How fast is the universe expanding? Quasars provide an answer

The H0LiCOW collaboration, a cosmology project led by EPFL and Max Planck Institute and regrouping several research organizations in the world has made a new measurement of the Hubble constant, which indicates how fast the universe is expanding. The new measurement challenges some of the most recent ones, potentially pointing towards new physics beyond the standard cosmological model. Measuring how far objects are across space has led to great discoveries, for example that our universe is expanding. The rate of this expansion is determined by the current Standard Cosmological Model, 'Lambda CDM', which puts the current expansion rate at about 72 km per second per megaparsec (a megaparsec is about 3.3 million light-years). This rate is called the 'Hubble constant' (H₀), and has been constantly refined for almost a century: a high-precision measurement of H₀ has profound implication both in cosmology and in physics. Now, the H0LiCOW collaboration has used new tools to independently calculate the all-important Hubble constant with 3.8% precision. The new figure agrees with recent independent studies, which are however in tension with the predictions of the Standard Cosmological Model, potentially pointing towards new physics. The work is published in five papers in the  Monthly Notices of the Royal Astronomical Society . A history of expansion The expansion of the Universe, based on the idea that the Universe originated with the Big Bang, was first proposed by the Belgian cosmologist Georges Lemaître.