Hecho con Indico
v3.2.5
Distances are one of the most important yet difficult to get quantities in astronomy. Normally, astronomers use redshifts (which are relatively easy to measure) as distance measure, but this only works if one assumes that there is a relationship between redshift and distance. The relationship between redshift and distance was first observationally verified in the 1920s by Edwin Hubble. He found that the further away a galaxy was, the galaxy would be moving away from us (i.e. redshifted) at ever faster rates. This was interpreted as being due to the expansion of the universe and the rate of this expansion is governed by the Hubble Constant. In more recent years, the Hubble Constant has been measured quite precisely by both direct distance measurements ("the distance ladder") and via model assumptions in observations of the Cosmic Microwave Background (CMB). There is currently a tension between these two measurements at the >4\sigma level. This suggests either new physics or systematics in the observations.