Western Sydney Amateur Astronomy Group

Speaker: Prof. Geraint Lewis (Sydney Institute for Astronomy - Sydney University)

Attending in person

Professor Geraint Lewis undertakes a broad spectrum of research. On the largest scale, his program involves looking at the influence of dark energy and dark matter on the evolution and ultimate fate of the Universe. Another aspect of his research uses the phenomenon of gravitational lensing to probe the nature and distribution of the pervasive dark matter and employs individual stars to magnify the hearts of quasars, the most luminous objects in the Universe. Closer to home, Geraint's research focuses on Galactic cannibalism, where small dwarf galaxies are torn apart by the much more massive Milky Way and Andromeda Galaxies. Using telescopes from around the world, including the 10-m Keck telescope in Hawaii, he has mapped the tell-tale signs of tidal disruption and destruction, providing important clues to how large galaxies have grown over time.

Topic: Heavenly Tensions: Is modern cosmology in crisis?

In this talk, I’ll explore the growing tensions in modern cosmology—observational discrepancies that may signal cracks in the standard model. I will start with the Hubble tension, a persistent mismatch between early and late-universe measurements of the expansion rate, which challenges our understanding of cosmic history. From there, we will examine the cosmological principle —the assumption of large-scale uniformity —and how emerging evidence of dipole anisotropies—directional patterns in the distribution of galaxies—may undermine this foundational idea. I will conclude with a “state of the nation” overview, assessing whether cosmology is facing a genuine crisis or simply entering a new phase of discovery.

Visitors wishing to attend in person or online via Zoom must email us to make a booking.