Why do we Experience a 'Flow' of Time?

[TheQuestionGuy14]

Einstein showed that the dustinction between past and future is an illusion using simultaneity, so, why do we experience a flow of time? Why is everything in the 'now' flowing toward the future, and not the past? Also, why do we all experience this flow the exact same way?

 

[Dale]

Einstein showed that the dustinction between past and future is an illusion using simultaneity,

Only for spacelike separated events.

 

[Ibix]

You misunderstand. At any given event there is a clear future (formally, the future light cone of the event and its interior) and a clear past (ditto the past light cone). All relativity does is add a third region outside both future and past light cones that can be arbitrarily divided into past and future for that event.

The reason we experience time the way we do is that we compare what we can see now to what we now remember seeing in the past. And we remember comparing what we saw a secong ago to what we saw before that. For whatever reason our brains model that as a continuously changing world instead of a continuously accreting view of a static 4d world.

As to "why do we all experience the world the same way": do we? I wouldn't be surprised if there's a fair bit of variation although with a high degree of commonality. But in any case the answer is obvious - that's what happens if you use nearly identical hardware to perform a task.

Regarding the "direction" of time, I'd suggest watching Feynman's lecture on entropy.

 

[PeroK]

Einstein showed that the dustinction between past and future is an illusion using simultaneity,

This is nonsense. If we take a sequence of timelike-separated events (what you do in a day, say), then every observer will agree on that sequence. No one will think you had your lunch before your breakfast.

 

[TheQuestionGuy14]

This is nonsense. If we take a sequence of timelike-separated events (what you do in a day, say), then every observer will agree on that sequence. No one will think you had your lunch before your breakfast.

Yes, as they are causal events, if there is huge spacelike difference we won't agree if they are simultaneous, thus technically seeing their future, as we may see it AB, but they see A, then B.

 

[PeroK]

Yes, as they are causal events, if there is huge spacelike difference we won't agree if they are simultaneous, thus technically seeing their future, as we may see it AB, but they see A, then B.

You claimed that the distinction between past and future is an "illusion". That is nonsense.

Simply take the sequence of posts in this thread as an example. Is that an illusion? Did you object to my post #4 in post #5 before I'd posted it? Could anyone make that interpretation?

 

[TheQuestionGuy14]

You claimed that the distinction between past and future is an "illusion". That is nonsense.

Simply take the sequence of posts in this thread as an example. Is that an illusion? Did you object to my post #4 in post #5 before I'd posted it? Could anyone make that interpretation?

No, sorry. I guess illusion is the wrong word. I used it as I got it from this quote:

https://www.brainyquote.com/quotes/Albert_einstein_148814

 

[PeroK]

No, sorry. I guess illusion is the wrong word. I used it as I got it from this quote:

https://www.brainyquote.com/quotes/Albert_einstein_148814

https://www.quora.com/Einstein-once...-How-would-a-physicist-explain-that-statement

 

[TheQuestionGuy14]

https://www.quora.com/Einstein-once-said-“For-we-convinced-physicists-the-distinction-between-past-present-and-future-is-only-an-illusion-however-persistent-”-How-would-a-physicist-explain-that-statement

Thanks. Didn't know that!

 

[PeroK]

Thanks. Didn't know that!

Nor did I.

 

[PeterDonis]

as they are causal events, if there is huge spacelike difference we won't agree if they are simultaneous, thus technically seeing their future, as we may see it AB, but they see A, then B.

@PeroK specified timelike separated events. For timelike separated events, their ordering is invariant; it doesn't depend on your choice of reference frame. Even if there is a large difference in the spatial coordinates of the two events in some coordinate chart, that does not change this fact. This fact is also true of null separated events (events that are linked by the path of some light ray).

The only pairs of events for which their time ordering is relative are spacelike separated events, but spacelike separated events cannot be causally connected; so any pair of causally connected events will have an invariant time ordering. That is why relativity is perfectly consistent with a "flow of time".

 

[pinball1970]

Einstein showed that the dustinction between past and future is an illusion using simultaneity, so, why do we experience a flow of time? Why is everything in the 'now' flowing toward the future, and not the past? Also, why do we all experience this flow the exact same way?

