EventHelge Kragh

From Zero-Point Energy to Dark Energy

According to the cosmological standard model known as the CDM model, the universe is in a state of accelerated expansion caused by dark energy, a strange kind of repulsive vacuum energy. Although this picture is only twenty years old, the roots of the concept of dark energy are much older. One of the roots can be found in a work by Walther Nernst from 1920. On the one hand, dark energy relates to the cosmological constant  appearing in Einstein’s field equations, such as first pointed out by Georges Lemaître in 1933; on the other hand, it also relates to the zero-point energy density of empty space. After a brief historical review of the idea of vacuum, the talk will focus on the concept of zero-point energy and how it eventually was incorporated into physical cosmology. If dark energy is a manifestation of, as usually held, it is still poorly understood. Physicists and cosmologists have not yet solved what is often referred to as the dark energy mystery.

Lecture 2

About The Speaker

2012 Helge

Helge Kragh is presently Professor Emeritus at the Niels Bohr Institute in Copenhagen, and has previously held positions at Cornell University, University of Oslo, and University of Aarhus, Denmark. His work covers the history of physics, chemistry and astronomy since about 1800. He is a member of the Royal Danish Academy of Sciences and Letters, and the recipient of several international awards, including the Abraham Pais Prize for History of Physics awarded by the American Physical Society. His latest monograph, co-edited with M. Longair, is The Oxford Handbook of the History of Modern Cosmology (Oxford University Press, 2019).