# Is the time dimension more fundamental?

• B
• thermia
In summary, the conversation discusses the concept of deleting dimensions and its implications. It is possible to imagine a flat-land universe without one of the three spatial dimensions, but impossible to imagine a universe without the time dimension. This leads to the question of whether the time dimension is more fundamental than the other three dimensions, but it is argued that it is just different. The conversation also touches on the idea of the "time arrow" and the possibility of multiple time dimensions. It is concluded that this may be a limitation of the human brain and its evolution. The conversation then delves into the mathematical concept of dimensions and their evolution, but the question of the "real" physical dimensions remains.

#### thermia

If we do the thougt experiment to delete one of the three spacedimentions we end up with a flat-land universe, which is fully possible to imagine (while probably not existing)
But if we delete the time dimesion it becomes inpossible to imagin. Whithout time there is no existence.
Could that mean that the time dimension is more fundamental than the other three?

Personally, I don't think it's more fundamental, just different. Flatland is an interesting mathematical construct but not, I believe, a possibility for actual existence.

thermia said:
But if we delete the time dimesion it becomes inpossible to imagin.
It's just a Euclidean space. I don't see the problem imagining it - we have been doing so since Euclid's time.

phinds said:
Personally, I don't think it's more fundamental, just different. Flatland is an interesting mathematical construct but not, I believe, a possibility for actual existence.
Thanks for your reply. Of course flatland is highly improbable. My thought came from my inability to imagine a universe without time.

Ibix said:
It's just a Euclidean space. I don't see the problem imagining it - we have been doing so since Euclid's time.
Well, I was tryiing to imagine physical universes. Euclidian space is just math.

itfitzme
thermia said:
If we do the thougt experiment to delete one of the three spacedimentions we end up with a flat-land universe, which is fully possible to imagine (while probably not existing)
But if we delete the time dimesion it becomes inpossible to imagin. Whithout time there is no existence.
Could that mean that the time dimension is more fundamental than the other three?
If you examine the measures of time in detail you will find that time is simply a measure of distance, more specifically a measure of cyclical distance. For instance, we measure time by counting the number of instances that the Sun moves around the Earth (celestial sphere).

thermia said:
If we do the thougt experiment to delete one of the three spacedimentions we end up with a flat-land universe, which is fully possible to imagine (while probably not existing)
But if we delete the time dimesion it becomes inpossible to imagin. Whithout time there is no existence.
Could that mean that the time dimension is more fundamental than the other three?

I'm not sure I would use the word fundamental, but your point seems trivially true. We can study motion and systems in 1, 2 or 3 spatial dimensions, but we always need a time dimension to get physics, as we know it.

thermia
itfitzme said:
If you examine the measures of time in detail you will find that time is simply a measure of distance, more specifically a measure of cyclical distance. For instance, we measure time by counting the number of instances that the Sun moves around the Earth (celestial sphere).
Yes, of course. But physisists have thught a lot about why the so called "time arrow" seem to be forced to go in just one direction, which may indicate that there is a fundamental difference between time and other dimensions.
I have been thinking that maybe all the dimensions are not created in exactly the same moment. I'm probably wrong but it is interresting to speculate about

PeroK said:
I'm not sure I would use the word fundamental, but your point seems trivially true. We can study motion and systems in 1, 2 or 3 spatial dimensions, but we always need a time dimension to get physics, as we know it.
Thanks for reply. I understand you see my point :-)

PeroK said:
we always need a time dimension to get physics

thermia said:
if we delete the time dimesion it becomes inpossible to imagin

Also, I can imagine exactly one time dimension and I can imagine not moving at all or moving forward in that one dimenion. I have no idea what is implied by multiple time dimensions. I also don't have any intuitions that I trust at all regarding time travel to the past.

I can easily imagine 0, 1, 2 or 3 space dimensions, and I have intuitions that I trust regarding the implications of more than 3 spatial dimensions even if I can't make a mental picture of them.

