owl

Still waiting and hoping for a reply from swansont (and still practicing patience.) Meanwhile the continuing focus on basic ontology. swansont: Please explain. Are not differences in gravity and velocity differences in physical parameters? In what case do two clocks 'tick' at different rates in identical physical environments? One more time on my basic unanswered question: “Must variable clock 'ticking' mean, beyond doubt, that 'time itself' is variable... which refers back to the basic question, What is time?”... or in other words, how is the following wrong?... "...physical processes slowing down does not automatically mean that some 'thing' time slows down... ontologically speaking." md65536: I have never claimed that different rates of 'ticking' are due to "mechanical error." A year still means one earth orbit by definition and in "the real world." If ten years (orbits) elapse while the above rocket is on its journey, and it's clock says that only five years have elapsed, then its clock is in error by by five years because of the effect of relativity, extreme velocity in this cased, not because of mechanical error. There is no need for insulting sarcasm. A deep inquiry into the meaning of time (ontology as relevant philosophy of science) is certainly not "spamming." As swansont said above, and I agree: This doesn't mean that the word "year" is now meaningless, or that all clocks everywhere are equally correct in "clocking" a year. That is why relativity makes adjustments as needed to agree on timing (as per GPS, etc.) We could make one galactic revolution the standard if we knew the period precisely... or to one full Bang/Crunch cycle, maybe the largest possible cosmic physical process) but those would require very small fractions for timing relevance to life on Earth. So one earth orbit makes a lot more sense as a standard, and its fractions are already very familiar. In what sense is time "malleable" if it is not some kind of "stuff," an entity? (Ontology.)..."traveling forward through" what? If "time travel is an experimentally verified reality" then can we travel forward to the end of that horse race (from the time travel thread) and then bet on the winner? How about visiting dead ancestors before they died, or is going backward in time off limits? Edit, a footnote: The rocket voyagers above will have probably "aged" only five years on their journey if their "physical processes" were slowed to half their usual rate on the journey, as was the rocket clock. This, however, is by no stretch of the imagination, "time travel."

I'm hoping that swansont will answer the questions in my last post... no hurry; I'm patient. md65536, I have no argument with your post on how GR and SR address time. But the old saw that time is that which clocks measure (a tautological argument in logical terms) does not address the ontological issue which is the subject of this thread (not "time according to relativity theory.") To illustrate, here is a quote from a link provided by DrRocket in the "time travel" thread. From Wikipedia on the Hafele-Keating experiment and later verification with more accurate clocks: (my bold) ...“effects on time” or “effects on clocks” is the ontological question asked as the thread topic. That is my "issue." We all know that clocks are variable, and relativity does a fine job of correcting for that variation in all kinds of situations (like GPS info.) But it makes a lot of difference whether or not time is malleable (as in "is time travel possible?") As you said, any physical process can be considered a "clock." No problem.This is not the issue. Put two clocks in motion at different velocities or in different gravity fields and they will "tick" at different rates. But compare the number of earth orbits (actual years, by the definition of what the word "year" means) to the "clocked years" on I ME's rocket, as above and the former will have observed ten orbits on the "earth orbit clock" while the latter will have recorded only five years on the rocket clock/calendar. If relativity insists that both are correct, then relativity is wrong. The rocket clock is clearly in error because of the well known relativistic effect, but that is no problem, because the correction provided by relativity adjusts for the five year discrepancy... just like GPS adjustments, which are essential for positioning accuracy.

