Tell me, do you think there is gravity existent in the expansion? If you think there is, does it come 'instantly' or does it 'propagate'. Can there be a defined 'space', measurable, without gravity? What would such a 'space' look like?

One-dimensional maybe?

So, would you be able to measure it?

If now gravity is what defines a 'space' and it 'propagates' it 'propagates in something you can't measure. Alternatively 'gravity' becomes 'instantly' in those new 'expansions'. In the first cause 'gravity' is a 'force' of some kind propagating in a unmeasurable 'medium'. But if it was so and space 'expanded' the gravity should 'weaken' with the distances growing. And so also possibly be expected to 'dilute' everywhere, as we might define it as of being of one 'quantity' inside SpaceTime, coupled to the definition of mass we use.

If it then comes 'instantly' we find that 'space' and 'gravity' is one and the same, then the question becomes from where that 'gravity' comes. In Einsteins definitions SpaceTime is a whole. The observer is what defines both 'distances' and 'time'. My definition won't be yours, but both will be as valid, as measured from our own frame of reference. So, if distance is a questionable thing, maybe that is what we should look at.

Then you have the possibility of us all 'shrinking' too, that would create the same impression. I'm not sure the 'room' needs more 'energy' to expand, but I'm pretty sure it needs 'gravity' to exist.

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There is one definition more you might use, or add, if we assume that gravity is coupled to energy, or possibly equal to 'energy' in some way. Then the rooms expansion might be a result of more gravity, or if you like, the quantity of gravity raising is a result of the rooms expansion

which is a pretty tricky one as it involves something growing as it 'produce' more 'gravity'. That one comes directly from the idea of a 'whole SpaceTime' where nothing ever gets lost, just transforms. So the 'energy' to expand could then be defined as coming from SpaceTime itself. It opens for the question of what 'energy' really is naturally. Myself I wonder about what 'distance' is