessarily differ, because the universe IS only one way and C will ALWAYS be measured at the same speed, by anybody stationary in an inertial reference frame. SR says better, what you are claiming. You are claiming that our FOR counts in determining the actual true measurements of reality, and anything else is a contrived abstraction. SR states that the contrived abstractions of any and all FORs are equally correct, and when taken together, will accurately describe reality, as it really is. Regards, TAR2 Edited October 6, 2011 by tar
tar Posted October 6, 2011 Posted October 6, 2011 the above was written last night, posted 8PM. This morning I had a waking thought that applies to this thread in several ways. Consider the concept of the ricochet. What it means to the establishment of self and FOR. And the difference in the path and meaning of a ricochet to a self in a FOR that is moving relative to a previously established one.
tar Posted October 6, 2011 Posted October 6, 2011 Owl, Perform a ricochet experiment, two straight lines in the flybyguy's FOR. Tell me what it looks like in our FOR. Are the lines straight, or curves? Regards, TAR2 what's' the REAL length of the lines?
owl Posted October 6, 2011 Author Posted October 6, 2011 (edited) Er. That's not how length contraction is measured in a particle accelerator at all. Here's a few resources you can look over: Here is part of what gleaned (with my comments interjected) from your links. russ watters, physorg.com For example, when a particle in a particle accelerator takes longer to decay because of relativistic effects, it also travels a longer distance than it "should", based on the same effect. But in the frame of the particle, it does not travel a longer distance than it should. "...because of relativistic effects..." relativistic effects are demonstrated. Perfect tautology, but it explains exactly nothing. Could I translate it to something like, 'the faster a particle travels the longer it lives and the further it goes?' Last sentence in quote affirms that each frame of reference has its own reality, i.e., there is no reality (real world) transcending FOR. From I Am an Engineer (same site): If you, however, look at the case from the perspective of the muon, the time is going at a 'normal' rate. The only way for the muon to reach the earth is if the distance were smaller (i.e. length contraction). "For a muon" Earth's atmosphere is much thinner than Earth science has measured it. Fine. Good thing muons don't dictate reality for all of us Earthlings. We like it around 1000km thick. DaleSpam (same site): The bunch length is contracted as predicted. The total amount of charge in a bunch increases as the length contraction increases. Basically, because of length contraction you can squeeze in more charged particles in a single bunch than you could without length contraction. I will need to study the meaning of "bunch length" for a hint of what this means... and why "more charged particles" can not be "squeezed into a single bunch" (like compressed) without length contraction. Maybe your boss can tell me. Mentallic (same site): Similarly, I'm just in search for any evidence to support length contraction without making it an assumption by the observation of the others. Me too, like “in the real world, independent of “as seen from extreme velocity FORs." From the second link, Stanford site on SR: The Speed of Light is the same for all observers. The first postulate -- the speed of light will be seen to be the same relative to any observer, independent of the motion of the observer Light is clearly a mysterious and quite versatile and insubstantial phenomenon. No argument with the above, but that does not make distances between objects in the real world longer and shorter (expanded and contracted) with every different FOR... as subjective idealism would have it, with FOR as an abstract version of "subjective." Physics is the same for all inertial observers. This second postulate is really a basic though unspoken assumption in all of science -- the idea that we can formulate rules of nature which do not depend on our particular observing situation. Agreed. Physics does " not depend on our particular observing situation"... like the FOR of muons "observing" the depth of Earth's atmosphere. Cap 'n: Very consistent, when you include it in the set of ideas that constitute modern physics, such as 4D Minkowski space. Would you please contrast this with my repeated comments on 3-D space plus elapsed time for movement rather than space and time somehow combined? (Ref: Brown and Pooley, Minkowski’s spacetime: a glorious non-entity.) Clearly inconsistent when you contrast it with the beliefs you personally hold. Me, personally? How about the overall philosophy of realism that the world exists and has intrinsic properties, objective shapes and relationships/distances between objects totally independent of FORs from which they are observed? "You can call me a dreamer, but I'm not the only one." (Paul McCartney.) Ps, I forgot the Feynman link: (Feynman) realized that at very high energies, the effects of relativity would cause each particle, in the frame of the other particle, to look like a pancake, because the lengths along the direction of motion are contracted. So “the effects of relativity” cause particles to look like pancakes from one frame to another. Fine. The Earth might look very squished and not at all spherical from your extreme FOR, but that does not make it so “in the real world.” It is a very real, substantial solid-ish object with a life and properties independent of how it is seen from the exstreme FOR. Edited October 6, 2011 by owl
Schrödinger's hat Posted October 6, 2011 Posted October 6, 2011 Me, personally? How about the overall philosophy of realism that the world exists and has intrinsic properties, objective shapes and relationships/distances between objects totally independent of FORs from which they are observed? "You can call me a dreamer, but I'm not the only one." (Paul McCartney.) For the n+1th time. Realism, relativity: They go together fine, it's just relativity's reality is 4D. Realism, relativity, presentism: They do not, you have to do something else make a constant speed of light work with presentism. That something else is unpalatable to most scientists as it goes heavily against Occam's Razor, but you're welcome to go read about it, I will even describe the logic that leads to this when I get around to coding some animations. Noone disputes realism. You keep presenting the options Relativity or realism whereas we keep presenting the options relativity or presentism So "the effects of relativity" cause particles to look like pancakes from one frame to another. Fine. The Earth might look very squished and not at all spherical from your extreme FOR, but that does not make it so "in the real world." It is a very real, substantial solid-ish object with a life and properties independent of how it is seen from the exstreme FOR. It can look squished from one FOR and spherical from another and still be real. But look in this context means more than just what you see. It means what appears to be the dimensions of the particles according to every instrument you have, after you have taken into account the effects of light delay. For those instruments to be lying when you are moving requires moving to be defined absolutely ie. 'he is moving', rather than 'he is moving relative to the car'. Otherwise you get inconsistencies. This is what we mean by a preferred frame.