I've been gone for an extra long holiday weekend, and just finished catching up here. I can't reply all at once, so please bear with me. swansont: Are challenges to accepted physics permissible? Reference: The topic is "Ontology of time" in the Speculations section. Can other respondents not question the meaning of "time dilation"as part of the topic so established?, i.e.,... Must variable clock “ticking” mean, beyond doubt, that “time itself” is variable... which refers back to the basic question, “What is time?” BTW, I agree with a lot of what mpg755 says, and it seems like imposing a gag rule on him just eliminates anyone here who might be an ally in sincere questioning of “mainstream science”, specifically the reification of time, the subject of this thread. Among many other statements mpg755 made, with which I agree, the following is brief and simple, and seems not yet answered: You, swansont said in another post that the physical environment was not what makes “time dilate”... as follows: I know that “you can't say who is moving and who is at rest,” (classical Einstein) but how does this negate the effects of the physical environment on clocks... like more or less force of gravity on them or more or less velocity as in the context of my previous posts? Also, please clarify my error, if there is one, in the following inquiry above: On second thought, if only five years have passed on the rocket voyagers timekeepers, they should arrive back on earth five years in the past relative to my proposed standardized earth/orbital reckoning of years, not five years in the future, right? The latter would require a faster clock/calendar on the rocket, but still be just as absurd, going back to the past or into the future... same kind of sci-fi nonsense, it seems. Basically my ontological question (thread topic)n has not yet been answered. I stated it as clearly as I could as follows: Or, in other words (still unanswered): PLEASE address this issue. swansont: I would have to agree with you here on the grounds that the human aging process, metabolism, etc, probably slows down to the same relative rate as the speeding rocket’s clock. But physical processes slowing down does not automatically mean that some “thing” time slows down... ontologically speaking. Still trying to sort this out...

DrR: From the perspective of logical argument, you continue to argue from “authority” (which is no argument at all) rather than specifically refuting my points, as in the several instances of "what I am arguing against” above. I made some cogent points. How about addressing them for a change.... like: From my post 80: You can ignore it but that doesn't refute or even address it. Now, to back up a bit... DrR: The fact? So then all inquiry into the ontology of time is settled because "the doctor" says so? Everything everywhere moves, and that “takes time”... event duration, whether measured or not. It can be a nanosecond (a local micro-event) or a full Bang/Crunch cycle (a macro-universal event...if that cosmology turns out to be true.) ...And you completely ignored my presentation of presentism (post 69), as it contradicts your "facts" about time. Then, rather than address the several Einstein quotes which contradict you, you sweep it all aside with: ... and dismiss all quotes you don't like with insistence that they didn't count... but only the "final product", GR. (Just how "final" do you think that "product" is?... Like the dogma that "relativity is the ONLY cosmology?")

I came to this thread again to clarify my reply to a thought experiment by I ME in the "Time Travel--Impossible" thread... his post #66 and my reply in 67. Hopefully this reply will also be relevant to swansont's objection: I ME wrote: I replied; So, to sort it out and provide a 'reality check' on what an actual year is see my post here on 5/26. We have an earth-commensurate measure of distance in the meter, which is (if I remember correctly) one ten-millionth of the surface distance from equator to pole. I thought that rather than saying that time is all relative to clocks' variable rates of 'ticking' at different velocities and gravity levels (and space rocket clocks/calendars being just as valid as observed earth orbits for "year" reckoning)... that a standardized year (one of the three) should become the earth-commensurate year standard... and divisions thereof. Also, our most accurate clocks situated at sea level would standardize the altitude/gravity factor, and on the equator would standardize the latitude/velocity factor. Then, when a rocket goes on a near-light-speed round trip and comes back with only five years elapsed on its clock/calendar while ten years have elapsed on earth, the 'reality check" is that, in fact, there have been ten earth orbits (actual years elapsed), monitored by the above synchronized, standardized earth-based clocks. So the rocket's time keeping error will be obvious, and the absurdity of arriving back five years in earth's future will be clearly debunked... along with "time dilation." Philosophically, all of the above is an argument against the relativity dictum "everything is relative"... and a "reality base"of empirical observation" (a precise measure of an earth orbit) for that argument.

