# Time dilation

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An analogy used to describe relativity doesn't make sense to me. The clock analogy. Where you have a man, at rest, holding a clock on earth. And you have another man holding a clock in a rocket blasting away from the earth at ?thousand Mph. From the perspective of the man on earth, the rocketman's clock would slow down in comparison with his own clock, at rest on earth.???

Isn't it true that there would be no change in time due to the perspective of the man on the rocket? To himself he is the one at rest and it is the clock wielding earthman, who is blasting away from him at ?thousand Mph. Taking in the perspectives of both men, wouldn't the supposed change in the eachother's clocks cancel out the time change event as being no change at all?

If correct wouldn't this suggest that rate of motion and/or the speed of light© has no observable effect on the propagation of time?

Another question is what observable evidence is/was there to support the advent of gravity. Why was weight, mass and buoyancy coupled with the energy fields not enough? Couldn't any discrepancies in the math be found in a missing anomaly of an already existing force. It seems that Einstein dismisses the ether as being non-existant or non-consequential, only to turn around and say the density of a massive object warps that very thing(space/ether) he had dismissed as being a medium to factor into calculation.

Space/ether is either a physical medium or it isn't. Right?

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An analogy used to describe relativity doesn't make sense to me. The clock analogy. Where you have a man, at rest, holding a clock on earth. And you have another man holding a clock in a rocket blasting away from the earth at ?thousand Mph. From the perspective of the man on earth, the rocketman's clock would slow down in comparison with his own clock, at rest on earth.???

Isn't it true that there would be no change in time due to the perspective of the man on the rocket? To himself he is the one at rest and it is the clock wielding earthman, who is blasting away from him at ?thousand Mph. Taking in the perspectives of both men, wouldn't the supposed change in the eachother's clocks cancel out the time change event as being no change at all?

Try to study Relativity of simultaneity https://en.wikipedia.org/wiki/Relativity_of_simultaneity

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If correct wouldn't this suggest that rate of motion and/or the speed of light© has no observable effect on the propagation of time?

We have empirical evidence that the rate of motion affects the passage of time. The theory that explains this is based on the speed of light being the same in all inertial frames of reference. And it's a pretty straightforward deduction that length and time have to be relative if c is invariant.

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An analogy used to describe relativity doesn't make sense to me. The clock analogy. Where you have a man, at rest, holding a clock on earth. And you have another man holding a clock in a rocket blasting away from the earth at ?thousand Mph. From the perspective of the man on earth, the rocketman's clock would slow down in comparison with his own clock, at rest on earth.???

Correct.

Isn't it true that there would be no change in time due to the perspective of the man on the rocket?

Correct.

To himself he is the one at rest and it is the clock wielding earthman, who is blasting away from him at ?thousand Mph. Taking in the perspectives of both men, wouldn't the supposed change in the eachother's clocks cancel out the time change event as being no change at all?

They don't cancel out. They each see the other's clock running slow. (Strange but true.)

Another question is what observable evidence is/was there to support the advent of gravity.

What is the "advent of gravity"?

The evidence of gravity is that things fall, planets orbit, etc.

Why was weight, mass and buoyancy coupled with the energy fields not enough?

Mass and energy are the main factors the define the amount of gravitation produced. (There are other things like momentum flow and pressure.)

Couldn't any discrepancies in the math be found in a missing anomaly of an already existing force.

When anomalies were seen in the precession of Mercury, all sorts of attempts were made to account for it by supposing extra mass (an unknown planet for example) changes to the force of gravity, etc. But none of these were found to match all the evidence.

Einstein's General Relativity predicts the observed precession very accurately.

It seems that Einstein dismisses the ether as being non-existant or non-consequential, only to turn around and say the density of a massive object warps that very thing(space/ether) he had dismissed as being a medium to factor into calculation.

You are mixing up space-time (the geometry of spatial and temporal distance between events) and the luminiferous aether that was once thought to be necessary for the propagation of light.

