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Status of the block universe in the field of physics
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The physical existence of the "past" and "future"? It appears to be a conclusion reached through physics, although it would appear to be a conclusion which has to be assumed.
It is not assumed, it is self evidently true. If we cannot rely on our sense of the passage of time, then how can we rely upon our other senses to tell us that spatial distances, or even matter itself exists?
The logical conclusion of your line of reasoning appears to be solipsism. That's fine, if you subscribe to that philosophy, but it doesn't allow us to do a lot of science does it?
If the past can not be relied upon to exist, then we can have no empirical evidence for anything, since the moment after any experiment ends, we can no longer trust its conclusions.
I don't see this as a physics discussion at all. If we accept your notion that time does not exist, then physics does not exist either.0 -
Time doesn't exist, so any answer would be entirely arbitrary.citrus burst wrote: »yes
Isn't there something about how two fermions cannot occupy the same space if they have the same quantum state, for example two electrons with an up spin cannot occupy the same space; it would follow that if there is more than one electron with an up spin, then they must be spatially separated. I would presume there is more than one electron in that quantum state, isn't there?citrus burst wrote: »Well matter is either a fermion or a boson. Fermions can't have the same quantum state. There wavefunctions might overlap, but they must be asymmetric
That could be wide of the mark, but there is something about how particles cannot occupy the same space isn't there, given certain conditions?0 -
It is far from self-evidently true; the spatial dimension of an object could possibly be considered self-evidently true, the temporal dimension certainly not, because we only ever experience the present moment.Maximus Alexander wrote: »It is not assumed, it is self evidently true. If we cannot rely on our sense of the passage of time, then how can we rely upon our other senses to tell us that spatial distances, or even matter itself exists?
Indeed, what about our sensorial experience indicates that there is a physical property of the universe, which we call "time", which passes?
I'm not sure how you arrive at that conclusion.Maximus Alexander wrote: »The logical conclusion of your line of reasoning appears to be solipsism. That's fine, if you subscribe to that philosophy, but it doesn't allow us to do a lot of science does it?
Why does the past have to physically exist for us to trust the conclusions of experiments we conduct in the present moment, whose results we observe in the present moment, and whose results we record in the present moment; bear in mind, the records of those results continues to exist in the present moment; if you can't trust the results people record, then science has no basis on which to stand.Maximus Alexander wrote: »If the past can not be relied upon to exist, then we can have no empirical evidence for anything, since the moment after any experiment ends, we can no longer trust its conclusions.
But even if what you are suggesting were correct, it wouldn't change the fact that the conclusion has to be assumed.
That is a non-sequitir, especially seeing as all physics experiments are, always have been and, dare I say, always will be conducted in the present moment; not the present moment "in time", but it will be the present moment when all experiments are conducted.Maximus Alexander wrote: »I don't see this as a physics discussion at all. If we accept your notion that time does not exist, then physics does not exist either.0 -
It is far from self-evidently true; the spatial dimension of an object could possibly be considered self-evidently true, the temporal dimension certainly not, because we only ever experience the present moment.
We do not only ever experience the present moment. We experience a great many number of moments which become the past. Those that we will subsequently experience lie in the future. This is certainly self-evident to anyone who exists.
Claiming that the past never happened is philosophy.Indeed, what about our sensorial experience indicates that there is a physical property of the universe, which we call "time", which passes?
Do you not witness things changing from one state to another?I'm not sure how you arrive at that conclusion.
Your position appears to be that we can not rely on our experience of time passing. If this is the case, then it follows that we cannot rely on any of our other senses either.
Thus, the only thing you could possibly deduce with certainty is the existence of your own consciousness. That is solipsism.Why does the past have to physically exist for us to trust the conclusions of experiments we conduct in the present moment, whose results we observe in the present moment, and whose results we record in the present moment; bear in mind, the records of those results continues to exist in the present moment; if you can't trust the results people record, then science has no basis on which to stand.
