ajb Posted July 9, 2016 Posted July 9, 2016 Well ! , for something so , overarching , important , necessary and interesting , we jolly well should try and find out , if we are scientists, this is our subject ( nobody else's ) ? It is a philosophy question. What I can do is give you an overview of linearising Einstein's field equation and how picking a gauge leads to the wave equation. That is, I can tell you how we understand gravitational waves within general relativity. I cannot tell you 'why' we have gravitational waves or 'why' they don't need some medium. I can just give you the phsyics.
Mike Smith Cosmos Posted July 9, 2016 Posted July 9, 2016 (edited) It is a philosophy question.What I can do is give you an overview of linearising Einstein's field equation and how picking a gauge leads to the wave equation. That is, I can tell you how we understand gravitational waves within general relativity.I cannot tell you 'why' we have gravitational waves or 'why' they don't need some medium. I can just give you the phsyics..Yes , I appreciate that Ajb. This was not realy directed at you personally . I just feel that a Middle of the road Philosipher is unlikely to even know where to start . As you say a strait math or physics professor who is already immersed in his/her own research , is unlikely to know , without dedicating his/her time , mental and dexterous thinking processes and possible observations to the subject. With a lot more thinking . It just feels like everybody is just " passing the baby ". When as I say it seems such a fundamental question , surely " the buck stops here !" Or the baby ! Why ........isn't there .......what most other oscillation/waves ..........have in our day to day experience ? ( a medium for waves ) Mike Edited July 9, 2016 by Mike Smith Cosmos
ajb Posted July 9, 2016 Posted July 9, 2016 As you say a strait math or physics professor is unlikely to know , without dedicating his/her mental and dexterous thinking processes and possible observation to the subject. I go futher and say that no-one knows. Philosophers may have some ideas, but they cannot prove anything that say. The question is just not a scientific one. It just feels like everybody is just " passing the baby ". Not really, we just understand there is a limit to what science can answer - and 'why' is not a question for science. When as I say it seems such a fundamental question , surely " the buck stops here !" We think that - in the context of science - it is not a fundamental question. It maybe a question for metaphysics - but don't expect and clear answeres.
Mike Smith Cosmos Posted July 9, 2016 Posted July 9, 2016 (edited) . But I am lead to believe , that the prerequisite to undertaking a PhD programme , The big thing to agonise over and get precisely RIGHT , before you start is :- WHAT IS YOUR QUESTION ? That is my question ? As iterated previously . :- .------------------------------- WHY is there not an ' Aether like Medium ' within space-time , for gravity waves to propagate? When nearly every other wave , vibration , and oscillation , in the entire Universe , uses such a type of facility to efficiently propagate its energy or information ? -------------------------------- I am off to Italy for two weeks starting tomorrow , up in among the mountains, away from everything . I will give it some serious thought while away . Either you guys or me may have a metaphysical answer by the time I return , or I may have fallen over a mountainside ! And felt and found the answer to Gravity ! Mike Ps. A friend of mine in Italy said to me a year or two back " Everything in Italy , is either Heavy , up Hill , or Hard Edited July 9, 2016 by Mike Smith Cosmos
imatfaal Posted July 9, 2016 Posted July 9, 2016 ! Moderator Note ... Most women drive cars very well and thoughtfully , but most of them do not know the engineering mechanism , and often put oil in the radiator . Men on the other hand usually know HOW everything roughly works, but are often more inconsiderate , and down right dangerous on the road . ... Mike - you are allowed a lot of leeway but this form of sexism and stereotyping is against the rules and will not be tolerated. Do NOT repeat this form of adverse characterisation of any group of people. Do not respond to this moderation within the thread. 1
