What Is Time and Why Do We Misunderstand It?

[thunderhadron]

Good afternoon fiends.
I am wondering what exactly is time. Some say, quite inaccurately which flows irrespective of everything.
I am pretty confuse in it.
Thank you in advance.

 

[ZapperZ]

Previous threads on this very same topic have had ugly endings, for the threads and for some of the participants involved. I strongly suggest that all participants (and the OP) heed the PF Rules that everyone had agreed to before proceeding. Do not say that you have not been warned.

Zz.

 

[harrylin]

Hi for sure the following threads will be helpful, especially the first one:

https://www.physicsforums.com/showthread.php?t=537940 "What is time"
https://www.physicsforums.com/showthread.php?t=543416 "How did Einstein Define Time"
https://www.physicsforums.com/showthread.php?t=577065 "The problem of time"

 

[Naty1]

Time is one of those things in science that is difficult to understand. But so is distance and mass, for example, if you stop and think about them. Each has its unique characteristics.

One good way to think about time: "Time is natures way of keeping everything from happening at once".

Time SEEMS to pass at some fixed constant rate; distance also seems to be fixed, say, between two objects on a table.

Yet Einstein showed us neither is 'absolutely' correct: time and distance varying according to different observers. It is the speed of light that is constant! In fact, what one rapidly moving observer sees as 'time' another rapidly moving observer interprets as distance. All this is incorporated into special relativity. That can also be confusing!

 

[K^2]

There are a number of related, and yet some what different concepts of time in physics.

Time is a coordinate in general relativity. It is special in that it has an opposite sign in the metric to the spatial coordinates.

Proper time is a bit closer to what most people think of as time. It's what you would measure with a clock. It's also the time that shows up as parameter in non-relativistic quantum mechanics, and you can think of it as the "age" of something.

And then there is time in sense of sequence of events. This is the tricky one. With the above two, forward and backwards directions in time are equivalent. And there is no "flow". Time as a coordinate just is. However, if you have a sequence of events that are casually related, you can always say that event 1 happened first, then event 2, then event 3. This is what we understand as the flow of time. You from five minutes ago definitely comes before you now, because you can think back to how things were five minutes ago.

This one isn't understood, and the reason for all of the confusion about the concept of time. The only hint we have is the entropy. Entropy always increases, so maybe entropy increase defines the time flow. It'd also make sense with information flow, as storing information requires an entropy increase. But this hardly takes care of all the questions, and it's practically untestable at this stage. So it's all very speculative.

If you want to know more about time as coordinate in space-time or about proper time, and why the clocks in different coordinate systems don't always match, this is a good place to ask these questions. If you want to understand why the time "flows", you won't get anything beyond guesses and speculation, so this is not a good place to discuss them. You'll just have to accept that nobody really understands it yet.

 

[apchar]

Time is natures way of keeping everything from happening at once. ;->

 

[davenn]

Time is natures way of keeping everything from happening at once. ;->

yeah that's my favourite quote :)

Dave

 

[Chronos]

Einstein held the throroughly pragmatic view that time is what clocks measure. But, of course he convincingly argued there was no such thing as an 'absolute' clock. For an engaging discussion, see http://www.iep.utm.edu/requires/.

 

[genericusrnme]

baby don't hurt me

oh wait, wrong song
There's already been about 100+ threads on this if you use the search function though

 

[VaqarAhmed]

Time is one of those things in science that is difficult to understand. But so is distance and mass, for example, if you stop and think about them. Each has its unique characteristics.

One good way to think about time: "Time is natures way of keeping everything from happening at once".

Time SEEMS to pass at some fixed constant rate; distance also seems to be fixed, say, between two objects on a table.

Yet Einstein showed us neither is 'absolutely' correct: time and distance varying according to different observers. It is the speed of light that is constant! In fact, what one rapidly moving observer sees as 'time' another rapidly moving observer interprets as distance. All this is incorporated into special relativity. That can also be confusing!

nature has autonomy?

 

[azizlwl]

Time is natures way of keeping everything from happening at once. ;->

Does this means there's place where all happening once as they say time is frozen in black hole. Or does it happened like BB where time started from no time.