I keep trying to address the thread topic, but DrRocket keeps trying to make it all about me and my supposed lack of understanding the 'real issues' here, i.e., DrR's understanding of relativity, "the ONLY cosmology," as applied to time travel. So, I will back up and take it one step at a time, focused on the the topic. Keep in mind DrR's claim that, "This has nothing to do with Einstein." From the link above to Gevin Giorbran's site... author of Everything Forever, Learning to See Timelessness... (disclaimer: I don't agree with a lot of his stuff, or with Einstein, albeit relativity blasphemy to disagree with the latter): Einstein: I agree. From a letter from Einstein to his friend, Besso, I disagree. Quoting Giorbran: Again, this means that everything that now exists and has ever or will ever exist... all exist now, in the present, "simultaneously." DrRocket: I asked DrR if he disputed the quotes by and about Einstein's take on time above. No reply, just continued attacks on me. The Doctor concludes: It really doesn't get any more absurd than this. I have distinguished many times between the conceptual meaning and the math involved in " content of fundamental physical theories," and I understand very well the former without being a mathematician, while DrR insists that the math is fundamental to understanding. And fundamentally, he believes that to disagree with him is to be wrong. He insists that I "argue against a strawman." I argue against everything existing at the same time (as quoted again above), against there being no difference between past, present, and future, and against time being "something" that can be "traveled through." I also argue against high speed space cadets determining how many years have elapsed by their slower clocks/calendars on an equally valid basis with how many times Earth has actually orbited the sun during their round trip journey. Anyone here interested in the time travel topic, or has this just become another Owl bashing thread? PS: I have expanded on my last point in my "Ontology of Time" thread (in Speculations) if anyone is actually interested in the topic.

The Truth according to DrRocket: Do you dispute the quote cited above: DrRocket: As usual you continue to presume that you know better than I what I do and do not understand, and as always without an argument in reply to what I actually stated... just bogus assertion of authority rather than specific argument.

We have been discussing the nature of time in the "Is Time Travel Possible" thread, and I recently posted a "reality check" there, contrasting clock time, with its undeniable variability (misnamed "time dilation" in the relativity community) with what a year (and its fractional divisions) means in "the real world," i.e., one earth orbit around sun. So then how could an earth commensurate (based on the natural cycles) standardized version of "clock time" be established? Greenwich Mean Time is of course the longitudinal time line for "time zone" reference around the globe, but we must also consider altitude and latitude as variables effecting clocks. So I propose that standardized elapsed time be based on clocks situated around the equator at sea level and synchronized with one of the three standard ways of measuring "the year" (sidereal, tropical, or anomalistic... We will need to pick one...) and all fractions thereof. Then we can put an end to the relativistic claim that "all time is relative" to what frame of reference a given clock is "ticking" in, i.e., high or low gravity field, fast or slow velocity, etc. Maybe, in the process, we can quit the ubiquitous reification of time that I have been bitching about... assuming that "it" is a variable entity. At least, recognizing time as an artifact of measurement of event duration, we would then have a global standard with which to compare all clock variations and get over "time dilation."

I ME, Please reply to my post 67. Have our variable clocks become the standard for relativity arguments based on "time dilation", or is a year still one earth orbit? If the latter, then days, hours, minutes, seconds, & on down are fractions thereof standardized by the above natural cycles ? If the latter, can we not admit instrument error for clocks and then credit relativity with corrective math for all such variation? More generally (to the forum) regarding time, anyone interested in presentism as relevant to "time travel?" Specifically, was Einstein correct in concluding that the past, present, and future all exist simultaneously as per the "world lines" of everything in the universe (including all three) all existing at once. Ref from article, "Timelessness": http://everythingforever.com/einstein.htm If I may interject a philosophical comment, the above not only implies strict determinism for the whole universe, but says that everything that ever existed still exists, which is blatantly absurd... as is "eternalism" in general as a philosophy of time. In contrast, here is Wikipedia's intro to Presentism: The controversy is very "real," which means that relativity's version of time (etc.) is not the matter-of-fact as presented here, particulary by DrRocket. BTW, nice try, Doctor, on weaseling out of responsibility for the "nuts" insult, but the veil was very thin, and I really don't "need" to "brush up" on my history or defend my sanity to know that you meant it as an insult. Further, "categorical denials" are not arguments addressing the points I have made in recent replies to I ME and to you.

