Do we ever real reach a moment in time?+

[Alan McDougall]

Hi,

 

If time flows smoothly like a river, how can we say we have reached a moment in time?

 

Or maybe time might move in disgrete packages, something like a movie frame, but then we must mix up movement into the argument<

 

What are your thoughts of the question?

[imatfaal]

!

Moderator Note

I think this is more philosophy than physics and have thus moved the thread - if you have a persuasive reason for it to return to Physics let me know.

[swansont]

Hi,

 

If time flows smoothly like a river, how can we say we have reached a moment in time?

 

Zeno's paradoxes have been solved.

 

 

Or maybe time might move in disgrete packages, something like a movie frame, but then we must mix up movement into the argument<

 

What are your thoughts of the question?

 

We haven't reached a point where we can tell if time is discrete.

[michel123456]

Hi,

 

If time flows smoothly like a river, how can we say we have reached a moment in time?

 

Or maybe time might move in disgrete packages, something like a movie frame, but then we must mix up movement into the argument<

 

What are your thoughts of the question?

Time does not flow like a river.

 

When you move, you don't say that "space is flowing". YOU are moving.

 

The same goes for time. Time is not flowing. YOU are displacing in time.

[MigL]

Are you sure about that Michel123456 ???

 

Its possible ( in some specific cases ) to be stationary in space.

How would you go about being 'stationary' in time, then ???

Edited April 24, 2013 by MigL

[swansont]

 

Its possible ( in some specific cases ) to be stationary in space.

How would you go about being 'stationary' in time, then ???

 

You have a fixed rate of motion through spacetime — your velocity four-vector is invariant with a length c. If you move spatially, the time portion of the motion decreases, i.e. there will be time dilation. The closest you can be to stationary in time is if you move arbitrarily close to c

[elfmotat]

 

You have a fixed rate of motion through spacetime — your velocity four-vector is invariant with a length c. If you move spatially, the time portion of the motion decreases, i.e. there will be time dilation. The closest you can be to stationary in time is if you move arbitrarily close to c

The time component of four-velocity increases when you move spacially. The length remains constant because the inner product isn't positive-definite.

[swansont]

The time component of four-velocity increases when you move spacially. The length remains constant because the inner product isn't positive-definite.

 

Yes, indeed. Sloppy/ambiguous wording on my part. I should have said the contribution decreases, owing to the - sign.

[michel123456]

Are you sure about that Michel123456 ???

 

Its possible ( in some specific cases ) to be stationary in space.

How would you go about being 'stationary' in time, then ???

Is it possible to be stationary in space? I wonder.

What is possible is to move at the same pace with other things. Standing at rest upon Earth's surface is equal to rotating at 40000 km/24h at the equator = roughly 1600km/h (twice the speed of a jumbo jet).

And you feel nothing while moving at that speed, exactly as you feel nothing while traveling in time.

[md65536]

Its possible ( in some specific cases ) to be stationary in space.

How would you go about being 'stationary' in time, then ???

Stationary in space is relative to a chosen frame of reference.

Why can't "stationary in time" be exactly the same, with a convention where you are always at time 0 in your chosen frame of reference and the time of past events is constantly increasing relative to you?

 

Edit: Nevermind, even if chose coordinates where you stayed at time 0, it doesn't mean you stay fixed relative to any event, while it does make sense to stay stationary in space relative to some object.

Edited April 24, 2013 by md65536

[michel123456]

Stationary in space is relative to a chosen frame of reference.

Why can't "stationary in time" be exactly the same, with a convention where you are always at time 0 in your chosen frame of reference and the time of past events is constantly increasing relative to you?

 

Edit: Nevermind, even if chose coordinates where you stayed at time 0, it doesn't mean you stay fixed relative to any event, while it does make sense to stay stationary in space relative to some object.

You were going right.

 

Both your edit & first sentence state that an event in the past is constantly increasing its "distance" (read "time") relative to you. That is correct.

