B Can we truly understand the concept of time?

[Levi Woods]

Out of my own curiosity I've looked at questions that physics can't answer yet, and this one "How does time move forward?" Seemed to be the most interesting to me. Any Theories?

 

[phinds]

Out of my own curiosity I've looked at questions that physics can't answer yet, and this one "Why does time move forward?" Seemed to be the most interesting to me. Any Theories?

"Why" questions are not well served by physics; they are more metaphysics / philosophy / religion. The answer to every "why" question can just lead to another "why" question.

Physics describes what is, and time is just what a clock measures.

 

[anorlunda]

Welcome to PF

https://en.wikipedia.org/wiki/Arrow_of_time

Please read that interesting article first. Then come back here if you have parts you don't understand.

 

[Dale]

Out of my own curiosity I've looked at questions that physics can't answer yet, and this one "How does time move forward?" Seemed to be the most interesting to me. Any Theories?

It is just geometry. Since there is only one timelike dimension a surface of constant proper time forms a hyperboloid of two sheets making a clear distinction between past and present. By the way, this does not require time to “move”, but the future and past are geometrically distinct.

 

[osilmag]

I have thought of it before as an entropy "concept". Where materials decay or give up energy as time goes forward and become restored or go back in time as energy is put into said things.

 

[osilmag]

For example the mitochondria in your body slow down their production of energy as time progresses. So in that example, time would be slowing down, but still moving forward.

 

[phinds]

For example the mitochondria in your body slow down their production of energy as time progresses. So in that example, time would be slowing down, but still moving forward.

Processes slow down. Time does not.

 

[zuz]

The fadter you travel, the slower time moves

 

[zuz]

Faster

 

[phinds]

The fadter you travel, the slower time moves

No, that is absolutely not true. You need to study time dilation.

YOU, right now as you read this, are traveling at almost the speed of light relative to a particle in the accelerator at CERN. Has your time slowed down any?

 

[zuz]

I believe it has been proven with atomic clocks on board the ISS sycronized with clocks on the ground

 

[phinds]

I believe it has been proven with atomic clocks on board the ISS sycronized with clocks on the ground

Are you saying that you think that the clocks tick slower or faster? That the time passes at a differnt rate on the plane/ground? They do not. If that IS what you think, then you are misunderstanding the physics involved and have confused differential aging with the local passage of time.

Please read post #10 again until you understand it.

 

[zuz]

I am saying that the clocks show a difference in how much time has passed

 

[phinds]

I am saying that the clocks show a difference in how much time has passed

Yes, that is correct. It does but this is NOT time passing at a different rate which is what your were previously saying was happening when you said " The fadter you travel, the slower time moves". Time moves at exactly the same rate no matter how fast you are traveling because how fast you are traveling is frame dependent but your wristwatch is not frame dependent.

 

[zuz]

These two clocks are recording the passage of time at two different speeds.

 

[phinds]

These two clocks are recording the passage of time at two different speeds.

NO NO NO they are not. You can keep saying something that is incorrect over and over but that does not make it right. I'm done with this thread.

 

[Nugatory]

I believe it has been proven with atomic clocks on board the ISS sycronized with clocks on the ground

What has been proven is that an observer on the ISS (ignoring the effects of gravitational time dilation so they don't unnecessarily complicate the problem) will find that their clock is ticking at a rate of one second per second while the Earth clock is running a bit slower - but also an observer on Earth will find that their clock is ticking at a rate of one second per second while the ISS clock is running slow.

There's no reasonable way of interpreting these facts as saying that "the faster you move, the slower time moves". Trying to do so just gets you to an apparent paradox (How can both both clocks be slower than the other?). Instead you have to understand the relativity of simultaneity and how anything you say about the rate of one clock relative to another must include a hidden assumption about what "at the same time" means. Google for "Einstein train simultaneity", and when you understand how it applies to time dilation you will be ahead of about 90% of the people who think they understand it.

 

[Nugatory]

This discussion of "the faster you travel, the slower time moves" is somewhat off topic for this thread. If @zuz or others want to continue it, they should do so in a thread of its own in the Relativity section... but please please please take a moment to look at some of the hundreds of posts we already have on the subject.

 

[lightarrow]

These two clocks are recording the passage of time at two different speeds.

Your incorrect idea is something that popular books have generated in the minds of an infinite number of students/interested people. It's something so deeply radicated in some of their minds that there have been hundreds of never-ending discussions of this specific subjects for at least a century.
Only those who have studied physics seriously for a lot of years are aware of your incorrect statement.

--
lightarrow

 

[lightarrow]

This discussion of "the faster you travel, the slower time moves" is somewhat off topic for this thread. If @zuz or others want to continue it, they should do so in a thread of its own in the Relativity section... but please please please take a moment to look at some of the hundreds of posts we already have on the subject.

