general relativity - How to test whether galaxies are moving away from each other in a static background or whether space is being created beween them?

Observations show that galaxies are moving away from one another on the macroscopic scale.

Now, scientists interpret this by saying this happens not because galaxies are really moving away from each other in a static background but because more and more space is created between galaxies.

Now how scientists can distinguish between the 2 scenarios? what made them believe in the 2nd and discard the 1st?