Cap'n Refsmmat Posted October 6, 2011 Posted October 6, 2011 Would you please contrast this with my repeated comments on 3-D space plus elapsed time for movement rather than space and time somehow combined? (Ref: Brown and Pooley, Minkowski’s spacetime: a glorious non-entity.) Rotating coordinates in four-dimensional spacetime causes space and time to "mix", making events which were far apart in time and close together in space become closer in time and farther in space, and so on. This can be used to explain all observed relativistic effects. However, I am not a textbook. I suggest you get one if you wish to learn the nature of Minkowski space. Me, personally? How about the overall philosophy of realism that the world exists and has intrinsic properties, objective shapes and relationships/distances between objects totally independent of FORs from which they are observed? Your overall philosophy of realism relies on the single assumption that these properties are intrinsic in three dimensions, which is the only assumption which must be thrown out. The rest of the philosophy can stay. I regret that evolution has not provided you with eyes which can see in the fourth dimension. So “the effects of relativity” cause particles to look like pancakes from one frame to another. Fine. The Earth might look very squished and not at all spherical from your extreme FOR, but that does not make it so “in the real world.” It is a very real, substantial solid-ish object with a life and properties independent of how it is seen from the exstreme FOR. It's real enough for the particles in the accelerator to behave very differently than they would in their "real" shape. If the "real" shape cannot explain the results of the experiment, what good is it?
tar Posted October 7, 2011 Posted October 7, 2011 OK, Confused again, as to the meaning of things. Brought on by the three Nobel winners who determined that the universe is accelerating. What does THAT mean. If the universe is a four dimensional manifold and time and space are sort of different aspects of the same thing, then time is just as enormous in some sense, as space is. This being the case, it is difficult for me to figure what someone might mean by the universe IS expanding. Especially since they come to this conclusion by looking as supernovae that were doing whatever we see them doing...billions of years ago. What reasoning allows scientists to declare what the universe is doing now, based on what they see it doing so far away in space and time? And it makes me wonder what is meant by statements such as the universe has x.x to the xx atoms in it. x.x times 10 to the xx NOW or x.x times 10 to the xx THEN? or always? If a particle exists for a nanosecond or for 13 billion years, is it counted once or a zillion times? I don't know. Confused again. And on simultaneity. If it is defined as two events happening at the same time to an observer in at least one frame of reference, then take me, looking at the stars. Everything I see is happening at the same time. So the events close, and the events far are still simultaneous. This is contrary to the imagined NOW that puts everything in the universe at the same 13.7 billion year old NOW. Perhaps I just need to watch the baseball game. The Yanks are either going to win. Or they are going to lose. I can handle that. Regards, TAR2
Schrödinger's hat Posted October 7, 2011 Posted October 7, 2011 Brought on by the three Nobel winners who determined that the universe is accelerating. If the universe is a four dimensional manifold and time and space are sort of different aspects of the same thing, then time is just as enormous in some sense, as space is. This being the case, it is difficult for me to figure what someone might mean by the universe IS expanding. Especially since they come to this conclusion by looking as supernovae that were doing whatever we see them doing...billions of years ago. What reasoning allows scientists to declare what the universe is doing now, based on what they see it doing so far away in space and time? We look to what happened at different times/distances and come up with a theory which explains what we see at any given time/distance. Some of the supernovae were billions of years ago, some were mere tens of millions. This is basically the premise of all science (things later behave as things earlier), just over a longer time scale. And it makes me wonder what is meant by statements such as the universe has x.x to the xx atoms in it. x.x times 10 to the xx NOW or x.x times 10 to the xx THEN? or always? If a particle exists for a nanosecond or for 13 billion years, is it counted once or a zillion times? That'd be 'around about that many in the visible universe' and always. The charges the atoms carry (mass, electric charge etc) don't go anywhere, so even if things get reconfigured there's still roughly the same number of atoms. Also things haven't really changed from being mostly hydrogen, so the number hasn't really changed all that much. One other thing to note: The visible universe is changing (we can see further back in time, and things are moving away). This will change that number, simply because it's a number based on what we could interact with, not the whole universe (which may or may not be infinite). I don't know. Confused again. And on simultaneity. If it is defined as two events happening at the same time to an observer in at least one frame of reference, then take me, looking at the stars. Everything I see is happening at the same time. So the events close, and the events far are still simultaneous. This is contrary to the imagined NOW that puts everything in the universe at the same 13.7 billion year old NOW. Nono, those things happened a long time ago in your frame. You won't see what's happening now on alpha centauri for four years.
