# Accelerating Expansion of Space-Time and Implications for Time Itself

1. Jun 30, 2013

### messyties

I have had a physics related question buzzing around my head for some time now, but have not been able to find the answer to it. I should state that have no training in physics, but have an interest in science and the universe.

The question; if space is accelerating, what are the implications for time? As space and time are intrinsically linked, I would think that there must be some follow on effect. I know that mass and the speed of mass affects time, but what about the stretching of space itself? If space is accelerating, does that mean that the speed of passing time may be accelerating as well? And, would there even be any way of measuring or calculating this?

Sorry if this question comes across as a bit dim or I am missing out on some vital bit of information.

Thank you in advance.

2. Jun 30, 2013

### phinds

The accelerating expansion of the universe has no effect on time.

3. Jun 30, 2013

### WannabeNewton

The scale factor (which measures the acceleration you speak of) multiplies the spatial measures of distance. It does not affect the time measure, as phinds noted (however the scale factor is itself a function of time of course). You are correct that in general space and time are inextricably "linked" to put it loosely but when speaking of space and time with regards to the history of the universe, what we do is separate the history of the universe into distinct "spatial slices" which represent the universe at an instant of time. We separate the two notions, so to speak.

4. Jun 30, 2013

### Naty1

I like the answers to these questions:

5. Jun 30, 2013

### Naty1

A perspective which supports that of posts #2,3 would be via the balloon analogy. It is reasonable to identify the radial [distance from the center to the surface] in the balloon analogy with cosmological time, but it is a non-linear scale. So the universe started at the center, current time in on the surface, the future is to the outside.

This also helps cement the concept that in cosmology one has to be sure that measurements take place at the same time.....in the balloon analogy, instantaneously on the surface of the balloon.

phinds explains the balloon analogy here:

www.phinds.com/balloonanalogy