 

[DeepSpace9]

Time is a figment of the imagination, IE Zeno Paradox and or Arrow Paradox.

 

[rbj]

Previous threads on this very same topic have had ugly endings, for the threads and for some of the participants involved. I strongly suggest that all participants (and the OP) heed the PF Rules that everyone had agreed to before proceeding. Do not say that you have not been warned.

so Z, can you be more specific about what to avoid?

it's interesting, but i went to the Wikipedia entry and they had recently had a good definition that just got yanked.

Time is the indefinite continued progress of existence and events that occur in apparently irreversible succession from the past through the present to the future.¹ Time is a component quantity of many measurements used to sequence events, to compare the durations of events and the intervals between them, and to quantify rates of change of quantities in material reality or in the conscious experience.

in raw wiki language they, until recently, had:

'''Time''' is the indefinite continued [[sequence|progress]] of [[existence]] and [[event (philosophy)|events]] that occur in apparently [[irreversible process|irreversible]] succession from the [[past]] through the [[present]] to the [[future]].<ref>http://www.thefreedictionary.com/in+time</ref> Time is a component quantity of many [[measurement]]s used to [[sequence]] events, to compare the durations of events and the intervals between them, and to [[quantification|quantify]] rates of change of quantities in [[scientific realism|material reality]] or in the [[consciousness|conscious]] [[qualia|experience]].<ref name=DefRefs01>

i thought that was a pretty good initial definition, before getting into what "time" means to various disciplines (like "time" as a 4th dimension in spacetime in physics or the conceptual reversibility of time regarding elementary anti-particles). i don't know why they recently took that out.

 

[Drakkith]

Time is a figment of the imagination, IE Zeno Paradox and or Arrow Paradox.

I don't agree. Whatever time may be it is as real as distance is. Otherwise clocks wouldn't move, particles wouldn't decay, etc.

 

[detective]

time is not a problem for the physical universe to have to grapple with...

time only becomes a problem when ''we'' invoke it with our conscious needs to reconcile a function or system that can't be understood...which then becomes a metaphysical issue

it appears that entropy and decay is not winning the war in the observable universe and ''time'' will ''travel'' in a forward motion for us, or millenium beyond to ''measure''...that is possibly a big reason why time is vexing ...

 

[Drakkith]

time is not a problem for the physical universe to have to grapple with...

time only becomes a problem when ''we'' invoke it with our conscious needs to reconcile a function or system that can't be understood...which then becomes a metaphysical issue

What?

it appears that entropy and decay is not winning the war in the observable universe and ''time'' will ''travel'' in a forward motion for us, or millenium beyond to ''measure''...that is possibly a big reason why time is vexing ...

And again, what?

 

[detective]

hello Drakkith and all .. sorry about the abstract nature of my posts...

..we experience the passing of time because it is important to our functioning and beyond that, to our ability to measure experimental data...but does the ''unconscious'' universe in the course of its function ''need'' that mandate ?

time is just a constant ... it cannot be stretched, dilated or stopped...it's only when we ask too much of its reason for being, that our understanding fails...and who has never pondered the question .. ''is there no beginning, nor end, to time ?''...

 

[Drakkith]

..we experience the passing of time because it is important to our functioning and beyond that, to our ability to measure experimental data...but does the ''unconscious'' universe in the course of its function ''need'' that mandate ?

The "need" for time is as valid as the "need" for distance in my opinion.

time is just a constant ... it cannot be stretched, dilated or stopped...it's only when we ask too much of its reason for being, that our understanding fails...and who has never pondered the question .. ''is there no beginning, nor end, to time ?''...

Perhaps we look too deep into it.

 

[detective]

yes i agree Drakkith .. the problem i find both with time and distance is the infinites (or infinities) the measurements thereof bring with them ..

problem being that we are repulsed mathematically and intellectually with the concept of something being infinite (we will never believe in a perpetual motion machine operating on our planet)...

.we want concrete answers to our endeavours, and the ''open ended'' nature of time and distance tend to make a mockery of our need for the constraints that we would innately prefer to exist ...