As soon as your experiment concludes, you have a result that was derived and recorded in the past. If you posit that time does not exist, how can you accept as evidence the result of an experiment that occurred in the past? If you accept that an experiment was performed in the past, then surely you must accept that time exists.But even if what you are suggesting were correct, it wouldn't change the fact that the conclusion has to be assumed.
That is a non-sequitir, especially seeing as all physics experiments are, always have been and, dare I say, always will be conducted in the present moment; not the present moment "in time", but it will be the present moment when all experiments are conducted.
On the contrary, all physics experiments, apart from those that are ongoing, were conducted in the past.
You have still failed to explain how this discussion is anything other than philosophy, or worse, semantics. You seem to accept that that things happened in a time before now, but you don't wish to call that "the past", or describe the distance between those events and the present as "time".
Your reasoning doesn't even appear self-consistent.0 -
You seem to be confusing "the present moment in time" with "the present moment"; another way of referring to the present moment is as "the now", or just "now". Ask yourself at regular intervals when you are doing something, is it "now" or is "the past", or is it "the future"; if you are honest with yourself you will always answer that it is now.Maximus Alexander wrote: »We do not only ever experience the present moment. We experience a great many number of moments which become the past. Those that we will subsequently experience lie in the future. This is certainly self-evident to anyone who exists.
The present moment is a dynamic "time", it is constantly changing; the states we refer to as "past states" are just former nows, which no longer exist - or at least, for which we have no empirical evidence, without assuming the conclusion. The moments, you refer to, which become "the past" you experienced as "the present"; all that's left is your memory of them, which is a psychological construct.
No one is saying that "the past" never happened, we're just saying that it doesn't exist anymore.Maximus Alexander wrote: »Claiming that the past never happened is philosophy.
I think I do; but if you are going to suggest that this implies the existence of time, you will have to demonstrate how it does.Maximus Alexander wrote: »Do you not witness things changing from one state to another?
No, my position is that we don't actually experience the passing of time, we assume that we do; that is, we make false deductions form what we do experience and conclude that time is real; it's a bit like someone believing that the earth is flat; it is just a misinterpretation of experience.Maximus Alexander wrote: »Your position appears to be that we can not rely on our experience of time passing. If this is the case, then it follows that we cannot rely on any of our other senses either.
Thus, the only thing you could possibly deduce with certainty is the existence of your own consciousness. That is solipsism.
Solipsism doesn't follow from that.
When the experiment was being performed it was performed in the present moment; if we had asked the scientists were they operating in the past or the present, they would have said the present; the experiment finishes and it no longer exists; the scientists aren't still doing the experiment out there somewhere, or somewhen.Maximus Alexander wrote: »As soon as your experiment concludes, you have a result that was derived and recorded in the past. If you posit that time does not exist, how can you accept as evidence the result of an experiment that occurred in the past? If you accept that an experiment was performed in the past, then surely you must accept that time exists.
When the results were recorded, they were recorded in the present; again, asking the scientists would confirm this; the recorded results continue to exist in the present, so that we can read them in the present and we can recreate the experiments in the present to confirm them.
None of this demonstrates that the past exists, or that time is real.
When they were conducted, it was the present; asking the scientists whether they were in the past or present would confirm this. Those experiments which have finished are not still being conducted out there somewhere in the universe - unless we assume the conclusion that they are.Maximus Alexander wrote: »On the contrary, all physics experiments, apart from those that are ongoing, were conducted in the past.
The question of whether past and future exist stems from Einsteinian relativity; is Einsteinian relativity science or philosophy?Maximus Alexander wrote: »You have still failed to explain how this discussion is anything other than philosophy, or worse, semantics. You seem to accept that that things happened in a time before now, but you don't wish to call that "the past", or describe the distance between those events and the present as "time".
I have no problem calling events which happened before now "the past", as long as we recognise that when they happened it was the present; you can confirm this by asking yourself "is it the present" at various intervals throughout the day; you should always answer yes, unless you have made a startling new scientific discovery. Look back on your memories then and ask yourself, was it the present when they happened; if you have asked yourself the aforementioned question periodically, then you should be able to conclude that those events which happened before now, actually happened in the present, when they were happening.
