why does time require matter ?


by phinds
Tags: matter, require, time
salvestrom
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#19
Jan23-12, 09:37 PM
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Quote Quote by phinds View Post
Did you, in that statement, mean that you believe time would be EXPANDING, or just that time would continue to exist (which would be consitent with the statement above) ?
Ah. Um. Prolly best I don't explain that. =D
Chalnoth
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#20
Jan24-12, 02:26 AM
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Quote Quote by phinds View Post
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.
Looks like this has been a pretty active thread, but I'll just chime in in response to this OP.

This can be made clear, I think, by marking a distinction between the dimension of time and the arrow of time.

The dimension of time exists regardless. It is there whether or not you have matter around to experience it. But if there is no matter, radiation, or anything else, then there is no direction to the dimension of time. In other words, there is no arrow of time.

An arrow of time only appears when you have a universe which is increasing in entropy. But an empty universe is just that: empty. It doesn't change in entropy at all, so it doesn't have an arrow of time. And when a new universe is born, its arrow of time could point either way, depending upon its initial conditions.
phinds
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#21
Jan24-12, 07:50 AM
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Chalnoth, thanks for that response. I think perhaps your concept is mathematically viable, although I'm not sophisticated to know, but the thing about it that doesn't stike a sympathetic chord in my thinking is that it would then seem to imply that the arrow of time, in this far future, would not have to be "pointing in the same direction", if you see what I mean, as it is NOW, and that doesn't seem to make sense.

I realize that NOT what you said, and it's an implication that I am deriving from your statement. You didn't say it could turn around, you said it wouldn't exist, but I continue to find it confusing and I can't seem to get a good handle on the distinction between the "dimension" and "arrow" concepts.

On the other hand, I just got up, so I'm mull it over a bit.

Thanks again.

Paul
Chalnoth
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#22
Jan24-12, 08:13 AM
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Quote Quote by phinds View Post
Chalnoth, thanks for that response. I think perhaps your concept is mathematically viable, although I'm not sophisticated to know, but the thing about it that doesn't stike a sympathetic chord in my thinking is that it would then seem to imply that the arrow of time, in this far future, would not have to be "pointing in the same direction", if you see what I mean, as it is NOW, and that doesn't seem to make sense.
Well, in the far, far future, the arrow of time will cease to exist in our universe. A new universe with a different arrow of time may be born from our universe, but will necessarily be disconnected from it (a new arrow of time within our universe would be a contradiction).

Quote Quote by phinds View Post
I realize that NOT what you said, and it's an implication that I am deriving from your statement. You didn't say it could turn around, you said it wouldn't exist, but I continue to find it confusing and I can't seem to get a good handle on the distinction between the "dimension" and "arrow" concepts.
Well, one of the ways this is classically described is with billiards. If you imagine an interaction where two balls collide, there simply isn't any way to know whether you're watching that video forward or in reverse. The far future of our universe will be like that: there will still be all sorts of quantum fluctuations of the vacuum, but a movie of those fluctuations will look the same whether played in either direction.

But if, instead, we imagine a break, where the billiards player strikes the 15 balls collected together, causing them to scatter, then we have a definitive arrow of time: the collection of 15 balls is a very low-entropy configuration, and it is obvious that this isn't an instance of fifteen balls coming together spontaneously to push off one other ball. It's an instance of one ball striking the collection of 15, breaking them apart. That definitive arrow of time is a consequence of the increase in entropy of the system. When the entropy stops increasing, there won't be any arrow of time any longer.
phinds
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#23
Jan24-12, 08:19 AM
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Quote Quote by Chalnoth View Post
Well, in the far, far future, the arrow of time will cease to exist in our universe. A new universe with a different arrow of time may be born from our universe, but will necessarily be disconnected from it (a new arrow of time within our universe would be a contradiction).
Yeah, that part I got OK.

Well, one of the ways this is classically described is with billiards. If you imagine an interaction where two balls collide, there simply isn't any way to know whether you're watching that video forward or in reverse. The far future of our universe will be like that: there will still be all sorts of quantum fluctuations of the vacuum, but a movie of those fluctuations will look the same whether played in either direction.

