Why is there a "now"?

[The Man]

You don't consider humans and video tapes to be part of the universe? The information of the past physical state is there in the present state, regardless of whether or not it is encoded in NTSC or PAL.

To that regard I now present this scholarly discussion and demonstration involving video tape and “now” from YouTube.

 

[sol invictus]

What specific way is it different? Why is cosmological redshift totally incomprehensible if we don't assign time a physical reality and just consider the universe to consist of stuff moving around?

Because our best theory of gravity - a theory that has been verified to be correct beyond any reasonable doubt - accounts for redshift via the curvature of a 4 dimensional spacetime manifold. Time is only slightly different than the three spatial dimensions in that theory. There is no other explanation known for cosmological redshift.

The relativity of simultaneity that keeps coming up is a kind of baby version of that.

 

[Zeph]

The cellular automaton I hypothesize implements all the rules of GR.

The speed of light would be simply one of the rules it implements.

At this point you lose me. If you just mean "nothing can go faster than light", then I somewhat understand your assertion. But if you include the warping of 4 dimensional space time in a large gravity field or as one approaches the speed of light, I do not see those as being explained by automata theory.

That time can be successfully dealt with as a dimension does not mean that it must be one, and a hypothesis such as this shows how that can be.

Hmm. The problem here is not unlike heliocentricism. It turned out that calculating planetary positions "as if" the planets had elliptical orbits around the sun worked quite well. But you could instead use cycles and epicycles, where (in the simplest version) the sun orbits the earth and other planets orbit the sun. But only those really highly invested in geocentricism found the latter complication worthwhile.

Here we are saying that the highly successful and elegant four dimensional space-time COULD be replicated in some kind of automaton which just happened to be programmed to simulate a relativistic universe. This seems to me not unlike cycles and epicycles.

After all, maybe all of reality as we know it is really a seamless simulation within a computer called "the Matrix", run by intelligent robots enslaving mankind. Unless we can find the cracks in the simulation, it's kind of hard to disprove.

But it also doesn't yield much explanatory insight.

Treating time as a dimension with specific similarities and specific differences from three spatial dimensions HAS on the other hand proven fruitful.

But that digresses. Let's see if your conceptualization does yield insights in the present discussion.

My original question is about "now". I see nothing in physics or cosmology which makes any distinction between a phenomenon that happened in the past, and one that will happen in the future. Both are just locations along a time dimension, which science does explain well in many ways. Missing from science (that I've encountered so far) is any account of the existence of a "moving cursor of now" which divides time into past and future.

I don't see how your automaton helps this. So instead of a mysterious special designated "now" point between past and future in the continuum of time, you have a special designated "now" state among the sequence of past and future states. The continuum of time as a dimension has been replaced by a sequence of automaton states, but the singling out of one particular "current state" is no better explained. There's still nothing to explain what "current" means in the big picture.

Zeph

 

[JoeTheJuggler]

What does "moving around in space" mean if there's no such thing as time?

Just what I was thinking.

The reason there's a "now" is because there's a "here". . . and vice versa.

 

[JoeTheJuggler]

Since this is the science subforum and not philosophy, I'll offer another answer:

It was selectively advantageous for humans to evolve a sense and concept of time. One of our strongest traits was living in complex social groups. Even cooperation in hunting involves ideas like, first you do this and then I do that.

 

[Zeph]

The reason there's a "now" is because there's a "here". . . and vice versa.

There is truth in that, but it's not the question on the table.

This has been discussed earlier in the thread. One difference is that there are (more than) quadrillions of "heres" with no one having any special significance in the universe. There's nothing mysterious about those
"heres" in terms of science, any more than a roadmap is mysterious. You can locate your here at my here+5m in the X, my here-20m in the y, and you can move freely from there to my here-2m etc.

But as far as we can tell, there's only one "now" shared by all of us. Nobody occupies "my now+4hrs" or "my now-12hrs", or moves around in that dimension. We are all held lockstep in this same special shared "now", a special moving location on the dimension of time.

My contention is that science has no tools (that I've yet seen; there's a reference I'm still looking for) to even discuss or measure the concept of "now". It handles time as a dimension very well, but there is in science no concept of a "cursor" pointing to any part of time which is more special or different than any other part, just as there is nothing special about your personal "here" or mine.

