The looming crisis in cosmology

Most of the universe is missing. Only 5% of it is normal matter, which makes up all the people, planets and stars we can see; the other 95% consists of mysterious dark matter and dark energy. Scientists have some hypotheses of what these enigmatic substances might be but recent astronomical observations have posed challenges to their ideas. Even worse, it could mean that there are cracks in the standard model of cosmology, the best scientific description of the universe’s evolution. It’s a nerve-wracking time for cosmologists—is everything they thought they knew about to come crashing down?

This is the first of two episodes that explore a looming crisis in cosmology. We examine what scientists understand about the evolution of the universe, and why their best model might be under pressure.