Two things one is biological, our experience of events. Why the events seem to obey rules is explained by entropy and the arrow of time. I like the sand castle analogy example.

 

[NoTe]

The conclusion in the end of the clip comes out of the blue to me. The fact, that entropy is increasing with time, is i.m.o. something completely different than the fact, that time is traveling in one direction. It says something about entropy, and nothing about time.

 

[NoTe]

P.S. I would say, that time is not at all 'traveling', and certainly not in a direction whatsoever. Events happen and have spatial and time coordinates in a certain FoR, that's all.

 

[stevendaryl]

The conclusion in the end of the clip comes out of the blue to me. The fact, that entropy is increasing with time, is i.m.o. something completely different than the fact, that time is traveling in one direction. It says something about entropy, and nothing about time.

Well, the characteristics of time that are most familiar to us do have to do with entropy. The biggest one: the fact that we remember the past and not the future has to do with entropy. And this is what gives us a sense of "flow" of time.

When people speak of time flowing in one direction, they mean our sense of time, not the dimension.

 

[NoTe]

OK @stevendaryl, I know what people mean, but I was trying to get back to the physics.

I think there isn't so much to time as many believe there is. It's just a scalar quantity that's very useful in almost every field of physics, but it's not something that's running or moving or flowing, it's a derived quantity that's only there, because of óther things running, moving or flowing. Well, that's how I see it, in physics. Of course, as a human being, it may feel different ('our sense of time').

 

[stevendaryl]

OK @stevendaryl, I know what people mean, but I was trying to get back to the physics.

I think there isn't so much to time as many believe there is. It's just a scalar quantity that's very useful in almost every field of physics, but it's not something that's running or moving or flowing, it's a derived quantity that's only there, because of óther things running, moving or flowing. Well, that's how I see it, in physics. Of course, as a human being, it may feel different ('our sense of time').

Since this is the relativity forum, I should point out that in relativity, time is not a scalar quantity, but is a dimension similar to the three spatial dimensions. There is a related scalar quantity called "proper time" that is closer to our intuitive notion of time passing according to our clocks.

 

[stevendaryl]

I think there isn't so much to time as many believe there is. It's just a scalar quantity that's very useful in almost every field of physics, but it's not something that's running or moving or flowing, it's a derived quantity that's only there, because of óther things running, moving or flowing.

Explaining time in terms of other things moving or flowing seems like circular reasoning, since moving is defined in terms of something being at different locations at different moments of time.

 

[NoTe]

Explaining time in terms of other things moving or flowing seems like circular reasoning, since moving is defined in terms of something being at different locations at different moments of time.

Yes I know :-) , but I still feel that it's not 'something of its own'...

About the scalar quantity: I meant this classically: not a vector, so no direction, just an amount, just a plain quantity. In relativity too, it doesn't have (or is) a spatial dimension all of a sudden, the quantity ct in the Minkowsky metric does. But that is not time. Or is it?

 

[pinball1970]

The fact, that entropy is increasing with time, is i.m.o. something completely different than the fact, that time is traveling in one direction. It says something about entropy, and nothing about time.

Are you asking what time actually is? If it is a real thing in itself? Or just a man made tool to explain relationships between co-ordinates/events?
I think that's is a different question to the original which was asking about human experience and flow of time.

 

[Mister T]

Yes, as they are causal events,

Causally connected events cannot have a spacelike separation. This follows immediately from the Principle of Relativity.

 

[NoTe]

Are you asking what time actually is? If it is a real thing in itself? Or just a man made tool to explain relationships between co-ordinates/events?

Yes.

I think that's is a different question to the original which was asking about human experience and flow of time.

Maybe. How people experience the flow of time isn't really a question to which physics can give a satisfactory answer. Since this is a physics forum, I tried to translate the OP's question into a physics question. But maybe that was not his aim (?).

Still I think, even within the physics community, there's a lot of misconceptions and/or misunderstandings about the entity time, and it's a thing that's interesting me highly and that I have given a lot of thoughts, so that's why I give my opinion here.

 

[Nugatory]

Are you asking what time actually is?

Yes

It's hard to improve on Einstein's answer: Time is what a clock measures.