 

But your brother is aging as you are. The "distance" (read "time') between you is not changing.

 

(edit)

you are "traveling in time" together with your brother the same way that you are "traveling in space" together with the surface of the Earth.

Edited April 25, 2013 by michel123456

[MigL]

As simply as possible...

 

Draw a space-time diagram where the X-axis denotes position and has units of 300000 km, and the Y-axis represents time with units of seconds.

A vertical line such as X=constant, indicates stationary position. A horizontal line, Y=constant, indicates stationary in time.

Note that a light cone has, in this instance, a V-shaped slope of +/-1 ( 45 degree ), and while a vertical line is perfectly acceptable, a horizontal one is NOT since it falls outside the light cone and implies FTL motion.

 

As swansont and elfmotat have hinted at, this applies to events and frames where v<c, not to massless particles such as photons where v=c.

[Alan McDougall]

If a person (a) is stationary in relation to a second person (b), who is walking towards him (a), time ticks slower for the second person (b) than the first (a). Thus the second person ages at an infinitesimally slower rate than the first person (a).

 

Thus relativity is in action , even at a walking pace.

[michel123456]

There are 2 ways of seeing things.

1. Let's say like the OP that time is flowing.

You have a body (that's you) sitting on a chair doing nothing and time is flowing.

In this situation the thing that exist is you and time is like a river. You are like a piece of wood floating in the river but the piece of wood is standing still while the river flows, meaning that the piece of wood is not transported by the flow of time. It is more like someone standing in the wind.

 

2. Now let's say that the object is "traveling in time".

You have a body (that's you again) sitting on a wheelchair that travels into a kind of substrate called "time", not so different than the other substrate called "space". You are a piece of wood transported by the river: time still "flows" but it is the body that travels.

 

No matter what 1 or 2 you chose, in both concepts there is always one body (that's you).

Which seems evident (you may ask yourself what I am going to).

 

There is no elongated, stretched, extruded 4D body that extends over time.

A body is a 3D reality, it is not the 4D sum of all body-events that one encounters over time.

IOW if an external observer looks at the river, the piece of wood is still a piece of wood. If you go back in the river you may find no piece of wood because it is gone.

 

If you understand what I mean.

Edited April 26, 2013 by michel123456

[MigL]

Make all the river analogies you want as no-one ever said time WAS a river. Just like an electron is not a small aphere or a wave, but it can at times act as either depending on the type of experiment, so will time act like a river under certain considerations. However what 'flows' is actually the 'now moment', at one second per second usually, since all events in space-time are fixed, past, present and future. This 'now moment' is like a vertical slit moving across a window pane as it moves foreward in time and the view changes ( we remember the past but have no recollection of future events ), however it moves foreward at differing speeds along the length of the slit due to differing conditions and the finite speed of light ( there is no universal now ), just like river currents are different due to differing conditions in the cross-section of the flow.

 

This is just an opinion of course, but you do see how difficult it is to describe complex phenomena like time using simple, everyday analogies ?

[Alan McDougall]

There is the theory of "Presentalism", where a person only exist in the present, the past is gone and no longer exist, and the future is still to come and also does not exist. Only the present moment reflects reality.

[tar]

How about external clocks?

 

Ones we move toward tick faster, (blue shifted). Ones we move away from, or move away from us, tick slower (red shifted).

 

If a twin leaves the other at a high speed, each would be red shifted to the other. If things are relative, there would be no distinction as to which one was aging more slowly, as they both would be ticking slower to the other.

 

A return trip, would cause a blue shifting for each while observing the other, and when they got together again in space, they should be the same age. No?

[michel123456]

There is the theory of "Presentalism", where a person only exist in the present, the past is gone and no longer exist, and the future is still to come and also does not exist. Only the present moment reflects reality.

Yes.

The consequence of presentalism is that if an hypothetical time traveler could go back in time, he would find nothing.

He would not find himself as he was some time ago, because the guy-he-was-some-time-ago is gone, he has traveled in time.

