# Is time a force?

## Summary:

Is time a force ?

## Main Question or Discussion Point

This is a puzzle to me, time dilation seems to be stating two different times can exist (at least), i am asking if this is the case not demanding it is so, please help. I do not have a science background so i will be listening closely to what those that do, have to say.

Momenta

Similar to the twins paradox (which isn’t a paradox at all if you take relativity of simultaneity into account) let us replace the twins with two clocks placed inside vacuum flasks then remove everything from the flasks leaving as close to nothing as possible around the clocks.

Clock 1 remains here as clock 2 takes the journey and undergoes time dilation then returns. The two flasks are then reunited and joined together through a vacuum lock so that there is only one empty space with two clocks inside.

50% of the empty space exists at one time and 50% of the space exists at another time, these separate regions may disperse and mix in any manner you like, be that staying around each clock respectively or atomize throughout the space, nevertheless the 50/50 division remains.(or does it?)

Empty space is often thought to contain nothing at all but this scenario shows empty space seems to exist at two different times, these different times -caused by dilation- are maintaining different spaces here, this implies there is some sort of force around every individual momenta of time-space keeping them separated.

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50% of the empty space exists at one time and 50% of the space exists at another time, these separate regions may disperse and mix in any manner you like, be that staying around each clock respectively or atomize throughout the space, nevertheless the 50/50 division remains.(or does it?)

Empty space is often thought to contain nothing at all but this scenario shows empty space seems to exist at two different times, these different times -caused by dilation- are maintaining different spaces here, this implies there is some sort of force around every individual momenta of time-space keeping them separated.
Because space is empty (i.e. have no features by definition), you cannot distinguish between two empty spaces. Mixing them does exactly nothing.

Ibix
Learn to draw Minkowski diagrams. Time as shown by a clock is simply the spacetime analogue of distance as measured by, for example, a car's odometer. Two cars leaving a factory and following different routes through space to the showroom will have different odometer readings. This doesn't cause anybody philosophical problems. But when two things follow different paths through spacetime and those paths are different lengths, people seem surprised that their path length measuring devices measure different lengths.

Because space is empty (i.e. have no features by definition), you cannot distinguish between two empty spaces. Mixing them does exactly nothing.
I think i am talking about time-space and perhaps features like the presence of physical properties in space, which can be identified through geodesics.

Time as shown by a clock is simply the spacetime analogue of distance as measured by
philosophical? I would not argue a science point with you ever but you're own personal philosophy means nothing here, with respect could you be specific about the actual puzzle because i am truly interested in anybody's answer. What i am seeing is evidence of two different times on the face of the clocks. I may be wrong but the twin paradox actually has a real life age difference, are you saying a twin never existed at a different time?

I think i am talking about time-space and perhaps features like the presence of physical properties in space, which can be identified through geodesics.
"presence of physical properties in space" is a hypothesis which have no experimental confirmation despite of repeative and exhaustive efforts from physics community. Simplest explanation is to assume the hypothesis is false (google "Principle of Relativity" and "Galilean Invariance").

Ibix
I would not argue a science point with you ever but you're own personal philosophy means nothing here,
"My own personal philosophy" is mainstream science - Minkowski's 1908 re-write of Einstein's 1905 maths. If you don't understand it, then trying to interpret what it means is going to be a problem for you.
could you be specific about the actual puzzle because i am truly interested in anybody's answer.
There is no puzzle here if you understand the resolution (or one of the many resolutions) to the twin paradox, as you say you do. You are simply adding bells and whistles to a straightforward scenario. You can do the twin paradox in vacuum (it's usually described in those terms). You can do it in air (the Hafele-Keating experiment, for example). You can do it in evacuated bell jars inside minisubmarines carried round in the bellies of whales. The clocks measure the "distance" (interval is the usual term) along the path they followed through spacetime. How they came to follow that path is just window dressing.
I may be wrong but the twin paradox actually has a real life age difference,
It does - see the Hafele-Keating experiment.
are you saying a twin never existed at a different time?
I don't think this question means anything. The twins' clocks show different elapsed times at the end of the experiment, certainly.

