roosh

The only unsupported claim is that the universe has a temporal dimension or that it, or systems within it, are temporally extended, because when we examine any supposed evidence which supports that claim we can see that, in actual fact, it doesn't support it at all, it is simply assumed; the empirical observation doesn't actually support it. We don't need to beg the question and we don't need to swap (1) and (2) above; where we start is with empirical observation and then draw our conclusions from there. While objects or systems do persist - they existed in the past, exist now and will exist in the future - they are only ever observed in the present. When we say that an object was observed "in the past" what we actually mean is that we made an observation in what was the present configuration of the universe but that configuration has changed. When we say we will observe an object "in the future", what is actually the case is that the present configuration of the universe will continue to change and when we make the later observation of the object it will also be the present. If we could make empirical observations of the future then we could know what tomorrow's winning lottery numbers are going to be, but we can't; instead we predict what they are going to be and we confirm or refute those prediction in what will become the present. Thought experiment It might be useful to consider an experiment, where we make an empirical observation of a clock. I'm thinking that a clock with hands might be easier to visualise, but we can use an atomic clock if needs be. Observing the clock we can see that the clock is only physically extended in 3 spatial dimensions; while the second hand of the clock moves around the face - with the precision of an atomic clock - we only ever observe clock, and the hand, extended in 3D spatial dimensions. While we might be able to remember where the hand was and predict where it will go, we only ever make our observations in the present. We can't make an observation of where the hand was, or will be, we only ever make an observation of where the hand is. Video recording It might also be suggested that we make a video recording of the clock and then we can re-wind the video and see where the "past" states of the clock; but what we will actually be looking at is a video image of the clock on equipment which is only extended in 3 spatial dimensions. It isn't a case of using human perception, it's a question of what the empirical evidence actually demonstrates. The claims remain the same because none of the "evidence" actually refutes the claim or demonstrates a temporal dimension. The question of whether we can only observe "here" is an interesting one, and it is one which would lead it's proponents to a position of extreme solipsism, a position that the rest of the universe doesn't exist, as you allude to. It isn't the position being advocated here though, because it would certainly seem that we can observe more than just "here". Our empirical observations would lead us to believe that we can also observe locations that are not "here", locations that are over "there", locations we can move to. Our observations would lead us to believe that the rest of the universe does exist, that objects are spatially extended, and that they can move around in 3D space. What we don't observe, however, is objects which are temporally extended and which move around in a temporal dimension. Even if the position of extreme solipsism were true, and it isn't the contention that it is, that would simply mean that scientific investigation is an investigation of the solipsistic universe, and we still wouldn't have any empirical support that objects within that solipsistic universe are temporally extended. When you were reading it though, it was the present. Try taking a hard copy of a book, read a page of it, then tear the page out and burn it. Can you read that page? No, bcos it is only possible to read the book in the present, or in it's present configuration. ---------------------------------------------------------------------------------------------------------------------------------------------------- We have to be careful what we mean when we say "the past was real". Let's just pretend we're having this discussion in "real time" for the sake of avoiding confusion. If we consider the configuration of the universe as it is now - let's refer to it as "now 1". Because the universe is constantly changing - or the matter within it is constantly moving - the configuration of matter that corresponded to "now 1" has subsequently changed. We refer to "now 1" as "the past", but when we said now, we said it in what was the present. So essentially, "the past" is never real and never was real; what was real, was the configuration of the universe in what was "the present". It might be useful to distinguish between the 4th variable and the 4th orthognal variable, because our empirical observations, of the physical world, don't actually bear out the idea that there is a 4th orthognal dimension; we make observations of objects moving around in 3 orthoginal spatial dimensions, but not in a 4th orthognal temporal dimension. The 4th orthognal dimension is a mathematical construct that is essentially arrived at by removing one of the other 3 orthognal dimensions - keeping the co-ordinates of one of the axes as 0. As for the 4th variable, what that is, is a value provided by an object/system which is spatially extended in 3 dimensions and which moves within those 3 spatial dimensions. What we are effectively doing is taking 3 dimensional motion, which happens to be very regular, and using it as a standard unit, which we use as the 4th variable. --------------------------------------------------------------------------------------------------------------------------------------------------- Apologies, I was just in "reply mode" and didn't realise at the time that you hadn't replied directly to me. With regard to the definition of "time", I think Einstein's statement translates to "time is what we read from a clock". That is the definition I would agree with myself. I wouldn't say that "time" is measured by a clock bcos this would suggest that "time" is something which is physically measurable. In the case of a an atomic clock what is actually being measured, or detected, is the microwave emissions of the electrons of caesium atoms, as they change energy. These emissions are simply detected and counted; there is no secondary property of the physical universe being measured or detected. These two points are related, so I've taken them together. The strawman that swansont is talking about is the claim that I am using a strawman definition of time and saying it doesn't exist. The point has been modified, however, to avoid what was proving to be a problematic term, the term "exist". Instead what is being argued is that our empirical observations of the physical universe don't support the contention that the universe has a temporal dimension or that matter within it is temporally extended; they only support the contention that matter within the universe is only spatially extended and/or that the universe only has 3 spatial dimensions - no temporal one.