Einstein ignore this because he derived the special theory of relativity from the simple assumption that the laws of physics (including Maxwell's equations and hence the speed of light) are the same for all observers. The presence of otherwise of a medium for light becomes irrelevant (it is completely undetectable and so may as well not exist). If you insist that light must have a medium then that medium is the electromagnetic field. (But there is not really any evidence that physically exists, other than a mathematical convenience.)

The medium for the propagation of light is irrelevant to gravity.

However, Eisntein himself did describe space-time as an ether (by analogy with something that pervades the entire universe) but went on to point out that it has no physical properties; it is not made of any material substance.

Space/ether is either a physical medium or it isn't. Right?

This depends on what you mean by the words "physical" and "medium". (And "space". And "is". And ...)

There are several long threads in the Philosophy section on this. Pretty much irrelevant to the science, though.

as universe is expanding at various speeds, the maximum being light speed,

Applying "speed" to expansion doesn't really make sense. It is a scaling effect. Therefore (by simple arithmetic) the speed of separation of two points in space is proportional to distance. So there are points which are moving apart faster than the speed of light.

Common mistake about light speed is to consider a max for it.

That is incorrect. The speed of light is the maximum speed.

Universal time variation= 0

We suffer time because we are not able to consider light speed! To have a conscious of it...

so our universe expand slower than the real universe. That difference gives us "time".

Meaningless nonsense.

Edited by Strange

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Try to study Relativity of simultaneity https://en.wikipedia.org/wiki/Relativity_of_simultaneity

In the explanation for this theory it suggests that the angle at which an event is viewed changes the time at which the events are viewed. The problem with this theory is that it leaves out important perspectives that can't be left out of the equation. In the wiki link it gives the example of a car in New York crashing (event A), and a car crashing in London (event B) at the the same time. Okay, so we can imagine for arguments sake that both cars have a clock that reads the same.

Then there are two observers. One on the ground who sees the events, as they happened, in their own time and his own time. (since he sees it as both events saw it) -and there's the rub. All the explanations for the relativity theory fail to factor in all variables of the equation.

The theory states that an observer from a plane flying between London and New York perceives the two events as not being simultaneous, as seen by both, the events and the earth bound observer. It doesn't make sense. I mean just pretend that you can view events A and B at the perspective of something like google earth instead of a plane. If you paused the crashing events at the moment of impact (which at this moment are simultaneous to three of the four factors in this equatative scenario). No matter who is watching, from what angle, the fact still stands that once paused in that moment, you could zoom in, out and all around, from all angles and distances, (as you might do navigating around google earth), the picture would show the moment of impact simultaneously.

If you used this model. pausing the world at the moment of impact, that picture would show one event at the moment of impact while the other event not at that moment of impact to the observer of a spacial deference. That would not only be a matter for perspective but a matter of having different events happening altogether. The event's perspective would change as the location of the observer changed. The perspective of the event itself is a part of the scenario that has to be accounted for. Unless a multitude of realities exist concurrently. Now we're getting a little out of scope.

The only way I could see this theory having any validity would be is if the event happened at such a distance from the observers that the light from the events reached the observers at two different intervals. And still should see the events as happening simultaneously. In this case the observers would have to be at great distances from one another. And that is supposing that light propagation is such that it's pictoral reflection is even able to travel beyond the life of it's source. As is widely accepted of the light of most stars we observe. Which I kind of doubt if someone really far away could be seeing the 2 year old ME running around.

We have empirical evidence that the rate of motion affects the passage of time. The theory that explains this is based on the speed of light being the same in all inertial frames of reference. And it's a pretty straightforward deduction that length and time have to be relative if c is invariant.

From my way of thinking, space and time (or the interval of motion from one point in space to another point in space) is relative to itself whether the speed of light is an invariant speed or not. The only way I could see light or it's speed being of any consequence would be itin some way physical impacting the event or observation. At that point I could agree that it is a factor that would effect the way something is observed. As of now the speed of light© is the equivalent of a yard stick. All be it the biggest yard stick, but a yard stick none the less.And when I think about the distance of a light year as one big yard stick, I don't see that yard stick dictating how or what's observed. It would be like changing from that yard stick to a meter stick depending upon who is looking. It seems illogical.

If the man in the rocket suffer no more acceleration, then, it's the same as if he was the one resting and the other moving from him. Twins... that maintain both of them into the same space-time dimension.

