Is Time Truly an Illusion or a Tangible Reality?

[magpies]

The real test for if something is real or not is if it can be destroyed right? So why don't we start work on a time bomb that destroys time it's self that way we can at once have the answer to these questions :)

 

[petm1]

We are all looking forward to our "time bomb", it is called death. Death does not stop time for everyone at once, just each of us in turn. What answers we will find beyond this change is everyone guess.

 

[ConradDJ]

I see time as a dilating area from every massive point within our visible universe, think light waves. We see time by putting the billions of photons from all the different light waves together as our individual presents. We may be able to map our world lines through space but it is our center connection that we map through time.

I'm not sure I get the picture you have in mind here... but I think it's important to try to envision what's going on in physics in some such way.

This seems to get at two profoundly distinct aspects of space and time -- on the one hand, the web of connections between things along their light-cones, through which we interact with the world at a distance. And on the other hand, the parallel progress each of us (as an entity with mass) makes through time as we stay more or less in the same place.

So much is "well-understood" in physics, theoretically -- that we haven't yet learned how to translate back into the world we actually experience. We still tend to imagine the universe as if it were Newtonian -- a vast, empty space existing over all time, in which things move around according to certain interaction-laws. In that picture, time is just a coordinate-axis.

But obviously no one experiences the world that way -- as if you could stand outside of space and time and see the whole thing at once. It seems that learning to imagine the world as we actually experience it, in real time, is a unique challenge...

 

[petm1]

the web of connections between things along their light-cones

Light cones dilate at c from every point, they are never static even when we are at rest with our surroundings. Time dilates at c from every point even in the dark the two motions are what I "see" as time

We still tend to imagine the universe as if it were Newtonian

Newton saw the world with gravity as an attractive force, with gr we think of gravity as a warping of space/time, but "if" the flow of time is outward from every point, and it is the same motion started at the big bang (or the little twist, if you think of big bang as an effect from a collapse), then I think of gravity as an outward motion. Each of these views make up gravity which is how I "feel" time.

But obviously no one experiences the world that way -- as if you could stand outside of space and time and see the whole thing at once. It seems that learning to imagine the world as we actually experience it, in real time, is a unique challenge.

Myself I think that time is the orthogonal part of reality, I am standing outside of the time inside of every atom including the ones that makeup myself, it is warping of time that makes up the edges in space.

 

[apeiron]

About 2.725 degrees K according to the CMB clock .

Note that if the CMB is taken as the true global clock, then the presence of mass distorts its rate. The void looks slightly cooler than it ought because some small percentage of the universe's total energy remains locked up as matter - quarks, electrons, neutrinos, dark matter. If this had been given up early on as radiation (if there had been no CP violation in matter-antimatter) then the CMB would still look a little warmer, and so the universe a little younger.

Therefore, to be accurate, the CMB is not a perfect clock. The existence of mass distorts its keeping of universal time. However, we could still calculate the contribution that the conversion of all remaining mass to radiation would make, and so get a "true" reading of the time. In terms of a global temperature or macrostate.

 

[Galteeth]

Scientific American ripped off this thread in their latest issue. Must be a slow news period. You would think the B-muon story would warrant more coverage.

 

[petm1]

There are no perfect clocks, only local clocks.

 

[Kglocc]

If you take the position of everything at in a 1/infinity fraction of "time" you get a map of the universe in a 3 dimensional matrix. Then once you quantify every possible future of every 1/infinity fraction of "space" you can predict the future with math.
Conversely, Time is relative? Time will fly having a good time. Time slows down when adrenaline is pumping and your mind is making more long term memories and connections. So, Time manifests itself as memory in humans? Are memories "real"?
Is "real" "time"?

 

[magpies]

Have you ever had a day that passed by in about one minute?

 

[gabrielh]

It's interesting that after stumbling upon this thread Scientific American releases http://www.scientificamerican.com/article.cfm?id=is-time-an-illusion" called Is Time An Illusion? Thought it might be worth sharing here.

 

[magpies]

Eh... slow news day. The reason physics papers don't use time like we normally do is because when you try to factor in for xyz amount of change the math can start to get insane. It's like trying to keep track of every object in a room vs just one of them.

 

[petm1]

It's interesting that after stumbling upon this thread Scientific American releases this article called Is Time An Illusion? Thought it might be worth sharing here.

Describing time as physical must count for thinking of time as real, I would think.

 

[Borg]

Describing time as physical must count for thinking of time as real, I would think.

Have you read the article? It brings up some interesting points about time, whether it really exists and how rethinking our views about the existence of time may be necessary if we are to ever come up with a Unified Field Theory.