My question, "What am I missing here?" in post 67 replying to I ME was a serious question about how ten years, defined as Earth orbits around the sun, can become five years (for the rocketeers) by virtue of a fast round trip in a rocket ship which slows down their clock and calendar. I also asked what it means to arrive back on earth five years in the future, i.e., before the events of those five years have even happened. These are reasonable questions, and calling me "nuts" for asking them is not worthy of a science forum, and it seems to violate Admin's recent warning against name calling here. As a retired psychologist, my professional opinion is that believing those situations to be possible demonstrates a state of mind out of touch with reality... no personal insult intended. And in accordance with the admin advice given me, I will not re-engage the ontology of spacetime topic again outside the philosophy section, regardless of DrRocket's persistence in insulting me. (...and veiling the insult as a McAuliffe quote does not make it OK.) Edit for correction. DrR's insult was directed to my reply to his last post, not to my reply to I ME. But the insult was just as inappropriate in either case. And, just to be clear, the present is universal, now everywhere, and time is the "clocked" duration of events from one "now" to another, between clicks of the "timer's" stopwatch... not some stuff woven together with space... which is... debatable as to what it is. Enough of that already.

DrRocket: I must question your use of "fact" in this context. Do you discard presentism out of hand, or have you studied it at all? "Present" means "now", and now is not a locally unique "environment" but everywhere present at once, without regard for lightspeed and the information it conveys (The province of relativity.) I'm interrupted by life's priorities so must cut this reply short. The above illustrates my point anyway. And, again, "spacetime" is not such a malleable matter of fact as relativity generally assumes... the other conversation which I will not again mention here in this forum section.

I ME, We all know that clocks run faster or slower under different conditions, as you described. ("Time dilation.") I suspect that people age more slowly in high speed (etc.) conditions as well. But the question is still unresolved for me how this proves that "time runs faster (or slower)" under the different conditions you mention. Is it just semantics or is there some actual entity, "time" which changes under these different conditions? Please refer to my "Ontology of Time" thread in the "speculations" section for the background behind my question. To be more specific... regarding your statement (and apparently accepted relativity theory... as per "the twins paradox" and such): Is there not a "reality check" here... that a year is one orbit of earth around sun? Speeding out into space and back in a rocket does not make ten earth orbits into five just because the rocket's clock and calendar says that only five years have elapsed. Or regarding your thought experiment: What could the last statement possibly mean? You come back to an Earth in which events have not yet happened and will not happen for five more years? Does this make any sense at all? Not to me! What am I missing here?

Drrocket: Spoken like a true dogmatist. Not all cosmology is based on GR. And "curved spacetime" as a central concept is still a hot debate among ontologists (whom of course you despise, to your discredit.) It would broaden your horizons to study those papers on spacetime compiled by Deiks and all those references provided by Ross. Please review Ross's comments on the difference between concepts and "the math." I understand the concepts just fine, thank you. Regarding your recent and continuing use of insults rather than rational argument, I have some sound psychological advise. Use "I statements" rather than "you statements." For instance it is perfectly legitimate to say that my comments sound inane, irrelevant, nonsensical, and like incoherent babble to you. It is quite another to say that all of the above is objectively or absolutely true, as if you have the only handle on reality and can legitimately judge everyone else accordingly. But maybe you are too full of yourself and your inflated sense of authority to know the difference. Science discussion need not be so personal and insulting as you make it. But as long as you harbor such a nasty opinion of all things philosophy-of-science, there can be no respectful conversation with you. Please tell me why you think "curved spacetime" (as an actual entity, a malleable medium) is essential to the predictive power of GR.

