The meditations below will lead us to the idea that our Experience can be as much as half a second to a second or so behind the time in the world around us and that this half second is not simply a delay: that we really are half a second or so behind the times. This "backwards referral in time of the subjective present moment" is a well-known problem in neurophysiology. The phenomenon was first observed by Benjamin Libet et al in a series of papers from 1965 onward that involved direct recordings from the brains of subjects. The following text asks us to listen and observe carefully, to explore the half second time shift for ourselves.
That the subjective present is behind the objective present would be an inevitable consequence of the existence of time extension because the half second of time extended Experience can only be accommodated in the objective past.
Listen to a clock tick. Tick it goes at the position of the clock in Experience. Listen to an orchestra, each instrument has sounds that extend into time at their position in Experience. Every part of our Experience extends into time.
We conventionally tend to think that the time in our Experience is like a succession of movie frames:
Our actual Experience is not much like this. Turn on a radio or listen to an orchestra. We hear the firm beat at the start of a bar of music then the whole bar and then that bar is gone and another bar replaces it. When we listen to music with a good quality stereo system or hear a live orchestra each musician has their own sound emanating at their own position. Each part of our Experience can contain extensions in time such as the bars of tunes occurring at each instrument.
The illustration of musicians on this page uses a line of notes to represent the changes over time but we have to listen to actual sounds to know what they are really like. It is useful to listen to stereo music while reading this section to get a feel for what is actually being described.
Take a moment to listen to a sound. It is out there in Experience. It is at a particular location and passes at that location. Sounds occur in space but they are arranged in time at their position in space. Experience, our model of the world around us, contains both space and time. Whether this space and time in the model is identical to the space and time of the world at large will be assumed at this stage.
when we look around things are out there, in Experience, and are seen simultaneously. Events are distributed in the space of our Experience and also simultaneous at the observation point. Perhaps each part of the space of Experience can have a series of sounds distributed in time and also be linked at a point, with time extension being created by the angular separation of events at the point.
It is easy to fall into the trap of trying to imagine that time extension occurs in space however, the time extension "out there", in Experience, does not extend in space but extends in time.
This all sounds very complicated but is actually obvious. Listening to a bird we find that the tweeting is at the position of the bird's beak. Listening to an orchestra the sound of the violin is at the position of the violin. Many things can be at a single position in our Experience. Many things are at the listening point in our Experience but spread out through time, out there, at their place in the space and time of our Experience. Sounds are extended in time at their position in Experience but project to the listening point which is "now".
As we discovered when exploring "Qualities", every point in our Experience can have many things that are spread out in space and time around it but also at a point.
Events have a direction from past to future
Our sense of the unfolding of time has a direction, we always feel as if we are listening into the future. Take the word "hello", we always hear it as if from the perspective of the "h" occurring first and the "ello" sounds extended into the future.
Were we to have events in our Experience arranged so that they receded into the past the word "hello" would begin at the "o" and, from the perspective of the moment when the "o" happens, the word would be "olleh", extending back in time.
Our Experience contains objects that extend into the apparent future for half a second to a second. If our Experience is actually extended in time then we do indeed have events stretching into the future in Experience. However, the future in our Experience extends no further than the present of the world outside our Experience. This is because what we consider to be the present instant is in the past of the world outside our model of it, as will be explored later.
To recap, sounds usually emanate from definite positions in our Experience such as a creaking door or clicking clock, and extend briefly into the apparent future at those positions.
If things in our observation can be laid out in time in a similar way to how they are laid out in space then time exists like space exists. Both space and time are defined by existing arrangements of things.
Before going any further we need a word for a time extended content in
our Experience. We need a term that applies to a sound that extends in
time, to a bar of a tune or the time extended motion of an arm etc. We
shall call these time extended forms "splashes". When I have a
sound in my Experience it is like a splash of events stretching into the
future. The splashes are sequences across what we call time at the
position in Experience of the violin, guitar, mouth, arm etc. that makes
the sound or other sensation.
How exactly are sounds ordered in our Experience? To maintain their immediate ordering the notes played on a violin would need to stretch into the future. Hearing sounds laid out into the future leaves the listening point well in the past of the latest sound (perhaps half a second or more).
