Why does does time permanently change but not space?

[ryan]

What is it about time that is different than the spatial dimensions when it comes its dilation?

Lorenz transformations have length contractions acting like a 2-way system. A meter stick's length will contract from the observer's frame as it speeds from being initially at rest with the observer. And as the meter stick slows back down to rest with the observer, the observer sees the meter stick go back to its original length.

But with time it seems to be only a one-way system. A clock that leaves a the rest frame of an observer to speed up will dilate. And when it comes back to rest with the observer, the clock will still be slower.

The time dimension and space dimension seem to be different in this respect, but why?

 

[PyramidHead]

What is it about time that is different than the spatial dimensions when it comes its dilation?

Lorenz transformations have length contractions acting like a 2-way system. A meter stick's length will contract from the observer's frame as it speeds from being initially at rest with the observer. And as the meter stick slows back down to rest with the observer, the observer sees the meter stick go back to its original length.

But with time it seems to be only a one-way system. A clock that leaves a the rest frame of an observer to speed up will dilate. And when it comes back to rest with the observer, the clock will still be slower.

The time dimension and space dimension seem to be different in this respect, but why?

First off, the word 'permanent' only makes sense with respect to the dimension of time, so the question is kind of circular. I don't know anything about Lorenz transformations, but I am familiar with the eternalist conception of time, according to which spacetime is a 4-dimensional object that does not change, and we are moving through it along its time dimension at a rate of 1 second per second due to the limitations of our conscious minds, not to something about time that is different from space. It can be distorted in local regions such that there is no way to chronologically line up all events in the time dimension, except by deferring to a particular perspective. The competing conception of time is the 'presentist' one, that says time essentially doesn't exist as a real quantity, since the past is already gone and the future does not yet exist; all that is left is an infinitely thin 'present' that is constantly changing. I like the eternalist interpretation myself, because it resolves a lot of questions such as perhaps yours, although I'm not positive because once again I don't have any background in physics to understand your question completely.

 

[ryan]

What is it about time that is different than the spatial dimensions when it comes its dilation?

Lorenz transformations have length contractions acting like a 2-way system. A meter stick's length will contract from the observer's frame as it speeds from being initially at rest with the observer. And as the meter stick slows back down to rest with the observer, the observer sees the meter stick go back to its original length.

But with time it seems to be only a one-way system. A clock that leaves a the rest frame of an observer to speed up will dilate. And when it comes back to rest with the observer, the clock will still be slower.

The time dimension and space dimension seem to be different in this respect, but why?

First off, the word 'permanent' only makes sense with respect to the dimension of time, so the question is kind of circular. I don't know anything about Lorenz transformations, but I am familiar with the eternalist conception of time, according to which spacetime is a 4-dimensional object that does not change, and we are moving through it along its time dimension at a rate of 1 second per second due to the limitations of our conscious minds, not to something about time that is different from space. It can be distorted in local regions such that there is no way to chronologically line up all events in the time dimension, except by deferring to a particular perspective. The competing conception of time is the 'presentist' one, that says time essentially doesn't exist as a real quantity, since the past is already gone and the future does not yet exist; all that is left is an infinitely thin 'present' that is constantly changing. I like the eternalist interpretation myself, because it resolves a lot of questions such as perhaps yours, although I'm not positive because once again I don't have any background in physics to understand your question completely.

What I said in the OP is really all you have to know to see that there seems to be something different about time in the scientific sense.

I like the "growing universe theory". We know scientifically that the past exists as per Einstein, but unlike Einstein believed, the future does not exist yet as per QM.

 

[Bronzeage]

One thing we should remember is we live in a physics special case. We are all very small bodies in close proximity(most of the time in contact with) a very large body. It's so large, to us, gravity appears to be constant and always pulling in the same direction. To us, space does not seem to change, but we have no real vantage point.

 

[ryan]

One thing we should remember is we live in a physics special case. We are all very small bodies in close proximity(most of the time in contact with) a very large body. It's so large, to us, gravity appears to be constant and always pulling in the same direction. To us, space does not seem to change, but we have no real vantage point.