owl Posted October 7, 2011 Author Posted October 7, 2011 (edited) Cap 'n R, Some review of unanswered questions and unaddressed comments before replying to your last post: From post472: There have not been any experiments confirming large scale* length contraction,...That leaves all relativity's claims about the validity of length contraction as applied to Earth, the Au, the meter rod and the distance through Earth's atmosphere not confirmed by experiments. Please answer the several unanswered questions/challenges in this regard in my last post(469). In post 475 I accepted your offer: My boss is a particle physicist. Anything you want to ask him? Yes, thanks.How are the "end points" measured in the accelerator? And how do those measurements confirm that the distance between them has been shortened by their respective high velocities? In other words, how does going faster make the distance traveled, or length between them shorter or contracted? No reply to these specific questions. Instead: Er. That's not how length contraction is measured in a particle accelerator at all. Here's a few resources you can look over: I looked them over and commented in post 480. Here are some unaddressed comments and unanswered questions from that post: Could I translate it to something like, 'the faster a particle travels the longer it lives and the further it goes?' I will need to study the meaning of "bunch length" for a hint of what this means... and why "more charged particles" can not be "squeezed into a single bunch" (like compressed) without length contraction. Maybe your boss can tell me. Maybe not. Some guy, Mentallic from the forum you linked writes: Similarly, I'm just in search for any evidence to support length contraction without making it an assumption by the observation of the others. I reply: Me too, like “in the real world, independent of “as seen from extreme velocity FORs." From your Stanford link on SR, the second postulate: ...we can formulate rules of nature which do not depend on our particular observing situation. My reply: Agreed. Physics does " not depend on our particular observing situation"... like the FOR of muons "observing" the depth of Earth's atmosphere. You: No comment on any of the above. Regarding Minkowski 4-D space: Would you please contrast this with my repeated comments on 3-D space plus elapsed time for movement rather than space and time somehow combined? (Ref: Brown and Pooley, Minkowski’s spacetime: a glorious non-entity.) No comment on others’ criticism of above, ever. Just more advice to read a good textbook on it, like the mainstream combination of time and space (forget the ontology of each and both together) as per Minkowski is not to be questioned. Then, of course, there is basic realism, repeated yet again (with bold emphasis): How about the overall philosophy of realism that the world exists and has intrinsic properties, objective shapes and relationships/distances between objects totally independent of FORs from which they are observed? Then again to my favorite example how things might look in extreme frames ("like pancakes") compared to all realistic descriptions: The Earth might look very squished and not at all spherical from your extreme FOR, but that does not make it so “in the real world.” It is a very real, substantial solid-ish object with a life and properties independent of how it is seen from the extreme FORs. You continue to dance around this point, invoking the 4-D space device* (a coordinate system) with a “who knows?” approach, all FORs being equally valid. So maybe Earth really IS squished nearly flat! You call this science? *About the “devices” of relativity (from post 475): Clocks slow down at high velocity (etc.), and "time dilation" is "devised."Three D objects and the distances between them in space look different from different perspectives/velocities, and "length contraction" is "devised."... (ed)... "Time and space" are taken for granted as some sort of entities... reified. (Not so, ontologically.) Again, this thread is about the philosophy of FORs as determining reality. I closed the above post with another summary, still not addressed: On the other hand, how "logically consistent" is the assumption that solid objects either change shape or their shape can not be known because of the great mystery of c and how things look from different frames of reference. Same for the natural/objective/intrinsic distance between objects in the real cosmos. The cosmos doesn't care how we look at it. It is as it is, and its up to science to find the best ways in all cases to investigate and discover "what it is", how it and its parts are shaped, how far it is between them and how all parts of it dynamically interact. (A little philosophy...) I'll post this and then go to your last post. Rotating coordinates in four-dimensional spacetime causes space