Imagine a word such as "got". We hear the whole word starting at the g and ending at the t. Although the word passes with time we never hear the word as "got" then "ot" then "t". We hear the whole word across time then it is gone. The listening point never gets to the t and the word never becomes "tog" such as it might if we heard it backwards in time. It is also as if we seem to jump from one word or bar of music to the next.
The sudden replacement of one sound quale by another is most obvious when we hear speech. Each word splashes into Experience and is replaced by the next.
Our Experience is loaded in "packets" or "buckets". Visual flashes have very short packets and can have a short extension in time. We cannot have a faster rate of seeing flashes than we can create packets and this is the origin of "flicker fusion" - where rapidly repeating flashes of light appear to become continuous. Each visual packet forms a splash.
Visual splashes should not be confused with other phenomena such as pesistence of vision. If we stretch out an arm and move a finger rapidly against a white background several effects can be seen as we focus on the background. Have a go, stare at a white wall and move your finger rapidly across your field of view. Most obviously we will see the vague form of the pink finger persisting along the path of the movement and a faint, dark afterimage following it. Persistence is a failure to replace the image of the finger with the background colour and the afterimage is an adjustment of the brain to the passing of stimulation. Both persistence and afterimages are the extension of the leading image of the finger in space, not in time. Neither persistence nor afterimages are signs of time extension in the leading image of the finger although each of the phenomena are extended in time themselves.
Auditory perception has a similar phenomenon to visual perception in which separate clicks fuse into tones if the clicks are presented sufficiently rapidly. This auditory fusion suggests that, like visual data, sounds occur in short packets. In the case of sound the packets are joined to form a much longer splash. Vision does not seem to link the packets into longer units. As an example a red light rapidly replaces an extinguished green light at a given place and the moment of transition is very short as one visual packet is superseded by the next.
Are we are at least half a second in the past?
The present moment in our Experience is always slightly behind the present moment on clocks outside Experience because it takes time for the electrical signals from our eyes and ears to be combined into visual and auditory images. What we view is slightly in the past because it is delayed in getting from its source to us. However, it was suggested above that what we consider to be "now" can be a half second or more behind the events at our senses. This would be a very long time for a simple transmission delay. There is another possibility, our observation point could be half a second or more in the past relative to events that are occurring outside our Experience, in the objective present.Although our Experience definitely has transmission delays is there any evidence that it is truly in the past compared with external clocks and not just delayed?
We can observe how our Experience is in the past by looking at the beta illusion. In the beta illusion flashing images or lights are joined together by continuous motion:
If two lights are near each other and flashed in succession it appears as if there is one light that is moving back and forth. If the lights are two different colours the single, illusory light, appears to have a wash of changing colour at near the midpoint of the flashing bars.
Colour change happens while the bar is in apparent motion (Vertically cover parts of the moving images above to see that nothing is actually moving. The movement that we are seeing is in Experience).
This shows that the final colour was available to the brain before the transition in colour was seen at the midpoint. The colour change is "interpolated" - positioned between two known points in both space and time.
It has now been confirmed that the brain models the motion in the beta illusion (see below) and this is powerful, additional evidence that our Experience is a model of the world in our brains.
We can see from the graphic above that our Experience is seriously delayed compared with the world outside our bodies. The model of motion cannot begin to be built until the second flash is received. In the case of a half second interval between flashes our Experience could be delayed by over a half a second. This appears to be a deliberate delay to allow any consequences of the first flash to be registered plus a relatively short transmission delay after the second flash. Once there is a long enough sample of events the brain then models these in space and time.
Of course, as discussed below, we can have reflex responses to events at intervals of less than half a second. However, our brains seem to wait for as much as half a second before computing the model of the world that becomes our Experience.
The beta illusion occurs even when the flashes or images are not repeated:
(Click on image to see the illusion. If your browser will not display it copy the file or use another browser)
This suggests that a quarter to half second delay for vision to enter Experience is normal.
The illusions above suggest that there is a delay of about a quarter to a half second before the brain can make a full model of events. However, this is a simple delay. It does not mean that the subjective present of Experience is at an earlier time than the objective world, it means that the subjective present contains data that is delayed.
The beta illusion invokes other qualities apart from simple visual events. It also involves a sense of motion that extends in time for half a second or so. We might expect that our subjective present is aligned with the beginning of the longest time extension associated with the beta illusion. If this were the case the subjective present could be a real half a second behind the objective present.