But why is dilation permanent and contraction not?

 

[Juma]

What is it about time that is different than the spatial dimensions when it comes its dilation?

Lorenz transformations have length contractions acting like a 2-way system. A meter stick's length will contract from the observer's frame as it speeds from being initially at rest with the observer. And as the meter stick slows back down to rest with the observer, the observer sees the meter stick go back to its original length.

But with time it seems to be only a one-way system. A clock that leaves a the rest frame of an observer to speed up will dilate. And when it comes back to rest with the observer, the clock will still be slower.

The time dimension and space dimension seem to be different in this respect, but why?

You are comparing apples and pears: A meter stick measures distance. A clock ticks of "positions" in time.
If you compare distances in both time and space I'll believe you will get more coherent results.

 

[ryan]

What is it about time that is different than the spatial dimensions when it comes its dilation?

Lorenz transformations have length contractions acting like a 2-way system. A meter stick's length will contract from the observer's frame as it speeds from being initially at rest with the observer. And as the meter stick slows back down to rest with the observer, the observer sees the meter stick go back to its original length.

But with time it seems to be only a one-way system. A clock that leaves a the rest frame of an observer to speed up will dilate. And when it comes back to rest with the observer, the clock will still be slower.

The time dimension and space dimension seem to be different in this respect, but why?

You are comparing apples and pears: A meter stick measures distance. A clock ticks of "positions" in time.
If you compare distances in both time and space I'll believe you will get more coherent results.

Say n seconds is length d in terms of the time dimension, and then we compare that to a meter stick and send them both on a very fast flight. Time contracts by say half d during n seconds and the meter stick also contracts by half. Now when the clock and the stick come back, we get the stick as if nothing happened, but the clock shows a permanent time/length contraction/dilation.

This must be a huge hint about how the so called 4th dimension of time is different from spatial dimensions.

 

[bilby]

You are comparing apples and pears: A meter stick measures distance. A clock ticks of "positions" in time.
If you compare distances in both time and space I'll believe you will get more coherent results.

Say n seconds is length d in terms of the time dimension, and then we compare that to a meter stick and send them both on a very fast flight. Time contracts by say half d during n seconds and the meter stick also contracts by half. Now when the clock and the stick come back, we get the stick as if nothing happened, but the clock shows a permanent time/length contraction/dilation.

This must be a huge hint about how the so called 4th dimension of time is different from spatial dimensions.

Both clock and stick accurately measure the time and distance (respectively) traveled in the reference frame of the spacecraft.

The clock shows the cumulative total of elapsed seconds; To get an analogous measure of total distance travelled, we would need to tally up the total number of metres traveled as measured by the metre stick on the spaceship, and compare that to the tally of metres traveled as measured using a stick that remains in the Earth's reference frame.

The length of the stick is analogous to the duration of a second on the clock; The total elapsed time on the clock is analogous to the total distance traveled.


Alternatively, you could say that while the ship is accelerating, the distance between seconds on the moving clock, like the distance between the ends of the moving stick, appears to have changed (from the perspective of an earthbound observer) - but on their return, the clock that went away, now measures one second as the same length of time as the clock that never left - and the metre stick that came back likewise gives the same measure as the one that stayed here.

 

[ryan]

Say n seconds is length d in terms of the time dimension, and then we compare that to a meter stick and send them both on a very fast flight. Time contracts by say half d during n seconds and the meter stick also contracts by half. Now when the clock and the stick come back, we get the stick as if nothing happened, but the clock shows a permanent time/length contraction/dilation.

This must be a huge hint about how the so called 4th dimension of time is different from spatial dimensions.

Both clock and stick accurately measure the time and distance (respectively) traveled in the reference frame of the spacecraft.

The clock shows the cumulative total of elapsed seconds; To get an analogous measure of total distance travelled, we would need to tally up the total number of metres traveled as measured by the metre stick on the spaceship, and compare that to the tally of metres traveled as measured using a stick that remains in the Earth's reference frame.