The easiest resolution is simple: "There is no scientific concept of 'now'". For some that would mean there is no "now", it's all illusion. (But it's a powerful "illusion", and we can't really begin to deal with consciousness without it. If "now" is an illusion, so may be everything we measure with science; in that way lies barren ground). For others it would mean that "now" is real but not within the tools of science - a until now major gap between our consciousness and science. There is no huge problem with that, but it's fascinating.

And maybe science will at some point find some bridge... that's what I'm hoping for, but I'll enjoy the view along the way.

 

[Zeph]

Since this is the science subforum and not philosophy, I'll offer another answer:

It was selectively advantageous for humans to evolve a sense and concept of time. One of our strongest traits was living in complex social groups. Even cooperation in hunting involves ideas like, first you do this and then I do that.

Go deeper, follow that thought.

First point - you are giving a reason for our developing a sense of time passing, just as we have a sense of sight which helps us model the physical world.

But how does it explain why we seem forced to all occupy the same magical moving moment of "now"? None of us can move away from that point in time. If there was any other choice, like being able to live 5 minutes ahead of others, that would have had an evolutionary advantage.

What would moving our personal "now" forward or backward mean? (There is no similar mystery about what moving our "here" means). Well, if you were "aware" of the unfolding of the universe, like which lottery balls will fall, five minutes before I was "aware" if it, I'd say your now had diverged from mine. I don't see that happening. (Urk, somebody is going to bring up precognition, despite the choice of forum I made for this topic). It's hard to describe even any abstract concept of moving your "now" which is not about awareness or consciousness, tho.

Second point in following your line of thought - so would "now" exist on a lifeless world without evolution? Or is "now" inherently about consciousness and life, and unexplained in the world of physics?

Zeph

 

[case#46cw39]

Why is there a "now"?

Wherever there is a Here (H), THAT is also Now (N), as opposed to Then or what was or will be (-N).
There is a Here.
So there is a Now.


The logic is sound, so the premises must be false, or the conclusion is true, due to that reason (H exists).

 

[The Man]

There is truth in that, but it's not the question on the table.

This has been discussed earlier in the thread. One difference is that there are (more than) quadrillions of "heres" with no one having any special significance in the universe. There's nothing mysterious about those
"heres" in terms of science, any more than a roadmap is mysterious. You can locate your here at my here+5m in the X, my here-20m in the y, and you can move freely from there to my here-2m etc.

There “are (more than) quadrillions of” “nows” as well. Your now, well now, is at a different temporal location from your now before and your now after. You seem to be trying to use “now” as a specific location in time which would be similar to claiming your current location is on route 66 at mile marker 476 going 80 MPH west. In fact not an uncommon location someone might assert, but the key point is that the spatial location in that assertion is changing. That is the real difference between spatial and temporal dimensions in physics, we are always moving in time and thus in space-time.

But as far as we can tell, there's only one "now" shared by all of us. Nobody occupies "my now+4hrs" or "my now-12hrs", or moves around in that dimension. We are all held lockstep in this same special shared "now", a special moving location on the dimension of time.

Please define this “only one "now" shared by all of us”. You will occupie your "now+4hrs" in, well 4 hours just as your now is you occupying your "now+4hrs" from 4 hours ago. You're just using diffent points of origin to establish some temperal location.

My contention is that science has no tools (that I've yet seen; there's a reference I'm still looking for) to even discuss or measure the concept of "now". It handles time as a dimension very well, but there is in science no concept of a "cursor" pointing to any part of time which is more special or different than any other part, just as there is nothing special about your personal "here" or mine.

The tool is the same, location, or more specifically coordinates. It is just that in the spatial case you are considering some static location yet in the temporal case you’re considering some changing location referred to as “now”. In the same spatial sense you are always where you are it is just that where you are can sometimes change. Again the difference is that your perception of when you are must always change and only in one direction.

The easiest resolution is simple: "There is no scientific concept of 'now'". For some that would mean there is no "now", it's all illusion. (But it's a powerful "illusion", and we can't really begin to deal with consciousness without it. If "now" is an illusion, so may be everything we measure with science; in that way lies barren ground). For others it would mean that "now" is real but not within the tools of science - a until now major gap between our consciousness and science. There is no huge problem with that, but it's fascinating.