To determine how far the subjective present can be behind the objective present what is needed is an example of modelling that involves events in Experience such as sounds which have a longer time extension than visual events.
Firstly notice that the s sound in legiSlatures is accurately interpolated into the word. This accurate interpolation suggests the following sequence of events occurred: most of the word without the s was received, the s was inserted and then the word was submitted to Experience.
The interpolation of the "s" sound needs most of the word to be received because the word could be "legitimate" "legible" etc. at the instant of the missing "s". This means that the sound waves that are the source of the word "legislatures" have ended when we start to hear the word so the word in our Experience is perhaps half a second late compared with the sound waves that correlate with it.
Having replaced the cough in the clip with an "s" the brain must deal with where to put the cough. I hear the cough at roughly the position in time of the "gisla" part of legislatures but cannot pin down its temporal position more precisely. The cough sounds like it is at a slightly different position in space from the word, perhaps due to a second person, even though we know it replaces the "s" in the sound wave data. There is an uncertainty in placing the cough relative to the word "legislatures" of about half a second; as we might expect if sounds happen in splashes that are half a second to one second long.
If Experience does not really exist why make a model that is almost a second late for us to experience it? The best test of whether the brain goes to the trouble of representing illusory motion is now to actually look at the brain. In the past 15 years MRI scanners have advanced to the state where even small areas of cortical activation can be visualised. The beta illusion (Muckli et al 2005, Larsen et al 2006) is indeed accompanied by the filling in of brain activity to represent the "illusory" motion. Do we really only "believe" that Experience exists? If this were the case then why does the brain bother to model "illusory" motion?
Our Experience is at least half a second behind the time in the world around us. If a clock ticks twice a second then the moment we hear the clock tick the actual clock is already starting the next tick. What we might believe to be the present moment is distinctly in the past relative to the actual clock. However, we hear the whole tick of the clock extended in time, out there at the position of the clock in our Experience (in our brain). More than a simple delay is occurring. Our listening point is truly behind the time of the rest of our body.
It seems there are three present moments. There is the objective present moment as measured by clocks in the world, the present moment of the start of a clock tick in our Experience and the present moment of our observation point.
If objects extended in time exist in our Experience then this would also apply to the brain. What being in the past by, say, half a second means is that some of our Experience resides in the past part of our brain. There are not just delays on the route from sensation to Experience, our Experience is also at an earlier time than our surroundings. Such a time difference between the "now" of our observation and the "now" of the world outside our bodies is inevitable if time exists and experience is extended in time.
How can I be half a second behind the times?
Given that our Experience contains events that are at least half a second behind the actual present moment how can we affect events? Suppose we are playing football, if we aim a kick at the ball half a second late it means missing the ball. We manage to play sports etc. because when we acquire skills we transfer the control of the skill to automatic parts of the brain that have shorter delays. This makes our Experience an observer of our body's skilled actions rather than the performer.
Experience is the end point of the processes that create it. Experience exists and it is in flux. Why is this done? Why is there an observation that is an end point that is at least half a second late relative to the world outside our bodies?
Why brain processes bring together data to make the observation that is our Experience seems to be a mystery. Even if the data in Experience were to lead to an output as an action or a further thought there seems to be no reason why the data should become Experience, after all, we can play football as a skilled activity without using the data currently in Experience to control our actions. It is likely that the creation of Experience itself is the principle objective of the body's actions and the brain's activity rather than controlling a ball on a football field.
Our bodies are there to create us rather than to perform actions. The actions are required to keep our bodies living so they can perform this task. That anyone would believe this were not the case shows how far modern humans have become footballers or workers rather than people.
The splashes of sound in our Experience arrive as fully formed patterns in time. This is possible because the "now" of our observation point can be half a second or more behind the inputs to our senses.How is a sound in Experience created? It could be laid out part by part over half a second and then connected to the present of the listening point or all at once as a four dimensional structure that extends from the listening point to the place and time of the sound in Experience. Either of these would seem the same in our observation.
The contents of Experience are laid out around the observation point. Just look around you. It is the angular separation of the contents at a point that creates the space of Experience and means the contents are simultaneously present at the observation point and also spread out in space and time out there in Experience.Are events fixed in time?
