Does time exist?

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  • #51
apeiron
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Consder, if we had a volume of space that was completely empty, a perfect vacuum, then would time pass within that space?
If there was nothing there to change and, therefore no change happened, could we say that any time passed?
A difficulty for this line of thought is that space is expanding (and so cooling). You can imagine a static space with no contents, but we exist in a universe where the thermodynamics is actually wired in.

It is true that at the heat death in a flatly balanced universe, there would be very little change - as little as possible change. But there would still be change. And the speed of light would still be the yardstick on this change.
 
  • #52
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Take this a step further; if we had a body in that space, a totally inert body (this is a thought experiment, so I can stipulate a body with no motion whatever, not even atomic or sub-atomic motion) then, if it never changed, would time pass in that space?
But even something inert, as long as it exists in our universe, has to have mass and/or some motion within it to make it exist? Otherwise, wouldn't it just be nothing.

I'm not sure about the nature of massless particles, Is there something inside that moves or causes it to move?
 
  • #53
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A difficulty for this line of thought is that space is expanding (and so cooling). You can imagine a static space with no contents, but we exist in a universe where the thermodynamics is actually wired in.

It is true that at the heat death in a flatly balanced universe, there would be very little change - as little as possible change. But there would still be change. And the speed of light would still be the yardstick on this change.
Maybe it could be a static space with no contents, but IF there exisisted a static space with no change happening within it, would time pass within it?

Is there any reason why it should?

Relativity tells us that there is no universal time, no absolute time, that time varies according to the prevailing conditions, therefore, I contend, there is no requirement for time to exist where there is nothing to measure it by.

Similarly if a body existed with a slow rate of change, if perhaps that change were not only slow but intermittent, for instance, experiencing an occasional flash of light, then would time pass slowly in that environment?
 
  • #54
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But even something inert, as long as it exists in our universe, has to have mass and/or some motion within it to make it exist? Otherwise, wouldn't it just be nothing.

I'm not sure about the nature of massless particles, Is there something inside that moves or causes it to move?
What if it had mass but was inert?
 
  • #55
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Maybe it could be a static space with no contents, but IF there exisisted a static space with no change happening within it, would time pass within it?

Is there any reason why it should?

Relativity tells us that there is no universal time, no absolute time, that time varies according to the prevailing conditions, therefore, I contend, there is no requirement for time to exist where there is nothing to measure it by.

Similarly if a body existed with a slow rate of change, if perhaps that change were not only slow but intermittent, for instance, experiencing an occasional flash of light, then would time pass slowly in that environment?
Perhaps not, but such a condition (where there is nothing to measure by) would seem by our reckoning to be a state of non-existence, since in order for "something" to emerge again we need causality, and hence, time.
 
  • #56
apeiron
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Maybe it could be a static space with no contents, but IF there exisisted a static space with no change happening within it, would time pass within it?
I think you have to question the easy assumptions you are making here. That you can have space without the time.

The way I approach it is that a lack of something is a definite fact in any systems view. You have to do something extra to achieve the suppression or removal of a possibility.

So space~time is created as a dichotomy. The idea of locations is about the suppression of motions, the removal of changes. Pure space is defined as a 3D host of static co-ordinates.

Then time is defined dichotomously as the dimension which sees the remaining possibility for change. Locally, all is a static set of points. But globally, there is now all this space across which you can roam and revolve and accelerate.

So to have space, you must create its antithesis - time. And vice versa. To have stasis, you must also create the possibility of what it is not, that is flux. And to have flux, you have to have what it is not, that is stasis.

The two opposites always need each other. And GR was about a way to reconnect them after Cartesian co-ordinates and Newtonian mechanics had so crisply divided them.

GR said, well actually in our universe, there is no pure symmetry breaking into absolute space and absolute time. Instead, for massive objects, they live in a bounded spacetime. So objects will find that if they try to get very fast (at light speed, objects would experience no time), then the compression in the temporal direction becomes matched by an expansion in the spatial one. The object becomes very large (orthogonal to the direction of motion) and heavy.

So under GR, it becomes clear that you have a quantity of spacetime, and you can maximise one or other aspect - the locations or the motions - but you can't completely eliminate one or the other.

Space without the matching idea of time, stasis without the matching idea of flux, just does not make sense. Even if we can imagine - once we have these two possibilities - worlds in which one aspect has become so suppressed as to no longer "exist".

(In cosmology, it is actually quite common that people imagine a time without space. People say what came before the big bang? Nothing. There was just empty time. Of course, this again seems as wrong as imagining a space without time, but I'm just pointing out that this is a widespread thought that is out there.)
 
  • #57
russ_watters
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This should have been locked when it first started. It is even less of a philosophical question than it was a physics question. And as a physics question, it isn't a wrong question, it is just an easy one: yes, time exists.

Thread locked.

[edit] And FYI, the other lines of discussion, like 'does time exist in a vacuum' (yes - ask yourself if a vacuum has no time, how can we ever move through it?) and 'is mass required for existence' (no - ask yourself if you can attach a number to the mass contained in an empty box) are also just misunderstandings of physics and not philosophical questions either.

Hey, and while I'm at it - If a tree falls in the woods, does it still make a sound? Yes. Just in case anyone was curious...
 
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