How the universe began—and how it is likely to end | Prof Carlos Frenk | TEDxDurham

Quick Overview

The standard model of cosmology ($\Lambda$CDM), which posits a universe dominated by dark energy causing accelerated expansion, is facing significant challenges from new data provided by the Dark Energy Spectroscopic Instrument (DESI), suggesting that dark energy is not constant but is declining over time, potentially leading to a future Big Crunch scenario rather than perpetual expansion or a Big Rip.

Key Points: Astronomers observe that all galaxies are moving away from us at a speed proportional to their distance, confirming the universe is expanding (0:12). Georges Lemaître first formulated the relationship $v = H0 d$ in 1927, known as the Hubble-Lemaître law, describing this expansion (0:42). The current understanding of the universe's composition is that only 5% is normal matter, 25% is dark matter, and 70% is dark energy, which opposes gravity and accelerates expansion (4:25). The DESI experiment has measured distances to over 40 million galaxies to track the expansion history of the universe through cosmic time (12:22). DESI data indicates that dark energy is not constant ($\Lambda$ is not a cosmological constant) but is declining over time, meaning the standard $\Lambda$CDM model is incompatible with the latest observations (12:50, 12:58). If dark energy diminishes, the universe might eventually collapse into a singularity (a Big Crunch) in about 30 billion years, suggesting a potential cyclical universe (15:08). The presentation concludes that a new paradigm is needed to describe the universe, as the current models based on constant dark energy appear to be broken (13:11, 13:59).

Context: The presentation by Professor Carlos Frenk at TEDxDurham discusses the current state of cosmological models, particularly the $\Lambda$CDM model, which incorporates a cosmological constant (Lambda) representing dark energy that drives the universe's accelerated expansion. Frenk traces the history from Lemaître's discovery of cosmic expansion to modern challenges posed by new data from the Dark Energy Spectroscopic Instrument (DESI), which suggests dark energy might not be constant, leading to potential alternative end-of-universe scenarios like the Big Crunch.