DrR: ... So Hawking's conjecture is the "heart of the matter" of the time travel question, but I have misrepresented your opinion of him in this context? How so? Quoting the intro to that conjecture: Oh!... All we need is "the technology to warp spacetime so that closed timelike curves would appear, allowing travel into the past." Now I get it! How exciting! Then I could go back and talk to Plato himself about “platonic ideals.”... I mean, you know, if Hawking thinks it’s possible, who am I to question?! DrR: Just finished it. What was the answer to the horse race question? I didn't find it in the thread. First, this present thread is a general inquiry as to the possibility of time travel, not: “Does Einstein's Theory of Relativity Support Time Travel? " The latter topic is based on the supposed time travel expertise of Mallet, whom you regard as “ renowned for being a nut.” Given the question, “Can we travel into the past or the future?,”and my above specific challenges to actually doing so, I agree that anyone who believes it is possible is a nut, or at least confusing science with science fiction. A technical objection: "CTC’s?" is used without previous reference. Then the whole discussion of whether "CTCs” are allowed proceed without spelling it out. Typical for all who take pride in speaking a special language and condescending upon the stupidity of those not familiar with specific shop talk. The rule is (or should be) first spell out acronyms, then use them, especially on a public forum. But if you don’t automatically assume that space has shape (Oopse, ontology again).... even without CTC clarification... (I'll let this one dangle.) I agree with “The Conqueror” that: Anyone know of verified visitors from the future? If so I will gladly "eat my hat." ajb: But the question at hand is about the possibility of those “real attempts.” Can we visit the past and future or not? (Ans: Not.) ajb: But it is obvious to everyone but sci-fi fans and general relativity theorists... which does the latter no credit! The test of the laws of physics must be empirical verification. If it is impossible to visit dead ancestors before they died (visiting the past) or to make a killing on horse races (visiting the future), then it is safe to say that time travel is not possible. The laws of physics don’t prohibit the “existence of god” either, but I will remain atheist on the grounds of no positive proof (and the conviction that it is a silly supernatural mythology) rather than lack of proving a negative.

I have never disputed those verifiable predictions, nor the three spatial dimensions and the time factor (movement from A to B or event duration.) "Flat" Euclidean space is an unfortunate use of the word flat, which applied only to planes before the mental/conceptual transition to non-Euclidean and all "higher dimensional" geometry. Space is most reasonably described and denoted as 3-D volume, not a "flat" plane. Volume/space is not "flat" except via a new invention for the meaning of "flat" by non-Euclidean mental/conceptual exercises and subsequent theories of "shaped space." Consider the possibility that gravity bends light around massive objects without the theoretical existence of malleable, curved "spacetime." Light acts as if it has an infinitesimal amount of mass in other experiments and situations too. Like the "box of mirrors" which gains inertia as if gaining mass with the intro of light bouncing around inside. Or the recoil when lasers are fired. It's not all set in concrete that light is absolutely mass-less, so the deals are not yet done on why light is curved by gravity/mass. (Oops!, this is way off subject again. Sorry.)