But if, instead, we imagine a break, where the billiards player strikes the 15 balls collected together, causing them to scatter, then we have a definitive arrow of time: the collection of 15 balls is a very low-entropy configuration, and it is obvious that this isn't an instance of fifteen balls coming together spontaneously to push off one other ball. It's an instance of one ball striking the collection of 15, breaking them apart. That definitive arrow of time is a consequence of the increase in entropy of the system. When the entropy stops increasing, there won't be any arrow of time any longer.
Helpful. thanks.
nihilius
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#24
Jan24-12, 09:34 AM
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Quote Quote by DaveC426913 View Post
If then cannot be true.


If thencannot be true.

Your statements are false regardless of whether there's matter or no matter.
Maybe, if we interpret motion as perception of motion, a settlement would be possible.
penomade
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#25
Jan25-12, 05:45 AM
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Well, one of the ways this is classically described is with billiards. If you imagine an interaction where two balls collide, there simply isn't any way to know whether you're watching that video forward or in reverse

the rate of accelerations differ when played backwards. Immediately after the collision, in forward direction, the speed of a ball maybe relatively high, but it gradually diminishes as it moves forward. And that shows when played in reverse.
Chalnoth
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#26
Jan25-12, 07:31 AM
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Quote Quote by penomade View Post
the rate of accelerations differ when played backwards. Immediately after the collision, in forward direction, the speed of a ball maybe relatively high, but it gradually diminishes as it moves forward. And that shows when played in reverse.
Ah, yes, well, for this thought experiment ignore friction.
shifty88
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#27
Jan25-12, 08:27 AM
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why ignore friction, wouldnt that be the force responsible for the ball slowing down
Chalnoth
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#28
Jan25-12, 08:55 AM
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Quote Quote by shifty88 View Post
why ignore friction, wouldnt that be the force responsible for the ball slowing down
Because I'm trying to draw your attention to the nature of the collision, not what happens before or after said collision.
shifty88
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#29
Jan25-12, 10:23 AM
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Quote Quote by Chalnoth View Post
Because I'm trying to draw your attention to the nature of the collision, not what happens before or after said collision.
Didn't see your big post about the 15 billiard balls being a metaphor to describe the arrow of time as a consequence of entropy.
I totally missed the 'metaphor'.
leonstavros
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#30
Jan25-12, 12:00 PM
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I just stumbled on to this thread and you got me thinking about time being dependent on matter so I thought if matter in quantum scales is probabilistic is time probabilistic also? I mean how can you time anything below the atomic scale?
budrap
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#31
Jan25-12, 12:21 PM
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There is no empirical basis for the assertion that time exists independently of the physical processes by which we claim to measure it and therefore while the assertion may raise interesting philosophical considerations it should be considered inconsequential to scientific thought. The concept of time is simply a useful human generalization that has arisen from repeated observations of physical processes.
phinds
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#32
Jan25-12, 01:24 PM
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Quote Quote by leonstavros View Post
I just stumbled on to this thread and you got me thinking about time being dependent on matter so I thought if matter in quantum scales is probabilistic is time probabilistic also? I mean how can you time anything below the atomic scale?
There are some interesting threads on this forum that discuss whether or not perhaps time is quantized in some way, but it's not a question that current physics is able to resolve.
phinds
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#33
Jan25-12, 01:25 PM
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Quote Quote by budrap View Post
The concept of time is simply a useful human generalization that has arisen from repeated observations of physical processes.
I'm not exactly sure what you have in mind with that, but it seems to overly trivialize time.
salvestrom
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#34
Jan25-12, 02:04 PM
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@budrap: Time is part of the way we measure the seperation of events. Whether we use human inventions such as the second, or simply say 'it took awhile', these things relate to an actual property of the universe that exists regardless of how we describe it.

@penomade: Only showing the moment of collision, which is quite reversible, is hiding the wider reality of the balls suddenly moving with no apparent cause, overcoming friction and finally striking the tip of the cue, using additional energy sucked in from sound to generate more force to shunt the cue away.
DaveC426913
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#35
Jan25-12, 05:27 PM
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Quote Quote by salvestrom View Post

@penomade: Only showing the moment of collision, which is quite reversible, is hiding the wider reality of the balls suddenly moving with no apparent cause, overcoming friction and finally striking the tip of the cue, using additional energy sucked in from sound to generate more force to shunt the cue away.
No. The process is reversible, and energy is conserved. It is just an unlikely sequence events events given entropy.
minio
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#36
Jan25-12, 06:12 PM
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Maybe stupid question, but if time is dependent on matter would there be time, if there are only photons? Or are they considered matter in this case?


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