 

[LouisB]

Taking the output t of a clock and putting it in equations like any other spatial parameters hide the differences between t and the other spatial parameters. There is no freedom to move in the reverse time direction. It is why the physical approaches which express changes not in terms of a spatial-like dimension t but using a relational approach as first proposed by Leibniz might be more appropriate.

 

[Nizzeberra]

I haven't read the posts in this thread, but the topic is right for yet another question about what time is. I watched the following movie:

http://www.disclose.tv/action/viewvideo/92385/The_Illusion_Of_Time__The_Fabric_Of_The_Cosmos/

Between 13:45 (especially from 15:30) and 16:25 they describe how time passes slower as you move faster through space. But note that "time passes slower" means "the mechanical movement of things (like the arms of a clock, or perhaps the motion of you body parts, like your feet while walking) slows down" (or the wheels of a car, or the compressor blades in an airplane's jet engine).

But since you need your feet moving at a certain speed to keep you velocity constant, or the wheels of the car spinning at a certain rate, they can't possibly be moving slower as we accelerate. That would look quite funky, as if you were sliding across the pavement of the road while your feet were standing still (and thus breaking the laws of physics)... So what do we REALLY mean when we say that "time passes slower"?

By answering that question, I think we take a step closer to the answer of what time is.

My attempt to an answer is the following... Everything (look at it at an microscopic level) is constantly moving through space at the speed of light. However, "standing still" simply means oscillating (vibrating) in random directions around a certain point in space. This oscillation is what we use to measure time in atomic clocks.

Motion in a certain direction is achieved by altering the probability of the oscillation to occur in that direction. The more we move in this "well defined" direction, the less "speed" or "energy" is left for motion in any other direction, and thus "time moves slower" (but it really isn't, it's in some sense constant).

This is my own model of reality, the way I understand things, and I think it works beautifully together with both relativity and quantum mechanics. The wave function in QM defines the "oscillation".

Any thoughts about this?

 

[chill_factor]

Interesting to note that entropy increase defines a "forward" direction in time, and time is affected by gravity.

Is there a link between thermodynamics and gravity? Indeed, could it be possible that gravity is an emergent property?

 

[Nizzeberra]

Interesting to note that entropy increase defines a "forward" direction in time, and time is affected by gravity.

Is there a link between thermodynamics and gravity? Indeed, could it be possible that gravity is an emergent property?

If you agree on my model of time (see my previous post), there are two different definitions of time. The first is the one you can measure - the vibration of particles. This is the "time" which is affected by gravity (actually, it's just the wave function that is affected by gravity). But time in this sense is not a real property of anything, it does not exist.

I know that the following is a very non-scientific statement, since science is about things you can measure... But real time can't be measured, and is "moving forward" at a constant pace. The word "forward" in this case only means that particles change states randomly within the space defined by the wave function, at a constant pace. Entropy and the direction of time are emergent properties of this process.

 

[salzrah]

Time does not exist. There is only a now- the present. Time is the measure of change. Think about it - one second is the change of the second hand from one point to another. We all perceive time differently based on our consciousness. The more conscious we are of something and change occurring, then the more we experience the present. Because those who are more conscious experience more of the present they essentially experience time in a greater quantity. For example, a person who is barely conscious doesn't experience the present continuously but in small amounts, leading to that person having a sensation that more time has passed when in actuality they just have not been perceiving the present to its full potential.
Have you ever tried solving a problem with your full attention/focus? Sit down and time yourself doing something that requires a lot of focus and attention and you will feel that a lot of time has passed when actuality it has not. Or you could say you "experience" more of the present relative to how much a second hand has changed.
We all know people who are great problem solvers, who think "fast", and exceptionally smart. Turns out, from all the people I know like this, they are usually self-unaware of how they behave showing signs of arrogance. However, they behave in that manner because their full consciousness is given to and concentrated on their surroundings and whatever problem they are solving or what they are reading or who they are talking to. This leaves little room to be self-conscious of what they're doing.
Once you realize there exists only a present will you then truly have control of your brain power. People like I just described also show good memorization skills, largely because the more conscious you are of something the better chances you have of remembering it. Living in the present brings you a strong conscious and powerful mind.