"presence of physical properties in space" is a hypothesis which have no experimental confirmation despite of repeating and exhaustive efforts from physics community. Simplest explanation is to assume the hypothesis false (google "Principle of Relativity" and "Galilean Invariance").
I understand i am happy to retract the word "physical".

"My own personal philosophy" is mainstream science
The clocks measure the "distance
This is meaningless philosophy. The clock only reflects the reality here.

Does this mean a twin has a real life age difference?

It does - see the Hafele-Keating experiment.
I believe it does too and that the clock reflects this real life fact.

I don't think this question means anything. The twins' clocks show different elapsed times at the end of the experiment, certainly.
I don't want to argue how real life facts don't mean anything, the clocks only reflect what is actually happening at the end of the experiment.

I think if there is an actual age difference then that happens with an actual time difference, obviously i am wrong but you lack a simple answer, i don't have a science background but i will take on board what you have said and study on, thanks anyway.

This is meaningless philosophy.
No, it's not. Proper time measures distances in spacetime (that is, lenghts of worldlines). You'll find that in almost every textbook on relativity, and arguing about that when, as you said:

i don't have a science background
is pointless.

Dale
Mentor
Time as shown by a clock is simply the spacetime analogue of distance as measured by
philosophical? I would not argue a science point with you ever but you're own personal philosophy means nothing here
His comment is quite well established science, for more than a century now.

The time shown on a clock is given by:

$$d\tau^2=-ds^2=dt^2-dx^2-dy^2-dz^2$$

which is a straightforward generalization (developed by Minkowski) of the Euclidean distance formula

$$ds^2=dx^2+dy^2+dz^2$$

The Minkowski formula is often called the spacetime interval, and the quantity $d\tau$ is called the proper time. Proper time is what a clock measures and is interesting because it is invariant under any coordinate transform.

Summary:: Is time a force ?

this scenario shows empty space seems to exist at two different times, these different times -caused by dilation- are maintaining different spaces here
Time is not a force, the units are wrong.

The “exist at different times” bit is wrong. When the clocks are reunited then they are at the same event in spacetime. That event will transform to a single event in any reference frame.

The clocks read different amounts because they took different paths to get there. This is exactly analogous to two odometers reading differently if they took different paths. If we both drive from Miami to New York but you go through Washington DC and I go through Chicago when we compare odometers in New York mine will read more than yours. Not because we exist at different places (we are both in New York) but because we took different paths.

The clocks different readings does not indicate some mystical property that can fill a vacuum flask and be mixed. It just indicates that different paths through spacetime have different “length”/spacetime interval/proper time

Ibix
I don't think this question means anything. The twins' clocks show different elapsed times at the end of the experiment, certainly.
To expand a bit:

A and B synchronise clocks. Do they 'exist at different times'? If not, how do you know? If so, how can their clocks show the same thing?

A travels and returns. Their clocks are desynchronised. Do they 'exist at different times'? If so, what does it even mean that their clocks are desynchronised? I mean, I exist at a different time from Albert Einstein. Is my watch synchronised with his or not?

B travels and returns. Their clocks are in sync again. Do they 'exist at different times'?

A travels and returns. Their clocks are desynchronised again. Do they 'exist at different times'? If they resynchronise their clocks, do they 'exist at different times'?
This is meaningless philosophy.
If 'a clock measures "distance" through spacetime' is meaningless philosophy, do you also regard 'an odometer measures distance through space' to be meaningless philosophy? If so, you would seem to be a pure instrumentalist, and I question what purpose there is to you asking any question about interpretation. If not, why is the latter not 'meaningless philosophy'? Why do you believe 'distance through space' to be a meaningful concept but 'distance through spacetime' not to be?
I think if there is an actual age difference then that happens with an actual time difference,
The elapsed times are different, yes. If this is all you mean by "the twins exist at different times" then I'd say that's a bad choice of wording. Just say that the twins experience different elapsed times between their meetups. With the cars, I'd say that they travelled different distances between meetups, not that they "exist at different distances". I'd struggle to know what the latter phrase meant, just like I'm struggling to know what your "exist at different times" means.