We can measure a multitude of things, but I don't think that makes them a dimension of the universe. For example temperature and velocity aren't considered dimensions, are they? --------------------------------------------------------------------------------------------------------------------------------------- It hasn't been defined to be impossible, it's simply a questioning of the empirical evidence available to us. There is empirical evidence that objects within the universe are both spatially extended and spatially separated; there is no empirical evidence that the universe, or the objects within it, are temporally extended, or temporally separated (in any physical sense). This is what leads to the conclusion that the idea of time as a dimension of the universe is unempirical and non-physical. ---------------------------------------------------------------------------------------------------------------------------------------------------------------- It's one thing to say that "time is what is measured by a clock" but another thing entirely to say that the universe has a temporal dimension. A clock provides a standardised unit for comparing systems which are spatially extended. However, neither the clock, nor the system being quantified, is temporally extended. So "time" doesn't a appear, empirically speaking, to be a dimension of the universe, or the objects within it. ---------------------------------------------------------------------------------------------------------------------------------- Again, there is no circularity in the reasoning; it's simply an investigation of the empirical evidence available to us. We don't start with" "time does not exist"; we start by observing objects within the universe being spatially extended and noting that there is no empirical evidence that the objects are temporally extended. From that we arrive at the conclusion that the idea of a temporal dimension is unempirical and/or non-physical. As for "observing the past", that is simply an impossibility, because observations can only ever be made in, and of, "the present moment". Indeed, when it comes to verifying your prediction, you will have to do so by reading this post in "the present moment".

We cannot make empirical observations of the past. We may have made empirical observations in, what we refer to as, "the past", but when those observations were made, it was "the present" (not present moment in time however). We cannot make make an empirical observation of something that happened 10yrs ago, we can't even make an empirical observation of what happened 2 seconds ago. Nor can we make empirical observations of "the future"; we can make predictions of "the future" but when we make the empirical observations to verify those predictions, it will be done in what we call "the present". As has been mentioned before, it might be more useful not to think in terms of "moments", indeed, "the present moment" doesn't, essentially, exist; there is no physical thing called "the present moment"; instead we've got configurations of matter in the universe. "The present moment" is simply a term we apply that means "now", which is the only "moment" in which we can make empirical observations. It's this lack of empirical evidence, that the universe is temporally extended, which means we should question the idea of time as a dimension. This still doesn't explain how you see two dots moving closer together, from two pieces of yarn which themselves are not moving. The question is how 2 static pieces of yarn, even if that is in 4 dimensions, can give rise to relative motion in the 3D universe. Simply stating that this is the case isn't sufficient

Just to be clear, what is being said is that it cannot be demonstrated, or that there is no empirical evidence, that the universe, or the objects within it, are temporally extended. This begs the question then, as to how exactly "time" can be considered a dimension of the physical universe.

Can you demonstrate that the universe, or objects within it, are temporally extended in a physical sense? EDIT: Bear in mind that the onus is on anyone trying to demonstrate a positive; someone trying to demonstrate a negative just has to outline how the evidence for the positive position is inaccurate or misinterpreted. 2nd EDIT: The empirical support for Einsteinian relativity is well known, so any links to any evidential support for it will be followed up with the question of how any specific experiment demonstrates that the universe is temporally extended, or how objects within the universe are temporally extended.