 

[petm1]

Yes I read the article.

 

[Theriault]

That's definitely one of the things it is.

"Up and down are different, because of gravity."

How does one establish up (or down) as a separate spherical radial from a gravity locus? Is gravity smooth or discrete in terms of directions from a locus? Does the size of a gravity locus ( planet vs ball bearing ) determine or change the spherical radial gravity direction arrays? It seems impossible for an object to have an infinite number of gravity vectors, so up and down are pretty useless generally as terms.

 

[Descartz2000]

"Is time real?" :
I think asking what 'real' means is confusing. I think it comes down to the following question: if there are no inherent value differences between 'present/now' states, then how can I claim any single 'now' state is more in existence than any other? If 'real' equates to 'existence', then yes, I would argue time is real.

 

[Descartz2000]

"Is time real?" :
I think asking what 'real' means is confusing. I think it comes down to the following question: if there are no inherent value differences between 'present/now' states, then how can I claim any single 'now' state is more in existence than any other? If 'real' equates to 'existence', then yes, I would argue time is real.

But, 'real' meaning it is all laid out in principle, it is there and valid when I am not experiencing it as a 'now' state. As a 'flow' or as a movement, time is an illusion. But in its entire lay out, it is real and existing.

 

[loseyourname]

The amount of attention this question commands has always perplexed me. Is distance real? Well, is there a distinction between me and the water bottle sitting on my desk two feet away from me? Sure. Is there a distinction between the difference between me and that water bottle and the difference between me and the grill sitting outside? Sure, one is farther away spatially than the other.

Well, is there a distinction between what I'm doing now and what I did yesterday? Sure. Is there a difference between that distinction and the distinction between what I'm doing now and what I did last week? Sure. One is farther away temporally than the other.

What people really seem to want to ask is whether these measures of magnitude of distinction are fundamental or if they require distinction to exist. Imagine a world in which only one indivisible object exists and it never changes in any way. Since it can't be distinguished from other objects or even from itself, space and time don't really come into play. But in the actual world in which we exist, in which many objects exist and they all change, space and time are as real as any other means of making distinctions, like color and magnetism and criminal backgrounds.

Anyway, the real problem in the OP isn't whether or not time is real, it's whether or not the future and past are real.

 

[Ivan Seeking]

This is a troubling question for me. Certainly there exists in our universe sequences of events which may or may not be undone easily. For example, I can walk 31 steps forward, then walk 31 steps backward and return to where I was. However, I can not easily unmix milk from my coffee after I have poured it in, though I shouldn't think it is impossible.

This isn't really what we mean when we think of the concept of "time". A simple sequence of events is something we can do or undo, but no one here thinks they can return to yesterday, or last year. When we think of time, we think of us somehow floating along in a bubble that we call the present, and behind us is the past and before us the future. We can not look forward into the future, but we can look behind us into the past and around us inside the bubble at the present. I personally suspect that this is really an illusion, and that the concepts of "past' and "future" have no physical meaning, but trying to prove it in any concrete way I think is beyond my scope for now. Any thoughts on this topic?

The question of whether time travel to the past is possible, has not been answered. Also, what might prevent a practical time machine from being built are practical limitations, such as the energy required. Other scenarios seem to allow that the past is real, but we could be fundamentally prevented from going there. In one scenario, a radiation feedback loop would destroy the entire effort, but that in itself implies that the past is real [actually, it depends on the assumption that the past is real].

 

[Ivan Seeking]

If the past were not real, would the equations from GR tell us that?

 

[Pythagorean]

If the past were not real, would the equations from GR tell us that?

It depends on what you mean. It's not as if the whole universe stepped through increments of time together, in sync. So what do you mean by past? The local past of a stationary chunk of space? GR tells us that time is not absolute, so the idea of "past", as we intuitively view it, is misleading.

Of course, I wouldn't say it doesn't exist; just that it doesn't exist as we know it.

 

[Ivan Seeking]

It depends on what you mean. It's not as if the whole universe stepped through increments of time together, in sync. So what do you mean by past? The local past of a stationary chunk of space? GR tells us that time is not absolute, so the idea of "past", as we intuitively view it, is misleading.

Of course, I wouldn't say it doesn't exist; just that it doesn't exist as we know it.

The laws of physics are assumed to apply everywhere. I don't understand your point. In the case of a time machine, we are talking about the past wrt the frame of reference of the observer.

 

[Pythagorean]

The laws of physics are assumed to apply everywhere.

What do you mean by that? It shouldn't contradict what I'm saying.

In the case of a time machine, we are talking about the past wrt the frame of reference of the observer.