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Mister T
Gold Member
The two flasks are then reunited and joined together through a vacuum lock so that there is only one empty space with two clocks inside.
There's a connection between the flasks. Let's say you open it for awhile and then close it back up. There is no experiment that you can perform on the space within the flasks, even in principle, that can determine whether or not the connection had been open for awhile. You have a distinction without a difference, and that means your distinction is physically meaningless.

ohwilleke
Gold Member
Summary:: Is time a force ?

This is a puzzle to me, time dilation seems to be stating two different times can exist (at least), i am asking if this is the case not demanding it is so, please help. I do not have a science background so i will be listening closely to what those that do, have to say.

Momenta

Similar to the twins paradox (which isn’t a paradox at all if you take relativity of simultaneity into account) let us replace the twins with two clocks placed inside vacuum flasks then remove everything from the flasks leaving as close to nothing as possible around the clocks.

Clock 1 remains here as clock 2 takes the journey and undergoes time dilation then returns. The two flasks are then reunited and joined together through a vacuum lock so that there is only one empty space with two clocks inside.

50% of the empty space exists at one time and 50% of the space exists at another time, these separate regions may disperse and mix in any manner you like, be that staying around each clock respectively or atomize throughout the space, nevertheless the 50/50 division remains.(or does it?)

Empty space is often thought to contain nothing at all but this scenario shows empty space seems to exist at two different times, these different times -caused by dilation- are maintaining different spaces here, this implies there is some sort of force around every individual momenta of time-space keeping them separated.
No.

A force is defined as something that changes the velocity of something acted upon. Time is a dimension and unit in which velocity and acceleration are measured. Thus, by definition, time is not a force.

In special relativity and general relativity, time is different from time in Newtonian physics, but it simply and plainly isn't a force in any of these cases because time is part of the definition of velocity (and of changes in velocity) and not a cause of changes in velocity.

A and B synchronise clocks. Do they 'exist at different times'? If not, how do you know? If so, how can their clocks show the same thing?
Ok I think I may have the answer here, the clocks never were at a different time and the clock that undergoes time dilation is always at the same time. Dilation does not mean slowed, if the time was slowed for one clock it would have to be -by definition- “at a different time” so no, you mean both clocks always exist at the same time, dilation is simply a time-space compression within a moving reference frame.

The problem here is that if the time dilation remains, then so to should all the other relativistic effects such as length contraction and they don’t, so no time is actually being slowed and a different time is the result.

Again, I don't have a science background so please explain why the younger twin isn't also length contracted?
You all seem to agree that time dilation is independent of length contraction here, teach me how this is possible.

phinds
Gold Member
2019 Award
You keep missing the point here.

Length contraction makes the length of an object seem different in different frames of reference, depending on the speed of the object in that frame of reference, BUT ... when the object is returned to a point where an initial measurement was made, it has exactly the same measurement because travel through space-time does not change the physical (as opposed to temporal) dimensions of an object.

Time contraction makes the time passing on a clock seem different in different frames of reference, depending on the speed of the object in that frame of reference, BUT ... when the object is returned to a point where an initial reading of the clock was made, it has a DIFFERENT measurement because travel through space-time DOES change the amount of time elapsed.

There are two different phenomenon going on and the difference between them is what is causing your confusion. They are Time Dilation and Differential Aging.

Even though a clock B that is traveling at relativistic speeds relative to a clock A, both clocks are ticking away at one second per second even though each seems to the other to be clicking slower than one second per second. That's time dilation.

Differential aging is simply the result of taking different paths through space-time.

