Scientists Tell Their Story
Cosmic Inflation
Cosmic inflation describes the extremely rapid expansion of the universe in the first tiny fraction of a second after the Big Bang. During this phase, space itself expanded exponentially, stretching microscopic quantum fluctuations into the seeds of the large-scale structures we observe today: galaxies, clusters, and voids.
Inflation explains several puzzles of the early universe, such as its remarkable homogeneity, the flatness of space, and the absence of unwanted relics predicted by particle physics. The rapid stretching also amplified tiny fluctuations in energy density, setting the stage for all subsequent structure formation.
The Cosmic Microwave Background
About 380,000 years after the Big Bang, the universe cooled enough for photons to decouple from matter. This released the Cosmic Microwave Background (CMB), a faint glow of radiation now observed across the sky. The tiny variations in temperature and polarization encode the distribution of matter and the initial conditions seeded by inflation.
By studying the CMB, scientists can infer the density of ordinary matter, dark matter, and dark energy, as well as the universe's geometry and expansion rate. It is a crucial observational cornerstone linking the first instants of cosmic expansion to the structures we see today.
From Fluctuations to Galaxies
The quantum fluctuations amplified during inflation eventually became the gravitational seeds around which matter gathered. Over millions of years, regions slightly denser than their surroundings attracted more matter, growing into stars, galaxies, and clusters.
Dark matter, though invisible, played a critical role in this process. Its gravitational pull accelerated structure formation and shaped the cosmic web — the vast network of filaments, voids, and clusters observed in the large-scale distribution of galaxies.
The Expanding Universe
The evolution of the universe from its birth to today is best described today by the Lambda-CDM model, which combines ordinary matter, dark matter, and dark energy. Observations of galaxy distributions, supernovae, and the CMB show that the universe has been expanding for 13.8 billion years, with dark energy now driving an accelerated expansion.
This framework allows scientists to connect the earliest quantum fluctuations to the observable universe, creating a coherent story from the birth of space-time to the large-scale structures we can map and study.
