Does the Universe Have its Own Clock and Period?

[Atlas3]

Does Universe Spacetime have clock of it's own? A period?

 

[PeterDonis]

I'm not sure I understand the question. What would it mean for spacetime to "have a clock of its own"? What sort of observation would you make to test whether it did or not?

 

[Chalnoth]

Does Universe Spacetime have clock of it's own? A period?

What spacetime are you talking about?

In general, I'd have to say the answer is no: clocks are built from matter. It would certainly be possible to use gravity as part of your clock design (in a way, the Earth's orbital period is a sort of clock). But you still need matter involved to make it work (if there's no Earth and no Sun, the "orbital period of the Earth" doesn't make any sense).

 

[bahamagreen]

Are you asking if the block (universe) has a clock (spacetime subject to change of configuration)?

I believe the block universe idea suggests that for the entire configuration of spacetime the "history" is fixed, but if the block universe can change configuration it would seem that the entire history would become different but still consistent (as we know it). We would not know of the change because it includes all of the history, including all the consistent memories. To track a change would require being "outside" of the changing spacetime with some way to compare the previous configuration to a subsequent configuration... but there is not accounting for "outside" and any measures from within a changing spacetime would always be consistent.

The closest thing I can think of is perhaps the Many Worlds interpretation - but instead of the many worlds you might have "many configurations" of spacetime, each generation of another world really being the expression of a change in spacetime configuration (and each of those changes presenting a consistent self history)... the Many Worlds is liked for its power and consistency but it also requires "thinking outside the block"... :)

 

[Atlas3]

Are you asking if the block (universe) has a clock (spacetime subject to change of configuration)?

I believe the block universe idea suggests that for the entire configuration of spacetime the "history" is fixed, but if the block universe can change configuration it would seem that the entire history would become different but still consistent (as we know it). We would not know of the change because it includes all of the history, including all the consistent memories. To track a change would require being "outside" of the changing spacetime with some way to compare the previous configuration to a subsequent configuration... but there is not accounting for "outside" and any measures from within a changing spacetime would always be consistent.

The closest thing I can think of is perhaps the Many Worlds interpretation - but instead of the many worlds you might have "many configurations" of spacetime, each generation of another world really being the expression of a change in spacetime configuration (and each of those changes presenting a consistent self history)... the Many Worlds is liked for its power and consistency but it also requires "thinking outside the block"... :)

I will need to familiarize myself with what you have described. I have considered many parallel universes of infinite size experiencing periodicity of life time. Big Crunch ending like a bang beginning. But other parallel universes experiencing their own time period independently. A massive universal period. A function of time normalized 0 to 1 period of expansion / contraction of each whole. Please keep in mind I am going to familiarize myself with the suggestions above as someone may be on this train of thought. I thank you

 

[Chalnoth]

I will need to familiarize myself with what you have described. I have considered many parallel universes of infinite size experiencing periodicity of life time. Big Crunch ending like a bang beginning. But other parallel universes experiencing their own time period independently. A massive universal period. A function of time normalized 0 to 1 period of expansion / contraction of each whole. Please keep in mind I am going to familiarize myself with the suggestions above as someone may be on this train of thought. I thank you

That's not a viable clock model, as there's no way to measure across different big bang/crunch events. Also, if there are many big bang/crunch events, chances are the period of time associated with each varies dramatically.

 

[Atlas3]

What spacetime are you talking about?

In general, I'd have to say the answer is no: clocks are built from matter. It would certainly be possible to use gravity as part of your clock design (in a way, the Earth's orbital period is a sort of clock). But you still need matter involved to make it work (if there's no Earth and no Sun, the "orbital period of the Earth" doesn't make any sense).

Time exists as a period of many things. Solar time for example is one. Earth rotation provides one for instance. Expansion of the universe has a period as well. We don't know the period of he universe.

That's not a viable clock model, as there's no way to measure across different big bang/crunch events. Also, if there are many big bang/crunch events, chances are the period of time associated with each varies dramatically.

Can you give a little explanation how you suppose the period would vary? I think it would as well but cannot put a few words on it. I have the same idea because it would vary depending upon the maturation of gravity for an event, and that would vary.

