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Wondering why, given an origin, one could not define another position based on two parameters, distance and direction. Distance is understandable as a singular thing, in itself, with any particular unit or number or scale assignable to it. If one was to dense pack spheres around an origin sphere there would be twelve directions possible, with each of these twelve an origin of its own, with twelve surrounding "directions". Given a particular task, a sphere size could conceptually dense pack all of space and any of the spheres could be located by counting out to a particular sphere in one of the twelve directions, calling that sphere your origin and counting the spheres in one of the twelve directions from there to your destination sphere. Conventionally naming the twelve A, B, C, D, E, F, G, H, I, J, K, L, could you not find a point in space by saying F594 to name your new origin sphere and then H3? Does seem clumbsy though, in that you could get to the same sphere by many different routes. And I certainly do not have the plan nailed down in so far as figuring out, how many new origin spheres one would have to use to describe the most difficult to "get to" spheres. Probably would wind up being a 6 parameter space. Sort of redundant if one can get to the same spot with three. BUT...if we could come up with a convention that could describe direction, with one number/symbol combination, then any point could be found by naming the direction, and then the distance.

Does seem to be a semantical question. Stars are born, have a "life"time, and die. So perhaps the answer is yes. But then hurricanes would have such a life. I suppose the question would arise anytime an entity, with temporary and self defining characteristics comes into being. In that such an entity has its own self to distinquish it from all else...while it is alive...and it is more than just the material and energy that it is made of.

Delta1212, Under the circumstances that one cannot objectively consider themselves a stationary frame of reference, it would be difficult to say that anything else was moving at a particular velocity. Since the other thing could just as well be stationary, and ones whole frame of reference could be moving, under what reasoning does one say a things clock is ticking slower, because of its velocity? I would still vote for considering here and now, a singlular place and time, from which all else can be referenced. There is no purpose or value in considering any other reference point as a starting or end point. Even if it is true that there are really an infinite number of "other" reference points, concievable, we have no access to the others, until we should get there ourselves. At which point we would still be in complete possession of our own frame of reference. And the separation from what we consider here and now, would be a matter of real time, and real distance. Our own frame of reference is still the only one available, and still includes, the rest of the universe. I have asked before, in other threads about which is true about the star 4.2 lys from here. That it exists now, doing what we see it doing. That it exists now, and we will not see what it is doing for 4.2 years. If there is only one instance of said star, there cannot be two answers to the question. One consideration must be real, and the other imaginary. Personally it seems the most real "timeline" that joins that star to this Earth is the one considering the arrival of light from that star, here, now. Its been the truth for as long as human history is. The consideration that that star "also" exists in a manner that will not present itself to us, for 4.2 years, is not "real" to us in any testable, meaningful way, except in the sense that its already proved itself existing 4.2 years ago, as its presenting itself to us now. We are insulated in time and space from that star's "actual" now. If we could get ourselves there, there would not be that separation any longer, and the Earth's Sun, would be in that same "dual" position as that star is in to us, now. There is nothing more understandable, and presently available to us, than the Earth's frame of reference. Why not use it exclusively to define, everything else? Regards, TAR2