We don't need circular reasoning, we can just ask the questions: Can we make empirical observations of "the past"? The answer is no. Can we make empirical observations of "the future"? The answer is no. We can only make empirical observations in, and of, the present moment. Hence, only the position that "now" is all that exists is supportable by empirical observation. It might be tempting to say that we made empirical observations "in the past", or that we will make empirical observations "in the future", but when we made those empirical observations we did so in what was then the present moment, and when we make empirical observations "in the future" it will also be the present moment. "the lack of such" refers to the lack of a physical, temporal distance, empirically, observable between events. That events don't happen at the same time doesn't mean that the universe is temporally extended, because unless "past" events continue to exist (within the overall structure of the universe) then there is no temporal extension, and certainly no physicality to the temporal separation of events. The fact that we cannot make empirical observations of "past" or "future" events means that "the temporal dimension" is unempirical. p.s. I'll look for a citation for the point about the reconciliation of QM and relativity. apologies, I did a p.s. on the post above; I'll try to dig one out. That isn't supported by any empirical evidence; we only have empirical evidence of one-way "time" dilation, we have to assume that it happens both ways. Again, from what I can gather - I'll have to dig out a citation for this as well - Lorentz's theory is equally supported by any empirical test of Einsteinian relativity and Lorentzian relativity doesn't involve two-way "time" dilation, it only has one, bcos it relies on an absolute reference frame", partly bcos his theory was based on absolute time. I would argue that such a preferred reference frame isn't required if "time" is not real, if it doesn't exist as a dimension; this is bcos there would be no absolute time, as there would be no time at all. It's not pertinent to the issue being discussed. Also, I haven't really given it much consideration. Remember that you can't prove a negative, so it is not possible to "prove" that "time" doesn't exist; instead, the onus is on whoever wishes to claim that it does, to provide evidence that it does. What can be done is question whatever evidence is presented In order for time to be considered a physical dimension of the universe (or a dimension of the physical universe), from an empirical standpoint, it would have to be empirically demonstrable that the universe, or matter within it, is physically, temporally extended. Since we can't make empirical observations of "the past" or "the future", then it isn't a position, which is supported by empirical evidence, that time is a dimension of the universe. Speculating that future scientific theories might reflect this fact isn't necessarily the core argument being made, it's simply a manner of highlighting the fact that, although we have a working theory now - which is not yet compatible with another eqaully successful theory - it doesn't mean to say that the theory won't be refined; since that is what happens to scientific theories. If it is a subject you enjoy thinking about and discussing, I would have thought you might have come up with something other than an assertion. It's being based on the limitations of empirical observation/evidence. We cannot make empirical observations of "the past" or "the future" so there is no empirical evidence to support the claim that the universe, or matter within it, is temporally extended, at least not in any phyiscal sense. And I would've gotten away with it, if it wasn't for those pesky kids We can only make empirical observations in and of the present moment. The use of words such as "past" and "future" reflect the evolution of the human language and our capacity for remembering/recording configurations of matter that we once observed in the present moment, but which have subsequently changed and can no longer, empirically, be considered physical; as well as our capacity to imagine/predict configurations of matter which will only ever manifest in the present moment, which equally cannot be considered physical. The use of quotes is not to scare, but to highlight that "past" and "future" never actually exist, they are never physical; they are only mental constructs and we only ever experience - and make empirical observations of - the present moment. My understanding of science is that we only, generally, accept things to exist if we have empirical evidence of them. There is no empirical evidence of "the past" or "the future". ---------------------------------------------------------------------------------------------------------------------------------------------------------------- It wasn't a straw man. The specific point which was being addressed was: The same is true of unicorns; you can't talk about unicorns without reference to a horse-like creature with a horn protruding from it's forehead. There are no objections to the idea that "time" is not physical, the issue is that it is being suggested that time makes up part of the overall structure of the physical universe. If the position is that the universe is not entirely physical, but partly metaphysical - as it would have to be, if it is being argued that time makes up part of the structure of the universe but isn't physical - then that is entirely different. The contention here is that "time" does not make up part of the physical universe; it is not a dimension of the physical universe; that it does not exist; or that the idea of the universe having a temporal dimension, is not supported by empirical evidence. There is no dispute here that "length" is just a mental construct; the difference is that we can make empirical observations of physical objects which are spatially extended, as well as spatially separated objects; while we are "here" we can make empirical observations of objects over "there"; whereas we never observe objects being temporally extended in any physical sense, and we can't make empirical observations of objects in "the past" or "the future"; hence the idea of a temporal dimesnion is unempirical, and certainly not physical. Physics does appear to deal with empirically observable evidence. That we use 4 mathematical variables doesn't mean that the universe has a temporal dimension. This is the point where we ask for a demonstration of how it does. Again, for the universe to be considered - in any physical or empirical sense - to have a temporal dimension, we would need empirical evidence that "the past" persists in the overall structure of the universe and/or that "the future" forms part of the overall, physical structure of the universe. If no such evidence can be provided, then we either agree that the idea of a temporal dimension is unempirical or that the temporal dimension is not physical - it could be argued that it is metaphysical perhaps, but I'm not sure that is a position that would sit too well amongst physicists. The contention here isn't that "time" isn't useful as a "system of measurement" - we have to be careful about what it is that we think we are measuring though. We can still use 't' co-ordinates to distinguish between events and to describe non-static systems but if we question what the 't' co-ordinate actually represents then we can see that, originally, what was being said was that, when the earth was in a certain point of it's rotation - with respect to the sun - you were sitting in a chair; but when the earth was at a difference point in it's rotation - with respect to the sun - you were standing up. What we are actually doing here is using movement, within the spatial dimensions of the universe, to describe other spatially extended events/systems; we're just taking a particular, spatially extended, system/event as a standard unit and using it to describe others. With the advent of more sophisticated clocks, we're just doing the same; with an atomic clock what we are saying, for example, is that when the counter read 1sec you were sitting in the chair, but when it read 10secs, you were standing up. What is being measured by the atomic clock is the number of oscillations of the caesium-133 atom, say, not a "temporal dimension"; what is being measured by a "second" is the rotation of the earth with respect to the sun, not a "temporal dimension". Neither the clock, nor the Earth, nor the Sun is temporally extended; at least not in such a way that is supported by empirical evidence of the physical universe. As has been mentioned, we can try and avoid problematic words such as "exist", by questioning whether or not "time" is a dimension of the physical universe. For "time" to be considered a dimension of the physical universe, then the universe would have to be physically extended in time - "past" and/or "future" configurations would have to make up part of the physical structure of the universe, and this would have to be supported by empirical evidence (as opposed to being assumed) - otherwise the idea of the universe having a temporal dimension would be unempirical and/or the temproal dimension would have to be metaphysical. That photos don't go blank is not evidence of this bcos photos are taken in the present moment and the photo which remains is not the phyiscal configuration of the matter which was photographed - it's a record of it - and it also is only ever observable in the present moment.