If the objective present is in the future why can't we change the future by changing our minds? It might seem like a paradox but the future events that are in our Experience have already happened because our observation point is at least half a second behind the events at our sense organs. However, events that are generated by the brain without external input may not be so heavily constrained, as will be discussed later.
ideas of the arrangement of events
There are several possibilities for how events might be arranged in Experience. The two most likely are that the observation point is moving continuously into the future or that it moves in discrete steps of about half a second each.
Both of these ideas must be adjusted to explain how splashes of events can have different durations and start and end at different times.
The difference in time extension between auditory and visual observations would mean that time extended visual events at the end of an auditory splash would not enter Experience until the word is almost over. Can there be two observation points at different times?
It doesn't feel like there are two observation points. It feels like there is only one observation point with splashes being updated at different rates.
Comparing the time extensions of auditory and visual events is very difficult. The image below is a fairly random succession of coloured squares presented for a quarter of a second each. Try saying the word "tat" while looking at the image:
I cannot reliably tell which colour occurs at the beginning of the word or at its end.
With practice I can make a succession of "t" sounds that synchronise with the colour changes. I can also arrange to say a short word such as "tat" when a particular colour appears and can then, with a little practice, vaguely identify the colour that coincides with the end of the word but then I am only attending to the ending.
What I cannot do is match the whole time extension of the "tat" to the
colours that lie along it in time. The alignment of sound
sequences with visual sequences over periods of less than a second is
unreliable at best. Also notice that if we look for a particular
colour, such as light green, it seems to persist longer than it would if
we focus on another colour. Our subjective estimates of the
relative timing of short events are highly variable.
The time extensions of auditory events are less than a second and usually around 0.5 seconds. When comparing these with visual events that objectively occur more rapidly it is quite possible that only a single visual event is in Experience during the auditory event despite it being objectively possible that three visual events could occur in this time.How can the observation point be "now" for both vision and sound?
The simplest explanation for how the observation point is "now" for both vision and sound is that the subjective "now" is always moving into the future in time for both vision and sound. The appropriate visual packet will then be contemporary with the listening point as it moves in time. However, this would seem to leave words being arranged backwards in time relative to the listening point (there are possible arrangements of events that might avoid this, see below).
Another possible explanation for how the observation point is "now" for both vision and sound is that the inaccuracy of the duration of qualia is exploited so that although, objectively, there should be two or three visual qualia in the time occupied by one auditory event only one is present in Experience.
Neither of these ideas for how events are arranged in Experience really encapsulate what it is like to see and hear events that are extended in time that have different durations and occur at different places in Experience. A more evolved model is developed below.Advancing time
A word has earlier and later parts within it but there is no cursor that represents the present flowing through each splashed word or splashed note.
The splashes keep coming and clocks advance in each splash so the observation point advances in time. If it were not for clocks advancing we might feel as if we were in an eternal present moment with splashes providing a half second of time into the future for our appreciation.
The progression from one splash to the next is like a jump at the observation point that is triggered at the end of each splash.
How can a succession of notes be at a point in time and space? It was
suggested above that arrangements extended in space could be brought
together at a point by adding a fourth dimension. It seems profligate to
add a fifth dimension to deal with arrangements extended in time,
however, something is bringing the notes together so that they are now,
at the present moment of the observation point, as well as time
extended. Introducing another direction for arranging events could,
according to the reasoning given earlier, accomplish this feat and allow
a sound quale to be at two places at once.
However, this is just a putative hypothesis. There could be other ways in which events ordered in time could be explained. The reason for mentioning dimensionality is to emphasise that physical explanations for Experience are conceivable. This allows us to say that we do not know how Experience becomes arranged in the way that it appears but we have no reason for supposing that Experience is non-physical.
To recap. We hear sounds out there, in our Experience (in our brains). The sounds extend in time. When our observation point is at the start of the splash the whole splash is present and it continues to be present until the observation point passes the time of the end of the splash.
The whole word "hello" is still present at the listening point when we hear the "o" sound. Even as the splash of the word "hello" becomes historical by a half second or so we can still have it in Experience as a whole sound that extends from the past to the future. It is as if the phonemes of a word or the notes in a bar become arranged in a way that takes them off the normal time axis. If there were another direction available for arranging events this would be possible.
Thus there are two reasons for introducing yet another direction for arranging events. The first is to provide the freedom necessary to create a listening point (a way of connecting the events at a point ) and the second is to allow the events to always extend into the future as the listening point is moving in time.