MD65536 and Delta121, Considering that everything is relative, relative to what is still going to be a consideration. I see no actual harm or "incorrect" thinking, to lay out an actual grid of wavefronts of light in the Sun's FOR and work out, everything else from there. Here of course you would have to "count" and label each wavefront to differenciate between "which" wavefronts are passing through E and which ones are passing through B and which ones B is passing through by virtue of his motion through the grid. For instance since this is a changing grid in that the wave fronts that left E last Saturday are now 7 lightdays out, the .5C B will NEVER encounter them. However his destination, one lightyear out, in the Earth's FOR, will not enounter those particular waves for 51 weeks. Conceptually, this view seems realistic to me, and things would "have to" happen that way. The "count" from behind would lag B's count, the count from infront would increase in rate, and when he got to the turn around point, the count in the direction of E would be "off" his own count by one year/s worth of the frequency of light he was counting, and the count of this frequency from the destination would have a 1 year surplus. Effectively putting B one ly away from Earth, as he is now experiencing the exact same numbered wavefronts, that the destination is encountering. Who is, or should be on what count of what wavefront coming from what apparent direction, should be figurable from any observer on the grid, moving in reference to the Sun's frame, at any v. That different positional observers are experiencing differently labeled wavefronts, ie. the 498,948th from event e with a duration of 500,000, or the 334th, is a matter of position in the grid. In fact, some positional observers, even in the Sun's FOR, far enough away have not even encountered wavefront 1 yet, and those very close positionally to e saw the whole event already and wavefront 500,000 is already a thing of their past. Time dilation doesn't factor in as an actual occurence, but as a shifting of mental position, without accounting for actual shifts in position on the grid. Maybe. Regards, TAR2 From a philosopical point of view, it is the mental shift between the "actual" now that all points must be experiencing simultaniously at "one" time, "this" time, which can only be experienced at once in an imaginary way, that is difficult to connect with the actual view which we have of everything happening at once, here and now, as the wavefronts hit our equipment, which is after all, actual reality, which puts our mental image of an "actual" now, into the imaginary category. I do not think it is hard to imagine another "not getting it", nor to imagine oneself in the same position.

Delta1212, So how exactly are we to determine how fast something is going? My sticking point is just this. If you say the traveler is traveling at 1/2 C, but he doesn't think he is traveling at 1/2 C, by what standard can we set his speed. He is either not traveling at 1/2 C by the Sun's standards, or he is not traveling at 1/2 C by his own. Regards, TAR2

Janus, Well thankyou, I think its beginning to sink in, again. That is what is "meant" by time dilation. Except I still am confused about all the laws of physics applying equally in any inertial reference frame. It seems that some do and some don't. Not ALL clocks are ticking as they should. The pulsar is not ticking in sync with the cesium wristwatch on the traveller's wrist. The speed of light remains constant, and does not carry with it, the velocity of the ship when light is reflected off or emitted from the ship, but the speed of incoming light, seems to vary, depending on whether you are figuring it, from the traveler's point of view and notion of time, or from the "standard" reference frame of the Sun and its environs, that we have fairly well modeled. Its in this, that I remain perplexed, as to what to call a distance, and what to call a time. Judging by the aberration thing, the view of the traveler would be quite disparate from the view of the same "local" area of the Milky Way, taken while stationary in the Sun's frame of reference. The traveler, if he was familiar with the model of the Milky Way, formed while considering the Sun as a frame of reference holder, would surely notice everything happening and be able to translate what he saw, back into consideration of the Sun's reference frame. He would know for instance, that he could not travel what was a lightyear's distance in the Sun's reference frame, in less than a year, no matter how fast he went. If he were to reach a spot, known to be a lightyear away from Earth, in what seemed to him to be only six months, he would also realize that he had made a trip away from Earth's "now" and a trip to the "now" of the distant point, which is one year, light travel time away from Earth. If he would stop for a breath and a muse at this point, he would realize that even if he traveled back at the full speed of light, he would not be able to make it back to the Sun's now, in less than a year. Why would he not figure his measurements and experiences were true and consistent with the Sun's frame of reference, and his age was consistent with the age of everything in the Sun's frame of reference, and he was displaced in position from the Earth, one year's worth? Regards, TAR2

Delta1212,<br /><br />Well yes, but if the pulsar ticks 1,495,203,938 times and then blows up, there are a finite, and definite amount of ticks which it has accomplished. Anybody, anywhere, moving at any speed, toward, away from or tangent to the pulsar, if they saw the first tick, and the explosion, would agree with anyone else that saw the whole thing, that it ticked 1,495,203,938 times. There is nowhere for the ticks to go but toward everywhere else. They all have to be accounted for, by two "nearby" and longlived observers, in the end. The count has to be the same. If the two parties are on different counts whenn they are close or far, that is understandable. If they approach the pulsar the count should quicken, if they depart from the pulsar the count slows, but whenever they get together, at the same spot, the count should be the same.<br /><br />Regards, TAR2 Janus, But what if the traveler's definition of a day is 1000 ticks of the pulsar? How could he figure it pulsed 2000 times every time it pulsed 1000 times? If he counted 365000 pulses, not only would he know he was gone a year, but he would figure he went the actual distance that he went, in the actual time it took him. Another ancillary question that arose in my muses on this topic. When the cesium clock in Colorado ticks to 100,000, what does a synchronized cesium clock on the other side of the planet read at that moment? Is the time it takes electrical/radio signals to reach from one to the other added, subtracted, or conventionally dealt with in some certain way? Regards, TAR2 I will have to read up on that abberation of light thing.