[swansont]

How about external clocks?

 

Ones we move toward tick faster, (blue shifted). Ones we move away from, or move away from us, tick slower (red shifted).

 

If a twin leaves the other at a high speed, each would be red shifted to the other. If things are relative, there would be no distinction as to which one was aging more slowly, as they both would be ticking slower to the other.

 

A return trip, would cause a blue shifting for each while observing the other, and when they got together again in space, they should be the same age. No?

 

No. Moving clocks run slow. Even though the frequency of the arriving signal increases when the sources are moving toward each other, the moving clock still runs slow

 

http://www.einsteins-theory-of-relativity-4engineers.com/twin-paradox-2.html

[PeterJ]

I read the OP as asking about the reality of instants of time. Contrary to Swansont I do not believe Zeno's paradoxes have been solved, and neither does one Australian physicist who recently wrote a paper about the reality of instants and whose name I forget.

 

I think this question is closely related to the issue of the true nature of the continuum. Thanks to Imatfaal I can refer to Weyl as having something interesting to say about this, since for him (as far as I can make out) a true continuum would have no extension and thus, in the case of time and space, no discrete instants or points. .

[swansont]

!

Moderator Note

Twin paradox discussion moved http://www.scienceforums.net/topic/74631-the-twin-paradox/

[Alan McDougall]

Time does not flow like a river.

 

When you move, you don't say that "space is flowing". YOU are moving.

 

The same goes for time. Time is not flowing. YOU are displacing in time.

 

How can you make a statement ("Time does not flow like a river") as if it were fact, please give me proof and reference?

[michel123456]

I made this statement in order to make the concept stronger

 

How can you make a statement ("Time does not flow like a river") as if it were fact, please give me proof and reference?

No proof. I may be wrong.

 

Reference?

Etienne Klein
wrote (sorry for my word-by-word translation from french) " We already
said that when the language speaks about time, it does it often in the
wrong way. What does it mean when, for example, we are repeating that
time "flows", "passes through", "vanishes"? This way of talking which
associates time with lability and escape, has become common. By the way,
it is not neutral. First of all, it is a language abuse. Nobody is
arguing that we may say that time is made from any thing that passes.
But to deduct that it is time itself that passes through is making a
shortcut and confusing content and container (“contenant et contenu”,
which means also subject and object). The succession of the instants of
time (past, present, future) is not the same thing that the evolution
(“succession”) of time itself. They (the instants) pass, it (the time)
does not. Then,, why is it more correct to say that time passes through
than to say that the road is moving (“le chemin chemine”) or that a
music book is singing? If we admit that any reality is temporal, saying
that time is passing through is equal to say that, in reality, what is
passing through is the sum of things and phenomenas that are containing
by time. In a few words, it is the entire reality that passes through,
and not time itself”
From « DOES TIME EXIST? ( LE TEMPS EXISTE-T-IL?)
» ed. Le pommier, 2002, pg 22,23. The smallest (and most condensated)
book on my bookshelves.

Etienne Klein is a physicist and phd in
philosophy, working at CEA (French Commissariat a l’Energie Atomique)
and professor at Ecole Centrale de Paris.

I agree with him: the entire reality passes through, and not time itself. Time is a container, like space. The container does nothing, the things inside the container are doing things.

Edited June 9, 2013 by michel123456

[Alan McDougall]

Hi michel,

 

I also postulate that time might be an illusion, by which for instance we need to measure movement. When you go into the mystery of time it can get very complicated because time is so interlinked with most of our life events

[michel123456]

Hi michel,

 

I also postulate that time might be an illusion, by which for instance we need to measure movement. When you go into the mystery of time it can get very complicated because time is so interlinked with most of our life events

Yes it gets complicated.

I don't think Time is an illusion though.

I think we are so much impregnated into time that we cannot understand it. We are like humans before Newton, finding so natural that up is up and down is down.

To me Time is something somewhere very deep into physics and not into metaphysics nor philosophy. IMHO.