The diagram above gives the impression that the observation/listening point is separate from the quale. However the quale is both at the observation point and at the position of the quale out there in Experience (as was described earlier in the section on Qualities. Nothing flows into the observation point).
Sound splashes clearly extend in time at a single place, out there, in Experience so any new direction for arranging events cannot be space-like. The new direction would be time-like in the sense that it is not spatial and contains events arranged in time.
The prominent sound events in Experience extend for about half a second of time. Every patch in our Experience has its own time and time extension. The observation point brings together all of the patches in Experience. The observation point IS those patches connected through a point.
Synchronisation of events in time
Sequences of gentle sounds that are at different positions are very difficult or even impossible to compare. A gentle note on a flute at one place may occur in Experience slightly later or earlier than an objectively simultaneous note on a guitar elsewhere in the room. Drum beats and loud sounds provide a reference point from which other musical sounds gain their location in time.
In the case of music there is almost always a dominant splash of sound in our Experience and the other splashes of sound elsewhere in the space of our Experience tend to start their time extension at the start of the time extension of this dominant sound. It is the genius of music to have formalised this feature of Experience into the structure of notes in a bar. If there is no dominant sound our attention moves from place to place, alighting on the sounds at different places and failing to synchronise them perfectly.
The time extension of sound has a similar extent to the time extension of bodily motion (each splash is about 0.5 sec long). When we dance our time extended bodily position synchronises with the time extension of the music which makes swaying or foot tapping in time to music entirely natural. Compared with sounds the time extension of our visual image is extremely short (perhaps a tenth of a second or less) so vision does not blend well with sound and bodily motion.
How sounds are affected by apparent distance away
The observation point seems as if it is at the centre of a hollow sphere of events, the events being on the inside surface with no events between the observation point and that surface. This allows the click of a clock to extend the same amount of time whether it is apparently distant or near to us. Were a distant clock really distant in Experience, rather than scaled in size to emulate distance, the clock would appear to go faster if it were further away because the time between ticks would subtend a smaller angle at the listening point. The distance of a sound from our bodies is marked by cues such as its intensity and the size of its source in Experience and the duration of the sound by its angular extent in time at the observation point.Moving in time
What do we mean when we say we are moving through time? As McTaggart discovered, you cannot both be moving through time and also be "in" time. To move through time whatever moves cannot be part of the fixed events that lie along the time axis. It is conceivable however that a point, such as the observation point, might move in time because it occupies no time or space.
The feeling of moving in time is due to a continuous comparison of one splash with the next and the total replacement of splashes in an asynchronous fashion so that they overlap each other.Our intuition of viewing from a point may answer the problem of how we can have moving in time in our Experience. Our observation point can simultaneously host a succession of events because the succession of events make angles through time at the observation point. However, although this permits a brief period of time to be in our experience there is no reason for the observation point to move. The observation point might connect to events spread over a half second of time but could be eternally fixed.
We could be stuck in a bubble of events a half second or so long.The idea that we are not moving in time is feasible because we only have a half second or so of obvious events in Experience. What we regard as "now" is actually a little bubble of events that extend for a half second or so. We were each a similar bubble five years ago. If time exists then there is a "me" five years ago who also exists and has not moved in time.
That there are multiple "me"s, each with a bubble of around a second of time as their Experience who stretch back to my birth is possible but disturbing.
Sleep and unconsciousness
How do we know we are the same person when we awake as when we fell asleep? If we get a bang on the head and become unconscious for a few seconds or minutes what happens to us when there is nothing? Sleep and unconsciousness add weight to the idea that we exist in bubbles. Our memories connect the bubbles. The only content of my Experience that might be a window on to the past is my memories but these could be recreated specially for review rather than providing any direct link back in time.
But could we possibly move in time?
Despite the possibility that we are eternally fixed in bubbles at a particular moment our deep intuition is that we are truly moving into the future. If we are to have any effect on the future something would need to actually move in time.
This intuition of moving into the future comes from our direct observation. Many splashes can occur in our visual experience whilst one splash is happening in our auditory or bodily experience. This gives us the feeling that time is moving forward. The overlapping of many splashes from all over Experience provides an immediate sense of progress in time. Each splash trawls out connections to other splashes and memory so gives a unified feel of progression at any moment.