And maybe science will at some point find some bridge... that's what I'm hoping for, but I'll enjoy the view along the way.

Nope, sorry, but the easiest resolution is that you unfortunately still seem to be missing the primary difference between how we perceive space and time as mentioned above and noted by others. The bridge you refer to was found about a hundred years ago, it’s called space-time.

 

[marplots]

My contention is that science has no tools (that I've yet seen; there's a reference I'm still looking for) to even discuss or measure the concept of "now". It handles time as a dimension very well, but there is in science no concept of a "cursor" pointing to any part of time which is more special or different than any other part, just as there is nothing special about your personal "here" or mine.

Special might be the wrong word. But there is a point where historicity becomes fixed. You might look at it as the top of a growing pile of "what already happened." As the pile grows and changes, so too does the top change it's location and state. What you are after is not a point but a condition.

Say you are piling dirt. There is no special place called "top" -- just a new description of the pile. Events work pretty much the same. "Top" is whatever I happen to measure it to be. If I have a trustworthy measuring instrument, I call it a clock and I compare the events happening on the clock with other events. Again, nothing special there either. You do the same thing with other measurements, compare one to another for length and so on.

I think I am missing the tasty mysterious element here though. Do continue to enjoy the meal.

 

[Vorpal]

This has been discussed earlier in the thread. One difference is that there are (more than) quadrillions of "heres" with no one having any special significance in the universe.

That's not a difference, because the exact same statement can be applied to time.

But as far as we can tell, there's only one "now" shared by all of us... We are all held lockstep in this same special shared "now", a special moving location on the dimension of time.

That's not just untrue, but as far as physicists can tell, the exact opposite is true. The reason why you don't think so has to do with the scale of experience your brain has evolved to perceive, not any fundamental aspect of the universe.

Suppose you and two buddies, Bob and Charlie, agree to shoot some pool at a local bar, and two of you arrive, while Charlie is running late. You call him up and ask, "where are you? We're already here." Naturally, 'here' only means the same location up to a certain level of precision (the bar), as the few feet of distance actually separating you and Bob is not relevant to your circumstances. For the task at hand, the difference between your "here" and Bob's "here" is too small to care about, though on a finer level, they are indeed different, and in other contexts you might care.

It's the same thing with "now", with the scale being that a foot of spatial distance corresponds to a nanosecond of temporal duration (c ~ 1ft/ns), so you're almost never in a position to care about the very small difference of your "now" and your buddy's "now", though fundamentally there is almost always a difference, just not one your brain is capable of perceiving directly.

Nobody occupies "my now+4hrs" or "my now-12hrs", or moves around in that dimension.

On the contrary, if you and your buddy were electrons, it may very well be that its now is your now minus 12hrs, or whatever. Many people have mentioned the relativity of simultaneity already. That you don't notice for ordinary circumstance is a result of the scale at which most human experience happens.

The fact that no one can turn around in time is purely a result of having just one time dimension--you can't rotate in one dimension; angles don't even make any nontrivial sense. Although there is a sense in which particles can "bounce back" and go the other way (at least, matter-antimatter annihilation can be interpreted that way in a logically consistent manner).

The easiest resolution is simple: "There is no scientific concept of 'now'". For some that would mean there is no "now", it's all illusion. (But it's a powerful "illusion", and we can't really begin to deal with consciousness without it. If "now" is an illusion, so may be everything we measure with science; in that way lies barren ground).

"Now" is exactly as scientific as "here". What's an illusion is your insistence that "there's only one 'now' shared by all of us." That's an approximation, just as saying "here" for positions close enough together to not matter. A very good approximation for the scale of experiences that humans have, but not true under a finer look.

 

[Thabiguy]

But as far as we can tell, there's only one "now" shared by all of us. Nobody occupies "my now+4hrs" or "my now-12hrs", or moves around in that dimension. We are all held lockstep in this same special shared "now", a special moving location on the dimension of time.

But that's not the case at all. Just look at your post: at the time you posted it, 2010-12-29 01:01 UTC, you asserted that we all share your "now", that nobody occupies "your now+x hrs" - but here I am, at 2010-12-29 11:22 UTC, posting this, directly disproving your claim. Julius Caesar doesn't share that "now" of yours either. Billions of people occupy times far away from the "now" you wrote about, including your own self as you read this.

