Decoding the cosmos - with Hiranya Peiris

Unravel the profound mysteries of the universe's explosive birth.

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This talk was recorded at the Ri on 26 April 2024.

Just a century ago, observational evidence established the existence of other galaxies besides our own. Soon afterwards, it was discovered that the Universe is expanding, driving a profound change in our understanding of the cosmos. In 1998, the prevailing cosmological paradigm was again upended by the discovery that the Universe's expansion is accelerating.

Since then, the remarkable progress in cosmology, spanning Peiris's research career, has been driven by the close interplay between theory and observations. Observational discoveries have led to a Standard Model of cosmology with ingredients not present in the standard model of particle physics – dark matter, dark energy, and a primordial origin for cosmic structure. The physical nature of these ingredients remains a mystery. The race to unravel this cosmic puzzle is now underway, motivating a new generation of ambitious sky surveys across the electromagnetic spectrum and using new messengers such as gravitational waves.

Peiris describes some highlights from her journey through this rapidly changing cosmological landscape in this discourse. She also discusses how laboratory experiments are helping us test new fundamental physics paradigms developed to explain cosmological observations.

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00:00 Intro
1:30 How do we know about the universe?
7:55 Tracing the light of galaxies
13:00 The Legacy Survey of Space and Time (LSST)
16:53 Mapping dark matter with gravitational lensing
22:30 How do we know how far away galaxies are?
32:03 Using machine learning to explore galaxies
35:50 Detecting dark matter in the lab
46:31 The Universe on a table-top
54:58 Condensed matter experiment and cosmology

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Hiranya Peiris holds the Professorship of Astronomy (1909) at Cambridge, the first woman to do so in the 115-year history of this prestigious chair. As a cosmologist, she delves into cosmic mysteries at the edge of our understanding, reaching back to the very first moments of the Universe after the Big Bang, often treading the path of high risk and high reward. She is noted for interdisciplinary research bridging fundamental physics with astronomical data. Peiris recently contributed to the anthology “The Sky Is For Everyone” and works to reach beyond traditional audiences for public engagement, including through science/art collaborations and live science/music events. Her work has been recognised by awards such as the Max Born Prize of the German Physical Society and the Institute of Physics (2021), the Eddington Medal of the Royal Astronomical Society (2021) and the Breakthrough Prize in Fundamental Physics (2018).
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