Cosmology

Cosmology is the scientific study of the origin, evolution, structure, and fate of the universe. It seeks to understand the large-scale properties of the cosmos as a whole, using theories from physics and observations from astronomy. Cosmology addresses questions about how the universe began, how it changes over time, and what its ultimate fate might be. The prevailing framework is a hot, expanding universe described by the standard model of cosmology, commonly referred to as the Lambda-CDM model.

Modern cosmology emerged from applying general relativity to the universe's large-scale structure, including Friedmann solutions for expanding spacetime. The experimental cornerstone is the discovery of the expanding universe by Edwin Hubble. The discovery of the cosmic microwave background in 1965 provided strong evidence for a hot early universe. In the late 20th century, inflation and precision measurements further shaped the model of a universe that began in a hot, dense state and has been expanding ever since.

The standard model, ΛCDM, posits a Universe dominated by dark energy (cosmological constant) and cold dark matter, with ordinary matter forming a minority. In the first minutes after the Big Bang, light elements were synthesized in nucleosynthesis; about 380,000 years later recombination released the cosmic microwave background. Over cosmic time, gravity amplified density fluctuations into the large-scale structures seen today, including galaxies and clusters. Observations of the CMB, distant supernovae, and galaxy surveys support this framework.

Open questions include the nature of dark matter and dark energy, the detailed physics of inflation, and the conditions at the earliest moments of the universe. Cosmologists use electromagnetic radiation, gravitational waves, and computer simulations to test models and refine parameters. Upcoming observatories and surveys aim to measure expansion history and growth of structure with greater precision, potentially revealing physics beyond the current paradigm.