PerfectLiquid

Since the development of the concepts of space-time and relativity, primarily by Einstein, we find that natural philosophy has been largely defined by a series of mathematical equations. While such quantitative descriptions have proven to be remarkably accurate and precise (especially QED), there has been a drift away from mechanistic physical descriptions of nature and towards increasingly abstract formulations. While Einstein, among others, was involved in starting this trend, he became increasingly concerned that the study of physics was abandoning the pursuit of fundamental mechanisms in favor of statistical descriptions such as quantum mechanics. Although he conceded that such approaches could readily account for experimental results, he expressed the view: "Some physicists, among them myself, can not believe that we must abandon, actually and forever, the idea of direct representation of physical reality in space and time; or that we must accept the view that events in nature are analogous to a game of chance." [The Fundaments of Theoretical Physics, Address before the Eighth American Scientific Congress, Washington, May 15, 1940; published in Science, vol 91, May 1940]. The challenge of this thread is to consider whether it is possible to mount a return to fundamental descriptions of what nature is, versus how nature acts. As the title suggests, can space-time be physically described in substantive terms that reasonably account for the properties of relativity? This query stands in contrast to certain basic assumptions that underlie quantum mechanics (i.e., that we will be unable to characterize the elements of nature responsible for the behaviors that are observed). Regards, Al

Hi Modest, I think you're right about branching off into a new thread. Since I'm a novice here, does "Space-time and Relativity" make sense? Thanks. Regards, Al

Hi Modest, Since we're on the subject of Einstein, it may be of interest to consider some of the other ways that he viewed space-time: 1. From his presentation at the University of Leyden (1920): "According to the general theory of relativity, space without aether is unthinkable." In later work, Einstein used terms such as physical space, physical properties of space, or physical structure of space in place of this reference to aether. 2. “Space is the primary phenomena and matter is derived from it as a secondary result .” [A. Einstein, “The Concept of Space,” lecture delivered at the University of Nottingham, 6 June 1930, Einstein's Balckboard - School of Physics & Astronomy - The University of Nottingham As summarized by Kostro, , “he [Einstein] finally came to the conclusion that four-dimensional space (the space-time continuum) constitutes a reality ontologically primary even to matter.” While these clips do not nail down his precise views on space-time, I think the second quote is instructive. If space-time was simply an abstraction that reflected the mathematical properties expressed in his equations, how can it be transformed into matter? While one could easily counter this point of view with a "Where's the proof?" query, it does raise a thought provoking question. How could something that is apparently as unstructured as space-time, lead to the formation of matter and the subsequent structured collections of matter like our own Milky Way? This is largely the same problem that dogs current views of the CMBR as representing remnants of the Big Bang. Without some form of preexisting structure / complexity (i.e., low entropy condition) in either case, there would seem to be a violation of the Second Law of Thermodynamics. Regards, Al

Hi Michael, I'll do my best to address your observations / queries: First a minor nit: a cesium clock depends on using cesium atoms to define a microwave frequency that produces maximal fluorescence in these atoms: From NIST: "Eventually, a microwave frequency is found that alters the states of most of the cesium atoms and maximizes their fluorescence. This frequency is the natural resonance frequency of the cesium atom (9,192,631,770 Hz), or the frequency used to define the second." These atoms are used to precisely maintain this frequency and thus the unit we call a "second." 2. It seems to me that you are recognizing that what we generally call time doesn't really exist. I refer to this as big "T" Time and it equates to the so-called dimensional Time. If we slice this up into the usual suspects, it becomes quickly evident that past and future don't exist, while the present appears to be sharply defined - psychologically that is. There was an interesting analysis done on this by Diego Meschini in his Ph.D. thesis (last year, whoops ignore that reference to the past ). If "now" is all there is, then there is no convenient way to place it within a dimension. So big "T" Time serves as a useful psychological construction, but it has no physical existence. Therefore, it isn't subject to dilation. 3. Moving on to little "t" time, this is the time that Einstein was addressing and it is the unit that serves an index for rates. Note that this little "t" time is what is being defined by that frequency associated with the cesium atoms. This does change in response to a gravitational field or motion through space (this last part is my interpretation versus Einstein's). So what is changing? I would argue that the best example we have for the so-called "arrow of time" is related to the neutral kaon. Perhaps this particle has some relationship to Clerk Maxwell's incompressible fluid that fills space and thus serves as a background mediator for little "t" time. Something is changing in the gravitational or motional setting, and I don't have a better marker. 4. The metaphorical stopwatch: if we refer to some sort of clock, then by definition it is measuring "t," not mediating it. For the mediator, as you can see from above, I would point to something that fills space (i.e., is space) and that somehow influences the rates of physical processes. This would amount to space-time, and I think Einstein got it mostly right. Please understand that this view will not get you an "A" in physics.;) Watching the clock and wishing you a prosperous future, I am Al