and time to "mix", making events which were far apart in time and close together in space become closer in time and farther in space, and so on. This can be used to explain all observed relativistic effects. "Rotating coordinates" in your "4-D" model of 'spacetime' ("rabbit pelt"... whatever,) does not not "cause" anything "mix" or rotate in the real world. The above reifies time and space. If time is the duration from one "now" to another, and space is the volume in which objects exist and move (see extensive arguments in "ontology of time" and "spacetime" threads), then "rotating (your) coordinates doesn't cause any object to move closer to or further from any other object in the real world, but only in your model. However, I am not a textbook. I suggest you get one if you wish to learn the nature of Minkowski space. The "nature of Minkowski space" is not a factual natural phenomenon for good students to "learn" about. Rather it is a concept with a hot debate around it. You continue to ignore that and my critical references (including the B&P paper cited above and the ISASS volumes of papers)... and treat the 'mainstream' as the only 'stream' of intelligent thought on the matter. Your overall philosophy of realism relies on the single assumption that these properties are intrinsic in three dimensions, which is the only assumption which must be thrown out. The rest of the philosophy can stay. See my repeated references to the Kelley Ross paper on Non-Euclidean Geometry and Cosmology... addressing the *assumptions* inherent in modeling space as four dimensional. The three axes of volume ( space and the objects in it) fully describe them, and time remains "that which elapses" as objects move. You are welcome to show me* how you think that is wrong or how space and time coalesce into an entity in the real world. I regret that evolution has not provided you with eyes which can see in the fourth dimension. If I were an M-theorist, I could challenge you to describe those extra seven dimensions (beyond 3-D and time) upon which cosmic Membrane is based. I would settle for the *"show me" above. It's real enough for the particles in the accelerator to behave very differently than they would in their "real" shape. If the "real" shape cannot explain the results of the experiment, what good is it? I would need to become an expert in that field (or get my above questions answered) to address subatomic length contraction. I will, however settle for an admission that Earth stays pretty much spherical regardless of extreme FORs, and the same for the usual suspects: The Au, Earth-Sun distance, the solid meter rod, and the depth of Earth's atmosphere do not really shrink as seen from extreme FORs. Or, in lieu of shrinkage, which you have disavowed, science can not know the true shape of Earth or the other lengths above, and all scientific epistemology has been made obsolete by SR's theory of length contraction. Edited October 7, 2011 by owl
Cap'n Refsmmat Posted October 7, 2011 Posted October 7, 2011 I would need to become an expert in that field Please do. I'm not going to bother answering so many questions when they are essentially "but if I throw out all the important parts of relativity, it's so absurd!" You can't, say, ditch 4D spacetime and then expect relativity to make very much sense.
owl Posted October 8, 2011 Author Posted October 8, 2011 Please do. I'm not going to bother answering so many questions when they are essentially "but if I throw out all the important parts of relativity, it's so absurd!" You can't, say, ditch 4D spacetime and then expect relativity to make very much sense. Does this leave anyplace at all for reason or common sense? All I was "throwing out" was the absurdity of length contraction/time dilation as describing a very distorted solar system, all bodies like flat pancakes and all, and the distances between planets and sun up to the observer's limited FOR. Not even close to realism. I can say "please explain 4-D spacetime" with something more than a rabbit pelt metaphor (spacetime is just a metaphor for our model of space and time) "and then expect relativity to make very much sense." (some sense, anyway.)
Cap'n Refsmmat Posted October 8, 2011 Posted October 8, 2011 Does this leave anyplace at all for reason or common sense? Plenty of places for reason; physics is based on it. "Common sense" is unfortunately a poor predictor of the nature of the universe. Appeal to ridicule isn't an argument against experimental evidence. I can say "please explain 4-D spacetime" with something more than a rabbit pelt metaphor (spacetime is just a metaphor for our model of space and time) "and then expect relativity to make very much sense." (some sense, anyway.) And I say I'm not a textbook. You need one to get a full explanation, unless you'd like to wait around for a few weeks while I write one.