Spacetime diagram folk. OK, suppose I get the math, but do not accept the answer. Every thing works out on the shift or transform from the one reference frame to the other, with the exception of sensibility. The "figuring" or "measuring" is done based on prior knowledge, and subsequent "forgetting" of the proper distances and times, and the replacement with new observations when required. What if we take a known clock, like a pulsar, and put it at a great enough distance away, that both the traveler and the stay at home see it in a direction 90 degrees from the direction of travel out and back. If the traveler would "measure" his distance and time off of this clock, would not everything work out to be the same time and the same length of trip, in lys and in years, for both the stay at home, and the traveler? So what exactly has been contracted and dilated? Regards, TAR2 Or for the 1000 ly away waver, suppose both the waver and the Earth observer, both had figured out when the pulsar first ticked, and both knew how many ticks it was on at any point. Let's say the traveler held up a sign,"one zillion and three", when the traveler waved. The Earth observer's count at the time of seeing the sign, should be one zillion and three plus 1000 years worth of ticks. The next day, when the traveler arrives, HIS count is one zillion and three, plus 1000 years and a day worth of ticks. Same as the Earth observer. Took him 1000 years and a day, to make the trip of 1000 lys. No length contraction or time dilation required. Except, at the halfway point, when he holds up the "one zillion and three plus 500 years worth of ticks" sign, the Earth bound observer would have to figure he aged 500 years, and traveled 500 lys in 12 hours. and we are back to michel123456's issue of "speed of approach".

Iggy, Oh. I didn't know I couldn't use the numbers, without admitting to length contraction and time dilation. I thought they could stand on their own. Regards, TAR2 Made intuitive sense to me that the red shift behind would be the recipricol of the blue shift ahead.

MD65536. Good advice. Although I think if I had the horsepower, I would have done it that way from the get go. Iggy, If I were to put numbers to the understanding, I think I would work with the peak frequency of black body radiation. Take that frequency and wavelength and figure how many actual waves there are, if one would take a static, instantanous, "now" picture of the space between here and the physical "turn around" point in our experiment. Counting the number of waves, I would have a number W. At the start of the experiment Earth would be at 0, the ship would be at 0 and the turn around point would be at W. Then I would start the experiment and start all three beating at that frequency and put a label on each wave and plot its position in the static fast as thought stage we have set up. Everything should add up, and the ship should count Earths beats as longer wavelengths and lower frequency, at a .577 to normal rate, and should count the turnaround point's beats at shorter more frequent rate of 1.732 of normal. By the time the ship reaches the turn around point, he will be at his own beat count plus W and will find his count of the Earth's beats is at his own beat count, -W. Regards, TAR2

