Acceleration/Deceleration

I'm thinking that velocity (meters/second) and acceleration (meters/second²) only make sense when you separate space and time.

When you combine space and time (spacetime), acceleration is the curvature of spacetime, just as if you plot a graph of the position of a ball thrown through the air as a function of time, you get a curve, a parabola. If spacetime is curved, the shortest path of the ball between two points will be curved.

Spacetime doesn't move or accelerate any more than the graph moves or accelerates.

I thought spacetime was expanding and accelerating?

This is way beyond my pay-grade,... but isn't acceleration/deacceleration is also relative in respect to a giving point which in this case would be the starting point...

Imagine if spacetime could accelerate or decelerate in all directions simultaneously?

Quantum physics is way above my paygrade, but I understand that a particle can be in two (2) places at the same time which is called “Quantum superposition – the quantum effect of where particles exist concurrently in multiple places.

So as a layman, I'd say... possible.

The effect would be the same as gravity.

That during deacceleration would be similar to Einstein's thought experiment when riding in a elevator.

Where is Jorrie when needed?

I don't think your analogy is useful or even survivable.

Imagine if spacetime could accelerate or decelerate in all directions simultaneously? The effect would be the same as gravity.

Simultaneous acceleration or deceleration in multiple directions is either the result of a catastrophic accident or a deliberate execution.

As a layman, using what we know I would agree…

On the other hand, on what we don’t know/understand, maybe.

Like the Big Bang,perhaps?

Mass tells spacetime where to bend.

Spacetime tells mass where to be.

So,my question is,could spacetime be accelerating, or decelerating in all directions,causing the effect we know as gravity?

Here is an interesting way to visualize the warped spacetime around a gravitating body similar to what you are saying. It shows a 3-dimensional slice of spacetime, a "movie" of 3 dimensions of space as time advances.

An object at rest or moving uniformly in this fabric of 3-dimensional space would appear as time advances to be attracted to the gravitating planet.

Can time be defined without the comparisons of their locations in space?

All time pieces use this principle,even atomic clocks.Time is the difference in states between two or more objects, or energy levels,so IMHO,time cannot be defined without a reference to motion or difference in energy levels.

If this is indeed the case,then space and time are inseparable.Time is moving at C,and like water flowing at C, in a river,as we accelerate upstream,the objects on the bank appear to be slowing down,and will become stationary when we finally achieve C speed.We do not have sufficient energy to achieve or overcome C.

I am surely displaying my ignorance of this matter,and I am trying top get a grasp in layman terms of what is really happening.

There seems to be an island of ignorance in my understanding of current theories of mass,gravity,speed,acceleration.

The shoreline of the island is slowly eroding,and eventually,I may be enlightened.

Thanks for all of the feedback and patience of everyone on this forum.