One of the nice properties of this definition is that it makes it clear that proper time, the thing that you experience as the flow of time, is what can be measured and is experienced as flowing.

 

[NoTe]

It's hard to improve on Einstein's answer: Time is what a clock measures.

I totally agree.

@ Nugatory: I haven't been on this forum so long (only a few months), but I remember a contribution of yours (in November?) that I was willing to react upon, but didn't at the time, unfortunately... (while at the same time I value your contributions very highly, and especially the contribution that ended with the lines I'm now referring to!):

You said something like: 'we are traveling into the future at one hour per hour'. It's precisely this kind of statements, that I have doubts about: it isn't so much untrue, but it's comparible with saying 'temperature is rising with temperature (at one degree per degree)' or 'mass is increasing with mass (at one kilogram per kilogram)'. Seeing it from a physics point of view, it doesn't really say anything, really. In the end, it's just the line y=x.

I stick to the idea of time being a scalar quantity, having no direction at all. In SR as well.

 

[pinball1970]

I stick to the idea of time being a scalar quantity, having no direction at all. In SR as well.

Lee Smolin wrote about the nature of time, it may interest you. "Time Reborn," 2013

 

[pinball1970]

It's hard to improve on Einstein's answer: Time is what a clock measures.

I will go with that, the equations are hard enough.

 

[PeterDonis]

I stick to the idea of time being a scalar quantity, having no direction at all.

Not as you are using the term "scalar quantity". Proper time is a scalar function; it is a mapping of real numbers to points on a timelike curve in spacetime. Proper time "flows" in the sense that this mapping is ordered, just as the real numbers are ordered: given any two points on the curve, the proper time numbers assigned to them will be ordered--one will be greater than the other. The point whose proper time number is greater is the "future" one of the pair. The numbers themselves don't have "direction", since a real number is just a number, not a vector; but the ordering of the numbers gives an ordering of the points on the curve, and that ordering is the "direction" of time.

 

[stevendaryl]

Yes.

Maybe. How people experience the flow of time isn't really a question to which physics can give a satisfactory answer.

But physics can say a lot about that, and the video about entropy did exactly that.

 

[stevendaryl]

You said something like: 'we are traveling into the future at one hour per hour'. It's precisely this kind of statements, that I have doubts about: it isn't so much untrue, but it's comparible with saying 'temperature is rising with temperature (at one degree per degree)' or 'mass is increasing with mass (at one kilogram per kilogram)'. Seeing it from a physics point of view, it doesn't really say anything, really. In the end, it's just the line y=x.

But you wanted to connect the question to physics, and as far as the physics of relativity is concerned, we live in 4-dimensional spacetime, not 3-dimensional space. We have a velocity through that 4 dimensional spacetime, and one component of that velocity is the number 1 hour per hour.

It's not completely vacuous, because it is possible to move at a velocity through the time dimension that is greater than 1 hour per hour. If you are traveling at 90% of the speed of light, then your velocity through the time dimension will be 2.29 hours per hour. That is, for every hour you spend traveling (according to your own watch), you will travel 2.29 hours into the future.

 

[strangerep]

Why is everything in the 'now' flowing toward the future, and not the past?

The construction of one of our best theories of physics (quantum field theory and the standard model) relies not just on the relativity (i.e., symmetries expressed by the Poincare group of transformation). It needs to be augmented by a concept of causality. I.e., a "forward-time" direction (actually a forward light cone) at every event on the spacetime manifold. "Why" it's there is still a mystery. Although there are tantalizing hints in General Relativity (in the behaviour of congruences of geodesics) these usually rely on some notion of positivity of energy, which is a kind of time direction in disguise.

Also, why do we all experience this flow the exact same way?

Nature seems to abhor sharp corners (discontinuities), and this manifests in the fact that nearby observers seem to experience the direction of time as the same (though not its "rate" -- think of 2 observers in relative motion). I.e., causality is a continuous ray field on spacetime -- there's no sudden change of causality direction between one point and another infinitesimally close point. This augments the usual concept of spacetime as a Riemannian space determined by a metric. (This can also be expressed in more high-falutin' terms of general topology, since spacetime is assumed to be a differentiable manifold, with locally-Euclidean topology.)