Say you travel by car, at 60 mph, from Washington DC, by the straightest possible route, when you get there, there will have been a change in your odometer reading of some amount. Make the same trip, but going by way of Chicago, but still going at 60 mph. When you get there, there will have been a change in your odometer reading. Would you really expect this to be the same change as for the first trip? Of course not, and yet you are puzzled by why different paths through space-time have the exact same kind of result.

They are Time Dilation and Differential Aging.
Yeah i got that as soon as i read back what i wrote, sorry about that. The time and length are compressed during travel and return when reunited

jbriggs444
Homework Helper
2019 Award
Ok I think I may have the answer here, the clocks never were at a different time and the clock that undergoes time dilation is always at the same time. Dilation does not mean slowed, if the time was slowed for one clock it would have to be -by definition- “at a different time” so no, you mean both clocks always exist at the same time, dilation is simply a time-space compression within a moving reference frame.
Whatever this means, it is not correct.

It is not clear what you mean by a clock being "at a different time" or "at the same time". Nor is it clear what you mean by time "slowed for one clock".

Possibly you are under the impression that time passes for the rest of the universe at a different rate for a moving clock than for a stationary clock. So, for you, the mental image is that each clock inhabits "different times", meaning universes wherein time passes at different rates. However, that is not how special relativity works.

To get a correct picture, I think that you need to step back from these broad brush mental pictures and start over with a careful picture done the scientific way.

Start with the notion of a coordinate system laid out in a grid using stationary rulers at right angles to each other. Identify one special intersection point. Mark it as (0,0,0). Identify coordinate directions for east, west, north, south, up and down (or x, y and z if you prefer). Label all of the grid intersection points with (x,y,z) coordinates.

Place clocks at all of the grid intersection points. Start the one at (0,0,0) ticking. Place clocks at all the other grid intersection points and synchronize them with the one at (0,0,0).

Details of the syncronization process are not terribly important as long as the process is symmetric. One choice is to use lasers and mirrors and make sure that the round trip time of light is spent half on the outbound trip and half on the return trip. Another choice is "slow clock transport" -- you take a clock, synchronize it at (0,0,0) and slowly walk it to its final home.

If an event occurs at any point in space and time, you can give it a coordinate by reading off x, y and z from a nearby grid intersection and t from the time currently displayed on the clock there. The notation for this is (x,y,z,t) for "the event at grid label (x,y,z) and clock value t".

You are now in a position to do some simple physics. You throw a ball from grid point to grid point. It starts at event (0,0,0,0) and it lands at event (0,0,1,5). What was its speed?

That is a question for you. [If it helps to make things concrete, the grid points are one foot apart (one light-nanosecond) and the clocks tick in nanoseconds]

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phinds
Gold Member
2019 Award
Yeah i got that as soon as i read back what i wrote, sorry about that. The time and length are compressed during travel and return when reunited
Sounds like you didn't understand what I wrote in post #16.

PeroK
Homework Helper
Gold Member
It is not clear what you mean by a clock being "at a different time" or "at the same time". Nor is it clear what you mean by time "slowed for one clock".
I mean existing at a different time or at the same time, i can see how it all makes sense if the whole universe exists at the same time but i think it also makes sense if the whole universe exists at different times, the term time means something different depending which universe you're referring to.

If a region of spacetime exists at a different time from another region of spacetime then time is like an (almost) massless particle. This time does not pass, it is fixed in time and space, i.e. different time=different space. To refer to time passing in the usual way is not what i mean by time here.

To say an object undergoes time dilation as it accelerates is just a way of describing an interval regardless what universe your talking about. Relativity or any other scientific is unaffected whether or not these massless particles exist or not. Dirac and Einstein certainly thought so.

I am reading all posts writing responses and looking up those links, its late nite.

Dale
Mentor
i think it also makes sense if the whole universe exists at different times,
Since you are persisting with your personal speculation, this thread is closed. We are happy to teach you science as it is understood and practiced by professional scientists, but we cannot do so if you insist on using your personal terminology and concepts.