Ask yourself, does your 8yr old self still exist? There is no empirical evidence that he does, so you would have to assume the conclusion that he does, if you wish to believe that the past still exists.
As for the distance between past events and now; there is no distance; past events are imaginary, there can be no distance between what is imaginary and what is real.
I would suggest your interpretation of my reasoning makes it appear inconsistent.Maximus Alexander wrote: »Your reasoning doesn't even appear self-consistent.0 -
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I disagree, I measure it all the "time." I don't think most scientist (speculation, I can't speak for all) would agree with your definition of what time is. They'd just define a temporal separation, in which their experiment occurred and make no distinction between past, present or future.Time doesn't exist, so any answer would be entirely arbitrary.
I think the whole point of modern science is to remove the "human" from the theory and make a general case.
That's an over simplification, used to give the idea of what the Pauli exclusion principle. It causes electrons to "stack up" in an atom and basically not collapse, into the nucleus.Isn't there something about how two fermions cannot occupy the same space if they have the same quantum state, for example two electrons with an up spin cannot occupy the same space; it would follow that if there is more than one electron with an up spin, then they must be spatially separated. I would presume there is more than one electron in that quantum state, isn't there?
That could be wide of the mark, but there is something about how particles cannot occupy the same space isn't there, given certain conditions?
And any way, quantum fermions have no defined location. They are "smeared" out, over a probability function.0 -
It's really quite simple, and not strange at all; either the block universe is a necessary consequence of Einsteinian relativity, or it is compatible with presentism; that is, either the idea, that past and future co-exist with the present, in 4D spacetime, is a logical necessity of Einteinian reltativity, or Einsteinian relativity is compatible with presentism; because presentism is simply the idea that past and future don't exist.
That's not what your last statement declared... at all. You were asking if there is a dichotomy regarding the nature of the universe.
As for your new statement above, I have answered it over and over and over and over. The theory makes no ontological commitments. It is 'compatible' with both.0 -
This is all well and good but a logical consequence of the block-universe is that the slices must occur in groups of at least three.
Consider the situation when a photon is absorbed by an electron. There would need to be one slice for the instant before the two become 'aware' of each other, a slice for the instant they do and a slice for the resultant state of the system, an excited electron and one photon fewer in existence.
All events would have to be sandwiched between before and after slices. But each slice is filled with other events too and these are also sandwiched between the same two slices.
Also, our perception of time would come from experiencing time-frozen slices at a certain rate.
What I'm wondering is how acceleration can affect that frame-rate, how can time-dilation occur? The block-universe model suggests that two people travelling in opposite directions, one to the east, the other going west, actually exist in two different slices of time in a very real sense. He might say five past nine and you might say six past nine and you'd both be right but how can information propogate backwards through time? How can the mass that exists in one slice communicate with the mass in another? (By phone.)
It seems to me that by travelling quickly, an observer would put himself, in terms of what he perceives, in an earlier slice of the universe. How would it be possible for someone not travelling as quickly to communicate with the quicker traveller?0 -
This is all well and good but a logical consequence of the block-universe is that the slices must occur in groups of at least three.
Consider the situation when a photon is absorbed by an electron. There would need to be one slice for the instant before the two become 'aware' of each other, a slice for the instant they do and a slice for the resultant state of the system, an excited electron and one photon fewer in existence.
All events would have to be sandwiched between before and after slices. But each slice is filled with other events too and these are also sandwiched between the same two slices.
Also, our perception of time would come from experiencing time-frozen slices at a certain rate.
What I'm wondering is how acceleration can affect that frame-rate, how can time-dilation occur? The block-universe model suggests that two people travelling in opposite directions, one to the east, the other going west, actually exist in two different slices of time in a very real sense. He might say five past nine and you might say six past nine and you'd both be right but how can information propogate backwards through time? How can the mass that exists in one slice communicate with the mass in another? (By phone.)
It seems to me that by travelling quickly, an observer would put himself, in terms of what he perceives, in an earlier slice of the universe. How would it be possible for someone not travelling as quickly to communicate with the quicker traveller?