Mike Smith Cosmos Posted July 9, 2016 Posted July 9, 2016 (edited) I go futher and say that no-one knows.Philosophers may have some ideas, but they cannot prove anything that say. The question is just not a scientific one.Not really, we just understand there is a limit to what science can answer - and 'why' is not a question for science.We think that - in the context of science - it is not a fundamental question.It maybe a question for metaphysics - but don't expect any clear answeres.. It seems strange to me that some of the most fundamental questions ( like WHY ) are unable to be answered directly by science . It's as if science is limiting its scope deliberately . I understand , it only desires proven , supported ideas. But even some of those are wrong occasionally. So one wonders why one can't just romance a little with a ' not quite so proven idea yet' , that just gives you the encouragement , scope and fortitude to go on ? I am not so sure that science in the early days, was quite so stricktured ? Metaphysics eh ? But woolly answers may lead on to a paradice land of scientific gems, which have been long hid or forgotten . Lurking down some dark corridor of potential discoveries? I realy love this curvature bit , in this whole area of Gravity . In the same way that a circle generates a wave if you extrapolate its displacement from the origin , against time . It's so, so tempting ! Mike Ps ( I really love my wife and daughters , and their daughters, they all keep me sane . I think . Or was it insane ?) I never did find the Key ! Edited July 9, 2016 by Mike Smith Cosmos -1
Strange Posted July 9, 2016 Posted July 9, 2016 So when a layperson asks questions about Relativity and Gravity, they are, like classical scientists, looking for cause and effect relationships. What property of matter causes geodesics to curve near them? Would the collision of two photons cause them to slow down as a result? What factors determine the strength of gravitational force? We have very specific and precise answers to these questions. But, apparently, they are not acceptable to Mike. Well, perhaps giving accurate answers to questions from the general public about Relativity and Quantum theory seems impossible because of the higher math knowledge needed. But as I look through hundreds of answers about general science questions, including those about gravity and relativity, I in fact see that one can make an attempt to give some sort of answer to just about any question without resorting to higher mathematics: Q: What keeps an airplane in the air: A: Four forces keep an airplane in the sky. They are lift, weight, thrust and drag. Lift pushes the airplane up. The way air moves around the wings gives the airplane lift. Q: What property of matter causes geodesics to curve near them: A: Matter produces gravity. We don't exactly know how this works because we do not have a sufficiently detailed theory of gravity that covers the graininess of matter and energy in a 'quantum theory of gravity'. ... This is a totally unreasonable comparison. You are comparing on the one hand a simplistic handwavy answer that doesn't really explain anything with a reference to a highly detailed explanation that admits to being incomplete. The first answer raises all sorts of questions such as: Where do those forces come from? Why does the air move that way? How is air able to exert a force on the wing? Why is air a gas and the wing solid? Some of these questions are just as hard to answer as anything about gravitation and, ultimately, come back to "because that is the way it is". .------------------------------- WHY is there not an ' Aether like Medium ' within space-time , for gravity waves to propagate? When nearly every other wave , vibration , and oscillation , in the entire Universe , uses such a type of facility to efficiently propagate its energy or information ? -------------------------------- Because we don't need there to be one and there is no evidence that there is one. If you think there is then you are not engaging in science; you are just making stuff up. . It seems strange to me that some of the most fundamental questions ( like WHY ) are unable to be answered directly by science . It's as if science is limiting its scope deliberately . I understand , it only desires proven , supported ideas. But even some of those are wrong occasionally. So one wonders why one can't just romance a little with a ' not quite so proven idea yet' , that just gives you the encouragement , scope and fortitude to go on ? You are missing the point. Science is constantly looking for new, unproven ideas. That is how it makes progress. But you vague "why" questions are not scientific. How would you model "why"? What experiments would you do to test "why"?
swansont Posted July 9, 2016 Posted July 9, 2016 . It seems strange to me that some of the most fundamental questions ( like WHY ) are unable to be answered directly by science . It's as if science is limiting its scope deliberately . I understand , it only desires proven , supported ideas. But even some of those are wrong occasionally. So one wonders why one can't just romance a little with a ' not quite so proven idea yet' , that just gives you the encouragement , scope and fortitude to go on ? Science limits itself to issues that it can test against observation. When science is shown to be wrong it's because of evidence. You can make models before anyone is able to test them, but they have to be testable in principle.
Moontanman Posted July 9, 2016 Author Posted July 9, 2016 I honestly didn't think this question was that difficult to answer, 383 posts wow!