tar Posted October 8, 2011 Posted October 8, 2011 (edited) Schrödinger's hat, From your #484: Some of the supernovae were billions of years ago, some were mere tens of millions.This is basically the premise of all science (things later behave as things earlier), just over a longer time scale. Well I understand that part of the reasoning...but the universe also evolved. Stars went through a few "stages". The heavy elements we find on Earth are not exactly Helium atoms. Some processes "made" them what they are. Stars had to live and die and the remnants had to have come back together and "cook" in a new nuclear furnace. It seem reasonable to assume that the supernovae from billions of years ago were residents of a "younger" universe, that had different characteristics, less heavy elements for instance, and possibly other important differences, that only "time" and evolution, one thing building from the results of the earlier process, could establish. In this regard, the "standard candle" of a supernova happening in a "young" universe seen at Z=6, might very well not mean the same thing as a supernova happening in a 13.6 billion year old universe that we see "nearby" and only "recently" happening. My confusion comes from how logical assumptions are carried through in one regard, and then ignored or discarded in other regards. Too often for my taste "esquitely precise" measurements and determinations are made, based on logically carrying forward from one assumption to those that follow logically and mathematically going deeper and deeper into the esoteric minutia, that the momentum takes on a truth of its own, unrelated to common sense and realty. If something unexpected is encountered, it might simply mean we are looking at it wrong. A lot of times when I read about theories and things like Bell's inequalities and such, I get lost in the logic of "well we expected it to look like this, but it looked like that, so this other thing must be the case" Huh? Were you wrong first time or not? What if we expected it to be the second way? Would then the third thing not have to be the case, but simply some other logical explanation of the second thing, might be the ticket, discarding the erroneous assumptions that brought about the surprise? Reminds me of Indiana Jones running into a huge skilful foe with glinting swords flashing in a dazzling display obviously outmatching Indy's strength and skill and stature. So Indy shoots him. Regards, TAR2 Owl, Were the lines in the flybyguy's ricochet experiment, the same length and straightness in his FOR as in ours? Would he not have seen the experiment, if we performed it, as having the same "odd" distance and curve? Serious question. I don't know why you are ignoring it. Do you not have an answer? Or is the correct answer contrary to your 3D only claim? Certainly your 180 IQ can handle anything my 130ish could throw at you. Try answering. I double dog dare you. Regards, TAR2 Edited October 8, 2011 by tar
owl Posted October 8, 2011 Author Posted October 8, 2011 Plenty of places for reason; physics is based on it. "Common sense" is unfortunately a poor predictor of the nature of the universe. Appeal to ridicule isn't an argument against experimental evidence. And I say I'm not a textbook. You need one to get a full explanation, unless you'd like to wait around for a few weeks while I write one. I wasn't asking for a mainstream, textbook account of length contraction. This forum has presented that argument extensively. My threads and sources are critical of some parts of relativity, and those criticisms have not been addressed here at all. The main theme of this thread, for instance, is that the philosophy of realism says that "the world" has a reality of its own, independent of how it is observed from various extreme frames of reference. ("Imagine no intelligent life"... etc.) How would things change if there were no observation and measurement from these extreme FORs. Not at all. So what shape is Earth? (How long is a meter rod, the Au, etc.) We don't know? Yes, we do know, and earth is not flattened like a pancake, even if it looks that way from the overworked FOR you length-contraction advocates have championed here. Is that an appeal to ridicule? That the very oblate spheroid description of earth is absurd/ridiculous is not because of me appealing to ridicule. And of course, there is no experimental evidence at all for the validity of such a description. How "reasonable" is it that Earth's atmosphere IS very much thinner "for a muon" than as measured by all our best tools of Earth science? Not at all reasonable. Again: All I was "throwing out" was the absurdity of length contraction/time dilation as describing a very distorted solar system, all bodies like flat pancakes and all, and the distances between planets and sun up to the observer's limited FOR.* Not even close to realism. ...and the solid meter rod "appearing" like 12 cm or so, and... TAR2: Were the lines in the flybyguy's ricochet experiment, the same length and straightness in his FOR as in ours?Would he not have seen the experiment, if we performed it, as having the same "odd" distance and curve? Serious question. I don't know why you are ignoring it. Do you not have an answer? Or is the correct answer contrary to your 3D only claim?... Sorry, but have found your posts lately rambling, full of tedious and irrelevant minutia/detail, bordering on incoherent, and mostly off topic. But, if you will refer me again to your "flybyguy's ricochet experiment" I will study it and reply... Btw, please explain what you mean by 4-D space.(Not just, 'everybody knows what Minkowski meant.') What fourth axis is there applying to 3-D objects and the volume of space itself. And I do recognize time as "that which elapses" as things move, i.e., not a static snapshot universe. Also time is not an entity, not an ingredient mixed with space (empty volume), becoming a mystery medium, "spacetime." Meanwhile, I'm gone again for the weekend. -1
Cap'n Refsmmat Posted October 8, 2011 Posted October 8, 2011 And of course, there is no experimental evidence at all for the validity of such a description. If this is your conclusion, then you do not yet understand the nature of relativity and how it works. Likewise with the arguments about the shape of the Earth and the nature of 4D spacetime. It's clear you do not want to learn from me, but rather to contradict everything I say, so I don't see the point of explaining. Physics does not require theories to avoid absurdity; nature has no such qualms. How "reasonable" is it that Earth's atmosphere IS very much thinner "for a muon" than as measured by all our best tools of Earth science?Not at all reasonable. I'd hate to be around when you read about quantum mechanics. 1
Schrödinger's hat Posted October 8, 2011 Posted October 8, 2011 I wasn't asking for a mainstream, textbook account of length contraction. This forum has presented that argument extensively. My threads and sources are critical of some parts of relativity, and those criticisms have not been addressed here at all. Could you post a list of links to all these sources? 15 pages of posts is a lot to trawl through to find them. The only paper I recall seeing a link to was the one on the redefinition of 'synchronised'. It took me a while to work out the consequences of such a definition, one of them is a non-constant speed of light. Light would wind up moving faster towards than away from you or vice versa. I'll address this in more depth when I finally get around to making those simulations. You often refer to others but don't post journal names/dates etc.