My contention is that science has no tools (that I've yet seen; there's a reference I'm still looking for) to even discuss or measure the concept of "now". It handles time as a dimension very well, but there is in science no concept of a "cursor" pointing to any part of time which is more special or different than any other part, just as there is nothing special about your personal "here" or mine.

Yes, I agree. Your personal "now" is not special, and it differs at different points in your world line, so there's no particular "now" to point to. - Science can of course pick a particular moment in time and talk about that, or talk about events that happen simultaneously or with some particular time difference, but you're right that there's no "part of time which is more special or different than any other part".

The easiest resolution is simple: "There is no scientific concept of 'now'". For some that would mean there is no "now", it's all illusion. (But it's a powerful "illusion", and we can't really begin to deal with consciousness without it. If "now" is an illusion, so may be everything we measure with science; in that way lies barren ground). For others it would mean that "now" is real but not within the tools of science - a until now major gap between our consciousness and science. There is no huge problem with that, but it's fascinating.

I agree with that simple resolution. "Now" is in the eye of the beholder, just like "here".

What would moving our personal "now" forward or backward mean? (There is no similar mystery about what moving our "here" means).

It would be a not very well worded phrase. "Moving" literally means that space coordinates change as time coordinate changes. It is thus a concept that already refers to both time and space, in a particular way. It isn't therefore clear how exactly "moving 'now'", as opposed to "moving 'here'", should be interpreted. Here are several possibilities:

1. You simply replace "space" with "time", and you get "time coordinate changes as time coordinate changes". That is true for anything, but doesn't tell us much.

2. You switch "space" and "time", getting "time coordinate changes as space coordinate change". That doesn't tell us much either, except that the thing does not occur in different places at the same time.

3. You actually didn't want to use the word "moving", but the word "changing". Our "here" can change, i.e. we can exist at different locations; what would it mean if our "now" could change, i.e. if we could exist at different times? And of course the answer is that we do exist at many different times throughout our lives and we're all familiar with the feeling of changing our "now" - forward, that is. (We're not familiar with changing our "now" backward, because we can't remember future events, and that is because of our structure and thermodynamics; Sol already hinted at this earlier in the thread.)

 

[RussDill]

Because our best theory of gravity - a theory that has been verified to be correct beyond any reasonable doubt - accounts for redshift via the curvature of a 4 dimensional spacetime manifold. Time is only slightly different than the three spatial dimensions in that theory. There is no other explanation known for cosmological redshift.

The relativity of simultaneity that keeps coming up is a kind of baby version of that.

Sorry for an off-topic question, but what happens to the energy lost due to the cosmological redshift?

ETA: Perhaps it isn't really lost because if the universe were to contract, the light would blue-shift? But I'm not sure if that is sufficient, since if the universe expanded, matter emitted a whole bunch of photons, and then the universe contracted, it would have more energy then before it expanded, no?

 

[Zeph]

How fascinating.

I can see that either I'm relatively stupid (which is not the subjective or objective reality feedback I've received so far in this incarnation) because I'm making a big deal out of something which seems trivially explained to the satisfaction of various others, or the concept I am trying to describe truly is very hard to convey, at least with my limited word skills.

I know that I'm not entirely alone in seeing this as an unexplained mystery; besides some others here who seem to understand what I'm driving at, the original question was not something I came up with, but from a special issue Scientific American on Time a number of years back. So I'll try a bit further to overcome my own verbal limitations, as an exercise.

All I would ask of the gentle reader is this: if it seems like my point is particularly shallow and obvious, at least consider that maybe I'm not quite that stupid and that I might be trying to convey something more subtle than comes across at first blush. It can't hurt to try to look a bit deeper.

I do realize that the whole issue is clouded by the relativity of simultaneity; however I find that to be a further twist which complicates this issue rather than providing an explanation. Yes, even if we reside in reference frames at rest with regard to each other, light takes about a nanosecond per foot to travel between us, so we don't really have a truly simultaneous "now" at that level. But that's just a tiny fuzziness - I'm talking about much more substantial effects.

