Enthalpy Posted June 24, 2014 Posted June 24, 2014 Relativity is already an old theory. To me, its correctness isn't any more a question for a handful of scientists. It results from thousands of engineers who use it daily with success.
swansont Posted June 24, 2014 Posted June 24, 2014 Doesn't that depend on your frame of reference? No, a step is an event and all frames have to agree that you have taken a step or not. The only disagreement is on the length of the journey, if measured by some length standard. A journey of a thousand steps will be a thousand steps in all frames.
Ophiolite Posted June 24, 2014 Posted June 24, 2014 It was a joke. Apparently not a very obvious, or very good one, but a joke nonetheless. Perhaps I should have said "Doesn't that depend more on your frame of mind than your frame of reference".
Delta1212 Posted June 24, 2014 Posted June 24, 2014 (edited) No, a step is an event and all frames have to agree that you have taken a step or not. The only disagreement is on the length of the journey, if measured by some length standard. A journey of a thousand steps will be a thousand steps in all frames. I did say thousand miles rather than steps, though. So the length of the journey will depend on whether you've started stepping and how quickly you step, although obviously all frames will agree on how many steps you took once you've completed the journey.It was a joke. Apparently not a very obvious, or very good one, but a joke nonetheless. Perhaps I should have said "Doesn't that depend more on your frame of mind than your frame of reference".I liked it, if that's any consolation. Edited June 24, 2014 by Delta1212
Ophiolite Posted June 24, 2014 Posted June 24, 2014 I liked it, if that's any consolation. It is. Thank you. As Les Dawson used to say "I appreciate your support. I wear it every day."
swansont Posted June 24, 2014 Posted June 24, 2014 It was a joke. And sometimes overzealous pedantry is as well.
Hazel M Posted June 24, 2014 Author Posted June 24, 2014 Is there any aspect of relativity in particular that you struggle to come to grips with? Rather than going on a whole tangent about it, maybe just pick one key issue you have and see if we can work from there. Thousand mile journeys begin with a single step and all that. Answer to first question. No, but thank you for wanting to help. ajb said it well. In science, if you can't provide a scientific argument, don't present. I cannot. As someone with no science background I just have the same reaction that all like me have - it makes no sense. Of course we are wrong as the replies to my first question indicate. Therefore, I see no sense in starting a debate based on that attitude. When I get to the point where I can ask an intelligent question about it, I shall. Not yet. Oh, I could but forums can get too drawn out and heated when talking on two very different levels. Answer to second statement, I hope you were speaking metaphorically. That's how I took it and you are so right. 1
swansont Posted June 24, 2014 Posted June 24, 2014 Answer to first question. No, but thank you for wanting to help. ajb said it well. In science, if you can't provide a scientific argument, don't present. I cannot. As someone with no science background I just have the same reaction that all like me have - it makes no sense. You, and everyone in a similar situation, have a choice to make: either become more informed, or defer to the expertise of others. Choosing the path that the experts agree, and even though it makes no sense to you personally, you'll accept it as true is not really a problem. Even scientists do this with material outside their field. You can e.g. test that GPS works, and trust the scientists who say that GPS relies on relativity and that it wouldn't work if relativity weren't true. The problem is when someone decides that because it makes no sense to them that it therefore cannot be true, or that it conflicts with their ideology and they decide to jettison reality in favor of the ideology. As long as you aren't headed down paths like those, things are OK.
studiot Posted June 24, 2014 Posted June 24, 2014 The book I referred to in post#8 should provide the non expert with a real feel for the subject, without needing to know the intricate details of the physics, via the history of who measured what and why, the proposed explanations, and what Katy did next.
Hazel M Posted June 24, 2014 Author Posted June 24, 2014 Thank you, studiot. It is on my list although goodness knows when I'll get to it. I am swamped with "to read" books right now. But, I shan't forget it.
robinpike Posted June 26, 2014 Posted June 26, 2014 The key point here is that every direct and indirect test of special and general relativity has shown them to be a good theory well in agreement with nature. Suggesting that every indirect test of general relativity has been shown to be in agreement with nature seems bit of a sweeping statement. For example, do we really know that black holes exist? - and assuming that we take that to be true, in what way have we tested / seen evidence that light (in general) cannot escape from a black hole?
ajb Posted June 26, 2014 Posted June 26, 2014 For example, do we really know that black holes exist? - and assuming that we take that to be true, in what way have we tested / seen evidence that light (in general) cannot escape from a black hole? I think this is irrelevant, as I still claim that there is no direct or indirect test (repeatable, independently verifiable and so on) that has shown general relativity to be a bad theory. The fact that evidence for black holes maybe right now not so good, does not mean that we have found a problem with general relativity. Indeed there is some evidence for black holes in the Universe. Moreover, because we have not tested every single prediction of general relativity in great detail does not mean we have identified a problem.
Hazel M Posted June 26, 2014 Author Posted June 26, 2014 You, and everyone in a similar situation, have a choice to make: either become more informed, or defer to the expertise of others. Choosing the path that the experts agree, and even though it makes no sense to you personally, you'll accept it as true is not really a problem. Even scientists do this with material outside their field. You can e.g. test that GPS works, and trust the scientists who say that GPS relies on relativity and that it wouldn't work if relativity weren't true. The problem is when someone decides that because it makes no sense to them that it therefore cannot be true, or that it conflicts with their ideology and they decide to jettison reality in favor of the ideology. As long as you aren't headed down paths like those, things are OK. Sometimes the problem is someone deciding the questioner is being difficult instead of just answering his questions and letting it rest. Sometimes the questioner really is sincere in questioning and not applying any ideologies or arguments at all. Just asking. Sometimes the way a questioner gets answered can cause more problems than solutions. Sometimes, with a good answer, the questioner will continue to study the subject; or, with a bad answer (an accusatory answer) will toss it all to the wind and say "forget it". Sometimes the questioner just needs time to mull over the good answer and absorb it. I have met too many people in my life who simply do not like to be questioned. I have never figured out why but they don't. Sort of a "what is is and take it or leave it". That, to my non-scientific mind - is not good science or good anything. Just my early morning thoughts. And thank you all for good answers. I'm still thinking. And yes, swanson, I agree with what you say. Just felt there is a bit more that needs added to the pot. Take care. Oh, P.S. GPS does not always work. Dare I ask why?
