How do tiny temperature fluctuations in the cosmic microwave background help explain galaxy formation?

The tiny temperature fluctuations observed in the cosmic microwave background (CMB) are fundamental to our understanding of how the universe evolved from a nearly uniform state into the complex structure of galaxies and clusters of galaxies we see today.12

These fluctuations, which amount to only about one part in 100,000, represent primordial density variations in the early universe. According to cosmological theory, these variations originated as quantum fluctuations in mass density during the period of inflation.134

The process of galaxy formation is explained as follows:

• Gravitational Growth: Following the inflationary period, these density fluctuations grew gravitationally over time. Regions with slightly higher density exerted a stronger gravitational pull, attracting surrounding matter.425
• Condensation: As the universe expanded and cooled, these dense regions allowed matter to condense into [protogalaxies].5
• Structure Formation: Over billions of years, these initial seeds of structure facilitated the coalescence of dark matter and ordinary matter, eventually forming the stars and galaxies that populate the modern universe.256

Measurements by satellites such as COBE and the Wilkinson Microwave Anisotropy Probe have confirmed that these fluctuations are consistent with the seeds required for the gravitational collapse of matter into the large-scale structures observed in the present epoch.124