GR tells us how matter shapes space and time, SR tells us how motion does. One could argue that such tools would be useful in constructing a model of an observer's past, but naturally, even predictive models don't have the final say on whether something is real or not.

It would be strange indeed, if an observer was able to reduce the entropy of the universe in his frame, while time-traveling (bound to be an entropy-increasing event). I can hardly perceive of how you'd ever travel backwards through time in the first place, or how you'd get the rest of the universe to cooperate with you.

a) either all "pasts" would have to be recorded somewhere physical (if that's even possible) so that you had something to "travel" to.

or

b) you'd have to somehow move all the particles back into the position of a past (but because simultaneity doesn't exist, I'm not sure how you'd ever manage to do that.)

To me, time travel on the same footing as intelligent design: that is, if you want to nitpick, it could be true, but it's highly unlikely.

 

[ConradDJ]

It depends on what you mean. It's not as if the whole universe stepped through increments of time together, in sync. So what do you mean by past? The local past of a stationary chunk of space? GR tells us that time is not absolute, so the idea of "past", as we intuitively view it, is misleading.

I agree it's important to point out that past and future have meaning from some particular standpoint in the world -- not globally. From any physical point of view, though, there is a "past" that was "real" once but isn't any more, and there (presumably) will be a future that isn't "real" yet.

It seems intuitive to expand the notion of reality to include everything that ever actually happened up till now, and maybe everything that ever will happen too. But that doesn't seem to describe the physical world very well, once we get beyond classical physics into quantum theory and /or relativity.

The basic problem with our intuition, I think, is that we want to "step outside" our own point of view and imagine the universe "objectively" -- as if all of space and time could be "seen" in some sense at once, without actually being IN it somewhere. As if we could put the universe and its history on our desks and look at it from all angles. But I think the lesson of recent physics is that "you have to be there." If you abstract from having a particular point of view IN space and time, you can no longer conceptualize the world consistently.

 

[apeiron]

I agree it's important to point out that past and future have meaning from some particular standpoint in the world -- not globally.

No, I would still suggest that the idea of locally symmetric time is an assumption, a helpful simplification, of Newtonian mechanics, carried over into relativistic mechanics. Backwards and forwards in time have no differentiation only in those kinds of theories.

But a thermodynamic model of reality does give you a basis for a "more realistic" view of time as an asymmetry. I don't mean thermodynamics as in Boltzmann's statistical mechanics - which, mechanically, locally, again defines no arrows - but thermodynamics as in the modelling of the dissipation of entropy gradients.

And regarding the universe, the average temperature, the cosmic background radiation, does give a global reference which can distinguish the past from the future. Everywhere, the universe is warmer towards its past and colder towards its future.

Of course, the local motion of bodies introduces local relativistic effects like the Unruh radiation. But generally speaking, there is a thermal gradient that marks an irreversible process, a one way direction for change, and hence a global arrow of time.

 

[Ivan Seeking]

What do you mean by that? It shouldn't contradict what I'm saying.



GR tells us how matter shapes space and time, SR tells us how motion does. One could argue that such tools would be useful in constructing a model of an observer's past, but naturally, even predictive models don't have the final say on whether something is real or not.

It would be strange indeed, if an observer was able to reduce the entropy of the universe in his frame, while time-traveling (bound to be an entropy-increasing event). I can hardly perceive of how you'd ever travel backwards through time in the first place, or how you'd get the rest of the universe to cooperate with you.

a) either all "pasts" would have to be recorded somewhere physical (if that's even possible) so that you had something to "travel" to.

or

b) you'd have to somehow move all the particles back into the position of a past (but because simultaneity doesn't exist, I'm not sure how you'd ever manage to do that.)

To me, time travel on the same footing as intelligent design: that is, if you want to nitpick, it could be true, but it's highly unlikely.

Nonetheless, we get real solutions using various schemes, and GR, suggesting that time travel to the past is theoretically possible. Therefore, it would seem that GR predicts that the past is real. Yes, no?

To me, your argument sounds a bit like saying that clocks in SR don't really run slowly as a function of speed, wrt a fixed observer, they just appear to run more slowly.

 

[Pythagorean]

Nonetheless, we get real solutions using various schemes, and GR, suggesting that time travel to the past is theoretically possible. Therefore, it would seem that GR predicts that the past is real. Yes, no?

I don't know about the formulation that does that. Is it something that is inferred from the model or something that was set out to be proven? If you have the link to the relevant paper, I may have more context.

More as an aside, my intuition is that the past is something that doesn't exist anymore, but that it is real, nonetheless, adhering to that definition.

To me, your argument sounds a bit like saying that clocks in SR don't really run slowly as a function of speed, wrt a fixed observer, they just appear to run more slowly.