tar Posted October 10, 2011 Posted October 10, 2011 (edited) Owl, I was not specific about a particular ricochet experiment. Any you care to formulate will do. There is no experiment we have been able to devise, to determine that we are moving through an ether that is the medium through which light travels. Any imagined such stationary reality, that we are moving through, seems not to be revealing itself to us. Our experiments seem to tell us that light travels at light speed, any time we measure it, going in any direction. It would indeed be wrong to assume that therefore we are stationary and everything else is moving. In fact we know we are moving, around our axis, around our Sun, around the center of our Galaxy, and the Galaxy has motion toward and away from neighboring Galaxies. There is not a reference point we can chose to determine our motion, that is not itself, moving. Yet "moving in reference to what" is a consideration we have to entertain when discussing velocity. The whole point of this thread, is whether or not there is a "real" universe, that exists without our measurements, and what the nature of that entity is. Not a soul here has indicated that they thought there was not a real universe that would continue to exist even if we were not here to see it. Your claim is that the real universe is the way you and all the humans that have witnessed it and measured it, figure it to be. Same claim that everybody on the thread it making. But you make an additional claim. That an observer traveling through our frame of reference at a relativistic speed (compared to our "stationary" coordinate system) will still see the Earth as round and a certain distance from the Sun, because "that is the way reality is." Where you are making an error, is by calling your frame of reference the "only" one that should be used to determine "reality" as it really is, when your whole main point is that reality exists regardless of whether or not anybody is looking at it. By performing a ricochet experiment in the relativistic observer's frame of reference, and then plotting that experiment against our frame of reference's coordinate system, you will find that the observer's measurements were correct, your measurements were correct...but the line the observer drew from himself, to an object and back, when plotted against our coordinate system, does not have the same length. We figure we are stationary and right about the way the universe is. The observer figures he is stationary and right about the way the universe is. Of the view that you, Owl takes, and the view that SR takes, which view is better at attempting to understand why and how both us and the observer are correct in observing the universe as it really is, independent of anybody looking at it? Regards, TAR2 Edited October 10, 2011 by tar
md65536 Posted October 10, 2011 Posted October 10, 2011 Not a soul here has indicated that they thought there was not a real universe that would continue to exist even if we were not here to see it. Not sure if I count as a soul but I'll say it. I think that reality as we observe or measure it is completely dependent on how it is observed, and that what exists independently of measurement is not anything like what we describe as reality. Note that this doesn't exactly fall into owl's dichotomy as subjective idealism. But I think he's sold his version of Realism so poorly (trying to associate it with "reality" when really he's describing things that are inconsistent with reality other than the reality he has set in his mind... I think it's more of an Absolutism that requires no correspondence with reality at all), that I'm willing to distance myself from "realism". My opinion is speculative and can be safely ignored in this thread. However I think it's worth posting it, because a scientist should never be so absolutely certain of anything that she takes it for granted and stops accepting the evidence, in favor of beliefs. What we "know" is not the final word; the best we can hope for is that our theories accurately describe the reality we know, and that the predictions of future theories will pass smoothly into our current theories (a correspondence principle).
tar Posted October 11, 2011 Posted October 11, 2011 md65536 , Not sure if I count as a soul but I'll say it. I think that reality as we observe or measure it is completely dependent on how it is observed, and that what exists independently of measurement is not anything like what we describe as reality. This is probably the case, but it is still a reality that exists regardless of our measurements. I am taken by the fact that a mechanical device will "sense" reality in an analogous fashion to the way we do. Sure, we designed the darn thing to "mimick" our abilities, so what would you expect, but still there is "something" to sense. The phonograph needle on the wax disc still records the vibrations. Even if nobody is around to play it back. The universe is very big, very old, and very detailed. More to it, than we can hold. Except, as a universe, it seems to me to not be doing only one thing at a time. And it seems to not be finished doing things. That is my hesitation in agreeing that a statement such as "the universe is accelerating" has any "real" meaning. We evolved along with the universe. We are made of its atoms. The patterns we carry have developed in the universe, on this planet. We are not capable, logically speaking, of doing anything that the universe can not do. Because we are examples of its nature. I would have to guess that reality is exactly as it appears to be. If one could take an "other than human" view of things as they really are, then it would not be a human view. I do not have to agree with Owl's model, or with Einstein's, or with Mohammed's or with Mose's, or with yours, to see the consistencies between them all. What is left, when all the imaginary considerations are subtracted, IS reality, as it really is. There is nobody to talk to about it, but other human's, and our inner "understanding" of our connection and belonging to it. Sure we can imagine being very small or very large or very old or very fast. We can even imagine all points in the universe happening "now". But it is certainly not a realistic view. No thing can see every location at once. Except us, when we look at the stars. Regards, TAR2