[quote name='CraigD;278462 ... True. I’ve been ignoring the gravitational time dilation in these thought experiments because it complicates things it’s small - For the 2 year (Rover time) trips we’ve been discussing' date=' about 0.05 seconds = [math']\left( 1 -\sqrt{1-\frac{2u}{6370000 \cdot c^2}} \right) \cdot 74790000 [/math] , where [math] 6370000 [/math] is the Earths radius in meters , [math]c[/math] the speed of light in m/s, exactly 299792458 which hardly compares to the couple of months difference due to velocity time dilation. ---Quote (Originally by PerfectLiquid)--- Doesn't the difference attributable to his speed point towards a preferred frame of reference? ---End Quote-- No. This is the real essence of relativity – the part of it that’s really relative. This post, however, is a bit overlong, as is my post-writing timeout, so I’ll save another batch of thought experiments addressing it for a later post. Hi CraigD, Masterful treatment of the problem. However, WRT the preferred frame of reference question, since we see time dilation occurring in the case of differences in speed (as in your example), this dilation is not symmetrical. In a truly relativistic sense, Homer appears to be moving away from Rover at the same speed as the reverse (i.e., Rover relative to Homer). But only Rover's clock reflects a slower rate of ticking. If it was truly relative, both parties should perceive the slowing down effect, but only one does. This suggests to me that the speed effect is relative to a background value (ideally stationary space-time to make the calculations simpler). This would be consistent with the asymmetrical effect on time dilation of a gravitational field (relative to a background of gravity-free space). Regards, Al

Hi Michael, Sticking to my understanding of time as a thermodynamic rate (order --> disorder), I would speculate that time is mediated by a background medium. While the notion of an aether is currently out of vogue, it may be useful to point back to the approach that James Clerk Maxwell took in the development of his famous electrodynamic equations. He assumed that an incompressible fluid filled space and that this was the medium that conveyed electromagnetic fields. Based on this view, he used two properties of free space (its permittivity and permeability - electrical and magnetic properties) to derive the speed of light. This strongly suggests (to me at least) that there is some medium present in free space that conveys energy through space. If true, then it is reasonable to suspect that something as pervasive as "time" might also be mediated by it. Please appreciate that this will be a minority view in the extreme, but if your interested in trying to grasp "time" from a substantive point of view, it may be worth a visit to the following link: physicsworld.com The article in that link reviews some careful work performed by experimenters at CERN who looked into the characteristics of a particle known as the neutral kaon. This particle seems to have very STRANGE properties...:) Regards, Al

Hi CraigD, Homer should be experiencing no force, since he is neither accelerating nor in a gravitational field. Rover on the other hand is in a gravitational field and is accelerating linearly due to the towing arrangement. The force that Rover experiences should be 9.2 times his mass. The time dilation that he experiences would be a combination of that produced by the gravitational field he is in PLUS that due to his linear speed (that is constantly increasing). Doesn't the difference attributable to his speed point towards a preferred frame of reference? Otherwise, there would only be an apparent difference (relativistic symmetry) versus a real difference (asymmetry)? This view will obviously not be universally shared. ;) Regards, Al