For us to truly move in time however there would need to be a phenomenon that is not fixed in time and space that affects our observation point. Without this our observation point would indeed be permanently fixed at the centre of its own bubble containing 0.5 seconds or so of events such as sounds and bodily motions.
A major problem with moving in time is how past Experience can be erased. This problem can also be expressed in terms of time extension, if time extension is possible then what prevents it from extending for seconds or hours, how is time extension in Experience kept brief? The existence of a fifth, independent direction for arranging events was mentioned above as a possible answer to this problem. Our Experience is like a series of short clips that are fairly long for words and movements but very short for vision. It seems that these clips extend in time but do not stay on the time axis for arranging things and when they end the clips are no longer directly accessible.
The access to these clips is through the qualia that connect them. If the qualia are not at the observation point then none of their content can be in Experience now. This would explain how the past can apparently disappear and be replaced by another time extended object but does not get us much closer to how the observation point moves along the time axis.
Suppose that we can move in time, if so then what is this self that moves in time? It is the historical Experience that stretches back to our birth being extended. We expand in time rather than move in it. But then why is the view always containing events at the boundary between the past and future?To recap, one of our deepest intuitions about the world is that we are moving into the future. Arrangements of events in time and space cannot move in time so something outside of time is required to account for our intuition. Without this postulated motion in time every moment of observation would be fixed in its own eternal bubble. One possible way in which we might know we are moving in time is if there is a quality that is extended in time for much longer than the other qualities. A sense of "time lived" that extends for hours, days or even a lifetime and grows more time extended as time goes by.
Why doesn't our Experience happen very slowly or be completed in a flash? The space of our Experience provides a clue to this timing of time because it is arranged as a sphere of events around a point. Events in Experience occupy angles that are projected from the observation point and the angular displacement cannot exceed 360 degrees. We can observe the relative spatial extent of objects by the proportion of the sphere around us that they occupy. In the same way as space is arranged around a viewing point time is arranged around the listening/observation point.
This arrangement of events around an observation point also seems to apply to events of a long duration. When we are forty years old time passes much faster than when we were ten. When we are eighty time goes twice as fast as when we were forty. This sense of time illustrates how we have a lifetime and pack ever more events into it. When we are ten another year is a tenth of a lifetime long but when we are forty it is a fortieth of a lifetime so a year seems four times faster when we are forty than when we are ten. A lifetime is the curve of time extension around our observation point that corresponds to the quality that seems to be time extended as long as our total Experience.
How this might be done is obscure, perhaps we maintain models of our lifetime and compare these with models of the duration of recent events or perhaps we do indeed have access to a crude model of our entire lifetime. If the models are shorter than our lifetime then this would make each bubble longer.
The way that the different time extensions of the contents of Experience are contained within each other explains why there is a rate of time passing as "seconds per second".
However, none of this explains how the observation point might move.
Movement is measured by comparing one movement with another, for instance comparing the repeating movement in a clock with the progress of an object in a straight line through space. It is clear that at the tenth tick of the clock the moving object is no longer where it was at the first tick of the clock. Has the object gone from its previous position in time or has it only become undetectable?
If a spinning disc only exists now it cannot contain any movement within it. At a true instant the disc has no motion so how can the spin continue into the next second? If we allow that the disc has an infinitessimal motion then the disc can spin but this amounts to conceptualising the disc as slightly extended in time.
Another way of considering the spinning disc is that at a true instant there is no information in the disc that tells us it is spinning. The information about spinning involves arrangements in time such as velocity and acceleration. If discs do not extend in time it is difficult to conceive of how they can continue to spin from one timeless instant to the next.
Movement in time is equivalent to communication through time. We have already noticed that Experience has events extended in time. This was attributed to a connection through the listening/observation point and this connection would be hosting a communication through time. This communication allows the start of one splash to be compared with the start of another and Experience to immediately contain "earlier" and "later" and "longer" and "shorter" intervals.
The speculation above on adding another, time like dimension as a way of hosting time extension and communication between times was mainly intended as an example of physical conceivability. There are other possibilities. There are several effects that can flow towards the past. A suitable candidate for this might be the electromagnetic "advanced potential" travelling backwards in time in a constrained environment such as cell membranes or somewhere else.
This is all incredibly speculative but does suggest that connections through time are physically conceivable. All we can know for certain at present is that we do not know how to explain our Experience but physical explanations are not inconceivable.
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