Slices are an arbitrary convention. Even if we interpret the block universe as a real, 4D object, there is no physical foliation.0 -
I'm not sure which statement you are referring to, or the dichotomy you say I was questioning.That's not what your last statement declared... at all. You were asking if there is a dichotomy regarding the nature of the universe.
This line of discussion has stemmed from a point which was made separate to the other points in this thread; it stems from the statement that we're either living in a block universe or a presentist universe.
So, contrary to the basis of your argument in the thread questioning the existence of time, relativity of simultaneity doesn't contradict presentism, and is actually compatible with it?As for your new statement above, I have answered it over and over and over and over. The theory makes no ontological commitments. It is 'compatible' with both.0 -
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So, contrary to the basis of your argument in the thread questioning the existence of time, relativity of simultaneity doesn't contradict presentism, and is actually compatible with it?
No, not contrary to anything I said. In the other thread, I have said multiple times that relativity is compatible with presentism if you presuppose special dynamics that are undetectable.
Your army of threads are all an attempt to argue that time does not exist. The above fact means you have not done so.0 -
Ah, OK, and so it is compatible with the block universe if we assume that past and future exist; which are, equally, if not moreso, undetectable.No, not contrary to anything I said. In the other thread, I have said multiple times that relativity is compatible with presentism if you presuppose special dynamics that are undetectable.
Not necessarily, they may all have been born out of that particular point of disagreement, but not all specifically to argue that time does not exist.Your army of threads are all an attempt to argue that time does not exist. The above fact means you have not done so.0 -
No, not contrary to anything I said. In the other thread, I have said multiple times that relativity is compatible with presentism if you presuppose special dynamics that are undetectable.
Surely 'presentism' only acknowledges the dynamics that are detectable, i.e., energy exchanges as they occur.
It is only by assuming a 'present', any 'present', that we can derive the laws of physics but we can get around this 'assumption' by saying that any 'now' can serve as a frame of reference.
An experimenter simply 'timestamps' a series of observations that are made during what the experimenter consistently would term as 'now', and those observations chart energy exchanges. Only what are perceived as events can have any validity as experimental data, all other data has to be deduced or recorded by a different experiment.
So, every valid piece of scientific data in existence comes from perceived events. What we don't, or can't, perceive has to be deduced and is therefore never experienced.
What use to science is the block-universe if it says nothing ontological about the universe? And why should this model be accepted over other, non-ontological models that are consistently dismissed out of hand in a manner that is comparable to how religion dismisses non-orthodox views?
Why the hero worship?
How does the block-universe predict the physics we have?
It doesn't. It is simply a way to visualise that which many physicists in the vein of Feynmann say can't, and even shouldn't, be done.
We can't experience what the sun is made of so we have to deduce it from data from events we can experience. But the events we experience are not the events we are trying to deduce, they are events caused by the photons that were created by the event we are trying to deduce. We have to collect many photons from many events in order to work out that the sun is largely made of hydrogen but we never experience the hydrogen directly.
So I'm just wondering, what aspect of Roosh is it that can be experienced by a being 50,000 light years distance away in 50,000 years' time apart from photons that bounced off him? These photons have no connection to Roosh, they are simply the result of events that occured in the space occupied by Roosh. That distant being should realise that what he experiences says nothing more about what Roosh is other than his possible position. That distant being could learn nothing about the fact that Roosh is a carbon based lifeform who breathes oxygen, or that he wears a tracksuit, the photons he receives tell him nothing, he can't even say where a particular photon originated, the surface of Roosh's eye or the surface of his retina would be indistinguishable.
I know it wasn't you who brought this up but you don't seem to take issue with the claim that a distant being can experience Roosh directly long after Roosh shuffles off this mortal coil.
We don't perceive events that occur, we try to deduce the events that occured from the events that we do experience, events like a photon interacting with a telescope.
Those who are experiencing a tsunami are not experiencing the earthquake that caused it and we don't say that hearing thunder is like being struck by lightning, so why should we say that the gamma rays that arrive at our detectors are a direct experience of a supernova explosion, that we are observing events from the past?
