I.11. Are galaxies really moving away from us or is space-time just expanding?


This depends on how you measure things, or your choice of coordinates.
In one view, the spatial positions of galaxies are changing, and this
causes the redshift.  In another view, the galaxies are at fixed
coordinates, but the distance between fixed points increases with
time, and this causes the redshift.  General relativity explains how
to transform from one view to the other, and the observable effects
like the redshift are the same in both views.

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