So, sorry, I don't think there's a "why" answer. We just have to keep working to find improved mathematical models of physics that correspond better with empirical results.

 

[NoTe]

But you wanted to connect the question to physics, and as far as the physics of relativity is concerned, we live in 4-dimensional spacetime, not 3-dimensional space. We have a velocity through that 4 dimensional spacetime, and one component of that velocity is the number 1 hour per hour.

I still don't agree. 4-Dimensional spacetime is a nice mathmatical concept dealing with events and Lorentz transformations between them, it's not existing of four spatial dimensions, though.

It's not completely vacuous, because it is possible to move at a velocity through the time dimension that is greater than 1 hour per hour. If you are traveling at 90% of the speed of light, then your velocity through the time dimension will be 2.29 hours per hour. That is, for every hour you spend traveling (according to your own watch), you will travel 2.29 hours into the future.

And now I couldn't disagree more! I know what you mean, but it simply isn't so. Saying that the other (not traveling) person is traveling with 2.29 hour per hour into the future with respect to the traveller is just as true, or untrue. Only in case the traveler returns, there will turn out to be a time difference between the two; what I was trying to argue, is that they will have measured a different amount of time, not a different kind of time ('faster' or 'slower'). That's completely different from 'traveling into the future' or formulations alike.

 

[Demystifier]

Well, the characteristics of time that are most familiar to us do have to do with entropy. The biggest one: the fact that we remember the past and not the future has to do with entropy. And this is what gives us a sense of "flow" of time.

When people speak of time flowing in one direction, they mean our sense of time, not the dimension.

The fact that entropy grows with time is certainly closely related to our subjective experience of the flow of time. Nevertheless, the fact that entropy grows with time is not sufficient to explain that experience:
https://fqxi.org/community/forum/topic/259

Moreover, the laws of physics are not sufficient to explain any experience:
http://philsci-archive.pitt.edu/12325/

 

[Sorcerer]

OK @stevendaryl, I know what people mean, but I was trying to get back to the physics.

I think there isn't so much to time as many believe there is. It's just a scalar quantity that's very useful in almost every field of physics, but it's not something that's running or moving or flowing, it's a derived quantity that's only there, because of óther things running, moving or flowing. Well, that's how I see it, in physics. Of course, as a human being, it may feel different ('our sense of time').

I see it more as a direction we move in, but I think your description is more "physical," so I suppose that is good. My only concern with the argument that time is just a concept is the things with real physical consequences that depend on it being more than that. For example energy, whatever that is, is linked directly to time through its conservation (and symmetrically, momentum is linked to space in the same way). This can't just be coincidence. Now, you might say energy is totally made up as well, but what it is used to represent is very real. There are just too many such "coincidences" for me to believe that energy is just a concept that has no application to the real universe. And so I can't just accept that time is merely a concept either.

Now granted, Minkowski space might just be a convenient theory that makes accurate descriptions/predictions, but how are you, conceptually speaking, going to get any closer? Every theory is going to have the same short coming, that it's just an explanation of the universe that works.

 

[NoTe]

@Demystifier: I had no time to visit your links (looking very interesting!), but I already do want to say this (perhaps prematurely):

Our experience of a flow of time is not a consequence of anything, other than the fact that that's what we call 'time' in the first place! What has been, we call the past and has a 'lower time value' (earlier) and what has to happen still, we call the future and has a higher time value (later). As physics developed as a science, it was a logical quantity to observe changes against. This led to a lot of useful relations, such as 'entropy increases with time'.

But still, that doesn't say anything about time itself as flowing or moving, other than as a function of time... Saying that time is flowing seems a subjective statement with no more meaning for physics than 'mass is increasing with mass' or 'temperature is increasing with temperature'. In fact: time is flowing with time.

 

[NoTe]

This can't just be coincidence. Now, you might say energy is totally made up as well, but what it is used to represent is very real. There are just too many such "coincidences" for me to believe that energy is just a concept that has no application to the real universe. And so I can't just accept that time is merely a concept either.

But that's not what I'm trying to say. Of course the quantities have real meaning, and moreover, are related by the laws of physics, that I value very high! The thing that I wás trying to explain, is that time is no more special, as a quantity, than f.i. energy or mass. But of course, I may be wrong.