We're not, we are experiencing an event caused by a photon being perceived now, in our present. The photon takes part in two events, the event that created it and the event that occured due to its subsequent absorption, perception. The two events are unrelated, they just have a photon in common and the photon is an object of chance. We can't detect the creation of a photon, we can only ever detect its absorption. Suppose the emitted photon is never absorbed, does that mean the creation of the photon never took place?
At least presentism does have ontological status, I perceive therefore I am. Whatever it is that I am, I am affectable. I put my hand in flowing water and the current exerts a force on my hand that I feel, I perceive a process of change occuring, but only because I participate in the exchange of forces. I see the water move and I feel it push my hand but still I might put my hand into a bucket of water to see if it feels as differently as it looks and I will deduce that water is made out of a substance that when in motion can produce a force.
There is no other way, stick a probe in and make it take part in the energy exchange process and come to conclusions based on what the probe perceives. The probe is only providing data when it is directly involved in collisions.
And it shouldn't take thousands of years of science to realise that. All the measurements we can make are through determinism. I can't tell you what it's like to be caught up in a tsunami, you have to be there when it actually happens. Touching my wet clothes is not experiencing a tsunami. When I am relating the experience, I'm not experiencing a tsunami, I am examining data directly obtained from being in one in the past.
So what do you have against presentism? And when did you decide that unmeasurable concepts are good for science?
At least determinism does allow us to make predictions albeit with certain caveats due to unknown variables or changes to variables. At least determinism roughly explains how everything in the universe will proceed from this point on.
Only collisions cause change, no collisions, no change. But change occurs. We see it, feel it, measure it. Collisions. If a system stops experiencing collisions then all its components travel away in a straight, Newtonian line and wouldn't be interacting with one another.
But then it wouldn't be a system would it? It would be debris of a system that no longer exist.
In order for there to be time between moments of change, we would have to explain how magnetic forces and charge 'switch off' between those moments. Because that's what the block-universe means, there are contiguous slices where the universe undergoes either no change of state at all or that any change of state is because all the components behave as if they are not subject to any forces and taking Newton's advice, continue in a straight line until acted upon again by a force that will come into affect in the next slice.
Do you see what I mean? There would be configurations of the universe where charge and magnetism wouldn't be manifest as an effect.
But there is no need for that since objects move as if they are subject to the constantly varying effect of gravity.
And another enemy of the block-universe is entropy. The 4-D universe can't see entropy, each slice is in perfect order. Especially if they were all created instantaneously. I am prepared to say that laws of thermal dynamics and therefore entropy are in fact ontological statements of the universe and they are presentism's best friend.
If we accept that the universe is constantly expanding then we can define entropy as - the tendency for the number of interactions that take place in the universe to become fewer as the universe increases in volume. If we can go with this then entropy is the result of an expanding universe as it undergoes cooling.
We might then ask - why does the universe have to go through a cooling process, why didn't it go from hot to cold instantaneously?
We're actually asking, how did time come to appear in the universe?
A determinist might say, well, if inertia, the tendency to resist change didn't exist then that is exactly what would have happened. Without inertia, the universe would have gone from total chaos to a state where all its components have their final velocities and trajectories. And in an instant.
There would be no universe.
But there does seem to be one so a determinist has to explain inertia and thermodynamics says enough.
Think of a bucket of boiling water that has been gently lowered into a glass tank of cold water and then the bucket is tipped so that it empties onto the floor of the tank. If we observed this experiment in the infra-red spectrum then we could follow the heat distribution process.
If the water is unagitated then we would notice that the volume of hot water maintains a border with the cold water for quite a long time. The heat seems to travel very slowly as the cold water begins to warm up.
This is because the only parts of the water that are 'aware' of a temperature gradient are the ones at the edge, The molecules that are located internally cannot 'decide' on the correct path because they are colliding with objects of equal energy. It is at the border where hot meets cold where the hot water gives up its energy and that same border tends to contain the internal energy.