No, not really, but that is my understanding of SR. If you were on board with the clock, for instance, you wouldn't observe time speeding up or slowing down in your frame.

 

[pallidin]

"Time" is an aspect of "change"
If NOTHING CHANGES, time is meaningless and can not exist.

 

[loseyourname]

No, I would still suggest that the idea of locally symmetric time is an assumption, a helpful simplification, of Newtonian mechanics, carried over into relativistic mechanics. Backwards and forwards in time have no differentiation only in those kinds of theories.

But a thermodynamic model of reality does give you a basis for a "more realistic" view of time as an asymmetry. I don't mean thermodynamics as in Boltzmann's statistical mechanics - which, mechanically, locally, again defines no arrows - but thermodynamics as in the modelling of the dissipation of entropy gradients.

Well, at least on this planet, we have a far simpler indicator of time direction: living creatures and born and then later die. It never happens in the reverse direction. Trees don't shrink into saplings and then seeds.

 

[apeiron]

Well, at least on this planet, we have a far simpler indicator of time direction: living creatures and born and then later die. It never happens in the reverse direction. Trees don't shrink into saplings and then seeds.

Agreed - but not necessarily that it is a simpler indicator.

I was making the familar argument that entropification is the global arrow of time. It points out the ultimate and irreversible direction of all change.

But as well as a direction, there is the question of rate. Time moves forward (entropy procedes) at some actual speed. For the universe it follows an asymptotic curve set by an expanding/cooling field of radiation - the CMB.

Now life and other kinds of dissipative structure are in fact examples of order or negentropy - an action against this general gradient. But then of course, living systems pay for their back-pedalling against the general flow by at the same time accelerating the local rate of entropification in their immediate environments. They create more waste heat faster than would otherwise exist by simpler processes, such as the redshifting of the CMB.

So you have the CMB cooling at it steady rate. Then you have more complex systems that accelerate that rate - and so pay for their own "deceleration", their own persistent order or lack of change as structured systems doing things like growing and metabolising.

So life exists by slowing time, the natural rate of entropification, you could say. But only by balancing the books by also accelerating it to the same degree. Overall, it balances out in the long run for the universe, confirming its global arrow and global rate.

I would certainly call that a complex indicator (though a simple one perhaps if we are just talking about direction, rather than direction and rate).

 

[loseyourname]

I meant simpler to observe, in the sense that it requires no knowledge of physics or special tools. There are other types of events that only happen in one direction. Rocks, for instance, don't ever fall from the bottom of a cliff to the top. Rivers never flow uphill. Explosions don't contract and become bombs. Bullets don't fly backwards out of targets and into guns. Abraham Lincoln's skeleton won't crawl out of his grave and grow flesh and then de-age into an infant.

Observation of these types of events would make it justified to say you're traveling into the past.

 

[Jonnyb42]

I do not know if it is real or not. My thought flow for this is: It is real, because I know of it, it is real. However, if 'real' meant I know of it, then everything would be real, and that word would no longer have meaning, therefore something is not real by simply knowing of it.
Since we can take measurements of time, then I suppose I am leaning towards it being real.

My comments on this matter is the fact that when we look at what has happened, I know that it was the only way things would ever happen. You think you make decisions, and you do, but what you may not realize at first is that that is the same decision you were going to make even a billion years ago. The future is going to be laid down exactly one way, and it will become just a part of the past.
It is like a solid with a 2 dimensional reference frame traveling through it, the solid doesn't change, (with time? uh oh) but yet the observer sees things as changing, it only sees in a 2 dimensional plane. The mechanics that underlie this references frame's movement through the solid, however, is of higher understandings, and mysterious at the moment.

 

[petm1]

Time is real and space is not or space is real and time is not, sorry for space/time to be real you need both. In my mind time is all that is real, space is how I see the "age" of the different photons creating the dilating image on the retina in the back of my eyes.

 

[petm1]

If you think of mass as the past and a "real" direction in time, we see it which ever direction we look in space, then where does that leave our future which I see as the "real" illusion of time.

 

[ThomasT]

But a thermodynamic model of reality does give you a basis for a "more realistic" view of time as an asymmetry. I don't mean thermodynamics as in Boltzmann's statistical mechanics - which, mechanically, locally, again defines no arrows - but thermodynamics as in the modelling of the dissipation of entropy gradients.

But isn't thermodynamics a bit problematic, conceptually? Why not just work on modelling the universe in terms of a global wave mechanical view of things based on some fundamental dynamical laws governing it's overall evolution? Is this simply out of the question because it would be, eventually, too complicated?