Sorry, I hadn't seen your post; anyway I didn't have the least intention to continue the discussion of that subject.

--
lightarrow

 

[Nugatory]

Sorry, I hadn't seen your post; anyway I didn't have the least intention to continue the discussion of that subject.

No problem, that's a fairly common occurrence when two people are posting at about the same time.

 

[David Lewis]

The faster you travel, the slower time moves. (I)t has been proven with atomic clocks on board the ISS synchronized with clocks on the ground.

That's correct. Time passes more slowly in your reference frame for people aboard the ISS.

 

[phinds]

That's correct. Time passes more slowly in your reference frame for people aboard the ISS.

Yes, but he thinks that time passes more slowly for the people aboard ISS in THEIR reference frame, which is NOT correct.

 

[David Lewis]

(H)e thinks that time passes more slowly for the people aboard ISS in THEIR reference frame,

I misread it. I thought he meant his time passes more slowly for the people aboard the ISS in their reference frame.

 

[SWB123]

Out of my own curiosity I've looked at questions that physics can't answer yet, and this one "How does time move forward?" Seemed to be the most interesting to me. Any Theories?

If you think about it 'time' is a 'consequence' of an object's existence and it's relative speed in 'this' physical universe.

'Time' is not observable until an object shows up in this universe. To answer your question the 'movement of 'time' is not taking place at all. 'Time' is also NOT an illusion which humans defined. Think of it this way, the universe is dying a thermal death, and when the very last electron is left to die time would still be in force and there will be a measurable amount of time from the disappearance of the next of the last electron (if there was anyone there to measure it), until the last electron expires. 'Time' itself may expire in measurable amounts (relatively speaking), but it does not move.

 

[alan123hk]

May I ask another question - how can one determine that time isn't moving backwards?

 

[jbriggs444]

May I ask another question - how can one determine that time isn't moving backwards?

You can't.

If we arbitrarily re-label the future as the direction of high order and low entropy and the past as the direction of disorder and high entropy then a human being embedded within such a universe will observe an ordered "past" and a disordered "future" as he moves from future to past.

[This is the thermodynamic arrow of time that appears in the reference referred to in post #3 above]

 

[Buzz Bloom]

If we arbitrarily re-label the future as the direction of high order and low entropy and the past as the direction of disorder and high entropy then a human being embedded within such a universe will observe an ordered "past" and a disordered "future" as he moves from future to past.

Hi jbriggs:

This confuses me. If I ignore "arbitrarily", it seems to be saying entropy correlates with increasing order. My limited understanding of thermodynamics tells me that entropy correlates with increasing disorder. Consequently I am guessing that you are saying that you are "arbitrarily" redefining "the future" so that entropy correlates with increasing order.

Regards,
Buzz

 

[jbriggs444]

This confuses me. If I ignore "arbitrarily", it seems to be saying entropy correlates with increasing order. My limited understanding of thermodynamics tells me that entropy correlates with increasing disorder. Consequently I am guessing that you are saying that you are "arbitrarily" redefining "the future" so that entropy correlates with increasing order.

Right. We have a perfectly normal universe with past = order = low entropy over on our left and future = disorder = high entropy over on our right. We flip the whole thing end for end putting the ordered/low entropy part on the right and the disordered/high entropy part on the left. And we paste on new labels for "future" and "past" with "future" still on the right and "past" still on the left.

For us on the outside, we can examine a human's regression from left (relabeled as past) to right (relabeled as future) as if it were a film running in reverse. For him on the inside without being able to see our labels, it is a perfectly normal futureward progression instead.

 

[lightarrow]

If you think about it 'time' is a 'consequence' of an object's existence and it's relative speed in 'this' physical universe.

'Time' is not observable until an object shows up in this universe. To answer your question the 'movement of 'time' is not taking place at all. 'Time' is also NOT an illusion which humans defined. Think of it this way, the universe is dying a thermal death, and when the very last electron is left to die time would still be in force and there will be a measurable amount of time from the disappearance of the next of the last electron (if there was anyone there to measure it), until the last electron expires. 'Time' itself may expire in measurable amounts (relatively speaking), but it does not move.

Infact if time would "move" , with respect to what would it do it? With respect to the Time?

--
lightarrow

 

[Buzz Bloom]

"How does time move forward?"

Hi Levi:

Since the verb "move" has been explained to be inappropriate, what other verb would you choose to express the concept of your intended question?

How about:
How does time advance from past to future?
or
What is physically taking place which corresponds to time advancing from past to future?

Hope this helps.

Regards,
Buzz

 

[David Byrden]

To the original question, I reply; why do you think that time moves forward?

