[Ethos_ (OP)]

Which concept of universal expansion is in the majority?

1. The expansion of space can only be expressed by the measure of distance between material objects within it.

Or.............

2. The expansion of space can only be expressed by the expanding metric of space itself.

There seems to be some controversy over this and I would really like to explore how the members here at NSF view this question.

Many thanks for your consideration...............Ethos_

[Pmb]

(1) can’t be taken literally since it’s necessary but not sufficient for that to be true. By this I mean that just because the distance between two objects is increasing it doesn’t mean that the space is increasing. After all the distance between a plane and an airport increases it doesn’t mean that the space between us and the plane is increasing.

(2) also can’t be taken literally since that is merely a description of the space which one assumes to be expanding

[Ethos_ (OP)]

(1) can’t be taken literally since it’s necessary but not sufficient for that to be true. By this I mean that just because the distance between two objects is increasing it doesn’t mean that the space is increasing.

So, are you saying that the expansion is not an expansion of the metric itself? That it is just the observed increase in distance between objects resulting from the energy release which occurred at the Big Bang. Or are you saying that both scenarios might be possible, and that we may not be able to distinguish between which of the two is at work?

[Pmb]

So, are you saying that the expansion is not an expansion of the metric itself?

I really don’t understand what you mean when you say “expansion of the metric.”

Can you explain what you mean by that, please? 

[Ethos_ (OP)]

So, are you saying that the expansion is not an expansion of the metric itself?

I really don’t understand what you mean when you say “expansion of the metric.”

Can you explain what you mean by that, please?

I'm sorry Pete, this is a term I have seen used to define the fabric of space.

http://burro.cwru.edu/Academics/Astr328/Notes/Metrics/metrics.html