#66 md65536,<br /><br />You are right to take back any suggestion that I am seeing this correctly. We would not want to mislead anybody actually trying to learn.<br /><br />I did, myself, think I was getting it, earlier on in the thread, but I lost it.<br /><br />I am thinking my on again off again attitude toward this, has to do with something I am figuring in the same manner as Delta1212. Perhaps it has something to do with the concept of simultaneity in terms of "when" something happens, and the shift one has to make between the instance of a thing, and the image of a thing.<br /><br />From a pure reality point of view, the most recent events in the universe are happening here and now, and everything else we see is old news, images of events that happened a millisecond ago, a lightmillisecond away, things that happened a second ago, a lightsecond away, and so forth, out to the Cosmic Backgroung radiation, that happened 13.8 billion years ago, 46 billion lightyears away.<br /><br />In addition, as best as I can figure it, there is only one instance of the universe, each and every piece and part of it, actually no older and no younger than 13.8 billion years old. And in this sense, a star 4.2 lightyears from us, is true, in two ways. One, we know it is happening now in a way we have no immediate access to, but that we can imagine is occuring in a way that will become "true" to our senses, in 4.2 years, when the light from that current event reaches our equipment. And two, we know the star is true, because we look up, and see the darn thing shining up there.<br /><br />If there are these two true instances of that star, which there is, then it is critical that when we speak of it, we declare which of the two we are refering to as real, or when we are referring to both the actual instance of the thing, and when we are referring to its presence in our sky and its effect on our senses and the world around us. Both "instances" of the thing, are very real to us, and neither is imaginary. Neither is "just a thought", or "just an image". There is only one instance of the thing, and it is happening now in both senses.<br /><br />Where I think Delta1212 and I are in agreement, is in the knowledge, that when something moves away from Earth at velocities approaching C, which is the speed at which the two instances or the two senses of a vastly distant thing are connected to each other, that something is actually making the trip, between the image type sense of the thing, and the actual thing. Staying in its own now, as something the exact same age, as the rest of the universe, but separating itself positionwise, and timewise, from Earth, and approaching positionwise and timewise, the actual now of the distant thing.<br /><br />No doubt, the math of relativity works out. But it seems to me, that you can explain the same numbers with the above understanding, and the red and blue shifts of what actual nows you are moving toward, staying at rest in relation to, or moving away from.<br /><br />Allowing one to perhaps explain a thing, without time dilation, length contraction and such things.<br />Perhaps.<br />Perhaps not.<br /><br />Regards, TAR2 Is the Mars rover doing something now? Is that thing its doing now the thing we see it doing now, or the thing we will see it doing in 14 minutes? One has to be specific about these uses of now.

md65536, So Tom does not think he has reached the turnaround point, when he turns around? He has not followed the plan, and turned around before he has gotten to the designated turnaround point. He has neither gone far enough nor long enough, or he has not traveled at the designated speed. I think we should take Tom's license away, for failure to follow instructions, and messing up the experiment. Regards, TAR2 P.S. Over the last 10 days or so, I have personally been dealing with a double vision issue. Most of the time I can fuse the two images, but my eye doctor has determined that my eyes are out of vertical alignment (have not yet grasped the concept, but have verified the issue by looking at an object through two paper towel roll tubes, and the image my right eye focuses on is "higher" and a little to the left from the image presented by my left eye). I mention this, because the fusing of the image presented to us by the Earth, and the image presented to us by Tom, is a difficult task. We can not put ourselves in a position where we have two actual images that are presented simultaneously for fussion, during the entire experiment. Our binocular observer has to have one eye in one reference frame, and the other eye in the other reference frame. I am sure that Minkowski space and Fourier transforms, and four vector analysis and such, have been designed for this task. However, I am woefully lacking in such skills, and keep hoping for a view that adds up and fuses, without the math.

Janus, Judging by Iggys approval I suppose you are right. However, running the same numbers from the travelers point of view, she sees the Earth age at .557 per year rate, for two years and then at a 1.732 per year rate for another two, on her way back. Making the stay at home and the Earth, 4.618 (1.154 plus 3.464) years older, which they are not. Although 4.618 x .866 would give you four years and I suppose that is what time dialation is for, it seems to add up for the wrong reasons. Regards, TAR2

xyzt,<br /><br />But if the "jump" is only in the turn around, how do you account for the traveling twin "aging" differently? Is she the same age as the stay at home, all the way out, then becomes a different age at the turn around, and then continues aging at the same pace as the stay at home, all the way back?<br /><br />And what is happening to the stay at home, that would account for the gap in his black dots? Should not his black dots be equally spaced for the whole trip?<br /><br />I am no longer as clear on the ts and the taus, as I though I was getting.<br /><br />I am still considering that what happens on the way out, in term of the traveling twin getting farther from the stay at home's now, and therefore closer to the now of the turnaround point, must be the opposite (time relationshipwise) as what happens on the way back.<br /><br />Also, I do not comprehend the meaning of v x/c2.<br /><br />What is that supposed to represent? I have a hard time understanding the speed of light, if time and distance are not already understood as invariant. And if they are to vary, vary from what fixed understanding?<br /><br />And one other little problem I have. What exactly is a square year? Wouldn't you need a fifth dimension to hold such a thing? Can you cube a year? What would you have, if you did? Or what quantity does C squared represent?<br /><br />Regards, TAR2