The length of the stick is analogous to the duration of a second on the clock; The total elapsed time on the clock is analogous to the total distance traveled.


Alternatively, you could say that while the ship is accelerating, the distance between seconds on the moving clock, like the distance between the ends of the moving stick, appears to have changed (from the perspective of an earthbound observer) - but on their return, the clock that went away, now measures one second as the same length of time as the clock that never left - and the metre stick that came back likewise gives the same measure as the one that stayed here.

Thanks, I think you're right bilby!

 

[Malintent]

well, it was Einstein that we think is correct in his theory of relativity.. which incidentally, if incorrect, would make GPS not nearly as accurate as it is.. it would be off by kilometers... but we all know and can observe that it is accurate within meters.

 

[Kharakov]

...

 

[Kharakov]

I'm not sure I'm parsing bilby's reply correctly. This is what I think, and I can't tell if it's the same:

The total (SR) time traversed is inversely proportional to the space traversed, as objects travel through a specific amount of spacetime at a time. So time 'discrepancies' accumulate over time (which we'll define by frequency of light emitted by some specific object (like H) at rest).

Length contraction is only while an object is in motion relative to another.

 

[ryan]

I'm not sure I'm parsing bilby's reply correctly. This is what I think, and I can't tell if it's the same:

The total (SR) time traversed is inversely proportional to the space traversed, as objects travel through a specific amount of spacetime at a time. So time 'discrepancies' accumulate over time (which we'll define by frequency of light emitted by some specific object (like H) at rest).

Length contraction is only while an object is in motion relative to another.

You might be seeing other mathematical connections here which is good, but I am not totally clear on what you are saying.

All you really have to know here is that parallel spatial dimensions and the time dimension contract/dilate to an observer when moving relative to the observer.

My mistake, like bilby and possibly juma pointed out, is that a clock measures the total "temporal distance" from the beginning of the journey. A meter stick is just a small segment of the spatial distance that is also contracting. So the clock is like a really long measuring stick that started from the beginning of the journey.

The thing that screws me up is that we are somehow only conscious of 3 dimensions, and the temporal dimension is hidden from us (the past does not necessarily have to be unobservable to us). Maybe highly evolved aliens can see/experience 4 dimensions and they would see the clock as sort of a long object extending through time, and it would be clear to them that it is just like a really long measuring stick contacting too.

 

[Malintent]

What is it about time that is different than the spatial dimensions when it comes its dilation?

Lorenz transformations have length contractions acting like a 2-way system. A meter stick's length will contract from the observer's frame as it speeds from being initially at rest with the observer. And as the meter stick slows back down to rest with the observer, the observer sees the meter stick go back to its original length.

But with time it seems to be only a one-way system. A clock that leaves a the rest frame of an observer to speed up will dilate. And when it comes back to rest with the observer, the clock will still be slower.

The time dimension and space dimension seem to be different in this respect, but why?

You are comparing apples and pears: A meter stick measures distance. A clock ticks of "positions" in time.
If you compare distances in both time and space I'll believe you will get more coherent results.

What's wrong with comparing apples with pears? They are both fruits, both sweet, both have an inedible core (ignore what they say about the apple core being a myth... that is fake news).

Anyway, who says times changes but space does not. that is false. both time and space change. Time marches forward and space grows larger.

 

[Kharakov]

I'm not sure I'm parsing bilby's reply correctly. This is what I think, and I can't tell if it's the same:

The total (SR) time traversed is inversely proportional to the space traversed, as objects travel through a specific amount of spacetime at a time. So time 'discrepancies' accumulate over time (which we'll define by frequency of light emitted by some specific object (like H) at rest).

Length contraction is only while an object is in motion relative to another.

You might be seeing other mathematical connections here which is good, but I am not totally clear on what you are saying.

First section: the faster something travels through space (relative to something else) the slower it moves through time (relative to something else). Time dilation adds up as an object travels through space relative to another object.

2nd part: length contraction only occurs while an object is in motion relative to another.