owl Posted October 11, 2011 Author Posted October 11, 2011 (edited) On Sept 30, Schrodinger’s hat replied to my statement: Reality as a whole, on whatever scale does not depend, for its existence or properties, on the different FORs from which it is observed. My "cosmos with no intelligent life" scene is an illustration of this principle. It wouldn't go away or change drastically sans observational FORs...as follows: On this we agree, and have always agreed. Maybe focusing on one point at a time will clarify my intent in this thread. Relativity is ‘all about’ frames of reference. ... “for a muon”... “for a near lightspeed traveler,” “for various observers" with various velocities relative to (or at rest with) that which is observed. Whereas, the intrinsic reality of the world/cosmos does not depend on the frame of reference from which it is observed. But of course science is not an omniscient god with an absolute FOR, so it must find the most accurate ways to observe and describe the “real world.” The epistemology of empirical science is based on such observations, and a reasonable scientific community must decide whether, for instance, the shape of Earth is best described by observations and records from hundreds of years of earth science, i.e., nearly spherical with precise measurements of both polar and equatorial diameter... or from a theoretical, never- been- done, near lightspeed fly-by FOR, which might “see Earth” as having a diameter an eighth or so of the above. It is really very simple. According to relativity’s dictum, “There are no preferred frames of reference”, either Earth’s shape changes radically with the FOR from which it is observed or it stays the same, but we can not know what that shape, in fact, intrinsically is. We can and do know the above to a very precise degree of accuracy. The theory of length contraction has never been demonstrated aside from highly technical interpretations of particle accelerator experiments. I trust the established epistemology of what we know about Earth’s shape (not just 'my version of reality'), which is to totally reject the length contracted version of earth as having a diameter of around 1000 miles. To believe the latter, based on “no preferred frame” and a theory with no demonstrated basis in reality is nothing less than a pseudo-science version of dogmatic fanaticism. We can apply the above also to the reality of an Au as precisely measured from Earth (see again my introductory quote), to the length of a meter rod as derived from a surface quadrant of Earth and measured “at rest with the rod”, and to the thickness of Earth’s atmosphere as around 1000km, though there is obviously no fine line between atmosphere and no atmosphere. Muons do not get to determine an equally valid measure of our atmosphere’s depth/thickness, even though “for a muon” it is radically thinner. I will let my case against length contraction rest with this post. Could you post a list of links to all these sources? 15 pages of posts is a lot to trawl through to find them. Criticisms start with assumptions about 4-D space. Here are Cap 'n R's comments on that from post three: ... A relativistic explanation would involve a four-dimensional spacetime which we view three-dimensional sections out of, and different frames of reference necessarily view different three-dimensional sections out of the four-dimensional (immutable) whole. Regarding 4-D spacetime: I have often cited Kelley Ross’ paper on the transition from Euclidean to non-Euclidean geometry and cosmology... and the *assumptions* inherent therein. http://www.friesian.com/curved-1.htm Also Brown and Pooley’s paper: Minkowski space-time: a glorious non-entity http://docs.google.com/viewer?a=v&q=cache:mq3qo9PLzlAJ:philsci-archive.pitt.edu/ See “Contents”, #4 on length contraction. Edit: An excerpt from that transcription didn't work... bad format. Please go to that section... on "a single rod assigned two different lengths..." These 4-D “cross sections” (often employed in Cap ‘n R’s “explanations) are based on an abstract coordinate system which *assumes* 4-D spacetime, which the above sources dispute. I have explained 3-D space and time-without-reification into "spacetime" many times. Cutting the above (bold) is a mental exercise. The solid rod itself stays solid regardless of what cross-sectional view of it "in 4-D spacetime" we advocate. I've got a ream of notes from different sources debating length contraction, but the above begins with the foundations in non-Euclidean geometry/cosmology and the resulting 4-D space concept. I’ll leave it there for now. If this (*) is your conclusion, then you do not yet understand the nature of relativity and how it works. Likewise with the arguments about the shape of the Earth and the nature of 4D spacetime. It's clear you do not want to learn from me, but rather to contradict everything I say, so I don't see the point of explaining. *(Ref; my): That the very oblate spheroid description of earth is absurd/ridiculous is not because of me appealing to ridicule. And of course, there is no experimental evidence at all for the validity of such a description. I see. The way relativity works is that Earth may actually be squished nearly flat, and the rest of science (besides relativity) might just be confused about the reality, if there were one, of Earth's shape. Again, please cite the experimental evidence for a squished description of Earth. You say, "It's clear you do not want to learn from me..." But you invited me to ask questions of your boss about how the particle accelerator experiments validate length contraction... I asked a few... you gave me three links which I studied and commented upon... with no reply from you. This is called "bait and switch" in the commercial world, and it is really unworthy of a sincere scientific dialogue. Physics does not require theories to avoid absurdity; nature has no such qualms. Please explain the latter. Nature does avoid absurdity while physics has no such need? Regarding the former, I know. Stephen Hawking published his singularity theory of cosmic origin, saying that all cosmic material came from a "point of infinite mass density and zero volume." (Wow!... All there is originally in a point with no volume!) I criticized the obvious absurdity of this in a science forum. He gave it up... not because of me, I'm almost sure... and gave his support to the M-theory. It depends, as I've said, on "eleven dimensions." Apparently no description of them is required to make it respectable science either. Authority and popularity does not make either of the above cosmologies true. I'd hate to be around when you read about quantum mechanics. Well, I already have to some extent. How about the part where "virtual particles" come out of nothing and then quickly disappear back into nothing? 