 

[Chalnoth]

Time exists as a period of many things. Solar time for example is one. Earth rotation provides one for instance. Expansion of the universe has

Looks like you were cut off.

It's possible to use the expansion of the universe to set a specific meaning for "now" (when the CMB has the same average temperature at every point). But it's still not really possible to use the expansion as a clock of any sort. Clocks typically depend upon having predictable, repeating behavior, and the expansion of our universe doesn't do that.

That is, you can use the expansion to sync up clocks that are far away, but you can't use it as a clock in and of itself.

 

[Atlas3]

I

Time exists as a period of many things. Solar time for example is one. Earth rotation provides one for instance. Expansion of the universe has[/QUOT

Time exists as a period of many things. Solar time for example is one. Earth rotation provides one for instance. Expansion of the universe has a period as well. We don't know the period of he universe.Can you give a little explanation how you suppose why the period would vary? I think it would as well but cannot put but a few words on it. I have the same idea but it is because it would vary depending upon the maturation of the universe, and that would vary with random circumstances after an event.

We would not exist to measure time across these events, as we would cease to exist as would our solar system, but time would continue in the absence of our solar timekeeping.

Looks like you were cut off.

It's possible to use the expansion of the universe to set a specific meaning for "now" (when the CMB has the same average temperature at every point). But it's still not really possible to use the expansion as a clock of any sort. Clocks typically depend upon having predictable, repeating behavior, and the expansion of our universe doesn't do that.

That is, you can use the expansion to sync up clocks that are far away, but you can't use it as a clock in and of itself.

The overall process of a repeating reconfiguration could be considered a pulse. Periodic but varying periods does not make a regulated clock but it does make a wave which could not be measured by us. But could be time proceeding. It can't be measured by us. We would not exist any longer nor would our reference frame for time. A reconfiguration would reset the maturation period which would vary. Also consider more than one universe experiencing this life.

 

[PeterDonis]

The overall process of a repeating reconfiguration could be considered a pulse.

All of these proposals (which are speculative) are still cases of matter changing configuration. None of them are examples of spacetime having a "clock of its own". So it looks like the answer to the question you posed in your OP is "no".

 

[Atlas3]

Can the fabric of space time be considered to exist in isolation of matter?

 

[PeterDonis]

Can the fabric of space time be considered to exist in isolation of matter?

Since there is matter in the universe, we have no way of testing whether spacetime could exist in a universe with no matter at all.

 

[Atlas3]

Since there is matter in the universe, we have no way of testing whether spacetime could exist in a universe with no matter at all.

Can spacetime be constructed without matter? Mathematically.

 

[PeterDonis]

Can spacetime be constructed without matter? Mathematically.

Yes, flat Minkowski spacetime is a mathematical solution to the Einstein Field Equation with zero stress-energy (and zero cosmological constant). But again, because there is matter in our actual universe, this mathematical solution does not describe it.

 

[Atlas3]

Yes, flat Minkowski spacetime is a mathematical solution to the Einstein Field Equation with zero stress-energy (and zero cosmological constant). But again, because there is matter in our actual universe, this mathematical solution does not describe it.

Can curved spacetime be described within Minkowski spacetime as a system?

 

[Atlas3]

Looks like you were cut off.

It's possible to use the expansion of the universe to set a specific meaning for "now" (when the CMB has the same average temperature at every point). But it's still not really possible to use the expansion as a clock of any sort. Clocks typically depend upon having predictable, repeating behavior, and the expansion of our universe doesn't do that.

That is, you can use the expansion to sync up clocks that are far away, but you can't use it as a clock in and of itself.

I agree it could not be used as a clock in the time keeping sense. But does the possibiltity of periodicity in expansion allow negative expansion?

 

[Atlas3]

Yes, flat Minkowski spacetime is a mathematical solution to the Einstein Field Equation with zero stress-energy (and zero cosmological constant). But again, because there is matter in our actual universe, this mathematical solution does not describe it.

