ESOF session shines a light on the dark side of our universe
Cosmologists can measure with increasing precision how the universe is expanding and changing. This is producing unexpected results and causing cracks in our picture of the universe. At the ESOF session The Dark Side of our Mysterious Universe, cosmologists, astronomers and philosophers will discuss what we know and what they expect us to discover in the coming years.
‘If we look at what we now know about the universe, we are in a unique situation,’ says Professor of Observational Cosmology Henk Hoekstra, one of the organisers of the session. ‘Cracks are appearing in our measurements and there are big conceptual problems too.’
One of the puzzles cosmologists are trying to solve is the existence of dark matter and dark energy. Dark matter is matter that we know exists, because of observed gravity, but cannot see. ‘Experiments are being done right now to detect dark matter directly,’ says Hoekstra. ‘That’s what Laura Baudis will talk about. And philosopher David Albert will talk about the more fundamental, existential questions within cosmology. Luigi Guzzo will give an overview of the data we will collect in the coming years and will focus on Euclid, a European satellite designed to study the dark side of the universe.’
For long it was thought that the expansion of the universe was decelerating. ‘They thought all the mass in the universe would decelerate this expansion. Researchers tried to measure this deceleration at the end of the 1990s but discovered it was an acceleration.’ This accelerated expansion can only be explained by dark energy: the energy present in the empty space. ‘Fundamental physics can’t explain why this energy is there. We don’t know what it is. We only know it’s there because the universe is expanding faster and faster.’
Accurate data will offer new insights
Hoekstra expects that the launch of the Euclid satellite will soon provide more clarity about what exactly dark matter and dark energy are. ‘Seventy per cent of the energy in the universe is dark energy but dark energy was only discovered 25 years ago. That is because its effects are very subtle. To measure these you need an enormous amount of accurate data.’ This data will be collected during the Euclid mission.
‘With Euclid we want to map the structure of the universe, the distribution of galaxies in particular. We also want to map the corresponding distribution of dark matter.’ These measurements can be used to test various theories about the universe in a very precise way. ‘Then it will become clear whether there are only cracks in the measurements and models or whether the entire theory has shattered. The measurement errors are so much smaller than in previous experiments that it will clear up lots of discussions.’
‘Is our universe unique or could there be several universes?’
More clarity on the expansion of the universe and dark energy will bring us closer to answering very fundamental questions. Hoekstra: ‘Is our universe unique or could there be several universes? Why is there a universe at all? Why does time have a direction? That’s the good thing about cosmology, that we deal with the things that we all experience but most of us aren’t aware of.’
Intrigued? Hoekstra recommends three videos by speaker and philosopher David Albert.
Text: Tom Janssen
Banner photo: ESA/Hubble & NASA
In 2022 Leiden is hosting ESOF: the largest multidisciplinary science conference in Europe. The tenth edition will be held in Leiden from 13 to 16 July, in close collaboration with EuroScience from Strasbourg. ESOF2022 is about seven themes: Sustainable environment, Cultural Identities and Societal Transformation, Space for science, Healthy societies, Freedom and responsibility of science, Science and Business, and Sustainable Academic Careers.