Cosmology [ FULL ⟶ ]

Just a century ago, we believed the Milky Way was the entire universe. Today, cosmology has a standard model: . It is a deceptively simple mathematical framework asserting that the ordinary matter (atoms) making up stars, planets, and life accounts for less than 5% of the universe. The rest is dark matter (27%) and an even more mysterious dark energy (68%). This model is extraordinarily successful, yet it rests on foundations that many physicists suspect are incomplete.

ΛCDM remains the best description of our universe’s history from one-trillionth of a second after the Big Bang to today. But like the epicycles of Ptolemaic astronomy, its increasing complexity (adding parameters to fix each tension) suggests it may be an approximation to a deeper theory. Cosmology is no longer a purely observational science; it is a high-stakes laboratory for fundamental physics. Whether ΛCDM survives or falls, we are living through a revolution in our understanding of the cosmos. cosmology

Is ΛCDM in trouble? Not yet. But it is certainly under stress. The framework is so successful that it would be foolish to abandon it for minor anomalies. However, the persistence and growing significance of the Hubble tension suggest we are not dealing with mere noise. Just a century ago, we believed the Milky