Mike Smith Cosmos Posted July 9, 2016 Posted July 9, 2016 (edited) We have very specific and precise answers to these questions. But, apparently, they are not acceptable to Mike. Because we don't need there to be one and there is no evidence that there is one. If you think there is then you are not engaging in science; you are just making stuff up. You are missing the point. Science is constantly looking for new, unproven ideas. That is how it makes progress. But you vague "why" questions are not scientific. How would you model "why"? What experiments would you do to test "why"? ?You must not think I do not appreciate your answers , in fact I look forward to seeing your ' avatar ' alerting me to , " his comments will make interesting and meaningful answers . " The issue about the medium , is purely I am fighting hard against my previous University physics learning and Deep Intuition built up through a lifetime of engineering . I either have my wires crossed and a badly installed intuition . Or , well , I suppose I could have fallen on my head while I was in the pram . But I have had a good life , reasonably successful in what I did , including communications of the concepts of Physics to school children . Children do not accept ' rote ' easily . Why sir , why sir , why ? I have dropped weights from on high, spun masses in giant circles , thrown buckets of water in circles over my head , seen through life what I have seen . Telling me there is Nothing there in space is counter intuitive , not correct if I have read the right articles and a total total surprise to me , if you are right and there is actually zero , nothing there , to help gravity communicate its effect across space . When I found out that electrons move extremely slowly through a conductor , like 4 mph, I was flabaghasted, I thought electrons traveled at near the speed of light through a conducting wire/ cable . No. The EFFECT travels practically the speed of light , as one electron relates to its neighbour , etc , the effect travels fast NOT THE ELECTRON . I suspect that something similar happens with photons ( not sure ) I have never heard anybody say this . But my suspicion is a photon goes nowhere very fast , I bet it is the photon energy or effect that travels at the speed of light . I imagine with Electro Magnetic waves behave the same way , it is the photon effect that travels across the Electro magnetic field at the speed of light . So yes I need a medium for this to happen . Similarly , only because I guess things happen in similar ways , I only 'Guess' gravity waves will do a similar thing if there is a field or medium through which to travel . So yes I would say , it does need a medium of some sort or other . I know this is near ' herracy ' to the establishment , but sometimes you have to follow your learning mixed with your observations mixed with your intuition . Se la vie My first book , I read as a little boy , was " how it works and how it's done . I have been on that quest all my life , and I will not stop until I drop . Perhaps I should write a book though I could not . Maybe a cartoon wallet . WHY THINGS WORK THE WAY THEY DO ,! Seeing as I am so keen to find out ! Mike Mike Edited July 9, 2016 by Mike Smith Cosmos
Strange Posted July 9, 2016 Posted July 9, 2016 Telling me there is Nothing there in space is counter intuitive, not correct if I have read the right articles and a total total surprise to me , if you are right and there is actually zero , nothing there , to help gravity communicate its effect across space . No one is saying there is nothing in space. There are all the things in space that have been mentioned previously. But those things are IN space. They are not "space". They are no relevant to the transmission of gravitational waves. So yes I would say , it does need a medium of some sort or other . Until there is some theory requiring that, or evidence for it, then your guess appears to be wrong.
Mike Smith Cosmos Posted July 9, 2016 Posted July 9, 2016 No one is saying there is nothing in space. There are all the things in space that have been mentioned previously. But those things are IN space. They are not "space". They are no relevant to the transmission of gravitational waves. Until there is some theory requiring that, or evidence for it, then your guess appears to be wrong. Shall we put a bet on it ? Mike
Strange Posted July 9, 2016 Posted July 9, 2016 Shall we put a bet on it ? What is the point? Either there is a need for your aether or there isn't (currently, there isn't). Either there is evidence for your aether or there isn't (currently, there isn't). What is there to bet on? That some new evidence comes to light in ... what, the next 24 hours? The next 5 years? The next 20 millennia?
disarray Posted July 9, 2016 Posted July 9, 2016 (edited) Mike asks "WHY is there not an ' Aether like Medium ' within space-time , for gravity waves to propagate? When nearly every other wave , vibration , and oscillation , in the entire Universe , uses such a type of facility to efficiently propagate its energy or information ?" I agree that the "Why" part of this is too vague. Really, I think that he is just making the observation that it seems improbable and inconsistent (with the 'norm') that gravity waves don't seem to need a 'medium' in which to propagate when virtually every other wave, etc. does....and that perhaps this apparent anomaly might be worthy of further investigation. (While others on this forum constantly retort, 'been there, done that....found nothing...maybe in the future...next question). So in a sense, asking "why" is a little 'presumptuous' in that it presumes the generalization that all wave-like 'entities' need such a medium, which is an 'intuitive' and unproven generalization based on mundane experience, not solid science. My own armchair philosophy hunch, which I supported with quotes from various science sites further above, is that space, 'time', gravity, and content (e.g., matter/energy/force) are all mutually dependent or inclusive. Thus, gravity (waves) could not propagate through some presumed 'nothingness' or 'multiverse fabric' without and until all of the four ingredients existed at once. So yes, space is an elusive and perhaps illusive concept (and maybe entity), but space/time/gravity/energy-force is, a combined 'product' that came into existence over 14 billion years ago...(not trillions or some indeterminate number), so, given mathematical speculations that there is indeed a 'multiverse' (i.e., other universes), it seems possible that the question is not really 'what is space that gravity and other things can travel through it' but rather what are all of these things combined...and that is where, I guess, one just gets back to the basic buck-stops-here answer that 'things just are as they are'. I tend to say "philosophical" as opposed to "scientific" hunch in this regard, because, apart from the opinions of various scientists, it seems to me that the Big Bang took place under what one might call 'primordial' or 'pristine' conditions, i.e., nothingness. (As Malraux, as I recall, once poeticized: "Being is the flaw in nothingness".) That is, there was no God with a particular personality that fashioned the universe in a particular way. Thus, as I think Leibnitz remarked, the universe could not be any other way than what it is....one could not just have 'space' or just have 'time' or just have 'gravity' or just have 'matter-energy', it's all or nothing. For Leibnitz then, the universe was as perfect as it possibly could be. Edited July 9, 2016 by disarray
swansont Posted July 9, 2016 Posted July 9, 2016 Shall we put a bet on it ? Mike You'd be betting on a match that was played a century ago.