And you can't have a talk about unicorns without referring to a horse-like creature with a single horn protruding from it's forehead, but that doesn't make them real. We could, potentially, have a talk about a "past" without reference to "time" though, if we investigate what a "past" actually is; when we do, we can see that it is just a former configuration of a previous present moment. "The past" only exists as a mental construct, or as a concept; it is a memory or a set of records which corresponds to the present moment before it changed to the current configuration. Even when our predictions of "future" configurations materialise, they will do so in the present moment. It is always the present moment, and it always will be - again, not to be confused with the present moment in time. I won't question what you mean by the term "exist", because I think we all have an understanding of it, even if the nature of that existence is open to question. To be temporally extended, the "past" and "future" states of an object or system must exist, otherwise it isn't extended temporally. If objects exist from one moment to the next, but the previous moment ceases to exist as soon as the next one arises, then there is no temporal extension. Given that there is no empirical evidence to support that either past or future states exist, then the idea of time as a dimension, or that objects are temporally extended is unempirical. Again, the idea of "moments" might be a bit misleading, not least because we associate them with "time"; it might be more helpful to think in terms of configurations of matter. When a configuration of matter changes, unless the "past" configuration persists in the overall structure of the universe, then the configuration of matter is not temporally extended. We don't need a 4th dimension to account for what we observe, not least because we don't observe a 4th dimension, we assume it. Systems in the universe, and the universe itself, undergoes change; there is no need for a 4th dimension to account for this. We can acknowledge that the matter in the universe used to be configured in a certain way, but has subsequently changed and is continuously changing. Only if we assume that the "past" and/or "future" configuration exists do we arrive at the conclusion that the universe is temporally extended. That's not to say that "the past" is an illusion, the "past" was real, but it's not anymore, and the "future" isn't real. We can't make empirical observations of either, so the idea of the universe being temporally extended, or having time as a dimension is unempirical. How does a change in phase demonstrate that it is temoporally extended? Only if the "past" and/or "future" states exist in the overall structure of the universe can it be said to be temporally extended; and there is no empirical evidence to support the contention that they do. The conclusion that time is a dimension can only be arrived at by assuming the conclusions that "past" and or "future" are physically real, that they exist, or that they make up part of the overall structure of the universe, however you wish to phrase it. ah, cheers. I think I have it now. ----------------------------------------------------------------------------------------------------------------------------------------------

That's not saying much though, it's just saying that we don't perceive the universe as frozen, but we would if we were looking at things from outside. It doesn't explain how relative motion can arise from "frozen strings", because it shouldn't, without some additional mechanism to explain it. I haven't really given much thought to it tbh, but as mentioned I don't think it represents the issue being discussed.

