Velocity of our universe through time?

[guss]

"Velocity" of our universe through time?

As long as there is any energy/mass at all in our universe, time will always be in a "slowed" state. So, let's say we have a universe with no energy and no mass. If we could measure the rate time, wouldn't that be a very important value? Realistically, would this ever be possible to measure/have we done it?

Further, if we can consider time an extra dimension, then would it ever be possible to compare the "velocity" at which we travel through this dimension to any other velocity, like the velocity of a bullet, in our universe? Wouldn't this number resemble c?

I've been thinking about this recently, sorry if I'm totally wrong. Thanks.

 

[guss]

Bump.

 

[JesseM]

As long as there is any energy/mass at all in our universe, time will always be in a "slowed" state.

"Slowed" relative to what? There's no absolute truth about how fast a given clock ticks in relativity, you can only compare two clocks which cross paths twice to see which has elapsed more time (or compare how fast they are ticking relative to a given coordinate system). The notion of comparing clocks in different "universes" that aren't part of the same spacetime, and thus can't cross paths or have their positions and times labeled by a single coordinate system, doesn't really make sense to me.

The idea of "velocity through time" doesn't really make sense to me either, since spatial velocity is defined in terms of change in position over time, and there doesn't seem to be a coherent way to define "change in time over time".

 

[Nabeshin]

The idea of "velocity through time" doesn't really make sense to me either, since spatial velocity is defined in terms of change in position over time, and there doesn't seem to be a coherent way to define "change in time over time".

Of course, you could try to define it as change in proper time with respect to some coordinate time, i.e $$d\tau / dt$$. This might get some of what is meant by "velocity through time" but indeed it's probably better to avoid such notions altogether.

 

[guss]

The idea of "velocity through time" doesn't really make sense to me either, since spatial velocity is defined in terms of change in position over time, and there doesn't seem to be a coherent way to define "change in time over time".

I was thinking you could somehow compare it to the normal rate of time I was talking about before. Or, more simply and generally, time at a standstill. It's just very odd to think about since there really is nothing that we know of to compare it to, other than itself, or itself in different circumstances.

 

[Feeble Wonk]

Perhaps this is an absurd concept, but it seems that what Guss is contemplating is whether there is a maximum "rate of time passage". If one accepts that time passage slows for anybody in motion (relative to other bodies in motion), or with mass and the associated gravitational force, what would the time rate be for a hypothetical body of zero mass at absolute rest due to the absence of any other body to have motion relative to. Sadly, I've had similar curiosity myself.

 

[guss]

Perhaps this is an absurd concept, but it seems that what Guss is contemplating is whether there is a maximum "rate of time passage". If one accepts that time passage slows for anybody in motion (relative to other bodies in motion), or with mass and the associated gravitational force, what would the time rate be for a hypothetical body of zero mass at absolute rest due to the absence of any other body to have motion relative to. Sadly, I've had similar curiosity myself.

Exactly! Similar to c. In fact, it would probably be directly related to c, or the same thing in a different form.

 

[JesseM]

Perhaps this is an absurd concept, but it seems that what Guss is contemplating is whether there is a maximum "rate of time passage". If one accepts that time passage slows for anybody in motion (relative to other bodies in motion), or with mass and the associated gravitational force, what would the time rate be for a hypothetical body of zero mass at absolute rest due to the absence of any other body to have motion relative to. Sadly, I've had similar curiosity myself.

What do you mean by "time rate" though? Rate relative to what? It seems like you guys are implicitly thinking in terms of absolute time, but one of relativity's counterintuitive features is that it removes the need for any such notion in physics, you can only define the "rate" a clock is ticking relative to some arbitrary choice of coordinate system and different coordinate systems can disagree about which of two clocks has a faster rate of ticking.

 

[Feeble Wonk]

True, Jesse... the answer to my question, obviously, is that time would pass at the rate time passes. My hypothetical zero mass body at absolute rest would feel time at the same "rate" as it would regardless of its circumstance. Yet... it seems that there should be something significant about the fact that time, in any other universe, with any other body, could not possibly pass more rapidly than with my hypothetical body. Ughh...

 

[John232]

The universe as a whole could not have a velocity through time since SR states that each individual object in it would only pass through time by a given amount as it had a velocity through that universe.