Dark Energy and the Expanding Universe: A Royal Society Talk on Cosmology and Outreach

Overview

An engaging Royal Society lecture on dark energy and cosmology. The speaker traces the history of the universe from the big bang to the accelerating expansion, explaining how gravity and quantum physics intersect on the largest scales. She discusses why the acceleration implies a mysterious dark energy composing about 70% of the universe, and surveys how collider experiments, atomic interferometry, and cosmological observations test competing models. Interwoven are personal reflections on science education, stereotypes, and outreach programs that aim to broaden access to physics for girls and underrepresented groups through initiatives like the I'm a physicist badge and work experience programs.

Introduction

The talk opens with a concise history of the universe, starting from the hot, dense state produced by the big bang, through the formation of nuclei, atoms, stars, and galaxies. Gravity dominates on large scales, pulling matter together as the cosmos expands. The surprising and tiny but persistent acceleration of this expansion over the last few billion years is highlighted, along with the observational evidence that earned the 2011 Nobel Prize in Physics.

Dark energy is named to describe the unknown cause of this acceleration, a mystery not explained by standard particle physics or gravity. The speaker emphasizes that understanding dark energy requires a synthesis of ideas across vastly different experimental arenas, from high-energy colliders to tabletop quantum experiments and astronomical surveys.