If all the hot molecules could sense the cold they would instantly obey thermodynamics but most of them find themselves on initial paths that lead from hot to hot and that is manifest as impudence (:)) to the 2nd law. But the law is strict, only paths hot to cold are allowed and the system is punished by a loss of energy. Impedence, resistance to change, only slows thermodynamics down, eventually, all systems lose their energy.
Inertia!
And the entire system, hot and cold is in motion even betwen collisions when energy is stored as momentum. The system undergoes constant change even when the energy is perfectly distributed among them - two systems become one that is itself subject to thermodynamic law.
But the main thing is that after perfect mixing, both of the original systems have ceased to exist and can be safely ignored by determinism.
Imagine that the bucket of hot water is a single photon. The number of molecules represents the energy of the photon and the tank could be an electron. The final state of the tank is the electron in a higher orbit.
Of course, the bucket is emptied with such force that all the hot molecules quickly find a colder one and the 2nd law is happy.
Another good example of inertia - look at the energy contained in the modern physics community and how it resists change by sticking to a hypothesis just because it is not broken yet.
Can you really justify your stance against presentism when it works so well at every scale and without the need to consider time as anything but a concept that allows us attach meaning to our observations of change.
It is not 'time' that flows it is the transfer of hot to cold that flows, energy.
It is not 'time' that speeds up or slows down, it is rates of exchange of energy between hot and cold systems that varies.
Energy - what there is
Presentism - where it is
Determinism - what happens next.
Now - existing there
Thermodynamics - the law.
Result - an observable universe that exhibits entropy.
And all this from assuming that the universe is constantly expanding.
Why have slices when you could have the whole cake?0 -
Surely 'presentism' only acknowledges the dynamics that are detectable
It doesn't. It says dynamical processes must physically dilate systems such that the speed of light is the same for all observers. This is accepted by advocates of presentism (or at least those who have done their homework), and they counter that eternalism is built on equally assumptive metaphysics.
The conclusion is the ontological existence or non-existence of an extended temporal dimension does not follow from the physical theory. The physical theory makes no ontological commitments. Hence, it cannot be used effectively to argue that time must exist or that time does not exist.0 -
Masteroid wrote:What use to science is the block-universe if it says nothing ontological about the universe?
It is a formalism that makes elegant predictions about what we observer in experiments ranging from gps satellite comparisons to particle decay to the very creation of particles themselves. With an accuracy of 0.00000000000010 -
It doesn't. It says dynamical processes must physically dilate systems such that the speed of light is the same for all observers. This is accepted by advocates of presentism (or at least those who have done their homework), and they counter that eternalism is built on equally assumptive metaphysics.
The conclusion is the ontological existence or non-existence of an extended temporal dimension does not follow from the physical theory. The physical theory makes no ontological commitments. Hence, it cannot be used effectively to argue that time must exist or that time does not exist.
No, relativity says all that. Presentism doesn't need to refer to time except to label that which does not exist. By understanding inertia and the 2nd law we can deduce the effect that is 'perceived' as flowing time but time itself does not take part in those processes. Time is irrelevant to a presentist because there is only now, the current distribution of heat in the universe. It's not 'time' that changes, it's the distribution of the heat and that is a deterministic process.
In other words, we can have a perfectly operational universe that is devoid of the concept of 'time' until it tries to describe something that no longer exits.
Is there room in the universe for it to have accurate memories of how it was?
And how can you get more ontologically committed than 'there is only now' and 'now is all there is'? Presentism leads to 'everything can be explained in terms of energy'. The only problem that presentism needs to solve is 'what is it about energy that causes it to fall apart?'.0 -
No, relativity says all that. Presentism doesn't need to refer to time except to label that which does not exist. By understanding inertia and the 2nd law we can deduce the effect that is 'perceived' as flowing time but time itself does not take part in those processes. Time is irrelevant to a presentist because there is only now, the current distribution of heat in the universe. It's not 'time' that changes, it's the distribution of the heat and that is a deterministic process.
