Two values for one constant – impossible, but true

The universe is expanding. That’s something astronomers have agreed on for a long time. Edwin Hubble, an American astronomer, was the first to discover that light from distant galaxies was shifted toward red frequencies by the time it reached us – which meant that the source of the light was moving away from us. The Hubble constant, which expresses how quickly the universe is expanding, was named in Hubble’s honor. It has a value of approximately (more on this later) 70 kilometers per second...