But I don't know if that is anything more than an observation of human brain evolution.

thermia and PeroK
Grinkle said:
But I don't know if that is anything more than an observation of human brain evolution.
Well, that's the wall we allways are running into, aren't we? :-)

Suppose that I lay out a two dimensional coordinate system with axes labelled x and t. Suppose further that I draw a graph that satisfies the equation: ##xt=1##

What grounds do I have for considering t more "fundamental" than x? Why am I forced to consider that position x evolves over time t. Why can I not with equal rigor declare that time t evolves over position x?

russ_watters
Of course that's correct but only in Eucledian mathematics. My question is about physical dimentions i.e.the "real" world.

thermia said:
Of course that's correct but only in Eucledian mathematics. My question is about physical dimentions i.e.the "real" world.
Lacking a measurement procedure, both are equally hypothetical. It is a distinction without a difference.

thermia said:
Could that mean that the time dimension is more fundamental than the other three?
It's different.
Does that mean that it's more fundamental? There's no answering that question unless someone provides a definition of "fundamental" that we can use to determine how fundamental something is and compare that with the "fundamentalness" of something else - and I'm not seeing that happening.

Asymptotic, Vanadium 50, russ_watters and 2 others
thermia said:
Yes, of course. But physisists have thught a lot about why the so called "time arrow" seem to be forced to go in just one direction, which may indicate that there is a fundamental difference between time and other dimensions.
I have been thinking that maybe all the dimensions are not created in exactly the same moment. I'm probably wrong but it is interresting to speculate about
And there's the problem, this imagined "time arrow" which supposedly might run in some other way. At it's core, physics is simply correlating on property with another. "Time" is label we give to one of these correlations. Fundamentally, physics is a study of how things change. There are cyclical changes that we recognize, the magnitude of voltage going up and down, the point end of the hand of a clock passing a mark "12" on its face, the change of a pulse of light as it goes down and back, reflecting off some distant mirror. The standards of weights and measures was devised so that we have a common reference for correlation. When we get down to the root of it, "time" is a measure of distance. A light year is the distance light travels compared to some other reference we have chosen as a cyclical distance. Time isn't some real property of space, it is the change of an object's position in space which we mark by correlating those positions to the swing of a pendulum that cycles in position in space.

itfitzme said:
Time isn't some real property of space

That remark is not physics, whatever else it may be. General Relativity models spacetime and gives very specific attributes to space and time.

Nugatory said:
It's different.
Does that mean that it's more fundamental? There's no answering that question unless someone provides a definition of "fundamental" that we can use to determine how fundamental something is and compare that with the "fundamentalness" of something else - and I'm not seeing that happening.
A clever answer, well worth to consider, thank you.

thermia said:
Yes, of course. But physisists have thught a lot about why the so called "time arrow" seem to be forced to go in just one direction, which may indicate that there is a fundamental difference between time and other dimensions.
I have been thinking that maybe all the dimensions are not created in exactly the same moment. I'm probably wrong but it is interresting to speculate about
I find it an interesting think to wonder. The single observation that come close to the arrow of time is entropy. But this, as far as I know, is simply that things tend towards spreading out evenly across space. Again, we're down to that fundamental point of measure of distance, whatever changed position.

I have made some effort at finding some fundamental measure of time that doesn't involve a measure of distance and haven't. Always, in there, is that requirement of comparison to some other thing displaced in a spatial dimension, by convenience a cyclical displacement.

thermia
itfitzme said:
I have made some effort at finding some fundamental measure of time that doesn't involve a measure of distance and haven't.

Does it make less sense to claim that a universe containing only a single static particle is getting older than to claim that same universe is expanding? For either case, I can't think of an experiment to define either older or bigger. My point is that I don't see how time is different from space in requiring some anchor points if one is to actually measure.

thermia said:
But if we delete the time dimesion it becomes inpossible to imagin.
I disagree 100%. A world without time is easy to imagine, it is just very boring.

itfitzme said:
I find it an interesting think to wonder. The single observation that come close to the arrow of time is entropy. But this, as far as I know, is simply that things tend towards spreading out evenly across space. Again, we're down to that fundamental point of measure of distance, whatever changed position.

I have made some effort at finding some fundamental measure of time that doesn't involve a measure of distance and haven't. Always, in there, is that requirement of comparison to some other thing displaced in a spatial dimension, by convenience a cyclical displacement.
Interresting, could you elaborate some more about this?

Dale said:
I disagree 100%. A world without time is easy to imagine, it is just very boring.
I would say, not boring rather inexisting

thermia said:
I would say, not boring rather inexisting
Of course it is “inexisting”. What exists is 3 dimensions of space and 1 dimension of time. Anything else is automatically non-existent.