A tiny fuzziness in measuring time doesn't change the dynamic that you cannot move your now forward or backward with respect to mine along the time dimension. If you were standing near me, there might be some few nanoseconds of relativistic fuzziness in trying to synchronize our concepts of "now", but you still cannot move your now a few hours apart from mine.

OK, somebody pointed out that your "now" as you read this message is different than my "now" as I wrote it, even by hours. Of course, both of our "now" locations move. That seriously misses the point. I'm saying that you cannot change your now *relative to my now* by 5 hours. By the time you read the message, we have BOTH moved our "now" forward by the same 5 hours, and the time I wrote it is 5 hours in both of our pasts.

We both travel into the future in lockstep - you can't stop or reverse or go faster or slower. This is fundamentally unlike x,y,z - where you can change your x completely independent of mine, without the slightest lockstep or synchronizing. The relative distance between your position in space (your here) and mine (my here) can and does vary freely. Your relative "now" cannot.

Your position in space relative to mine is also subject to tiny relativistic as well as quantum mechanical fuzziness. But you can still move your relative "here" vs mine around in space by far larger measures that that fuzziness. You however cannot move your "now" in such a mannor, or detach it from mine (beyond that relativistic fuzziness).

There's also a reaction time fuzziness; but again, it's far smaller than hours.

If we describe spacetime as four dimensions, "now" is a special hyperplane sweeping through the time dimension - at the exact same pace and time location for everybody. And we all experience that same sweeping hyperplane, where the future becomes the past. Nobody's consciousness arrives there first. There really is no similar phenomenon in the spatial dimensions.

Substitute "change" for "move" if you wish. I agree the words are imprecise. We are so embedded in the "now" that don't really have good words in English for describing metatime so it's all an approximation. This is not unique to my (borrowed) question. Even leaving the concept of "now" out of it, the physicists' description of "the frozen river" is hard to phrase in English - the concept that the whole timeline exists "at the same time" sound self contradictory, but isn't.

 

[RussDill]

I dunno, to me now and then is no different than here or there. If I want to communicate with someone there, I can't do it now, I must do it then. And if someone received a message from here, I can't of sent it now, I must of sent it then.

I think looking at Feynman diagrams and those space-time cone thingies really helps. There is really no such thing as a now. If a traveler were traveling towards you near the speed of light, things that happened in your brain in one order happened in a different order according to the traveler.

I'm pretty sure your problem is a consciousness one, and not a time one. It gets even more confusing when you think, well, I can effect the future but not the past, but then realize that the only thing special about the future vs the past is entropy. Particle interactions look the same both ways. Did a particle decay, or was as isotope formed due to a collision of other particles? Depends on which direction you consider is the future.

 

[Zeph]

Please define this “only one "now" shared by all of us”. You will occupie your "now+4hrs" in, well 4 hours just as your now is you occupying your "now+4hrs" from 4 hours ago. You're just using diffent points of origin to establish some temperal location.

Just in case, I'll answer this more directly; forgive me if you have already extrapolated the implicit responses from other postings of mine.

What I'm saying is that quite unlike our "heres" where the spacial distance varies wildly and freely, the time distance between your now and my now is always zero (give or take tiny relativistic fuzziness). Likewise everybody else's. This synchronistic "now" is a very special (albeit changing) location on the time axis, and is not explained by physics (that I've seen yet).

That we take this so strongly for granted is a measure for how ubiquitous it is; so much so that we can fail to notice that science and physics (that I so far know of) doesn't even have any handle on it.

Again the difference is that your perception of when you are must always change and only in one direction.

You are on the same track I followed; time is not like the other dimensions because of that inexorable "change" and "directionality". You seem to agree that you can't stop where your "now" is located on the timeline, and you can't move it backward, unlike spatial dimensions. But we can explore that a step further, look for other differences. We all change our the time location of our "now" together. To use your route 66, all conscious beings (at least) appear to be traveling in convoy, nobody's "now" is significantly ahead or behind on the route, nobody can change their position relative to others on the time axis. The location of that convoy of consciousness is what we call "now".

Nope, sorry, but the easiest resolution is that you unfortunately still seem to be missing the primary difference between how we perceive space and time

Yes, I think it does have something to do with how we perceive it, or with consciousness. At least, I have trouble conceiving how a moon rock would experience a "now" concept that separates "past" and "future", even though I do believe it has a measurable timeline which is very accessible to physics.