But in this case, when the movement stops, they should have the same age...

to this we must notice that one his actually moving. Giving a direction... as universe is expanding at various speeds, the maximum being light speed, the one moving at light speed would actually slow down his time to 0 when light speed max is reached.

Common mistake about light speed is to consider a max for it. Max if Inifinity. We can only observe a range of speed I would call material light speed.

Universal time variation= 0

We suffer time because we are not able to consider light speed! To have a conscious of it...

so our universe expand slower than the real universe. That difference gives us "time".

Time is just the consequence of an error between the real universe and what we can perceive of it. The more you can see, the slower time goes. And that counts for everyone. We re living in the same space time, but, depending on your intellectual skills, time stretches from one to the other.

Cheers.

Charles Rouffilange

Ah but you have to remember that it is only when accelerating from one extreme to another that the acceleration is felt.

And in reality both the rocket and the earth are in motion at an equal rate from the perspective of the other. That is what makes the clocks being different for either of them illogical. And I suggest that one thing has to effect another physically to be relative at all. This is why time as measured by the speed of light© is just that only a measure and has no physical bearing on observable reality.

But I am stunned at how little we know about the reality we live in. You are right about being aware of the true nature of things. I just wonder at how much we could gain by paying attention to what is rather than what we make believe it is.

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From my way of thinking, space and time (or the interval of motion from one point in space to another point in space) is relative to itself whether the speed of light is an invariant speed or not. The only way I could see light or it's speed being of any consequence would be itin some way physical impacting the event or observation. At that point I could agree that it is a factor that would effect the way something is observed. As of now the speed of light© is the equivalent of a yard stick. All be it the biggest yard stick, but a yard stick none the less.And when I think about the distance of a light year as one big yard stick, I don't see that yard stick dictating how or what's observed. It would be like changing from that yard stick to a meter stick depending upon who is looking. It seems illogical.

I'm not sure what "relative to itself" means. You can certainly construct a model with absolute time and space; the problem is that nature doesn't behave that way. It does, however, behave the way you'd expect if c is invariant. If you want to construct a model with a variable c, go right ahead and do it. Find out what it predicts, and then compare it to experiment.

Some of our fundamental constants are now based on on c being invariant and subsequently having a defined value. It doesn't seem to be a problem.

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In the explanation for this theory it suggests that the angle at which an event is viewed changes the time at which the events are viewed. The problem with this theory is that it leaves out important perspectives that can't be left out of the equation. In the wiki link it gives the example of a car in New York crashing (event A), and a car crashing in London (event B) at the the same time. Okay, so we can imagine for arguments sake that both cars have a clock that reads the same.

Then there are two observers. One on the ground who sees the events, as they happened, in their own time and his own time. (since he sees it as both events saw it) -and there's the rub. All the explanations for the relativity theory fail to factor in all variables of the equation.

The theory states that an observer from a plane flying between London and New York perceives the two events as not being simultaneous, as seen by both, the events and the earth bound observer. It doesn't make sense. I mean just pretend that you can view events A and B at the perspective of something like google earth instead of a plane. If you paused the crashing events at the moment of impact (which at this moment are simultaneous to three of the four factors in this equatative scenario). No matter who is watching, from what angle, the fact still stands that once paused in that moment, you could zoom in, out and all around, from all angles and distances, (as you might do navigating around google earth), the picture would show the moment of impact simultaneously.

If you used this model. pausing the world at the moment of impact, that picture would show one event at the moment of impact while the other event not at that moment of impact to the observer of a spacial deference. That would not only be a matter for perspective but a matter of having different events happening altogether. The event's perspective would change as the location of the observer changed. The perspective of the event itself is a part of the scenario that has to be accounted for. Unless a multitude of realities exist concurrently. Now we're getting a little out of scope.

The only way I could see this theory having any validity would be is if the event happened at such a distance from the observers that the light from the events reached the observers at two different intervals. And still should see the events as happening simultaneously. In this case the observers would have to be at great distances from one another. And that is supposing that light propagation is such that it's pictoral reflection is even able to travel beyond the life of it's source. As is widely accepted of the light of most stars we observe. Which I kind of doubt if someone really far away could be seeing the 2 year old ME running around.

