What is Time?

[Truthseeker]

What is length? One can give what is called an operational definition. One way might to be compare the length of a thing to a meter stick. And so for time: One explains how to construct a particular kind of clock and start it. Or one could use the pulses of his heart when he is well-rested. You can think of some other operational definition of time.

How is the age of the universe determined? Look for the oldest-looking galaxy and estimate its age. Currently the redshift of a distant galaxy is used to calculate its age according to a numerical procedure worked out by astronomers over many years or maybe now they just use a chart of the relationship between the redshift of a distant galaxy and its theoretical age.

[Truthseeker]

I think yes, there is a real universal time.

Maybe, but I don't know how to construct a clock that gives universal times. Won't you try to describe the specific procedure for constructing such a clock? (see my last post).

[klaus54]

Maybe, but I don't know how to construct a clock that gives universal times. Won't you try to describe the specific procedure for constructing such a clock? (see my last post).

Universal time would of necessity include a universal notion of simultaneity, right? (Or not?)

If so, SR rules out such a notion, and SR has never failed a test.

If c were "infinite", then signaling would be instantaneous -- and that would make for a very strange cosmos!

[Eis__]

Universal time would of necessity include a universal notion of simultaneity, right? (Or not?)

If so, SR rules out such a notion, and SR has never failed a test.

If c were "infinite", then signaling would be instantaneous -- and that would make for a very strange cosmos!

SR is not helpful here. Our Universe is similar to a surface of a large lake, c is similar to viscosity, light and other particles - to waves. On average, the area (= quantity of visible materia) is the same, but it is constantly renewing, like the water on the surface of lake mix with deeper layers. To measure universal time, you should be a lot faster, than speed of light. We can measure Milky Way time similarly. It's size is about 100,000 ly, how can we travel from one bound of it to the opposite within a human lifespan? There are a lot of possible solutions to this, but definitely we should no travel by surface, but at least by air.

[JimL]

Maybe, but I don't know how to construct a clock that gives universal times. Won't you try to describe the specific procedure for constructing such a clock? (see my last post).

What if, theoretically speaking, we take the universe to be finite, and clocks could be placed around the outer edges of an expanding universe, as the universe expands would all the clocks remain in sychronization?

[shunyadragon]

What if, theoretically speaking, we take the universe to be finite, and clocks could be placed around the outer edges of an expanding universe, as the universe expands would all the clocks remain in sychronization?

Our own universe is most likely finite like all other possible universes. The Timeless greater cosmos is most likely infinite.

The time issue of all the clocks I cannot address. Maybe, if all the clocks are moving at the same speed. One possible problem is the outer edges of our universe may be merging into the timeless greater cosmos.

[klaus54]

SR is not helpful here. Our Universe is similar to a surface of a large lake, c is similar to viscosity, light and other particles - to waves. On average, the area (= quantity of visible materia) is the same, but it is constantly renewing, like the water on the surface of lake mix with deeper layers. To measure universal time, you should be a lot faster, than speed of light. We can measure Milky Way time similarly. It's size is about 100,000 ly, how can we travel from one bound of it to the opposite within a human lifespan? There are a lot of possible solutions to this, but definitely we should no travel by surface, but at least by air.

???

[klaus54]

What if, theoretically speaking, we take the universe to be finite, and clocks could be placed around the outer edges of an expanding universe, as the universe expands would all the clocks remain in sychronization?

Our universe has no "edge". What does that even mean?

[klaus54]

Our own universe is most likely finite like all other possible universes. The Timeless greater cosmos is most likely infinite.

The time issue of all the clocks I cannot address. Maybe, if all the clocks are moving at the same speed. One possible problem is the outer edges of our universe may be merging into the timeless greater cosmos.

Relative to what?

[klaus54]

What is length? One can give what is called an operational definition. One way might to be compare the length of a thing to a meter stick. And so for time: One explains how to construct a particular kind of clock and start it. Or one could use the pulses of his heart when he is well-rested. You can think of some other operational definition of time.

How is the age of the universe determined? Look for the oldest-looking galaxy and estimate its age. Currently the redshift of a distant galaxy is used to calculate its age according to a numerical procedure worked out by astronomers over many years or maybe now they just use a chart of the relationship between the redshift of a distant galaxy and its theoretical age.

