Does Time Cease to Exist Without Matter?

[salvestrom]

... In fact, space and time are viewed by physicists, and the mathematics of relativity theory, as qualities of the gravitational field of the cosmos that have no independent existence...

This is a mainstream view?

 

[Chalnoth]

This is a mainstream view?

Yes. Space-time is curved, and gravity describes that curvature and how it is related to matter.

 

[salvestrom]

Yes. Space-time is curved, and gravity describes that curvature and how it is related to matter.

That isn't the portion I was seeking clarification on. I was inquiring about the statement that neither have an independent existence. The link he is quoting from goes as far as to state without gravity both vanish.

 

[Chalnoth]

That isn't the portion I was seeking clarification on. I was inquiring about the statement that neither have an independent existence. The link he is quoting from goes as far as to state without gravity both vanish.

That's exactly what I'm saying though. When we talk about gravity, we are quite literally talking about space-time itself and how space-time behaves (with or without matter).

 

[Grimstone]

I have read in serveral posts here that the concept of time in a total void is meaningless. That is, many scadzillions of years from now, assuming the expansion continues and black holes evaporate, and all goes REALLY dark (yes, I'm talking about a LONG time), the concept is that time loses its meaning because there's no way to measure it.

This really is perhaps one of those silly semantic arguments that I usually do not care for but this one is bugging me for some reason.

I GET completely the fact that you can't MEASURE time without matter but the concept that time just stops passing doesn't make sense to me. It is a somewhat pointless distinction, since even if time goes on, nothing HAPPENS. It's just the concept that "time stops" that bothers me and that SEEMS to be what I'm hearing from some of the threads here.

I'd appreciate any comments anyone has on this? Do you think time doesn't exist if you can't measure it because there's nothing to make clocks out of (and even no subatomic interactions to measure your ticks by) ?

Thanks,

Paul

By the way, I put this in cosmology since I can't think where ELSE to put it ... if a mod wants to move it, fine by me.

Think of time as a river. with nothing to "notice", one drop of water looks exactly as the others, and so seems that nothing is happening. but the rivers does continue.

 

[Chronos]

Dr. Sten Odenwald has been a research astronomer for NASA for nearly 20 years. He currently directs the NASA outreach program. You can't get much more mainstream than that.

 

[phinds]

Think of time as a river. with nothing to "notice", one drop of water looks exactly as the others, and so seems that nothing is happening. but the rivers does continue.

Fanciful and literate, but I don't get any scientific underpinning to your statement.

 

[petm1]

3)The major difference between the time-like dimension and the space-like dimensions is that have no control over our speed or direction through the former.

Would the twin's paradox beg to differ?

Are the time or spacetime dimensions independent of matter-energy or simply manifestations of their interactions?

Or are matter-energy manifestations of time, after all the present is always local to matter?

 

[budrap]

Yes. Space-time is curved, and gravity describes that curvature and how it is related to matter.

Spacetime can be curved locally but I don't believe there is any empirical evidence that it is curved on the cosmological scale, is there?

 

[budrap]

Or are matter-energy manifestations of time, after all the present is always local to matter?

The distinction is that we directly observe matter and energy but only indirectly infer space and time from matter-energy behavior.

 

[Chalnoth]

Spacetime can be curved locally but I don't believe there is any empirical evidence that it is curved on the cosmological scale, is there?

Um, yes. That's what the expansion of the universe is. Space-time curvature.

 

[budrap]

Um, yes. That's what the expansion of the universe is. Space-time curvature.

I'm not sure what you think the expansion of the universe has to do with this but the universe on the large scale appears to be flat according to NASA:

http://map.gsfc.nasa.gov/universe/uni_shape.html

And if the cosmos is not flat then there is no cosmological scale (as opposed to local) gravitational field, otherwise it would not be flat, no?

 

[Chalnoth]

I'm not sure what you think the expansion of the universe has to do with this but the universe on the large scale appears to be flat according to NASA:

http://map.gsfc.nasa.gov/universe/uni_shape.html

And if the cosmos is not flat then there is no cosmological scale (as opposed to local) gravitational field, otherwise it would not be flat, no?

Flat in space, not space-time. Or perhaps more to the point, it is possible to choose particular coordinates (the CMB rest frame) where the spatial curvature is at least small, at most no more than one percent the current matter/energy density fraction.

But this doesn't mean that the space-time curvature vanishes. In fact, if you calculate the space-time curvature in a spatially-flat universe, you find it has only one term that is directly related to the Hubble expansion rate H. If you have spatial curvature as well, then there is an additional term due to the spatial curvature.

 

[ExecNight]

Time and space are thought to be a consequence of gravity. Theoretically, without gravity, there would be no time or space -
re: http://www.astronomycafe.net/gravity/gravity.html

What about dark energy and its non-gravitational affect on our universe?

 

[budrap]

Flat in space, not space-time. Or perhaps more to the point, it is possible to choose particular coordinates (the CMB rest frame) where the spatial curvature is at least small, at most no more than one percent the current matter/energy density fraction.