Strange Posted July 9, 2016 Posted July 9, 2016 Mike asks "WHY is there not an ' Aether like Medium ' within space-time , for gravity waves to propagate? When nearly every other wave , vibration , and oscillation , in the entire Universe , uses such a type of facility to efficiently propagate its energy or information ?" The "medium" is space-time. That is what is curved by the presence of mass-energy. That is what the waves are "in" (or "of"?). But this is not acceptable to Mike. My question is: why is it not acceptable? He has reluctantly accepted that the "medium" of electromagnetic radiation is the complex mathematical abstraction called a field (which may or may not correspond to something that physically exists - that again is a philosophical, not scientific, question). But, for some reason, he is not prepared to accept the existence of the much more common-sense and intuitive thing we call "geometry". We are all familiar with distances, angles, lines, curves, etc. And we can accept that distances can be measured and can change. But somehow this isn't good enough. WHY?
Mike Smith Cosmos Posted July 9, 2016 Posted July 9, 2016 (edited) The "medium" is space-time. That is what is curved by the presence of mass-energy. That is what the waves are "in" (or "of"?). But this is not acceptable to Mike. My question is: why is it not acceptable? He has reluctantly accepted that the "medium" of electromagnetic radiation is the complex mathematical abstraction called a field (which may or may not correspond to something that physically exists - that again is a philosophical, not scientific, question). But, for some reason, he is not prepared to accept the existence of the much more common-sense and intuitive thing we call "geometry". We are all familiar with distances, angles, lines, curves, etc. And we can accept that distances can be measured and can change. But somehow this isn't good enough. WHY? .Because 'it or they ' are not 'tangible things ' , they have no substance , they ( the geometry, distance measurement, time measurement , calculated curvature , maths formulae ) can all be written on a piece of paper and put in my back pocket . If you are saying ah but they are recorded figures from a measurement you or somebody else ' took ' from some tangible thing , somewhere out there in outer space , then fine . But I was unaware that anyone had made any such measurements. As far as I can make out , I stand to be corrected, 3 dimensional coordinates have been defined ( X,y,z ) and points specified ( not measured) and various maths calculations , superimposed on the 3D lattice , calculations made and theories , realised with resulting figures . All on paper or in a computer. O.k so maybe the maths , stacks up to suggest curvature , but I am at a loss as to any measurement apart from presumed stars , etc . I cannot see how a theory can be generated without any data , attained from the site , ( space somewhere ) . Even if the somewhere was 10 feet up in the air , just above head height . It's all space , and this bit of space has a few extra bits in it . ( like atmosphere , somebody's head ) etc -------------------------/////---------//---------------/////------////////// Most of the world is doing its best to acquire something . A bit of land , pile of money notes , a bar of gold , a house , a car , an I pad , It is ironic that we are discussing something ' invisible ' that we are arguing , about , whether it ' is there ? Is there a medium for gravity waves to pass through ? I suppose it's better than a poke in the eye with a sharp stick ? ------------------------------- Clearly, something did come across all that Space-time , when the LIGO experiment measured it , that blip ? The question here ,is did it come here across " nothing , or some form of medium " , so that the ripple arrived like a wave on the ocean arrives at the sea shore ? _______________________________ So:- I am putting my bet on : The medium of SPACE-TIME , consists, of :- the ABSOLUTE total amount of mass-energy of the 'Universe ' ( Everything , black ,white , green everything) , spread out across ALL of space like some form of very thin " Consommé - Soup " , containing these various lumps , here and there ( stars , planets and galaxies, black holes ,etc ) Link to Consommé soup :- https://en.m.wikipedia.org/wiki/Consommé So. If you want to do any , measuring, geometry, or time keeping , you will have to do it in the 'Soup' . That's where I am ' In the soup ' _______________________________ Mike Edited July 10, 2016 by Mike Smith Cosmos
Strange Posted July 10, 2016 Posted July 10, 2016 . Because 'it or they ' are not 'tangible things ' And yet they hold you in your chair, cause obvious visible effects like gravitational lensing, and allow us to detect events happing billions of light years away. How much more tangible do you need them to be? Any material medium that you propose is, by definition, totally undetectable and therefore not tangible.