The purpose of the other thread was to see what the generally accepted status of the "block universe" is, within the field of physics, not to question it's validity. The reason for it was bcos I thought it was a widely accepted concept, due to it's prominence in the mainstream, pop-science documentaries, and bcos physicists such as prof. Greene seem to champion it. Personally I don't agree with it, but as I said, that wasn't the purpose of the thread. The term "exist" (and it's variants) tends to cause a bit of consternation, but it needen't, bcos we can ask a simple question: is there existence? The answer is unquestionably yes; that we can pose the question is verification of that. It sounds like a philosophical question but it isn't really. Existence is just a label we apply to our experience of the universe. We only ever experience the present moment; empirical observation is only possible in the present moment. We can't observe "the past", nor can we observe "the future". For an object, X, to be temoporally extended it's "past" and "future" states would have to be physical. The lack of empirical evidence that this is the case means that there is no empirical support for a temporal dimension. Indeed, it made them in "the past", but "the past" is no longer exists, and "the future" doesn't exist - "past" and "future" are not physical - so the clock is not extended temporally; it only ever operates in the present moment.

Not as a dimension anyway. A remarkably successful model which is, at present, not reconciled with the other, arguably, most successful physical theory. From what I can gather, that reconciliation could be made easier if relativity had a more absolute notion of time. Incidentally, non-existent time is very similar to absolute time. "Time" wouldn't be used any differently, clocks would still be employed. The idea of reciprocal (two-way) time dilation would, however, be removed, something for which there is no empirical evidence of - there is only evidence of one-way time dilation. The question, of whether or not objects without spatial dimensions exist, was not representative of the issue. It would have been more representative to ask, if objects didn't have spatial dimensions would I say spatial dimensions didn't exist. If the neither the universe nor the objects within it were not spatially extended, then I would say that spatial dimensions do not exist. Questions such as, what is time in physics is a question of physics; the word "exist" can prove to be a stumbling block but we can circumvent that by asking if time is actually a dimension, as opposed to questioning the existence of time. By demonstrating that neither the universe, nor the objects within it, are temporally extended we can highlight that "time" does not have any dimensional quality. While it might be considered a dimension in contemporary physics, that doesn't necessarily mean that it is, just as Newtons contemporaries believed that time was absolute but our contemporaries no longer accept that. It doesn't really bother me that much tbh, it's just something I have an interest in and enjoy discussing.

that does seem to be the case alright. In discussions elsewhere I spoke about it assuming it was widely known, but a good few people had never heard of it. Einsteinian relativity does seem to necessitate that "past" and "future", to some extent exist or persist. If you picture a spacetime diagram where a bullet is fired towards a house and two observers are moving relative to each other, at the moment when the observers cross paths each will disagree with the location of the bullet, with one saying it is close to the house than the other. For observer A (to label them) the bullet will be located at a tree, for arguments sake, while observer B will say that it has passed the tree. For observer A, the location of the bullet according to B will represent a location the bullet will occupy in the future while, for observer B, the location of the bullet according to A will represent a location occupied by the bullet in the past. Apologies for not posting the diagram, but someone else drew it. I can dig it out if necessary.