I am studiing differential calculus in KHANACADEMY. I will check SR later. If you know nesessary math then you can try to check it now.

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!

Moderator Note

Please note that the disruptive hijack from Char lie has been split and placed in speculations. Please ignore any remnants here that could not be moved.

http://www.scienceforums.net/topic/102121-hijack-split-from-time-dilation/

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Ah but you have to remember that it is only when accelerating from one extreme to another that the acceleration is felt.

I'm not sure what you mean by that. You can feel even very gentle acceleration - like a train pulling away slowly.

And in reality both the rocket and the earth are in motion at an equal rate from the perspective of the other. That is what makes the clocks being different for either of them illogical.

I assume that by "illogical" you mean it doesn't make sense to you.

But the thing is, measurements of reality confirm this is what happens. So you need to adjust what you think is "logical".

This is why time as measured by the speed of light© is just that only a measure and has no physical bearing on observable reality.

Time is not measured by the speed of light.

I just wonder at how much we could gain by paying attention to what is rather than what we make believe it is.

This is what science attempts to do by relying on objective measurements, rather than what people think is "logical".

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In the explanation for this theory it suggests that the angle at which an event is viewed changes the time at which the events are viewed. The problem with this theory is that it leaves out important perspectives that can't be left out of the equation. In the wiki link it gives the example of a car in New York crashing (event A), and a car crashing in London (event B) at the the same time. Okay, so we can imagine for arguments sake that both cars have a clock that reads the same.

Then there are two observers. One on the ground who sees the events, as they happened, in their own time and his own time. (since he sees it as both events saw it) -and there's the rub. All the explanations for the relativity theory fail to factor in all variables of the equation.

The theory states that an observer from a plane flying between London and New York perceives the two events as not being simultaneous, as seen by both, the events and the earth bound observer. It doesn't make sense. I mean just pretend that you can view events A and B at the perspective of something like google earth instead of a plane. If you paused the crashing events at the moment of impact (which at this moment are simultaneous to three of the four factors in this equatative scenario). No matter who is watching, from what angle, the fact still stands that once paused in that moment, you could zoom in, out and all around, from all angles and distances, (as you might do navigating around google earth), the picture would show the moment of impact simultaneously.

Assume that our "ground" observer is exactly half-way between London and New York. (actually floating somewhere in the Atlantic.) Our plane, passes directly overhead at the same instant as the light carrying the information of the two crashes reaches the ground observer. The ground observer, knowing that he is halfway between the two events and that his position relative to the crashes has not changed between the time they happened and when the light reaches him, determines that the two crashes happened simultaneously, since the light from each crash took an equal time to reach him.

The observer in the plane who is also halfway between The two crashes, also notes that the light from these crashes arrive at the same time. However, he also knows that he was not halfway between London and New York when the crashes took place and the light he sees at this moment left each crash.

Now we need to consider the invariant speed of light. "invariant" in this case means That each observer(ground and plane) measures the same value for the speed of light as measured relative to himself of ‎299792458 m/s. This means the ground observer measures the light from each crash coming at him at ‎299792458m/s relative to the ground, and the plane observer measures the light coming from each crash coming at himself at ‎299792458 m/s as measured with respect to the plane. What this means is that the time it took for the light to cross the distance between each crash and himself depends on what the distance was between them when the crash occurred, and he was obviously closer to London than New York when either crash happened. This means that it takes less time for the light from the London crash to reach him than it does for the light from the New York does. But, as we noted above, he sees the light from both crashes at the same moment. So if the light coming at him from each event, which is traveling at him at the same speed from both events, and the events were at different distances from him when the light left them, he can only conclude that the events that created the light did not happen at the same time by his watch.

Also, It is not the position of the observer relative to the events that determine whether or not he will determine if they took place simultaneously or not, but his relative motion with respect to the events. (a ground observer located at different points between London and New York, would still conclude that the crashes happened simultaneously even though he would see the light from each crash at the same time, because he would factor in the respective distances between the crashes and himself. Also a plane some what ahead of or behind the plane in the example would not see the light from the crashes at the same time either, but when they factor in their distance from either crash at the moment of seeing each light, they will determine that the crashes happened at the same different times as the plane in our example does.)