The bridge you refer to was found about a hundred years ago, it’s called space-time.

I would agree that's the bridge between time as a dimension and the spatial dimensions, and in fact that's one of the prerequisites for understanding what I'm trying to say. Time as a dimension (and it's relationship with gravity) is dealt with by relativity. That's your route 66 metaphor, time as a continuum or dimension with extent and direction. But the concept of "now" is not - a special inexorably changing point on that route shared by all of us.

Again, you are on a similar track of reasoning.

Zeph

 

[RussDill]

What I'm saying is that quite unlike our "heres" where the spacial distance varies wildly and freely, the time distance between your now and my now is always zero (give or take tiny relativistic fuzziness). Likewise everybody else's. This synchronistic "now" is a very special (albeit changing) location on the time axis, and is not explained by physics (that I've seen yet)

I still don't see the special. There are a whole lot of people who the spacial positions I've been in, especially if I consider just one coordinate, such as x, but even at all three, there are still plenty. For instance, I was recently in line at disneyland. The point I was occupying was previously occupied by the person in front of me, and in from of them, etc.

Also, the time distance is only zero to people who you are currently interacting. Your time distance to Newton is significantly more, or to you yesterday.

 

[Zeph]

I still don't see the special. There are a whole lot of people who the spacial positions I've been in

OK, so their "here" at some point in time can match (in ECEF geocentric coordinate space) your "here" at some other point in time. But how does that relate to my assertion that the spatial delta between your "here" and my "here" varies freely (which INCLUDES your potential overlap at disneyland but does not require it), while the time distance from your "now" and my "now" is always zero, plus or minus relativistic fuzziness. Your observation seems quite consistent.

Also, the time distance is only zero to people who you are currently interacting. Your time distance to Newton is significantly more, or to you yesterday.

Heh heh. As I see it, you are reinforcing my point. First, I would agree that we can only *perceive* the (approximately) zero distance between our "now" and somebody else's "now" when we are interacting with them. But it always happens when we do, whether we have been apart for a long or short time; that's remarkable. To use The Man's route 66 and my "convoy of consciousness", we can only perceive that others are in the convey when we look out the window towards their vehicle. But every time we look in that direction (interact with another conscious being) they are still there. Maybe they dissappeared when we looked away (between phone calls, say) and magically reappeared just when we interacted again (with zero time distance between nows), but probably their now still existed in between and was still there when we looked back out that window.

And, we have other reason to believe it. For example, if their "now" were to start verging into my "now" + 5 hours in the future, they might start winning a lot of lottery tickets, even if I wasn't interacting with them at the time (grin). I'm not entirely serious, because I'm not sure what effects it would have to have our consciousness at a different "now" location then other people - could it look like precognition? I don't know.

Anyway, even granted that we don't perceive the zero distance between our "nows" when we interact, that zero distance is still pretty interesting and quite unlike other dimensions.

As for Newton - he's no longer in the route 66 convoy. His consciousness no longer partakes of the shared now. His life history has a starting and ending point in the time dimension (which I concede physics handles well), but he's not part of "now", he's not riding the moving cursor. That's why we cannot interact with him. You and I could interact right now, by telephone (again, with milliseconds of time fuzziness), crossing space freely except for the (mostly light) limitation of c and relativity. Or I could fly there and talk in person. But we both equally cannot have a talk with Newton. It's not because we can't move to the physical lcoations (ECEF) where his "here" resided. And if I could move my "now" back a few hundred years so that it overlapped his "now", then we could interact. But that's my point - we cannot move our "now" cursor forward or back from the convoy's, cannot slow or speed it up - we are all in lockstep, moving our shared "now" one year further away from the absolute time of Newton's death every year, whether we want or not. Absent relativistic effects, your "now" moves just a fast away from Newton's death as mine does. But we can each move our "here" distances from his phsical home independently closer or further at will, because there is no lockstep of "here" as there is with "now".