 

[Drakkith]

Between 13:45 (especially from 15:30) and 16:25 they describe how time passes slower as you move faster through space. But note that "time passes slower" means "the mechanical movement of things (like the arms of a clock, or perhaps the motion of you body parts, like your feet while walking) slows down" (or the wheels of a car, or the compressor blades in an airplane's jet engine).

It also means that nuclear decay half lives are longer, which is not mechanical. This is one way to verify the validity of Special Relativity. Take a radioactive substance with a known half life and accelerate it to a very very high velocity, then measure the decay rate. It will be reduced by a rate equal to the amount of time dilation.

But since you need your feet moving at a certain speed to keep you velocity constant, or the wheels of the car spinning at a certain rate, they can't possibly be moving slower as we accelerate. That would look quite funky, as if you were sliding across the pavement of the road while your feet were standing still (and thus breaking the laws of physics)... So what do we REALLY mean when we say that "time passes slower"?

No, this is not what would happen. If you were able to run at 0.99c, your feet would be moving VERY quickly, fast enough to propel you at 0.99c relative to the ground. They HAVE to, otherwise you wouldn't be moving. Keep in mind that your feet are stationary with respect to the ground whenever they touch it and are propelling you forward.

This is my own model of reality, the way I understand things, and I think it works beautifully together with both relativity and quantum mechanics. The wave function in QM defines the "oscillation".

Your model makes absolutely no sense in regards to real physics, nor are personal theories and models allowed on PF. The wave function is a mathematical formula in quantum mechanics describing the quantum state of a particle and how it behaves. This does NOT include any such vibrations at c.

Interesting to note that entropy increase defines a "forward" direction in time, and time is affected by gravity.

Is there a link between thermodynamics and gravity? Indeed, could it be possible that gravity is an emergent property?

The possibility may exist, but current models don't say anything about that.

I know that the following is a very non-scientific statement, since science is about things you can measure... But real time can't be measured, and is "moving forward" at a constant pace. The word "forward" in this case only means that particles change states randomly within the space defined by the wave function, at a constant pace. Entropy and the direction of time are emergent properties of this process.

What use is it to bring something to a science forum that isn't capable of being supported by observation and evidence?

 

[Nizzeberra]

So we agree.

My statement about "constant motion at c" was bold. Sorry about that. I have thought this over one more iteration now.

Think about a particle standing absolutely still. First of all, it isn't possible, and as a rhetorical question I can ask "why"? But let's assume it is possible. What could you say about the passing of time looking at this particle? Nothing, since time could as well be standing still (time can't exist without energy, and vice versa).

So time has to be defined as a sequence of state changes in particles. X number of state changes equals 1 second. This is something you can observe, and this is the definition of time, as far as I know. Do you have any other definition?

Now let's rephrase my statement about "constant motion at c"... Everything is "moving" in the sense things are changing some state, at a constant rate. If things aren't, then the very common statement used when discussing relativity "if standing still in space, you are moving through time at full speed" is false, due to the definition of time. (Is this a false conclusion?)

So if time is "rate of state changes", time is always constant and never slows down, if looking at the sum of events. The only thing that happens when accelerating something close to c is that the state change "moving some distance along the direction of motion" becomes more likely while "let's do some radioactive decay" becomes less likely. You can see motion as discrete little jumps since particles "teleport" randomly within the "cloud" defined by the wave function when it collapses (using the Copenhagen interpretation).

So if you are only looking at a single type of event (like radioactive decay), then yes, time is slowing down. But if looking at the sum of events, time is constant. Am I wrong? (And is this a personal theory of mine, or mere conclusions, personal or not)?

 

[Drakkith]

Think about a particle standing absolutely still. First of all, it isn't possible, and as a rhetorical question I can ask "why"? But let's assume it is possible. What could you say about the passing of time looking at this particle? Nothing, since time could as well be standing still (time can't exist without energy, and vice versa).

Surely you aren't suggesting that time doesn't pass for objects in their minimum energy state or for free particles that are at a standstill in their own frames of reference?