'Something out of nothing' (like in "where did it all come from before the bang?") is a cheap magicians hat trick, or pseudo-science 'sleight of mind.' And those entangled particles... how do they keep in touch "at a distance" and do the same spin reversals at the same time? Maybe the bar has been lowered for what qualifies as science. Or we do observe "action at a distance" and still can't explain it. I'll go with the latter. Same for gravity. Edited October 11, 2011 by owl
Cap'n Refsmmat Posted October 11, 2011 Posted October 11, 2011 Maybe the bar has been lowered for what qualifies as science. Or we do observe "action at a distance" and still can't explain it.I'll go with the latter. Same for gravity. What qualifies as science is what can provide a consistent and clear explanation of our experimental results. Quantum mechanics and relativity do this exceedingly well, despite their strangeness. It may be the case that space is not four-dimensional, that there is no such physical thing as a "wavefunction", or that Schrodinger's cat isn't simultaneously dead and alive. The point of science is not to argue that these theories must be absolutely true descriptions of reality. The point of science is to determine whether they are adequate models of reality, however it behaves and however it "actually" works. For example, even if the universe is powered by mischevious gnomes, it's still true that relativity and quantum mechanics provide accurate models of their behavior. If the experimental evidence suggests gnomes behave exactly like they would in a four-dimensional Minkowski spacetime, we may use that as a model of the universe, even if we really live on a seven-dimensional hypersphere powered by LSD-addled micrognomes. Physics cannot pretend to define what the universe actually is. That is the realm of metaphysics. Physics can only seek to build models which accurately represent the universe's behavior. If you cannot present experiments against theories, then you are arguing against their metaphysics, not their accuracy as a model -- and metaphysics is not relevant to a practicing physicist.
tar Posted October 12, 2011 Posted October 12, 2011 (edited) Further "off topic" ramblings. If an object is visible to us (at any wavelength), then, in an expanding universe, it was closer to us, the day before it emitted the photons than the day it emitted the photons. What that object is doing "now" is of little concern to us. The photons we receive from it tommorrow, though, are of concern. So it is the photons we receive from the object today, that define its position in "our" reality. Likewise, in defining that object's "effects" on us, we were never concerned with it's location at an "abstract" location in space and time, as much as we were concerned with the gravity and photons we were receiving from it, at the speed of light "in reality". Historically, that object had to be with us, since we were "first" able to see it. And it's effects on us have been constant and cumulative, though perhaps "diminishing" as our spatial separation has grown. Thus, an entity, located at a particular place and time, such as a human, or a rock, is subject to the "conditions" at that spacetime coordinate, that include to no small amount, the arrangement of the universe around that point. Close things, are of just as much of an "immediate" concern as far things. Looking up at a plane crossing infront of the cresent moon on a starry night, the plane, the moon, and the stars, are all present. They exist in the here and now. They are real. Regards, TAR2 Edited October 12, 2011 by tar
owl Posted October 12, 2011 Author Posted October 12, 2011 What qualifies as science is what can provide a consistent and clear explanation of our experimental results. ... If you cannot present experimental results... Yet again: "Please cite the experimental evidence for a squished description of Earth" or any observable instances of length contraction. Physics cannot pretend to define what the universe actually is. That is the realm of metaphysics. Is it "pretentious" of physics or Earth science (pretending to be metaphysics,) to describe what shape Earth actually is? Ps: I said: I will let my case against length contraction rest with this post. Sorry but we are clearly not done yet until you cite evidence for length contraction. And 'it looks good on paper' (the "model") is not experimental evidence.
Cap'n Refsmmat Posted October 12, 2011 Posted October 12, 2011 I have given a number of observable evidences of length contraction on various scales (particle accelerator to entire atmosphere to GPS satellites). Relativity has predicted the results of every experiment made to test it, most of which rely on length contraction and time dilation. You can find these in textbooks. Length contraction is a direct logical consequence of the constant speed of light. You can find this derivation in a textbook, such as Einstein's. Physics does not pretend to describe what shape Earth "actually is." It describes what values will be given when we perform a certain experiment designed to measure Earth. It may be the case that God deliberately alters our measurements to mislead us, but physics can accurately predict the altered measurements. 1
Recommended Posts