DrRocket: I will read the link and get back to you on it. (Patience can be helpful among busy people, even us crappy stupid pigeons.) What I "need" is for me to decide, not you. You could benefit from (no need projected) a study of what ontology is for science rather than your constant bitter prejudice against all philosophy. DrR: The "heart of the matter" for the scientific community as a whole is not Hawking's theories, in any case, though you obviously elevate him to near infallibility (with proper disclaimers, of course.) Dr.R quoting Hawking: These questions are often the focus of philosophy, but not exhaustive. For instance there are the more contemporary questions in the specific realm of philosophy of science, like the 'not dead yet' question, "What is spacetime?; Is it or not an entity or malleable medium in the real world?" Doctor Rocket vehemently wants this question (and me with it!) to go away, but it won't, as lots of not-so-stupid philosophers and scientists are still working on the question... often together in mutual respect. Imagine that! And what a premature pronouncement of death for philosophy followed by zealous evangelism for his version of scientists as saviors of the world! Hawking: I have studied several mainstream scientists over the years (no citations on the tip of my tongue) who think very much less of him as a scientist than you do,DrR, and I am among them, at least as an amateur scientist (one who "loves it", but not a pro.) Here is my best example of his non-scientific, even grandiose hyperbole. (I am in fact a retired psychologist who has seen lots of grandiosity, both "on the couch" and in such "celebrities" as Hawking): His cosmology of a primordial singularity as the origin of the universe is the most absurd statement ever to be uttered by a scientist, in my personal opinion... that all cosmic matter came from a singularity of "infinite mass density in a point of zero volume." (Look at his site for conformation... maybe deleted by now, however, but surely still on record.) Yet DrR has the highest regard for this pop fame (formally, popular and famous) scientists, and, I presume, his M-Theory buddies, now that they are all in the same camp. (The modern metaphysicians of physics.) DrR: That would be ontology as you understand it, which is minimal or not at all, as per your interest in it.

So... no replies at all on the substance of the transition beyond Euclid or on Ross' quite intelligent examination of how we got to the "curved space" of non-Euclidean geometry... as applied to "Is space infinite?" Rather just slurs like painting me as a creationist (Yikes!... now how was that relevant again?) or a bird brained pigeon trying to play chess with you real people, but just crapping all over the board. This kind of "crap" you are purveying is not worthy of science. Btw, Ross said, "it may be that intrinsically curved spaces can exist in reality..." not that they do in fact exist. Likewise 4-D space "may exist" but no one has clue what it would mean or be in the real world... Just a mind game like, "a curved line requires a plane;... a curved surface requires volume;... so, therefore a "curved volume" (space) must exist in a 4th spacial dimension. (Forget whether "it" exists at all or not.) And how about those curved line orbits of planets and such "actually" being straight lines in curved space. Very "sophisticated", this concept of curvature being intrinsic to one manifold but extrinsic to another (mental) manifold... but nonsense! And how about those parallel lines finally intersecting "in infinity" as a math concept (without real world referent?)How "real" is that "infinity"... or does anyone give a hoot about what is real in the actual world ( the focus of ontology.) But enough on this already! What, still no 'wall out there' as the end of space?) How does it end, again, if its not infinite?

DrRocket: Really!? It would seem that a deep understanding of what time is and is not (ontology) would be quite relevant to the question, "Can we travel through it?" Anyway you continue to dodge the horse race question; and visiting the past is just as absurd, or we could "go back in time" and visit with our dead ancestors before they died, which would in many cases be before we were born!? This is science? No, clearly just sci-fi.

Iggy: I haven't studied what I just said that I've studied? I didn't know that you were such a "seer" that you know me (and what I've studied) better than I know myself! I have no need to show you that I understand the paper... to pass your test, I do not agree with all of it... your wrong assumption. Iggy quoting Ross: Iggy: "It may be" quite a few variations (did you read the whole paper or just cherry picking?), including that concepts may exist in the human mind without a referent in the real world that can be observed and verified.(Read his ontology on this.) Now, what was the whole paper telling me again that I missed? I have run down every reference he mentions and understand all of it very well. (Incidentally, I must now set you straight about your constant insistence on how stupid you think I am. I am hoping you tell the truth, as I do. Please tell me your IQ by PM and I will tell you mine.) As you know, I have no qualms about questioning the ontological assumptions central to GR's "spacetime, but what you don't know is that the "cause" (you know, "cause and effect") of this confidence is that I was born at the high end of the scale, and never lost interest in open scientific inquiry... including the "questioning authority" thing which many textbook scientists here obviously despise.

