A portion of the Hubble eXtreme Deep Field in full UV-vis-IR light, the deepest image ever obtained. The different galaxies shown here are at different distances and redshifts, and allow us to understand how the Universe is both expanding today and how that expansion rate has changed over time. (NASA, ESA, H. TEPLITZ AND M. RAFELSKI (IPAC/CALTECH), A. KOEKEMOER (STSCI), R. WINDHORST (ARIZONA STATE UNIVERSITY), AND Z. LEVAY (STSCI))

Sorry, Astronomy Fans, The Hubble Constant Isn’t A Constant At All

If your Universe contains any matter at all, a constant Hubble parameter is absolutely impossible.

Our observable Universe is an enormous place, with some two trillion galaxies strewn across the abyss of space for tens of billions of light-years in all directions. Ever since the 1920s…