Thank you for your answers to my questions. It astonishing to me that I had the physical thought to think was a possibility. I came up with this without being taught or research. I had a moment of pure physics one night. Actually cosmology. I only reached a point in education recently to formulate questions to what i imagined in my mind one night. I have been pursuing this in college for a few years since. Now I am finding out things like this are possibilities in fact. Its amazing and thank you again.

 

[PeterDonis]

does the possibiltity of periodicity in expansion allow negative expansion?

If by "negative expansion" you mean "contraction", then yes, there are mathematical solutions that describe contracting universes.

 

[Atlas3]

If by "negative expansion" you mean "contraction", then yes, there are mathematical solutions that describe contracting universes.

can the contraction and expansion be a cycle without a crunch or bang mathematically? I was told it occurs like a step function, however, after big bang in theory.

 

[PeterDonis]

can the contraction and expansion be a cycle without a crunch or bang mathematically?

No; at least, not with classical GR. There are speculations that quantum effects might allow a "bounce" scenario where contraction turns around and becomes expansion before a crunch/bang occurs; but those are just speculations at this point.

 

[Chronos]

The 'block' universe concept has been widely discredited. See http://en.wikipedia.org/wiki/Eternalism_(philosophy_of_time) and https://[URL='http://www.facebook.com/BrianGreenePhysicist/posts/613446525347598']www.facebook.com/BrianGreenePhysicist/posts/613446525347598[/URL] for discussion.

 

[Atlas3]

The 'block' universe concept has been widely discredited. See http://en.wikipedia.org/wiki/Eternalism_(philosophy_of_time) for discussion.

It's over my head. Never read such discussion.

 

[russ_watters]

Note that you do not need a periodic process to have a usable clock, you only need a process with a predictable pattern or rate. You could, for example, measure the speed an object is traveling at, then use distance measurements (whenever you want) to calculate elapsed time. As long as the speed is predictable (it doesn't even need to be constant), you can use it to calculate time. Indeed, the age of the universe is calculated in exactly that way.

Because of that, in my particular dialect (Philadelphian), we use time and distance interchangeably.
Q: "How far are you from Philadelphia?"
A: "About 35 minutes."

 

[Atlas3]

No; at least, not with classical GR. There are speculations that quantum effects might allow a "bounce" scenario where contraction turns around and becomes expansion before a crunch/bang occurs; but those are just speculations at this point.

What type of geometry, in the shape sense, is the current model. That may not be possible to demonstrate. I was shown a depiction of a balloon inflating with the matter within. I was also shown that we are within a horizon surrounded by CMB in all directions I think. I think my questions of construction of ( not necessarily ours ) geometry have been answered as much as I was interested. I at least have an idea of the Euclid geometry to further consider. This thread was started about a time definition because I wasn't sure about how the time dimension in geometry was included in math. I recommend closing the topic. I will ask later about a flat metric for further inquiry after I get a better question.

 

[Atlas3]

Note that you do not need a periodic process to have a usable clock, you only need a process with a predictable pattern or rate. You could, for example, measure the speed an object is traveling at, then use distance measurements (whenever you want) to calculate elapsed time. As long as the speed is predictable (it doesn't even need to be constant), you can use it to calculate time. Indeed, the age of the universe is calculated in exactly that way.

Because of that, in my particular dialect (Philadelphian), we use time and distance interchangeably.
Q: "How far are you from Philadelphia?"
A: "About 35 minutes."

This is something I may want to discuss. I'm learning this bulletin board. Can I quote this reply when starting a new thread or maybe we could open a conversation to rattle this reply around some time? Thank you also for the reply.

 

[Atlas3]

What would it mean for spacetime to "have a clock of its own"?

The time parameter as it pertained to Euclid geometry and spacetime construction. The range as needed from initial to end for definition. That dimensional component I think has a particular range. My original post was actually titled poorly. I've added a little more comprehension of it though. Also I asked in a separate thread which was vague about dilation. Dilation only in the mathematical sense and how it applies to the dimension of time mathmatically for construction of a geometry. Two related questions. If someone would prefer to edit this thread it may be of more use. Especially the title. Thanks for helping me.