Believe it or not, I actually agree with DrRocket's general answer to the above!, regardless of his technical exposition, which still doesn't address the 'challenge of the wall... and beyond.' However good one is at technical circumlocution it still doesn't answer this thread's question. Again, as I requested yesterday "Somebody tell me about the end of the universe." Otherwise it will remain, as is, without end, which is what infinite means in this context. Iggy: Now we are getting somewhere. You have no idea what I know about "non-Euclidean space" and what ontological assumptions it requires. I have studied the transition from Euclidean to non-Euclidean geometry in depth and have often repeated quotes from my favorite paper on the subject, The Ontology and Cosmology of Non-Euclidean Geometry, by Kelley Ross. Seems that you still have not read it. Here again is the link. http://www.friesian.com/curved-1.htm

DrRocket, You have completely ducked the time travel question, the focus of this thread and specifically my last post... see key words "horse race." Theories of gravity are not the subject here. (Apologies to the OP.) I just thought that quantum theory was a viable alternative to GR theory vis-a-vis gravity, which might belie your certainty. Still, observed curvature of objects' paths of travel does not prove that spacetime is an entity which "curves" and guides objects.... Just to be clear about what the ontology addresses, whether you are interested or not.

Iggy: What do you think is the difference between finite and infinite. Maybe you just don’t know the difference. Infinite means endless, no end or boundary. Reality check: Think about the difference between empty space, which can not, logically, "end," and the stuff in space, which mayor may not be a finite amount of 'cosmos' out there... the stuff in space. What limit? Please describe! Not really 'self imposed" but logically cogent, and I think irrefutable. Think about "shape" as mentally imposed upon the universe... all there is, space and its known contents and beyond what we can know. Beyond that mentally imposed "shape" is... what? Even "nothing" as an answer is infinite space, regardless of what it may contain. Yes, whatever is beyond our present cosmic event horizon is "unknowable." But we can know (and I do know) that there can be no "end of the universe" regardless of the fact that the infinite remains unknowable. Somebody tell me about the end of the universe, and try to make sense. This should answer you too, Stringjunky. I not let's talk.

I transcribed this post from the time travel thread for relevance of content. No one here has yet answered these obvious questions: If the universe is not infinite, how does it end, how is it "bounded", and finally, yet again, what could possibly be beyond any proposed wall out there but more space (whatever it contains,if anything)... infinite space? Just a logical, reasonable question from the realm of a-priori epistemology, a realm of science/philosophy which DrRocket would not have studied given his disdain for it. DrRocket: I think that it is a good thing to question scientific authority, especially when abandonment of reason is the requirement for "passing the tests" and getting your all-important credentials. True science stays open minded, and I have many times said that I am not questioning the "mountain of evidence for GR," but only its reification of space, time, and spacetime. We are safe to just say what we see, like objects traveling in curved paths without saying that curved spacetime (without ontological examination) makes that happen. I'll finish with one of my favorite quotes from Kelley Ross' "Ontology and Cosmology of Non-Euclidean Geometry":

DrRocket: But seriously!... How did you get out of the ongoing present? Could you see what you typed in real time (not just in imagination) before you typed it, from actually "traveling" 30 seconds into the furure? Can you jump to the end of a horse race before it starts and bet on the winner? Either you don't have a clue what the thread is asking or you don't take the question seriously. I didn't say I agreed with everything published by Deiks or the ISASS, just that they are examining what spacetime actually is, rather than, with GR, simply taking it for granted as an established fact, like you do. (BTW, how does quantum gravity theory fit in with your absolute certainty that "curved spacetime," as per GR, is the only valid explanation of how gravity works?) I answered the rest of your post in the Is Space Infinite thread.

Time travel means we can go back to the past or go forward into the future or both. If this were possible we could visit the past before we scrambled the egg, or further back, before it was laid; and if we could visit the future we could visit as yet unborn progeny. Make of it what you will, but time travel is not possible, however interesting it is as a device for science fiction. DrRocket, as always you use "spacetime" as a given matter of established fact. I'm guessing you didn't read any of the material I suggested on the ontology of it. Fine, but that doesn't make its critics wrong just because you refuse to even engage in the conversation on the subject.