We can imagine any physical process drawn out on the space-time graph. A flying bird appears there as a tube of meat in the sky. Nothing changes. Nothing "moves forward".

You're really asking a question about human perception, not about time.

David

 

[David Lewis]

Since the verb "move" has been explained to be inappropriate, what other verb would you choose to express the concept of your intended question?

We need to at least explain what we mean by "move" in this situation. (We encounter a similar problem when distant galaxies "move" at superluminal speed.) "Move" can be a misleading term without further qualification.

 

[phinds]

We need to at least explain what we mean by "move" in this situation. (We encounter a similar problem when distant galaxies "move" at superluminal speed.) "Move" can be a misleading term without further qualification.

Which is why it is NOT normal to say that distant galaxies move away from us. The more well-defined (for that case) term is that they recede. Recession velocity is not proper motion, so there is no confusion.

 

[jerromyjon]

Out of my own curiosity I've looked at questions that physics can't answer yet, and this one "How does time move forward?" Seemed to be the most interesting to me. Any Theories?

Asking the question as "By what means does time progress" isn't really a question physics would answer. If I were to ask the physicists of the world to answer a question about time, it would be "Does time progress in discreet steps or is there infinitely smaller scales after milliseconds, nanoseconds, picoseconds..."

 

[zuz]

According to Wikipedia cosmonaut Sergei Krikalev is 22.68 milliseconds younger then he would have been if he had stayed on Earth.

 

[Buzz Bloom]

To the original question, I reply; why do you think that time moves forward?
... You're really asking a question about human perception, not about time.

Hi David:

Unfortunately the OP writer had not participated since the OP, so it is difficult to guess what his intended question meant. For the purpose of post, this is my best guess.

Q: What is physically taking place which corresponds to time advancing from past to future?​

My answer is the following.

A: As time advances from past to future, entropy increases.​

Do you think that this Q and A is about human perception rather than about the physics of time?

Regards,
Buzz

 

[jbriggs444]

My answer is the following.
A: As time advances from past to future, entropy increases.

That accounts for a direction -- an "arrow" of time. It does not account for the rate. Lots of physical processes proceed at rates that correlate well with one another. So we calibrate a scale based on this and call it "time".

 

[Buzz Bloom]

That accounts for a direction -- an "arrow" of time. It does not account for the rate. Lots of physical processes proceed at rates that correlate well with one another. So we calibrate a scale based on this and call it "time".

Hi jbriggs:

As I read the OP, it is not asking anything about the rate of time changing. My interpretation of the OP is that it is asking for a description of a physical process that implies that time is changing, and the change is in the direction of past to future. I am not completely happy with the answer I gave, and I was hoping for a better description than that. The problem I see with my answer is that if the universe were in a state of equilibrium, then entropy would be stable, and as I described the process, time would not change. Intuitively that seems wrong, but I may be mistaken.

Regards,
Buzz

 

[David Byrden]

Do you think that this Q and A is about human perception rather than about the physics of time?

I think that particular question is about human perception, whether it was supposed to be, or not.

Just as this question is about human perception; "Why are the stars so far away?"

We can respond with physics-related reasons why the stars are where they are, but "far away" is the questioner's perception.

David

 

[Levi Woods]

Hi Levi:

Since the verb "move" has been explained to be inappropriate, what other verb would you choose to express the concept of your intended question?

How about:
How does time advance from past to future?
or
What is physically taking place which corresponds to time advancing from past to future?

Hope this helps.

Regards,
Buzz

How time advances from past to future is what I was going for.

 

[David Byrden]

It's hard to explain something that doesn't really exist. The presence of a noun "Time" in the language doesn't imply a corresponding real-world entity.

But, having a general idea of what you're asking, I will try to give you an insight.

Imagine if "time" didn't always move forward, but looped around such that we would eventually repeat the past. You would either
[1] be completely unaware of this, so you'd still come here and ask the same question,
or
[2] you'd be aware of it, which implies that you would remember the previous loop, which implies that you could take different actions and cause a different outcome this time around, and then "time" would no longer be looping. That's a contradiction. It cannot arise.

David

 

[bhobba]

This is a far from trivial topic and requires a whole book to discuss it - with no actual answer at the end of it - but of course along the way your understanding of the issues involved is deepened. I think there are a couple of books on it - the one I recently read is the following:
https://www.amazon.com/dp/0393285235/?tag=pfamazon01-20

My advice is before discussing this topic to become acquainted with the issues involved from a book like the above.

Bottom line is in physics the best definition of time is it is what a clock measures. Go into it deeper - eg the relation of time and entropy - and at the end of it you are aware of a lot new and interesting things - but nothing really is resolved - its still - time is what a clock measures. Time, like space and other foundational things in physics is quite difficult to pin down, beyond simple, almost trite statements.

Thanks
Bill