imatfaal Posted June 26, 2014 Posted June 26, 2014 ....Oh, P.S. GPS does not always work. Dare I ask why? I always assume it is some miscreant at the USNO playing silly buggers with the atomic clocks. GPS as an idea works well; sometime when the theory is put into practice with cheap electronics you get hiccoughs. If you do not understand or have a niggle with some aspect of relativity no one will mind rehearsing the ideas, in fact we love it and we all learn through it - we tend to look less favourably on dogged refusal to accept an idea merely due to personal incredulity.
Hazel M Posted June 26, 2014 Author Posted June 26, 2014 I always assume it is some miscreant at the USNO playing silly buggers with the atomic clocks. GPS as an idea works well; sometime when the theory is put into practice with cheap electronics you get hiccoughs. If you do not understand or have a niggle with some aspect of relativity no one will mind rehearsing the ideas, in fact we love it and we all learn through it - we tend to look less favourably on dogged refusal to accept an idea merely due to personal incredulity. Nothing ever works perfectly. I have had more than one cab driver argue with me when I told him he was going down a dead end street. GPS knows better than I do. The fun came when he had to back up and turn around. That's when I kept my mouth shut. <G> I know scientists like to challenge each other and worry an idea this way and that. And they enjoy very much explaining. My point, in too many words, was that sometimes we make assumptions that the questioner is being stubborn when all it amounts to is that he is still mulling over what he has been told. No ulterior motives at all. Just thinking.
Nicholas Kang Posted June 26, 2014 Posted June 26, 2014 (edited) A true scientist will challenge each other to reveal the secret of the nature to the public and benefits human race. Edited June 26, 2014 by Nicholas Kang
Strange Posted June 26, 2014 Posted June 26, 2014 Suggesting that every indirect test of general relativity has been shown to be in agreement with nature seems bit of a sweeping statement. For example, do we really know that black holes exist? - and assuming that we take that to be true, in what way have we tested / seen evidence that light (in general) cannot escape from a black hole? I think this example is backwards. Every test is consistent with relativity. But not every possible prediction has been tested. So we have evidence for black holes, even if not absolutely certainty, and that is consistent with GR. On the other hand, not every possible solution to the equations necessarily exists; for example, I'm not sure anyone really expects white holes to exist. A true scientist won`t think of challenging each other Definitely not true. The way that science proceeds is by scientists challenging each other and, more importantly, challenging existing theories.
Nicholas Kang Posted June 26, 2014 Posted June 26, 2014 Stephen Hawking tells you Black Hole doesn`t exist at all. Do you think he had actually seen a Black Hole before? So, no more black hole, but grey hole.
swansont Posted June 26, 2014 Posted June 26, 2014 I always assume it is some miscreant at the USNO playing silly buggers with the atomic clocks. Just this morning, in fact. Embezzled a few nanoseconds out of petty cash while I was at it. GPS as an idea works well; sometime when the theory is put into practice with cheap electronics you get hiccoughs. Indeed - the fault is almost certainly with the receivers. The GPS signals are there (and robust from that viewpoint) but signals are somewhat easily lost or scrambled once they get to earth. 1
Nicholas Kang Posted June 26, 2014 Posted June 26, 2014 We are wrong to use GPS? It is our fault? I think it is more of Nature`s fault. We invented GPS and we semmed like making a huge mistake by inventing it. So, we should blame ourselves?
ajb Posted June 26, 2014 Posted June 26, 2014 We are wrong to use GPS? It is our fault? I think it is more of Nature`s fault. We invented GPS and we semmed like making a huge mistake by inventing it. So, we should blame ourselves? By receivers swansont means the equipment on the ground, not the actual people using the GPS. The physics of GPS is sound and relies on relativity. This is quite independent of the your actual GPS machine in your hand always working.
Nicholas Kang Posted June 26, 2014 Posted June 26, 2014 But we created the equipment. So, we are the source.
Hazel M Posted June 26, 2014 Author Posted June 26, 2014 Just this morning, in fact. Embezzled a few nanoseconds out of petty cash while I was at it. Indeed - the fault is almost certainly with the receivers. The GPS signals are there (and robust from that viewpoint) but signals are somewhat easily lost or scrambled once they get to earth. "Almost certainly". What is it they used to say about computers? They are only as smart as the person who put the information in. Whoever set up that particular system simply failed to learn that the street dead ends due a highway whizzing by. Nothing wrong with the system at all other than failure to check a map or take a walk around the neighborhood. Am I wrong?
Strange Posted June 26, 2014 Posted June 26, 2014 We are wrong to use GPS? It is our fault? I think it is more of Nature`s fault. We invented GPS and we semmed like making a huge mistake by inventing it. So, we should blame ourselves? I don't think it is a mistake. It has enabled all sorts of things which would have been really hard before. It is used to measure the movement of land on either side of geological faults, is is used to track migrating animals (so we can better understand and, if necessary, protect them), the availability of accurate time anywhere in the world has all sort of uses. It was used in measuring the speed of neutrinos (even if they got the wrong answer!) It is useful for surveyors and cartographers. The only negative thing is when people depend on advice from a cheap navigation system.
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