If the space time continuum is...?

Question

relative to the observer how is it that scientists are sure that the rate of expansion of the unverse in increasing?

Answer 1

Edwin Hubble demonstrated that all galaxies and distant astronomical objects were moving away from us ("Hubble's law") as predicted by a universal expansion. Using the redshift of their electromagnetic spectra to determine the distance and speed of remote objects in space (kindda like a radar gun on planets), he showed that all objects are moving away from us, and that their speed is proportional to their distance, a feature of metric expansion. Further studies have since shown the expansion to be extremely isotropic and homogenous, that is, it does not seem to have a special point as a "center", but appears universal and independent of any fixed central point.