That is far different from your claim of “inpossible to imagin”. I can imagine lots of non-existent things, and a universe without time is one of those.

itfitzme said:
When we get down to the root of it, "time" is a measure of distance.
Do you have a professional scientific reference for this? Not just that some practical measuring devices use a measure of distance to measure time, but one that actually makes this general claim that time is a measure of distance?

itfitzme said:
I have made some effort at finding some fundamental measure of time that doesn't involve a measure of distance and haven't.
Decay time of unstable fundamental particles.

Dale said:
Of course it is “inexisting”. What exists is 3 dimensions of space and 1 dimension of time. Anything else is automatically non-existent..
That's an assumption, maybe you are right

thermia said:
That's an assumption, maybe you are right
All of the evidence supports the assumption. That is what science is about.

Besides, you adopted that assumption in the OP, so it is odd for you to reject it now. You started out stipulating that you were talking about non-existent imaginary universes, but claimed that a universe without time is impossible to imagine. I disagree with that, it is easy to imagine.

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We know that all particles are moving round at very high speeds in the micro world. The static picture we see in a mountain not moving for example, is only a statistical average of the various random motions of the constituents. Now, since the unit of speed is space divided by time, we see that space and time are firmly locked and can't be separated. Thus there is no way of telling which is more fundamental than the other- space or time. This makes velocity or momentum the most fundamental property of the universe we live in. Statistically however, one can average time out or space out leaving a quantity changing with space only, or changing with time only.
It is possible to artificially separate space and time however, by associating space with linear motion and time with circular motion. This is quite in tune with what we actually do in practice, as we measure time using oscillations of some sort. But this is only artificial, since to measure distance using light for example, we need to count the number of rotations or the time of flight as in modern official definition of the meter.
The counting of rotations/oscillations to measure time have the property that the count can only go up giving the required arrow of time. The zero of time (the present) can be chosen to be any number of rotations, with past before the zero and future after the zero. Finally since time is firmly related to motion, one can say the time has started with the first motion in the universe and will not stop before every motion stops everywhere.

thermia
Riadh said:
We know that all particles are moving round at very high speeds in the micro world. The static picture we see in a mountain not moving for example, is only a statistical average of the various random motions of the constituents. Now, since the unit of speed is space divided by time, we see that space and time are firmly locked and can't be separated. Thus there is no way of telling which is more fundamental than the other- space or time. This makes velocity or momentum the most fundamental property of the universe we live in. Statistically however, one can average time out or space out leaving a quantity changing with space only, or changing with time only.
It is possible to artificially separate space and time however, by associating space with linear motion and time with circular motion. This is quite in tune with what we actually do in practice, as we measure time using oscillations of some sort. But this is only artificial, since to measure distance using light for example, we need to count the number of rotations or the time of flight as in modern official definition of the meter.
The counting of rotations/oscillations to measure time have the property that the count can only go up giving the required arrow of time. The zero of time (the present) can be chosen to be any number of rotations, with past before the zero and future after the zero. Finally since time is firmly related to motion, one can say the time has started with the first motion in the universe and will not stop before every motion stops everywhere.
Thank you Riadh for an extensive reply, well worth to consider.

This is what I gathered from wikipedia (it is mentioned that time is different from the spatial dimensions)
In fact they are mentioned under two different titles... the three being referred to as "spacial dimensions" and the other as "temporal dimension"

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thermia
thermia said:
If we do the thougt experiment to delete one of the three spacedimentions we end up with a flat-land universe, which is fully possible to imagine (while probably not existing)
But if we delete the time dimesion it becomes inpossible to imagin. Whithout time there is no existence.
Could that mean that the time dimension is more fundamental than the other three?