Length is not Lorentz invariant, but space-time intervals are L-invariant. It (measured length) varies between observers in moving frames. Within our Earth reference frame, a meter is well-defined (actually by the distance light travels in vacuo in one second.)

[Eis__]

???

I assumed that our Universe is flat (in 4th dimension), like a surface of a sea... At least scientists thought that this is close to reality a few years ago. Common example that comes to mind, of traveling with a speed that exceeds speed of light, is a tunneling effect. Not sure if this is right explanation, but visible materia fluctuates around the surface, leaving it for a short time. In that short period of time it can achieve speeds more than c. If you take the materia off the surface, it is not influenced by viscocity anymore, and can have infinite speeds. This is a simplest model, that comes to mind.

[JimL]

Our own universe is most likely finite like all other possible universes. The Timeless greater cosmos is most likely infinite.

So what does motion, the expansion of a finite part of the greater cosmos into the greater cosmos itself tell us about the nature of the relationship between motion and time. It would seem that time is just a human construct of sorts in which things move timelessly within eternity. Afaics, its either that, or motion itself is an illusion!

The time issue of all the clocks I cannot address. Maybe, if all the clocks are moving at the same speed. One possible problem is the outer edges of our universe may be merging into the timeless greater cosmos.

So perhaps then, real time, for our universe at least, has a speed equal to the speed of the expansion of the universe. If things within the universe are moving at relative speeds to that of the speed of the expansion then time, relationally speaking, passes more quickly or slowly between them. I don't know, I'm no Einstein, and my brain is starting to hurt thinking about it. Just throwing ideas out there!

[shunyadragon]

Relative to what?

Relative to each other.

[oxmixmudd]

So what does motion, the expansion of a finite part of the greater cosmos into the greater cosmos itself tell us about the nature of the relationship between motion and time. It would seem that time is just a human construct of sorts in which things move timelessly within eternity. Afaics, its either that, or motion itself is an illusion!

So perhaps then, real time, for our universe at least, has a speed equal to the speed of the expansion of the universe. If things within the universe are moving at relative speeds to that of the speed of the expansion then time, relationally speaking, passes more quickly or slowly between them. I don't know, I'm no Einstein, and my brain is starting to hurt thinking about it. Just throwing ideas out there!

The big problem with talking about time is that most of the terms we use to talk about time have time as an assumption. If you think about it, a verb, any verb, assumes there is this thing called time. Because 'to do' or to be 'an action' involves change, which implies time.

LM uses the definition, 'time is what we measure with clocks', which is to me also a bit circular, or perhaps just not sufficient. I am quite convinced that time can be 'detected' by any sequences of changes, no matter how aperiodic or chaotic they are. But that kind of measurement, while it shows evidence for time, does not allow any sort of comparison of time , i.e. one reference frame vs another, unless perhaps one has some sort of quasi-period that can be derived from the statistical properties of the chaotic changes themselves. And so it would seem to me time is more fundamentally 'that thing which is the basis of change'. Without time, there is no change, no evolution, no life, no death, just a fixed multidimensional 'thing'.

Jim

[Truthseeker]

The big problem with talking about time is that most of the terms we use to talk about time have time as an assumption. If you think about it, a verb, any verb, assumes there is this thing called time. Because 'to do' or to be 'an action' involves change, which implies time.

But an operational definition of a clock does not have that problem (assuming you did read post #181 [operational definition]).

LM uses the definition, 'time is what we measure with clocks', which is to me also a bit circular, or perhaps just not sufficient. I am quite convinced that time can be 'detected' by any sequences of changes, no matter how aperiodic or chaotic they are. But that kind of measurement, while it shows evidence for time, does not allow any sort of comparison of time , i.e. one reference frame vs another, unless perhaps one has some sort of quasi-period that can be derived from the statistical properties of the chaotic changes themselves. And so it would seem to me time is more fundamentally 'that thing which is the basis of change'. Without time, there is no change, no evolution, no life, no death, just a fixed multidimensional 'thing'.

But timekeepers do use statistics continuously to maintain their cutting-edge clocks.