xyzt, What confuses me about the experiment, is the question of why does not the opposite aging effect happen during the return trip. Let's say for example that the traveler keeps track of two similar pulsars, 180 degrees from each other, one in the direction of the outbound trip, and one in the direction of the Earth. On the way out, she counts pulses from both, and finds the one she is headed toward is ticking faster then it did when she was stationary on Earth (where the similar ticks were established) and the one in the direction of the Earth is ticking slower. On the way back however, the pulsar behind the Earth is now blue shifted and ticking faster, and the one behind her is red shifted and ticking slower. When she gets home, and adds up the ticks she has experienced exactly the same number of ticks from each, and this number agrees with the count of the stay at home twin. She would not consider herself a different age then her twin. To solidify this argument, consider the fact that we see the light from a star 4 lys away, 4 years after the light is emitted, however there is only one instance of that star. We cannot consider it both existing as we see it, and existing presently sending out light which we will not see for 4 years. Well we can, but we have to define carefully which "instance" of the star, we are considering. As the traveling twin goes out, she remains as only one instance of a person, but her increasing distance from Earth causes her to be continually separated from Earth's point of view, and continually closer to the "imaginary" now of the star we know is emitting light that takes four years to get to us. If she should reach the star, she would be in its present moment for real, and it would then be Earth, which to her would appear as it was four years before. Still took her the appropriate time to get there, and will still take her, the appropriate time to get back. She should be as much older as the time it took to make the trip. Regards TAR2

Well, I am sort of seeing what your saying, or should I say, what spacetime diagrams are saying. Thanks. Regards, TAR2

Well, OK, the equations work out, and agree with experiment, Still not sure though what proper time is. Couple reality questions on the twin thought experiment though. If red makes a turnaround, would that not mean she would have to expend a great deal of energy to "brake" back into our FOR for that moment where she is no longer traveling at a v away, and is then traveling at a v toward us. For that moment (which could hardly be in reality a short moment) she would have to return to our frame of reference (blue's frame) and then through whatever wonderful technology, regain her .6C velocity back in blue's direction. Being that the given in the experiment is that she is already traveling at .6C as she passes the Earth at the start of the experiment, there is an assumption that it took her some time (and a great deal of energy) to accelerate to that speed. The same conditions of reality would hold, during the turnaround, and she would first have to expend the energy to slow to a stop (back in blue's FOR) and then build up the tremendous speed again, for the return trip. Seems the only way to avoid a return to blue's frame of reference would be to travel in a circle, in which case, the diagrams would have to be refigured, and she would be in a constant state of acceleration, plastered against the wall of her vessel, that was opposite the center of the circle. Also, not included in the thought experiment, is any effect that her bow may be experiencing, different from her stern. The light from the rest of the galaxy is extremely red shifted hitting her stern and extremely blue shifted hitting her bow. Off at right angles to her motion things would look about right, but although light is hitting both her bow and stern at C, the frequency is likely doubled in front and halved in back. This unbalance of energy hitting the craft, should have a slowing effect. As well as imbalance of heat. She would KNOW which way she was headed, and could not fool herself into thinking she was stationary. Regards, TAR2

michel123456, Not sure I am wrong about the two experiencing the same thing. If red is considered stationary, blue makes the turnaround, and red does not notice this til later. If t and t' are not equal in the twin experiment, then similarly t' and t are not equal. Being that they are unequal in the symetrically opposing ways during the whole adventure, and they started out equal and ended up equal, there would be no reason to call one twin older than the other. And being that they both experienced the same number of ticks of the pulsar, I would argue they are both the same age at the end of the adventure. Regards, TAR2 Can not red be exchanged with blue and blue with red in any of the above diagrams?