geordief Posted July 10, 2016 Posted July 10, 2016 (edited) We have very specific and precise answers to these questions. But, apparently, they are not acceptable to Mike. One of those questions in the post you directly answered (in the preceeding post)was What property of matter **causes geodesics to curve near them?"I thought this was a question that had not been answered. I thought Einstein had somehow figured out that if the spacetime model was curved in the presence of mass then it would correctly predict physical phenomena to an extraordinary degree of accuracy but that the actual rationale was lacking. After all nearly everyone disbelieved Einstein at first and it was only his correct predictions that got his theory respectability. I do not doubt there is a reason why mass causes spacetime to curve but I thought I had picked up that this was not yet known -and I have yet to come across any theory as to why it does that. Now I accept I may have badly misunderstood and would love to be disabused of that understanding if that is the case.. ** should be mass-energy ,I think. Edited July 10, 2016 by geordief
ajb Posted July 10, 2016 Posted July 10, 2016 (edited) I do not doubt there is a reason why mass causes spacetime to curve but I thought I had picked up that this was not yet known -and I have yet to come across any theory as to why it does that. What we do know is that any 'stuff' that has energy-monentum can act as a source of gravity via Einstein's field equations. We know that solutions to Einstein's field equations are a metric on (given) smooth manifold that is (in general) not simply R^4. We know that geodesics on spaces that are not R^4 are usually not straight lines (not even sure what that means in general). Observationally, we know that matter follows geodesics when under only the influence of gravity. Why have no idea why 'stuff' acts as a source of gravity, we just know that it does and how to mathematically model this. Edited July 10, 2016 by ajb
geordief Posted July 10, 2016 Posted July 10, 2016 What we do know is that any 'stuff' that has energy-monentum can act as a source of gravity via Einstein's field equations. We know that solutions to Einstein's field equations are a metric on (given) smooth manifold that is (in general) not simply R^4. We know that geodesics on spaces that are not R^4 are usually not straight lines (not even sure what that means in general). Observationally, we know that matter follows geodesics when under only the influence of gravity. Why have no idea why 'stuff' acts as a source of gravity, we just know that it does and how to mathematically model this. More or less as I thought then . The only(respectable) idea I have come across that seems to parallel this effect may be "extremal aging" but iI have not been able to grasp the idea very well.
ajb Posted July 10, 2016 Posted July 10, 2016 More or less as I thought then . Good ... so this makes me wonder what kind of answers Mike is looking for.
Mike Smith Cosmos Posted July 10, 2016 Posted July 10, 2016 (edited) Good ... so this makes me wonder what kind of answers Mike is looking for..I am here on the bus, on the way to Bristol airport. Waiting with ' bated breath ' ...he ..ha...he Do come up with the answer , before take off ! I am going to do an experiment with gravity , while flying at 30,000 feet . I intend to jump out of a flight door . My wife is going to observe me to see if I fall in a curve. Not totally sure of my recovery procedure ? In the mean time , I am giving 'thought to , the gravitational field permeating all of space , and how this field is affected by a massive body like the earth. The ambient field is affected, by all the immence amount of mass contained in the sphere of Earth . This in some ways distorts the ' otherwise fairly homogeneous field spanning the rest of space . Quite what interaction is going on , I am not sure ? This interaction may give clues as to the nature of the gravitational field itself ? Mike Edited July 10, 2016 by Mike Smith Cosmos
ajb Posted July 10, 2016 Posted July 10, 2016 Do come up with the answer , before take off ! There is no answer to 'why' gravity works. We observe that it does and can build good models of it. That is really the best you are going to get. Sorry is that does not feel enough, but that is the way it is.
Mike Smith Cosmos Posted July 10, 2016 Posted July 10, 2016 (edited) There is no answer to 'why' gravity works. We observe that it does and can build good models of it. That is really the best you are going to get. Sorry is that does not feel enough, but that is the way it is..In this case I would have thought the ' How it works ' in real terms' will lead to the Why it works the way it does ? Like what is pushing what with what , or what is pulling what with what . I know there are supposed gravitons in the ' standard model ' But just how the Earth is pushing up against this medium of gravity field I have proposed , I am not sure . The rubber sheet model is too upside down in its modelling , it invokes more questions than answers . I am trying to think of an alternative to a rubber sheet model ? Like large dense swarm of honey bees surrounding the earth , pressing down on us . ( joke ) Mike Edited July 10, 2016 by Mike Smith Cosmos
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