If you used this model. pausing the world at the moment of impact, that picture would show one event at the moment of impact while the other event not at that moment of impact to the observer of a spacial deference. That would not only be a matter for perspective but a matter of having different events happening altogether. The event's perspective would change as the location of the observer changed. The perspective of the event itself is a part of the scenario that has to be accounted for. Unless a multitude of realities exist concurrently. Now we're getting a little out of scope.

Relativity preserves all events. According to both observers, both crashes occur, the time on the clocks on each car at the moment of the crashes all agree, etc. What they do not agree upon is whether or not these events occurred at the same time by their own watch. Different things do not, and can not happen. For example, just because one crash happens before the other according to the plane doesn't give the plane any power over preventing the other crash. The Relativity of Simultaneity, length contraction and time dilation, work in concert together to make sure that "reality" remains consistent while maintaining the invariant speed for light.

The only way I could see this theory having any validity would be is if the event happened at such a distance from the observers that the light from the events reached the observers at two different intervals. And still should see the events as happening simultaneously. In this case the observers would have to be at great distances from one another. And that is supposing that light propagation is such that it's pictoral reflection is even able to travel beyond the life of it's source. As is widely accepted of the light of most stars we observe. Which I kind of doubt if someone really far away could be seeing the 2 year old ME running around.

You don't need large distances for this to be the case, any separation of the events would require a non-zero time for the light to propagate from them to an observer. The only difference the distance (and the relative velocity of the observers) makes is in the degree of the difference. With a a real life plane flying from London to New York, the amount of time difference between the New York and London crashes according to the plane is going to be exceedingly small. For a spaceship traveling from Earth to Alpha Centauri at 0.5c, The same difference would work out to be a couple of years.( events at Alpha C and Earth considered as simultaneous according to someone at rest with respect to both, would happen two years apart according to the space ship).

From my way of thinking, space and time (or the interval of motion from one point in space to another point in space) is relative to itself whether the speed of light is an invariant speed or not. The only way I could see light or it's speed being of any consequence would be itin some way physical impacting the event or observation. At that point I could agree that it is a factor that would effect the way something is observed. As of now the speed of light© is the equivalent of a yard stick. All be it the biggest yard stick, but a yard stick none the less.And when I think about the distance of a light year as one big yard stick, I don't see that yard stick dictating how or what's observed. It would be like changing from that yard stick to a meter stick depending upon who is looking. It seems illogical.

Again, you have to take into account just what an invariant speed for light means.

A spaceship is passing Earth. There is a space buoy located some distance from the Earth that the space ship is headed for. If we assume that the buoy is one light year away as measured by the Earth, then the light arriving at the Earth left the buoy 1 year ago according to the Earth, and the buoy is still one light year away when the light arrives.

The space ship sees this same light as he passes the Earth, however, according to him, the light he is seeing now is light that left the buoy when it was further away than it is now. If he factors in how fast he is moving relative to the buoy and the information he gets from the light from the buoy, he will determine that the buoy, at the moment he passes the Earth is less than 1 light year away, even though the Earth measures the distance between ship and buoy at that moment as being 1 light year. The invariant nature of the speed of light does effect the comparison of yardsticks between relatively moving observers.

This is not illogical. The logic of Relativity has been thoroughly vetted, and its predictions confirmed again and again. When you say it "seems illogical" what you are really saying is that it is counter-intuitive. It goes against how intuition tells us things should behave. The problem with basing arguments on intuition, is that it can mislead you. Our intuitive sense of time is based on everyday experience, But in everyday experience we don't deal with the types of speeds at which relativistic effects become noticeable. Thus we tend to treat time and space as absolutes because we can't measure the small differences between this model and the Relativistic one. In the same way early people assumed the world was flat because over the small distances they were accustomed to dealing with, the difference between Flat and the Earth's curvature was too small to notice. It wasn't until they started to deal with larger distances that the difference amounted to enough for some people to start to notice it.

