Speaker: Geraint Lewis (University of Sydney)

Title: Confronting the Cosmological Principle: How secure are the foundations of the cosmos?

Abstract: For nearly a century, the cosmological principle has been the bedrock of our understanding of the universe. But what if this foundation is starting to crack? In this talk, I describe how we have used quasars and radio galaxies to test the assumption that the cosmos is isotropic and homogeneous. We know that the Cosmic Microwave Background displays a strong dipole, attributed to our motion relative to the local Hubble flow, and if this motion truly defines our cosmic frame, its imprint should appear elsewhere. Indeed, we find a dipole in large-scale surveys of cosmological sources, and whilst the direction agrees, the amplitude does not, diverging sharply from expectations based on the CMB. I will explore possible explanations for these tensions and ask whether they signal new physics or a fundamental shift in our cosmological worldview.

• Date:
  June 16, 2026, 2:30 p.m. – 3:30 p.m.
  
  
• Location:

  AIP; Kirch building, Conference room

  
  
• Contact:
  Marcel Pawlowski
  mpawlowski@aip.de