In other words, we can have a perfectly operational universe that is devoid of the concept of 'time' until it tries to describe something that no longer exits.
Is there room in the universe for it to have accurate memories of how it was?
And how can you get more ontologically committed than 'there is only now' and 'now is all there is'? Presentism leads to 'everything can be explained in terms of energy'. The only problem that presentism needs to solve is 'what is it about energy that causes it to fall apart?'.
I don't think you've understood what I said.0 -
I don't think you've understood what I said.
You seem to suggest that time is 'God-like', it exists in and of itself and cannot be directly detected so science cannot comment on its existential status but it is evident by its 'works'?
I'm saying that a God-less universe would be no different to this one.
I think you are being very strict about the terms 'presentism' and 'eternalism' since if time is not objectively in existence then both camps might just be having trouble with definitions.
If Special Relativity is not a theory of time but gives a very good approximation of some other 'real' phenomenon then SR could realise that it would be correct to say that time does not exist but something else exists that makes time appear as if it does. SR could be refined and determinism can remain a contender.
Then presentists could also acknowledge the non-existence of time and everyone would have the same frame of reference.
I think that 'time' is a red-herring. There are no points in time, justs states of existence. Time doesn't pass, existence changes.
You might say that the present is no more unique than the past or future but 'now' has a very important distinction - it is the only place where there are degrees of freedom and it is degrees of freedom that give rise to the uncertainty of the future.
Events that occured in the past cannot be changed. Emitted photons cannot become un-emitted. Events of the past cannot take part in future events although photons created in those events can. The past is simply the universe when it was hotter. But 're-heating' the universe wouldn't recreate the past, it would just make the universe change in a different way.
Photons can't be un-emitted and old men can't be stuffed back into their mothers.
At least with the spacial dimensions I can get back to where I was.
And 'simultaneity' isn't the issue it's made out to be either. "In special relativity there can be no physical basis for picking out a unique set of events that are all happening simultaneously in "the present"." But that is not the same as saying 'the present is not a unique set of events that occur simultaneously'.
In order to take a snapshot of the universe as it exists at any 'now' one would have to stop all the processes of change in the universe until all the positional data had been gathered. Clearly, this is not feasible so straight away, we find there are limitations to what we can measure.
But the biggest mistake I think you are all making is in relation to what is being observed when we observe an event. We don't observe events, we interact with shrapnel created by events. So what we observe does not inform us of what state the universe is in now, observations inform us of the state of our perception mechanisms now. We don't observe the events that cause perception, we deduce them.
Now is the place where change occurs and perception is how we detect it but we can never observe an event as it occurs, not ever, not in any frame of reference since observation relies on data collected after and as a result of the event we are trying to observe. Perception itself is another set of events. We need two events to occur for perception to take place, an emission event and an absorption event.
Information has a speed limit so distance is the determining factor when it comes to how quickly debris from one system can be detected by another.
When I observe a distant star I am not observing the star as it was, I am observing old photons as they are. But those photons convey no data concerning age or distance, they say nothing about the current state of the system that created them and in any case, one red photon is pretty much the same as any other red photon.
So 'now' is very difficult to pin down and any perceiver can only ever hope to roughly approximate now. But the star I deduced above has moved and it has been creating new photons all the while and there is a universal now that simultaneously has me observing the star in its old position, the star in its new position and all the unabsorbed photons in all of their positions that were ever created by the star. All of that would exist simultaneously in some allegedly non-preferred reference frame which would be in common with all the systems in the universe.
Now, you might argue that the simultaneous events that take place in a given 'now-slice' might be largely dependent on the angle at which the slice was cut since there will always be a set of simultaneous events occuring on any chosen slice. This might seem to support the non-preferred reference frame view but I can think of two counterweights that would cause the universe to choose a particular slice. Tilting the the slice so that one end is in the past and the other in the future would cause an accounting error for conservation. If the existent universe consisted of future events in one direction and past events in the other then that would mean that the universe is more expanded and cooler in one direction while being hotter and denser in the other. This would give rise to a very dynamic system as the universe attempted to equalise the pressure. (And yet we seem to have trouble understanding how symmetry was broken.)