But this doesn't mean that the space-time curvature vanishes. In fact, if you calculate the space-time curvature in a spatially-flat universe, you find it has only one term that is directly related to the Hubble expansion rate H. If you have spatial curvature as well, then there is an additional term due to the spatial curvature.

No, the spatial curvature that you allude to is not "at least small", it is unobserved. That the observations constrain any possible curvature to a very small amount does not in any way support the view that such a curvature actually exists.

 

[Chalnoth]

No, the spatial curvature that you allude to is not "at least small", it is unobserved. That the observations constrain any possible curvature to a very small amount does not in any way support the view that such a curvature actually exists.

You're not understanding.

There is a difference between spatial curvature and space-time curvature. There is little or no spatial curvature. There is, however, space-time curvature, and that manifests itself as the expansion.

P.S. I realize now that my wording was a little misleading there. The next part, after the comma, is an accurate description: "at most no more than one percent of the current matter/energy density fraction," there is, naturally, no constraint on how small the spatial curvature can possibly be.

 

[budrap]

You're not understanding.

There is a difference between spatial curvature and space-time curvature. There is little or no spatial curvature. There is, however, space-time curvature, and that manifests itself as the expansion.

P.S. I realize now that my wording was a little misleading there. The next part, after the comma, is an accurate description: "at most no more than one percent of the current matter/energy density fraction," there is, naturally, no constraint on how small the spatial curvature can possibly be.

I understand what you're saying, I just don't understand its relevance to my original point that there is no observational evidence of spacetime curvature by a cosmological gravitational field (which should be observable in space if it existed).

 

[Chalnoth]

I understand what you're saying, I just don't understand its relevance to my original point that there is no observational evidence of spacetime curvature by a cosmological gravitational field (which should be observable in space if it existed).

What? Why would you think that? It is trivial to show that you can have a universe with non-zero space-time curvature but zero spatial curvature. A flat, homogeneous, expanding universe is just such a universe. The expansion itself is the space-time curvature.

 

[salvestrom]

The expansion itself is the space-time curvature.

As far as I've read the expansion is considered a growth, with the creation of new space such that the expanded space is no different (from NASA's website: they even state it is a prediction of Einstien's). Since space is observed to be flat and is as distant from any source of mass as you can get, then there can be no curvature of time either, i.e. Coordinate Time.

 

[Chalnoth]

Since space is observed to be flat and is as distant from any source of mass as you can get, then there can be no curvature of time either, i.e. Coordinate Time.

Why would you think this?

 

[Chronos]

Since light and gravity propogate at the same velocity, if you can see a star the gravity of that star is tugging at you. Given that gravity is treated as the curvature of spacetime under GR, spacetime is curved. Assuming you could find a place in the universe where no light had yet reached, there would be no gravity hence no curvature. We can see the light emitted by the surface of last scattering [CMB], so it would appear such a place does not exist in this universe.

 

[salvestrom]

Since light and gravity propogate at the same velocity, if you can see a star the gravity of that star is tugging at you. Given that gravity is treated as the curvature of spacetime under GR, spacetime is curved. Assuming you could find a place in the universe where no light had yet reached, there would be no gravity hence no curvature. We can see the light emitted by the surface of last scattering [CMB], so it would appear such a place does not exist in this universe.

I totally accept the statements you make - I realized this in another thread on redshift. But such places are as free from gravity as anywhere you're going to find. The curvature is surely so minimal as to be negligable? Also, such places are expanding. Won't this be negating gravity? Flattening spacetime?

Not to be picky, but I assume you meant observable universe at the end there? =D

 

[budrap]

Since light and gravity propogate at the same velocity...

That is a theoretical statement only. The speed of gravity has never been directly measured.

http://math.ucr.edu/home/baez/physics/Relativity/GR/grav_speed.html

 

[Chronos]

Kopeikin and Formalont claim to have measured the speed of gravity in 2003
http://www.csa.com/discoveryguides/gravity/overview.php. This finding has been challenged by several scientists [including Steve Carlip], but, Kopeikin has vigorously defended the study [e.g., http://arxiv.org/abs/astro-ph/0311063] . The Newtonian view was the speed of gravity is infinite, but, I doubt any mainstream scientist takes that seriously anymore - albeit some 'fringe' personalities [e.g. Thomas van Flander] have argued the case. I don't recall anyone claiming it was slower than light.

PS Yes, I intended the observable universe. I tend to refrain from invoking the unobservable universe. The important point here is that gravity, like light, permeates the entire observable universe, hence some amount of spacetime curvature is present everywhere in the observable universe. While it is obviously miniscule in intergalactic space, the extent of curvature is irrelevant within the context of this thread.

 

[salvestrom]

I draw a lot. Line work. That's just pencil on paper. A line image has a lot in common with the universe. The graphite markings can be mass and the unmarked paper is spacetime. It can be realized that both are needed to complete the picture. Without the blank page seperating the lines we have a single blob of grey. Without the lines we have an undefined blank page.

It initially seems that the blank page is far less affected by the absence of the lines than vice versa. I currently own an utterly untouched sketchpad. It hasn't ceased to exist because it hasn't been drawn in. It's still a sketchpad. If only in potential. As for spacetime, in the absence of mass or energy, it will just sit there, uncurved, unloved, writing songs any emo goth band would be proud of. But the undefined blob of matter has almost no physical definition. It has no length in any direction and no time passes. It is missing two of three basic quantities with which we define much of the universe. While the spacetime is missing only one.

