The DemystifySci Podcast

When Cosmology Refuses to Do Physics – Dr. Brian Keating, DemystifySci #392

Jan 11, 2026
Dr. Brian Keating, an experimental cosmologist and professor at UC San Diego, dives deep into the cosmic microwave background (CMB) and its pivotal role in understanding the universe. He discusses the complexities of measuring the CMB and questions whether its near-perfect black body spectrum can be explained by early-universe plasma. The conversation explores assumptions about the Big Bang, the constraints of hydrogen physics, and how different physical systems can produce such precise spectra, all while addressing the clash between measurement and interpretation in physics.
Ask episode
AI Snips
Chapters
Books
Transcript
Episode notes
INSIGHT

CMB As A Precision Thermometer

  • The CMB is observed as an almost perfect black body spectrum, which cosmologists use as a precise thermometer of early-universe conditions.
  • That precision is central to the narrative tying a hot, dense past to observed elemental abundances and expansion evidence.
ANECDOTE

Instrument Builder Perspective

  • Brian Keating describes his role as an experimental cosmologist who builds instruments rather than invents theories.
  • He highlights projects like the Simons Observatory as pinnacles of instrument construction.
INSIGHT

Planck Spectrum And Measurable Deviations

  • A perfect black body follows the Planck/Bose-Einstein distribution characterized by a single temperature parameter.
  • Deviations (Compton Y, chemical potential) are measurable and constrained to very small values in the CMB data.
Get the Snipd Podcast app to discover more snips from this episode
Get the app