If we had evolved and developed under conditions where Relativistic effects were noticeable in everyday life, it would not seem counter-intuitive, and would in fact seem to be perfectly natural.

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Correct.

Correct.

They don't cancel out. They each see the other's clock running slow. (Strange but true.)

What is the "advent of gravity"?

The evidence of gravity is that things fall, planets orbit, etc.

Mass and energy are the main factors the define the amount of gravitation produced. (There are other things like momentum flow and pressure.)

When anomalies were seen in the precession of Mercury, all sorts of attempts were made to account for it by supposing extra mass (an unknown planet for example) changes to the force of gravity, etc. But none of these were found to match all the evidence.

Einstein's General Relativity predicts the observed precession very accurately.

You are mixing up space-time (the geometry of spatial and temporal distance between events) and the luminiferous aether that was once thought to be necessary for the propagation of light.

Einstein ignore this because he derived the special theory of relativity from the simple assumption that the laws of physics (including Maxwell's equations and hence the speed of light) are the same for all observers. The presence of otherwise of a medium for light becomes irrelevant (it is completely undetectable and so may as well not exist). If you insist that light must have a medium then that medium is the electromagnetic field. (But there is not really any evidence that physically exists, other than a mathematical convenience.)

The medium for the propagation of light is irrelevant to gravity.

However, Eisntein himself did describe space-time as an ether (by analogy with something that pervades the entire universe) but went on to point out that it has no physical properties; it is not made of any material substance.

This depends on what you mean by the words "physical" and "medium". (And "space". And "is". And ...)

There are several long threads in the Philosophy section on this. Pretty much irrelevant to the science, though.

Applying "speed" to expansion doesn't really make sense. It is a scaling effect. Therefore (by simple arithmetic) the speed of separation of two points in space is proportional to distance. So there are points which are moving apart faster than the speed of light.

That is incorrect. The speed of light is the maximum speed.

Meaningless nonsense.

"What is the "advent of gravity"?

The evidence of gravity is that things fall, planets orbit, etc."

When describing how things fall you don't need a force called gravity. Weight, buoyancy, density and trajectory are enough to explain how things fall, float, or fly. So the mere observation of something falling does nothing to prove or describe a gravitational force.

And if Einstein believed that the ether had no physical properties then how could he also believe that the very same non-physical provision is physically warped by Gravity when explaining light curvature?

And the evidence of an electromagnetic field is in the different ways it can be detected and produced, i.e. antennas and electric motors. What is used to detect the force of gravity and has anyone ever reproduced a gravitational force? I can think of any that aren't achieved using some type of centrifugal or G force which could also predict and describe using weight, density, buoyancy and trajectory.

"The medium for the propagation of light is irrelevant to gravity."

The medium (or the conduit in which it travels) is very relevant to gravity when it is said to warp/bend that conduit, change the direction and range of propagation. i.e. light curvature.

" This depends on what you mean by the words "physical" and "medium". (And "space". And "is". And ...) "

By space I mean the distance in between to points of reference.

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"What is the "advent of gravity"?

The evidence of gravity is that things fall, planets orbit, etc."

When describing how things fall you don't need a force called gravity. Weight, buoyancy, density and trajectory are enough to explain how things fall, float, or fly. So the mere observation of something falling does nothing to prove or describe a gravitational force.

Things like weight and bouyancy only exist because of gravity.

It is simpler to describe all the effects you mention in terms of a single underlying force. You could, I suppose, try and produced a unified theory of the motion of planets, tennis balls, and the universe based on secondary factors such as weight and buoyancy but I think it would rapidly get pretty messy.

Can you show how to describe the orbits of planets just by reference to weight, bouyancy, etc? Can you derive Kepler's laws from that?

And if Einstein believed that the ether had no physical properties then how could he also believe that the very same non-physical provision is physically warped by Gravity when explaining light curvature?

His theory describes the changing geometry of space and time. That geometry can be curved.

" This depends on what you mean by the words "physical" and "medium". (And "space". And "is". And ...) "

By space I mean the distance in between to points of reference.

You have neatly sidestepped the question. What do you mean by "physical"?