I'm biased. While open minded to a number of odd possibilities, I increasingly lean toward the notion of spacetime as being utterly fundamental to everything, and not something to be sidelined. The above paragraph might seem to support that particular personal Pisa. And yet a philosophical tone in this post and in my own mind, which seems hard to resist, points out that these three things belong together and are as insperable as spacetime was for Einstien.

So, perhaps my answer to the OP's question is that time doesn't require matter... but the universe - and my artwork - is a lot more interesting when all three are around. =D

 

[phasl001]

So back to the subject, time doesn't require matter (as it is considered a dimension). It will exist as long as the universe creates it.

-Phil

 

[phinds]

So back to the subject, time doesn't require matter (as it is considered a dimension). It will exist as long as the universe creates it.

-Phil

Welcome to the forum.

You have expressed an opinion as a categorical statement of fact. Do you have any physics to back it up? This forum is not big on unsupported speculation.

 

[salvestrom]

Welcome to the forum.

You have expressed an opinion as a categorical statement of fact. Do you have any physics to back it up? This forum is not big on unsupported speculation.

Let's be fair. The poster may not know they are stating an opinion. Part of the point of the forums is to smooth over the gap between media interpretation/spin of science and, well, science. Joke incoming, do not read if allergic to humour: media spin is a spin-∞ particle. It's always changing and never returns to the original form, regardless of how you turn it. One must acquire knowledge of the original state of the system to learn anything. ;)

Time is either a proper dimension or not. The 'not' covers a range of possibilities, perhaps, but currently maths treats it as a pseudo-dimension. It works to do so, but there's no actual reason, just based on that maths, to catagorically state the case either way.

As a proper dimension it makes things rather neat and tidy, which is great. Symmetry is neat and tidy. But that doesn't mean the universe will oblidge.

 

[phasl001]

Time is a dimension. In theory (One that is widely accepted), space & time is the fourth dimension mentioned by Albert Einstein. In our Universe, which was created perfectly balanced, has many specific laws that govern it. Laws that could have been different if the slightest change occurred at the creation of our Universe (Big Bang or use your theory of everything). For all we know, at the end of our Universe (emptiness), another big bang can occur INSTANTLY also taking an eternity or an infinite amount of time to occur, all at the same "time" (kind of like the theories of a black hole). Our current laws and dimensions do not apply in that state. You are right, it is an opinion and I should have explained it more clearly. In the end of it all, theories are opinions, they are just more widely accepted because it makes sense.

 

[DaveC426913]

In the end of it all, theories are opinions, they are just more widely accepted because it makes sense.

This is not true. Theories are not opinions, they are models that match the facts we observe. And how widely accepted they are is directly proportional to how well they match the facts.

 

[phasl001]

This is not true. Theories are not opinions, they are models that match the facts we observe. And how widely accepted they are is directly proportional to how well they match the facts.

Yet a theory remains unproven even if it has facts to back it up, therefor it is a highly scientific opinion, because anyone might think otherwise. For example, global warming, many believe that it is cause by increased carbon dioxide levels in the atmosphere. It is fact that carbon dioxide levels have risen and it is also fact that the Earth is warmer than it really is. Regardless of the theory, it remains unproven and only a matter of opinion on what exactly is warming the earth. Sorry to go off topic, but I believe you are wrong. Which is my opinion :)

-Phil

 

[DaveC426913]

Yet a theory remains unproven even if it has facts to back it up,

Theories are never proven. That is not the purpose of a theory.

therefor it is a highly scientific opinion, because anyone might think otherwise.
For example, global warming, many believe that it is cause by increased carbon dioxide levels in the atmosphere. It is fact that carbon dioxide levels have risen and it is also fact that the Earth is warmer than it really is. Regardless of the theory, it remains unproven and only a matter of opinion on what exactly is warming the earth.

Yes. There are competing theories. Do not confuse that with opinions. This is a a separate topic. If you wish to understand scientific theory, feel free to open a new thread about it.

 

[mathal]

Just a guess.

To the degree that gravity between particles has a diminishing effect on their inertial motion WRT each other, regions of space far from all receding galaxies will contain molecules of hydrogen which will separate from each other. Eventually each will be entirely alone in it's own observable universe. But even then each molecule will have virtual particles to interact with. There will still be time.

mathal

 

[Spourk]

My first response to the OP was, "When you die, does the universe dissappear?"

The answers are just as philosophically confusing.

What I am getting from this thread, in short, do things still happen? If you were to pop into that universe, would you start to get really bored? That would be an indication that time still exists, BUT, without your boredom and you, there would be no one to measure it, so the question is kind of moot in the end.

Everything we see now indicates that time is going to pass with or without you, the entire crux is, "can it be measured, and if it can't, does it matter?".

 

[petm1]

The simple answer is matter and it's associated energy, of which we are all a part, are what we count as time. The space we "see" is the difference between the emission and reception of a photon upon reception in the present or just another duration.