The fight over the Hubble constant

When it comes to the expansion rate of the universe, trying to get a straight answer isn’t easy. That’s because the two best ways of measuring what’s known as the Hubble constant are giving different results. As each method becomes increasingly accurate, the gap between widens. Is one of them wrong? Or is it time to rejig the Standard Model of Cosmology? Madeleine Finlay investigates the so-called ‘Hubble tension’ with Prof Erminia Calabrese. Help support our independent journalism at