The universe still seems to be expanding faster than it ought to

The bright Cepheid variable star at the center of the image, RS Puppis, rhythmically brightens and dims

By Leah Crane

The heat death of the universe is coming for us, but we don’t know when. The cosmos is constantly expanding, and the speed of that inflation is measured by a value called the Hubble constant. We have two ways to determine this rate, and they have always returned different values, leaving researchers at an impasse. A new study of the stars we use to measure the distance to other galaxies has deepened the divide.

One way we search for the Hubble constant is to start at the beginning. We can look at the cosmic microwave background (CMB) – a relic of the first light to cross the cosmos after the big bang – and see how fast the universe was expanding back then. Models of how