It also means that the paths of emitted photons would be dependent on their direction and the speed of light would not be constant. We'd notice this.
If the universe contains all energy and all energy takes part in expansion then the current volume of the universe is the story so far, up until now.
We can then say that the configuration of all energy, that is the set of simultaneous events plus the distribution of free energy, that occurs when the universe it at its largest volume is the 'universal now'.
Because the universe constantly expands and energy cannot be still, 'now' is in constant flux. 'Now' is the thing that is changing. The present is where it's at, where the work is being done according to the 2nd law.
So 'now' can be considered to be in motion.
All energy existed as the past, all energy exists in the present and all energy will exist as the future, carried by 'now' on a wave of constant change, forever.
Whether we can utilise it or not, doesn't this 'universal now' qualify as an absolute inertial frame of reference?0 -
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If nothing changes in each slice then how can each slice be different.
Although, if a 3-D space is taken as a set of starting conditions, then the time dimension can be viewed as points along which an iteration of a transformation process is applied to that space, x amount of time causes x number of iterations.
But even here, it is the same space being transformed as opposed to being copied, pasted, transformed and then being presented to perception.
The idea that time is a force that transforms is much more palatable than time being the entire set of events that constitute the past, present and future of the entire universe.0 -
If nothing changes in each slice then how can each slice be different.
Although, if a 3-D space is taken as a set of starting conditions, then the time dimension can be viewed as points along which an iteration of a transformation process is applied to that space, x amount of time causes x number of iterations.
But even here, it is the same space being transformed as opposed to being copied, pasted, transformed and then being presented to perception.
The idea that time is a force that transforms is much more palatable than time being the entire set of events that constitute the past, present and future of the entire universe.
General relativity says you cannot map one slice onto another. The closest we can get is applying a metric to similar slices.0 -
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General relativity says you cannot map one slice onto another. The closest we can get is applying a metric to similar slices.
Okay, I'm a little unsure if we disagree on anything here.
We are not saying that 'moments' in time are like 'addresses' of memory locations that contain a particular configuration of the universe are we? That the same address always yields the same universe?
And if we are, there is the requirement of knowledge of one configuration in order to 'deduce' older and newer slices by applying a metric to known initial starting conditions?
But we are definitely not saying that the time component of the co-ordinate contains the precise information about both the metric to be applied and how it is applied (assuming time-dilation events that occur need to be considered locally), are we?
Do you think that all future and past events exist simultaneously and persistently? If the sun exists as a mass in an infinite moments of time, that is an awful lot of mass that it local to us in time terms. 3-D space may only experience one mass of the sun but there is a great deal of hidden mass either side of any particular 'present'. That amount of mass could be expected to have a huge effect on points in 4-D space.
Dark energy maybe?
Anyway, I chose option 5 in the poll, I think the block-universe model is a philosophical concept that does have a place in physics.
Like 'time' does.0 -
I'm not sure what you mean. Do you mean how we use relativity to produce technological innovations?
In a sense.
I gather it is the case that the block-universe is just a simple way to apply relativity.
Kind of like a refined algorithm. An algorithm that says very little about that which it processes. And it gets results.
In a similar way to how accountants improve their efficiency by noticing patterns and employing 'tricks' they develop with experience.0 -
In a sense.
I gather it is the case that the block-universe is just a simple way to apply relativity.
Kind of like a refined algorithm. An algorithm that says very little about that which it processes. And it gets results.
In a similar way to how accountants improve their efficiency by noticing patterns and employing 'tricks' they develop with experience.
The major benefit of the formalism is the exploration of physical laws. For example, the unification of space and time to form spacetime similarly applied to energy and momentum gives 4-momentum. A unification of electricity and magnetism produces the electromagnetic field tensor.
In short, when we look at things from a spacetime perspective, seemingly different phenomena are revealed to be facets of a deeper, simpler phenomenon.
Other examples include the use of Feynmann diagrams, which are drawn in a spacetime context.0
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