 

[slatts]

In Post #21, Chalnoth claimed the block universe view to be "widely discredited", although the Wikipedia piece he refers to seems noncommittal, and I've never heard of the guy who texted Brian Greene with some objections to it. (Sorry, Chalnoth; the quotes editing doesn't seem to be working right now.) I googled this issue extensively this past week, and that's not my impression.at all.

The most comprehensive discussion I found is on Stanford's encyclopedic site, heavily revised in 2013 and found here:

http://plato.stanford.edu/entries/spacetime-bebecome/

The block universe view can be traced back to Einstein, both through his own writings and through a biographer who was a friend of his. "Andromeda Paradox" brings up a raft of sites referring to some of the situations that resulted in it, and I'd say it's at the heart of Special Relativity, or, at least, of the diagramming taught to Einstein by his physics teacher, Minkowski, who developed the method for it.

I'm sure that that view (that the past, present, and future all exist) is vastly stronger than it was before it started taking shape with the 1918 experimental confirmation of relativity (which integrated time with space), and much stronger than it was even as recently as 1981, because of inflationary theory that (together with limits on the relevance of spatial separations below a certain tiny size that result from Heisenberg's Uncertainty Principle) leaves it perhaps looking kind of unlikely that there aren't innumerable replicas of ourselves living in innumerable replicas of our "observable region" right at this instant, and that there won't be even (vastly) more replicas of the entire "local universe" (including that entire "observable region") scattered through a multiverse between now and the infinite future, although most of those replicas may be on scales of size that are self-consistent, but different from our own.

The view that the past, present, and future all exist seems counterintuitive because it doesn't explain the sensation that time flows. Thing is, since electrons do circulate through our nervous system, our impressions do flow, and the Stanford piece concludes with a description of light cones on a very small scale, moving along world lines, as possibly the best explanation of that flowing sensation.

 

[PeterDonis]

Everyone, please be aware that the "block universe" is philosophy, not physics; it's an interpretation of SR, not a theory in itself. As such, it's really off topic for this thread, and indeed this forum.

 

[PeterDonis]

The time parameter as it pertained to Euclid geometry and spacetime construction. The range as needed from initial to end for definition.

If you mean the range of the "time" coordinate needed, this depends on your choice of coordinates. For example, even in flat Minkowski spacetime, you can choose coordinates for which the range of the "time" coordinate is $- \infty$ to $\infty$ (standard inertial coordinates, for example), but you can also choose coordinates for which the range of the "time" coordinate is finite (the coordinates used for Penrose diagrams, for example). So the allowed range of the "time" coordinate doesn't really tell you anything physical.

If you mean the range of proper times that are present on a timelike worldline, this will depend on the worldline. In flat Minkowski spacetime, every timelike worldline has an infinite range of proper time, i.e., $\tau$ goes from $- \infty$ to $\infty$. But in Schwarzschild spacetime, for example (i.e., a black hole), there will be timelike worldlines that end at a finite $\tau$ (the ones describing objects that fall into the hole and hit the singularity).

So there isn't really a unique "time parameter" that is built into spacetime itself.

 

[slatts]

I did just now find mention of a really interesting "timepiece" that might be read by someone entangled with it, but not by anyone outside its system. It's either one of a pair of entangled photons, whose polarities are switched to signal either of two values of time that depend on the amount of it that they spend passing over one or another of some metal plates that are varied in thickness. The experiment (by Moreva and several of her associates) is described in the 2013 paper, "Time from quantum entanglement", and seems supportive of Nomura's contention that time might be an emergent phenomenon in a local universe (like our own) of the past- and future-infinite multiverse described by Nomura in his 2012 paper, "The Static Quantum Multiverse": Time's passage might not be apparent to any being outside it, but, to us, would of course be as familiar as the times and street names on a bus timetable.

 

[russ_watters]

This is something I may want to discuss. I'm learning this bulletin board. Can I quote this reply when starting a new thread or maybe we could open a conversation to rattle this reply around some time? Thank you also for the reply.

Either would be fine with me, but as you can see, I may not notice...