So if time is "rate of state changes", time is always constant and never slows down, if looking at the sum of events. The only thing that happens when accelerating something close to c is that the state change "moving some distance along the direction of motion" becomes more likely while "let's do some radioactive decay" becomes less likely. You can see motion as discrete little jumps since particles "teleport" randomly within the "cloud" defined by the wave function when it collapses (using the Copenhagen interpretation).

The Copenhagen interpretation of QM has nothing to do with what time is. Particles do not sit there and constantly change states while free. The wave function describes where a particle might be upon measurement, it says nothing about what the particle is "actually doing" when you aren't measuring it.

So if you are only looking at a single type of event (like radioactive decay), then yes, time is slowing down. But if looking at the sum of events, time is constant. Am I wrong? (And is this a personal theory of mine, or mere conclusions, personal or not)?

Yes, you are incorrect. Time is actually passing at a different rate for different observers in different situations, such as different velocities or different positions in a gravity well.

So time has to be defined as a sequence of state changes in particles. X number of state changes equals 1 second. This is something you can observe, and this is the definition of time, as far as I know. Do you have any other definition?

I don't think this is a definition of what time is, just one way to measure time.

Now let's rephrase my statement about "constant motion at c"... Everything is "moving" in the sense things are changing some state, at a constant rate. If things aren't, then the very common statement used when discussing relativity "if standing still in space, you are moving through time at full speed" is false, due to the definition of time. (Is this a false conclusion?)

Things do not have to change states in order for their to be time though. An atom will gladly sit in its minimum energy state forever until a photon impacts it, promoting it to an excited state. While in its minimum energy state the atom is NOT constantly changing states. Do you know what "state" means?

 

[Nizzeberra]

Surely you aren't suggesting...

First of all... Minimum energy state does not equal zero energy. A temperature of absolute zero is not possible. There is always a small temperature. And what is temperature if not vibration? If "minimum energy state" means "absolute rest", and no time can be measured, time does not exist, since science is about the things you can measure.

Second, a wavefunction collapses when "observed". The only thing needed to observe a particle is another particle. If the entire universe would consist of a single (stable) particle, the concept of time would be pointless. And if you can't measure time, time does not exist (since science is about the things you can measure). So you need at least two particles, and two particles will always "vibrate" (change states, in my definition of state as "position (x, y, z)" is a state) regarding each other. It will just take more or less "time" before they "observe" each other and the wave function collapses. After the collapse, each particle's wave function will "expand" (or whatever you want to call it) as the position will become more and more diffuse with time, until it collapses when the particles interact again. This process is what I call "changing state" (since the position has changed).

I can't imagine a particle with a constantly well defined position, if not constantly observed. But can particles and/or fields be constantly interacting, or do they just interact very frequently? I would like to say "frequently", since that would explain the small unavoidable vibration (temperature) every particle has. This frequency at which they interact, is the frequency of state changes I'm talking about.

 

[robinpike]

My attempt to an answer is the following... Everything (look at it at an microscopic level) is constantly moving through space at the speed of light. However, "standing still" simply means oscillating (vibrating) in random directions around a certain point in space. This oscillation is what we use to measure time in atomic clocks.

Motion in a certain direction is achieved by altering the probability of the oscillation to occur in that direction. The more we move in this "well defined" direction, the less "speed" or "energy" is left for motion in any other direction, and thus "time moves slower" (but it really isn't, it's in some sense constant).

Any thoughts about this?

Hi Nizzeberra,

That is a very perceptive idea as to how the rate of time can appear to change, for a system that has a fundamental rate of time that is constant (such as that given by the constant speed of light).

Have you any more ideas on this as an explanation?

Robin

 

[robinpike]

Yes, you are incorrect. Time is actually passing at a different rate for different observers in different situations, such as different velocities or different positions in a gravity well.

Take the example of a plant that grows more slowly in winter than in summer. Because we understand how plants grow, we can draw the conclusion that the plant's slow growth is not down to the rate of time changing for the plant, but down to a non-time related factor - in this case temperature and the amount of sunlight being reduced.

What is the basis to conclude that two particles moving in relation to each other, have a different rate of time? And which one has the faster / slower rate of time?