By the way, I agree that this is somewhat about consciousness. In particular, one might say that the only existence of "now" is in the realm of consciousness, and that physics so far has not really grappled with consciousness in general successfully. From that viewpoint, I think that the concept of "now" is one of the bleeding edges of the gap between consciousness and hard science. "Now" cannot be measured or explained by science, so far as I can tell.

For some suitable definition of "real", that means that "now" is not real. But that would say more about how one chooses to define the English word "real" (what it includes and excludes) than about the actual fabric of reality; it's a change of the map, not the territory.

Anyway, that's why I consider the existence of a "now" dividing future and past to be a central unexplained mystery. I was hoping to get some ideas about dealing with "now" within science, and I did get some references and some good discussion.

Since you bring up the reversibility of time, by what mechanism do you recall the past but not the future? Yes, we can vaguely say "there is some kinda asymmetry because of entropy", but do you have any mechanism by which entropy has imprinted models of past events in your neurons but not of future ones? (Or why the craters of the moon reflect its past history but not its future?) If so, maybe that would give some hints for my question.

Thanks for the thoughts.

Zeph

 

[Zeph]

To use The Man's route 66 and my "convoy of consciousness", we can only perceive that others are in the convey when we look out the window towards their vehicle. But every time we look in that direction (interact with another conscious being) they are still there.

Sorry, before somebody picks on my wording, a better way to say this would have been "if their vehicle is still there (eg: they are still conscious), it's still in the convoy of now traveling exactly together, not moving ahead or dropping behind in the time dimension". Obviously they can drop out, as Newton has.

And note that I am not saying "the same number of seconds have elapsed for them as for us". Only that by the time we are interacting within the same inertial frame again, our "nows" will synchronize within the small limits of necessary fuzziness.

Zeph

 

[Vorpal]

A tiny fuzziness in measuring time doesn't change the dynamic that you cannot move your now forward or backward with respect to mine along the time dimension. If you were standing near me, there might be some few nanoseconds of relativistic fuzziness in trying to synchronize our concepts of "now", but you still cannot move your now a few hours apart from mine.

And as was already noted, that's merely an accident of the scale of normal experience. And a technological accident as well, since if you and I had the mass of an electron, this would be possible without significant difficulty.

We both travel into the future in lockstep - you can't stop or reverse or go faster or slower. This is fundamentally unlike x,y,z - where you can change your x completely independent of mine, without the slightest lockstep or synchronizing. The relative distance between your position in space (your here) and mine (my here) can and does vary freely. Your relative "now" cannot.

Not so. You can only change your 'here' freely up to the effort you put it, whether it costs in gasoline or your own muscles. But then this is really like the difference in nows--if you had oodles of energy to play with as you saw fit, you really could make the advance our nows go faster or slower, with a difference of hours or more instead of the tiny nanoseconds they usually are. Again, the only difference is scale.

There's also a reaction time fuzziness; but again, it's far smaller than hours.

What I'm saying is that quite unlike our "heres" where the spacial distance varies wildly and freely, the time distance between your now and my now is always zero (give or take tiny relativistic fuzziness).

You completely miss the point. With a relativistic rocket, it really could be hours even if you're nearly at the same spatial location. So your re-iteration to "it's not hours" is not anything fundamental.

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Look, I know where your trying to go (or at least I think I do); I just don't see why you're making a big deal of 'now'. Say you're walking down the sidewalk when you realize you forgot something, so you turn around and go the other way. Nothing special. So why can't you do the same with your past? Well, an obvious difference is that your turning around involved actual turning--your operation was done in more than one spatial dimension. If you were in a very tight cramped corridor, it wouldn't be available to you.

Ok, you then might wonder why can't you reverse your direction without turning around. After all, you can walk backwards; it's slower, harder, and makes you more likely to fall on your butt, but hardly impossible. And here, yet again, the answer has to do with scale: if you were an electron, then it could happen to you, at least in the sense that there are physical processes that are empirically indistinguishable from an electron bouncing so hard that it starts going in the opposite time direction. It is only your size and the sheer number of particles that are your constituents that make it effectively impossible that the same kind of thing could ever happen to you.

'Why is our experience one-directional in time?' is a very interesting question, having much to do with probability and information (or its physical mirror, entropy). So is 'why is the universe 3+1 dimensional?' But in either of those questions, I don't see any relevance to making 'now' have any more specialness than 'here'.