Spacetime is treated as a physical entity in physics isn't it? Essentially, it's a question of whether or not time is a dimension of the universe. For it to be a dimension of the universe the universe and/or the objects within it must be extended in that temporal dimension; this would require "past" and/or "future" states to exist and persist. This isn't supported by empirical observation. Indeed, and these regularly occurring oscillations provide us with a very useful standard unit, in which we can express all other processes; using this standard unit allows us to meaningfully compare different processes to each other. However, as with the processes or objects measured by a clock, the clock itself is not temporally extended; it is, however, spatially extended, that is, extended in 3 spatial dimensions. Hence, time is not a dimension. The present moment (not to be confused with the present moment in time) is all that is ever empirically observable, so that is the only position that can be supported empirically. For it not to be true, "past" and "future" must exist, and indeed they might, but to arrive at the conclusion that they do one must assume those conclusions, which is where the true circularity lies. It might be more helpful to think in terms of configurations of the universe, or the matter in the universe, instead of "moments" - bcos we tend to think in terms of "moments in time", which is part of the issue. The configuration is constantly changing. Only a single configuration ever exists and that is the configuration that corresponds to the present moment. The "past" configuration has changed and so, no longer exists; the "future" configuration doesn't exist yet. We are in complete agreement on this; the past existed, past tense, but it no longer exists. Again, it might be more helpful to talk in terms of dimensions; objects are extended in 3 spatial dimensions and objects are spatially separated in 3 spatial dimensions; objects and events are not extended temporally and are not separated in a temporal dimension, because the past has ceased to exist and the future doesn't exist yet; only the present configuration exists, hence no temporal dimension. I agree, but I would say that "time" is a system of measurement (not necessarily like the systems of measurement used to measure the spatial dimensions of an object, or the spatial separation of objects) and the phase of an oscillation provides a useful standardised unit which we can use to compare different systems/processes, in a meaningful manner. The phase of an oscillation doesn't, however, demonstrate a temporal dimension. The ruler is placed beside the object it is measuring, for arguments sake, but the ruler is also spatially extended. A clock is just a counter which is not temporally extended, just like the object or system it measures. Hence, no temporal dimension. --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- p.s. does anyone know how to stop individual replies from getting lumped in together?

@Endy I don't think we would. We are part of and observe a dynamical system; there is no need for a temporal dimension to observe events. Events occur, some preceding others, we have memory of "past" events and can imagine "future" events, which is what gives rise to our idea of time as a dimension. Just events occuring and the power of observation is necessary to observe events. That doesn't really explain how relative motion can arise from "frozen strings". Indeed, we don't and we can't (observe objects having a temporal distance). ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- What a clock measures, an atomic clock for example, is the mircrowave emissions of electrons of a caesium atom, say, as it changes energy; these microwave emissions are detected and counted and that is what is displayed on the counter. There isn't a secondary, physical, property measured nor is it the measurement of a dimension. What clocks of old measured was the rotation of the earth with respect to the sun. Clocks are essentially just repetitive cycles which are used as a unit of comparison. If we imagine someone who bounces a basketball with amazing regularity, that could be used as a clock, but nowhere in that process is a physical property called "time" measured, nor is it a measure of any dimension. We could express other processes in terms of that bouncing basketball and then compare them to each other. But it doesn't represent a temporal dimension. That is essentially how I refer to "time", as a man-made system of measurement - using naturally occurring processes as a means of comparing different processes in a meaningful manner. We need a standardised unit otherwise we would be comparing apples and oranges. ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- if the universe had no spatial dimensions, then I would say that spatial dimensions do not exist.

Time is treated as a physical property of the universe, unless physics deals with measuring the non-physical. I am familiar with it, thanks; I use it on a daily basis. You should, perhaps, question what a clock does, and precisely where in the processes of a clock the physical property called "time" is actually measured, or how a clock demonstrates that the universe has a temporal dimension. I'm sure you will agree that the universe exists, indeed, all that exists is the universe. The question is whether or not time is a property of the universe. Objects appear to be spatially extended and separated, hence the 3 spatial dimensions. Only a single moment ever exists, the present moment, and the configuration of the universe that corresponds to "now". Hence, there is no temporal dimension to the universe. Regardless of how time is defined, unless past and future exist, then the universe does not have a temporal dimension. Defining "time" into existence is circular reasoning and doesn't make it a physical property of the universe. But the universe is not temporally extended, hence no dimension. A distance between points might be a length, but it is this spatial distance between them that means that the universe has a spatial dimension; the lack of such with regard to time means that the universe doesn't have a temporal dimension. Also, I would question the idea of "empty space" not having anything physical which persists. There has to be something empty space because there cannot be nothing, as in absolute nothing, becuase absolute nothing implies non-existence and the universe is only made up of that which exists.