Have you ever tried, say as instructional entertainment, to formulate basic mechanics without the variable called time? For example, instead of taking length, mass and time as fundamental magnitudes, take strength, length and speed. The first challenge you will find is to propose an operating procedure to measure speeds. The procedure to measure forces gives a little less problem. And the procedure for measuring length has been known since ancient times. If you do it, if you make observations and prepare data tables, in a short time you will see in the tables reasons to assume some hypothesis that inspire confidence. They inspire you at least within the limitations of your experiments. And you will also understand without much complication the need to define a function dependent on the force, the path traveled and how aligned or oblique the force is with respect to the path traveled. That is to say that defining work will be an obvious necessity. You will arrive intuitively and easily at the theorem of mechanical work and kinetic energy. And you would arrive even if you had never gone through a physics classroom or read anything about Newton. You would formulate a basic mechanics without introducing the time variable. And if after all that you want to establish a time definition, you will notice that there is no unique way to formulate a function ## t ## that satisfies the definition of time. The definition and function that you decide to adopt as a time formulation have no univocal relationship. You will also see that within the limitations of the experimental setup you have done, your tables of experimental values give a constant result when you divide the data of one column by the data of another, within the same row. That result does not change from one row to the others. So it is not wrong to assume that this quotient is a constant of each body that you have used in the tests. It is not wrong to suppose that to each body corresponds a value of that quotient, being that value independent of the speed, the force and the other conditions. That value is the mass and, only within the limitations of your essay, you have reason to consider it constant. The constant mass hypothesis complicates the form of the time function, whichever option you choose to formulate it. We could say more, but a button is enough to show.

The good thing about this didactic game is to understand that physics is not a fruit that nature has made and is hanging from a plant and is completely done, waiting for us to simply see it and take advantage of it. Physics, from its most basic beginnings, is a product that is made by mixing observations with logic, logic with supposed ideas (hypothesis), hypothesis with voluntary decisions to define magnitudes and functions, in a partially arbitrary way. The game of building basic physics without the definition of time teaches us to be prudent, austere and in favor of everything that helps avoid dogmatism.

Regarding time, it is an abstract function and it is impossible to build an instrument that directly measures time values. Everyone obtains data that is entered into the variables of the time function and gives a result that, conventionally, we decided to accept.

slow said:
Have you ever tried, say as instructional entertainment, to formulate basic mechanics without the variable called time? For example, instead of taking length, mass and time as fundamental magnitudes, take strength, length and speed. The first challenge you will find is to propose an operating procedure to measure speeds. The procedure to measure forces gives a little less problem. And the procedure for measuring length has been known since ancient times. If you do it, if you make observations and prepare data tables, in a short time you will see in the tables reasons to assume some hypothesis that inspire confidence. They inspire you at least within the limitations of your experiments. And you will also understand without much complication the need to define a function dependent on the force, the path traveled and how aligned or oblique the force is with respect to the path traveled. That is to say that defining work will be an obvious necessity. You will arrive intuitively and easily at the theorem of mechanical work and kinetic energy. And you would arrive even if you had never gone through a physics classroom or read anything about Newton. You would formulate a basic mechanics without introducing the time variable. And if after all that you want to establish a time definition, you will notice that there is no unique way to formulate a function ## t ## that satisfies the definition of time. The definition and function that you decide to adopt as a time formulation have no univocal relationship. You will also see that within the limitations of the experimental setup you have done, your tables of experimental values give a constant result when you divide the data of one column by the data of another, within the same row. That result does not change from one row to the others. So it is not wrong to assume that this quotient is a constant of each body that you have used in the tests. It is not wrong to suppose that to each body corresponds a value of that quotient, being that value independent of the speed, the force and the other conditions. That value is the mass and, only within the limitations of your essay, you have reason to consider it constant. The constant mass hypothesis complicates the form of the time function, whichever option you choose to formulate it. We could say more, but a button is enough to show.

The good thing about this didactic game is to understand that physics is not a fruit that nature has made and is hanging from a plant and is completely done, waiting for us to simply see it and take advantage of it. Physics, from its most basic beginnings, is a product that is made by mixing observations with logic, logic with supposed ideas (hypothesis), hypothesis with voluntary decisions to define magnitudes and functions, in a partially arbitrary way. The game of building basic physics without the definition of time teaches us to be prudent, austere and in favor of everything that helps avoid dogmatism.

Regarding time, it is an abstract function and it is impossible to build an instrument that directly measures time values. Everyone obtains data that is entered into the variables of the time function and gives a result that, conventionally, we decided to accept.
The way we chose to measure time is of course arbitrary and thus an abstract function. But time it self, regardless of how we measure it, is obviously fundamental physics.

slow
thermia said:
time it self, regardless of how we measure it, is obviously fundamental physics.

I have no reason to affirm or deny that opinion. I just want to confess that it does not seem obvious to me.

Dale said:
I can imagine lots of non-existent things
I try to imagine two or three non-existent things each day before breakfast...

Dale
Mark44 said:
I try to imagine two or three non-existent things each day before breakfast...
My breakfast egg this morning was very close to become non existent :-) (Now time for bed)