Originally Posted by thomheg

We observe something. That is certainly a valid statement. What is that?
Stuff in space?? We see it that way, but the term 'space' is ill defined. What actually do we call space? We can measure distances and angles, that creates geometry and that space. Now we observe that kind of space to be curved, i.e. near the sun. Here is we concentrate on the fact, that space could be curved.
Why could space be curved? Well- it's a definition: space is empty, has a geometry and light moves with c. Straight lines could be curved by masses nearby.
Now we have to find out, what system could have such a behavior. In fact we know already, because GR calls it spacetime. So our observations are based on whatever that is. We don't know, what that actually is, but we are sure, our understanding of space and time must have a foundation in spacetime, because otherwise GR wouldn't work.
Are there any hints, that we observe anything else? Particles for examples or fields or whatever? I would say no, we don't, because all kinds of things including particles and fields could be modeled that way.
Now back to the expanding earth. It would violate, what I call the particle concept: tiny entities, that join together, build atoms and these all other things, that move through space and time, driven by invisible fields.
The growing earth is not compatible with this concept. A growing earth would rule out the particle concept and we would have to find something totally different to explain our observations. Why? The earth is growing from within (if growing) and that is a place a particle could not reach. Along with the growth we could not keep a number of conservation laws. This is quite a thing and would be at least interesting to research.