You can always ask, or you could accept what the watch actually does and it's usefulness. How do we measure time, or more specifically, how is the physical property we call "time" measured by a clock?

is it the same amount or the same ratio? the answer might lie in the effect gravity has at the sub-atomic or quantum level. it is also odd, however, how the alternative could give rise to reative motion; as was mentioned by someone else, the idea of objects, or particles, as frozen strings, relative motion would not result from that. --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- I don't doubt the model works, but it is, currently, incompatible with an equally successful theory. From what I have gathered a timeless theory would probably be more compatible with quantum theory. For now though, I'm content just to question it.

By real I simply mean physical as in a part of the universe. The universe is real, or perhaps it might be more definitive to say that the universe exists; what form it exists might be a separate question. To say that time is not real is simply to say that it does not make up part of the universe. No, but it does require measurement or detection. It can't be demonstrated that time is measureable, unlike the 3 spatial dimensions. Although they persist, they only ever exist in the present moment, hence they are not extended in time, or do not have a temporal dimension. There is no circularity in that. The point is that objects are extended in 3 spatial dimensions but not in a temporal one. It's not to say that the past didn't happen, it's that it no longer exists. We have records and memories of it, but it is no longer physically real, or physically exists - in the manner that it used to exist. In order for time to be considered a dimension of the universe, then past and/or future have to physically persist, otherwise there is no dimensionaly quality to time. We can use a 4th, non-spatial variable but it's use in a mathematical sense doesn't mean it physically exists. Indeed, we can only make it orthognal to the spatial dimensions by removing one of the spatial dimensions (keeping it's value as zero) and putting in the time "dimension". Still, however, even when specifying the configurations, only one configuration - corresponding to a single value of the 4th variable - is ever real. The configuration isn't extended in that 4th dimension, whereas it is extended in the 3 spatial dimensions.

not if the mechanisms of the clock itself, as opposed to time, are affected.

@swansont Change doesn't require time to occur, it's our observation of change that leads to our idea of "time". We see systems change and we remember (record) "past" states and imagine (predict) "future" states, but "past" and "future" states aren't real, only the present configuration of a system is real. Just because time is not real, that doesn't take away it's usefulness as a system of measurment. We can still use "time" to label different configurations of the universe but this doesn't mean that "time" is a dimension of the universe. If we take two configurations of the universe, "the past" configuration and the present one. Only the present configuration is real, the past configuration has ceased to be real, it is now just a memory or a record. We make empirical observations of objects in the universe as being extended in 3 dimensions and objects in the universe are spatially separated in 3 dimensions, however, only the present configuration of the universe is real, it, or objects within it, are not extended temporally, because neither "past" nor "future" configurations are real. Since empiricism? I'm sure you understand the idea of objects having length, breadth, and heighth, this is what it means to be extended in 3 dimensions; also, objects within the universe are spatially separated along 3 dimensions. For time to be considered a dimension of the universe the universe, or objects within it, would have to be extended in theis, so-called, 4th dimension i.e. they would have to be extended in time - otherwise time cannot be said to have a dimensional quality, or the universe, and the objects within it, cannot be said to have a temporal dimension. Saying that points exist in a single dimensionless place is somewhat telling, because it says that points don't have dimensions, therefore, being infiinitely narrow is a disqualifying factor. The issue is that the universe isn't made up of a single points, but rather a collection of points, which themselves are spatially separated along 3 dimensions. Also, macroscopic objects are made up of a collection of points and those macroscopic objects are observed to be extended in 3 spatial dimensions. The same, or even similar, is not true of time, however. Only the present moment, or rather, the present configuration is real. "Past" and "future" are not, so neither the universe, nor objects within it, are extended in a temporal dimension; hence, time is not a dimension. You can, and we do. A 4th dimension isn't required for a non-static configuration, all that is required is for change to occur, and the amount of energy in the universe is sufficient to ensure that the configuration doesn't remain static. Our notion of time as a dimension comes about from our observation of change, or at least, our misinterpretation of that observation. We remember "past" configurations and imagine "future" ones, but only the present confiugration is real and physical. The universe doesn't have a temporal dimension, we just imagine it to have one because of those memories and projections. --------------------------------------------------------------------------------------------------------------------------------------- Likening the universe to a frozen tangle of threads is essentially the block universe concept, but it requires the assumptions that both past and future are real, as well as the assumption that time is real/physical and can be measured. Part of the latter assumption requires the assumption that clocks measure this property called "time", even though this cannot be demonstrated. Further, in a universe where the worldlines of objects are like frozen threads i.e. static and unmoving, there would be no relative motion, without some other mechanism to explain it, which in itself would require a further assumption. We can drop all of those assumptions, however, and investigate the concept of time and the idea that clocks measure this property called "time" and realise that nowhere in the process of a clock is something called "time" ever actually measured. In an atomic clock, for example, what is actually measured is the microwave emissions from the electrons of a caseium-133 atom, say; these emissions are measured and counted and this count is used as a standardised unit of comparison. Nowhere is a secondary, physical property, or dimension, measured. ------------------------------------------------------------------------------------------------------------------------------------- for some reason the replies to endy and swansont are getting lumped together. I've tried separating them - quoting specific posts and replying and replying independently using the quick reply function - but whenever I submit the separated posts, they just get lumped back in together. EDIT: and I see this one has too