But what about the pulsar. Would both twins not count the same amount of pulses?

swansont, Perhaps it should move to twins paradox, but from my point of view, it has more to do with philosophy in terms of the perspective that we truely hold. If we have a here and now, that we consider the moment we are in, we are bound by that moment, in that we have no "other" perspective, from which we can witness, or calculate, both twins at once. We can either put ourselves in the shoes of the other, in which case the relative velocities, and the ticking of time are exactly the same in both cases, or we can stay with one or the other for the whole duration and witness the red and blue shift of the other, the slow arrival of messages on the way out trip, the rapid arrival on the way back, and the reunion years later, when both would report the exact same experience of the other. There is no vantage point, outside of time and space, from which we can view both at once. There is no vantage point, outside of time and space, that can track both, simultaneously, receiving instant information about position and the ticking of each clock. Both clocks tick, and never leave the others reality. It all has to add back, with no incongruities, in both cases. Regards, TAR2 Consider a third triplet with a ship and a velocity and a course that would keep him exactly the same distance from both of the others. He would always have both the others in view at all times, and be the middle man. Then consider a fourth, inbetween the first and third, and a fifth inbetween the first and forth...and so on. Hypothetically you could make an argument, that nobody's clock ever ticked slower, and they all just keep ticking along. Or consider both twins counting the pulses of a distant pulsar. When the twin returned and they gave each other the count, it would be exactly the same.

How about external clocks? Ones we move toward tick faster, (blue shifted). Ones we move away from, or move away from us, tick slower (red shifted). If a twin leaves the other at a high speed, each would be red shifted to the other. If things are relative, there would be no distinction as to which one was aging more slowly, as they both would be ticking slower to the other. A return trip, would cause a blue shifting for each while observing the other, and when they got together again in space, they should be the same age. No?

Monday's Assignment Die, But a principle is of our design. There is a thing, causing us to derive the principle, but as you say, there could be other explanations. The thing itself remains extant, and complicated, and extremely capable of continuing to be, without us writing the ultimate equatiion for it. How we can refer to molecules is a matter of grain size, taking what we know works, and applying it on another scale. There do seem to be analogies that carry through...but not all components operate exactly as imagined. We find descrepencies, things that are happening differently, because the scale is different. Brownian motion for instance happens under a high powered microscope, and is a reality on that scale that doesn't exhibit itself at the grain size we normally operate under. On our scale of size and duration, a rock is rather hard and solid. On the molecular level, it turns out to be mostly space and fields of magnetic and nuclear forces. Same principles that operate here, don't apply there. Except here is there, and there, here. So the principles are more of our design, put into place by us, to describe what applies, IF one was to shift to a particular grain size, and define the size and duration under consideration. Doubtful that the principle itself has any way to be real, without the manifested reality from which we derive it. Regards, TAR2

ydoaPs, Though, being that we already know how to refer to something, there is an automatic requirement for a referent and a referee. It was the automatic nature of the "idea" of refering that I was alluding to. That this must indicate we have already done a step, before we have anything to think about, or anything to say about a thing, or anything in mind to point another toward. First there is a thing, that causes us to sense it, then we have some analog representation of this thing that we judge against, compare with and otherwise measure in relationship to other stuff we have sensed and remembered in this analog representational way. The "meaning" of a statement, or a thought, is a denoting of the original object. A representation, a symbolic reproduction of the original, "meant" to stand for the original. Frege, in "sense and reference" might be trying to explain in a complicated way, an activity we have already automatically accomplished. Regards, TAR2

There seems to be a "switch" of position required to use the word refer. That is, you have to be already assuming a two position setup. There is the thing as it is. There is the reference to it. If we all know what it means to refer to something, then the argument is over, and we are all realists. Science's job is to make the references as accurate and consistent as possible.

Did the quick study. Out of 67 languages in Google translate, the God good and Devil evil similarity did not show up once. One or the other pair showed up occasionally, but the similarity is pretty much accidental.