Hi Michael, This is a good question that may not be so easy to answer, or that will likely produce many answers. IMO - time is the rate at which entropy increases, that is, it is a parameter that reflects how fast order moves towards disorder. This would represent time from a thermodynamic perspective. I expect that others may offer reasonable alternatives, but this works for me. A partial quote from Einstein: "People like us, who believe in physics, know that the distinction between past, present, and future is only a stubbornly persistent illusion.":) Regards, Al

Hi Michaelangelica, Water turns out to be my inspiration, but it isn't sufficiently perfect (i.e., near zero viscosity) for my purposes. I am actually very interdisciplinary and do not claim to be a physicist. I think this has helped, but only time will tell. I'm really more of a natural scientist. How about you? Thanks for the welcome. Regards, Al

Hi lemit, If you like physical analogs, you'll love my approach. If you like data-driven approaches, I think you'll be pleased. If you like complex math, you'll be disappointed (at least so far). Like Clerk Maxwell, I am trying to physically understand the phenomenon (especially gravity), before going after the math. You can see why this puts me at variance with quantum mechanics, but I'm not discounting their work, especially QED. Thanks for the hello. Regards, Al

I believe this is sound (or is that light) advice :). One thing to watch out for are treatments that suggest that time dilation is completely relative (i.e., symmetrical). The twin moving at the higher rate of speed (relative to space-time?) should exhibit the slower rate of time as measured by his/her clock. Note that in Einstein's original example, he avoids this issue by making one object stationary by definition. He was not the first to consider relativistic time dilation (e.g., Lorentz and Poincare), but he nicely brought together this with other relativistic aspects into his famous special relativity package. Note that he also tossed out the need for an aether in this special package, but later realized that an aether (or physical structure associated with space-time) was required by general relativity. Funny that this latter idea was never brought forward through time... ;) Regards, Al

Hi Moontanman, Thanks for the welcome. I hope that my somewhat irreverent views succeed in planting some fundamental seeds in the minds of a few aspiring physicists that might visit here. There seems to be an overabundance of mono-culture amongst the experts. Looking forward to both sharing and listening. :confused: Regards, Al

Hi Pamela, Thanks for the welcome. Since you seem to be fond of Einstein, you might be interested in my reply to Little Bang at http://hypography.com/forums/philosophy-of-science/3650-what-is-time-70.html#post278225. I continue to marvel at how little I was taught (or learned) about him in school. I wish that I had studied German, so that I could check out some of his work first hand. Take care. :eek2: Regards, Al

Hello Little Bang, It seems that you disagree with the good Dr. Einstein as well: "From this there ensues the following peculiar consequence. If at the points A and B of K there are stationary clocks which, viewed in the stationary system, are synchronous; and if the clock at A is moved with the velocity v along the line AB to B, then on its arrival at B the two clocks no longer synchronize, but the clock moved from A to B lags behind the other which has remained at B by 1/2 tv^2/c^2 (up to magnitudes of fourth and higher order), t being the time occupied in the journey from A to B." [On The Electrodynamics Of Moving Bodies, June 30, 1905] Note that only constant velocity is invoked in this example, and this characteristic of Special Relativity has been tested and confirmed. Naturally, for an object to exhibit constant velocity, it has to exhibit positional displacement (i.e., motion) as well. All the best, Al

If you give a little more thought to this issue, you may find that reliance on either velocity or acceleration in trying to understand time dilation has a built-in problem. They are both measurements that are indexed by time... You may want to take a step back (or is it down?) to displacement. Both gravity and motion share the phenomenon of time dilation as well as this fundamental quality of displacement. You may argue, What are they displacing? I would answer that they both represent matter displacing space-time. Gravity is the result of a static displacement, while motion (assuming little gravitational effect) represents dynamic displacement. This, in my mind at least, converges Clerk Maxwell's approach with Einstein's understanding. Alternative views? From the aether, Al