We only ever observe objects in the present moment (not to be confused with "the present moment in time"), in what we term as "now". The trajectory of an object represents past states, or locations, which no longer exist, as well as possibly representing future states of the object. When an observation is made, it can only made in the present moment - we can't observe "the past" we can only observe the present. That's not to say that "past" observations were never real, they were, but they have ceased to be real. So the trajectory of an object, moving with respect to the observer, represents configurations of the object which are no longer real ("past" configurations) and configurations which are not yet real ("future" configurations). The object is not extended in time, as it is extended in space, it exists only in the now, the present moment.Objects, therefore, do not have a temporal dimension, it is our memory of "past" states and imaginings of "future" states, which lead us to believe that they do. But those memories and imaginings are not physically real, they are mental constructs.

Physical in the sense that it is a dimension of the physical universe; that it makes up part of the physical universe that we exist in. The present moment is dynamical, it is constantly changing, or at least the configuration of particles in the universe is constantly changing. "Now' in itself is not a physically existing thing, 'now" is just a label we apply to the configuration of matter in the universe. The argument is not that nothing in "the past" ever existed, it's that it no longer exists; more accurately, that the configuration of the universe that we refer to as 'the past" no longer exists. We can observe the three spatial dimesions of macro objects with the naked eye, we never observer objects having a temporal dimension; we only ever observe objects in a single moment, not extended in time. We might remember past configurations of matter and be able to imagine future configurations (as well as predict them) but this doesn't mean that the objects are "extended in time", because past configurations no longer exist and future ones do not exist; they only ever exist - according to empirical observation - in a single, dynamical, dimensionless moment, "the present moment"; hence, they do not have a temporal dimension.

It does seem to necessitate it.

One of the consequences of Einsteinian relativity is that past, present, and future have to co-exist - which is what gives rise to the concept of the block universe. We differentiate between two objects having the same spatial co-ordinates by using a man-made, system of measurement which we call "time". We use "clocks", or repetitive processes, as standardised units of comparison for that purpose. This however is not evidence that time exists or is physical, because nowhere in the process of a clock is something physical, called "time", ever measured. What is actually measured in a clock is the number of times the repetitive process occurs. EDIT: Two objects never have the same spatial co-ordinates in any given moment, but because only one moment ever exists there is no dimensional quality to "time". Objects have spatial dimensions, but not temporal ones, for that reason.

Orbits, spins, motion, and decay are not time dependent, the measurement of them is. None of them are evidence that time is physical. Neither is the order in which events occur; the tree growing, dying, and falling over doesn't demonstrate that time is a dimension of the universe. Each stage of the process ceases to exist as the following one manifests; each stage exists only in "the present moment". That makes it dimensionless. For time to be a dimension of the universe it requires that past, present, and future co-exist. If only the present moment exists then time is not a dimension.

Hi guys, I'm just trying to get an idea of the status of the block universe concept within the field of physics. On the one hand, the impression that is created in the mainstream, through TV series such as NOVAs the Fabric of the Universe, as well as through other sources, is that the block universe concept is the logical conclusion of Einsteinian relativity. The distinct impression that is created is that, if the mathematics of Minkowski spacetime represent an underlying physical structure of the universe, then the block universe is the embodiment of that physical structure. On the other hand, some people simply dismiss it as a philosophical concept which makes no testable assumptions, and so, has no place in physics. I am interested to hear peoples opinions on this; is it a logical necessity of Einsteinian relativity or is it just a philosophical concept which has no place in the field of physics; is the view that is propagated in the general mainstream reflective of the thinking within the mainstream of the field of physics?