Two primary strategies exist for estimating the Hubble constant. The first involves monitoring nearby objects, such as supernovae and pulsating stars called Cepheid variables, to gauge their distances and velocities away from us. The second strategy entails studying the cosmic microwave background, the afterglow of the Big Bang, to understand the universe’s initial conditions and calculate its expansion rate since that time.
Unfortunately, these two methods produce inconsistent results. Data from the cosmic microwave background suggest a slower expansion rate, approximately 67 km per second per megaparsec, whereas observations of nearby supernovae and Cepheid stars indicate a quicker pace of about 73 km per second per megaparsec. Addressing this discrepancy, known as the Hubble tension, holds significant implications for understanding the universe’s evolution and fate.
Recent advancements in technology, specifically the deployment of the JWST, have provided new tools to address the Hubble tension dilemma. The JWST offers sharper resolution and improved precision compared to its predecessors, enabling researchers to analyze more than 320 Cepheids in two galaxies with remarkable accuracy. These new observations reveal a roughly threefold enhancement in precision compared to the Hubble Space Telescope, although the results generally align with Hubble’s previous distance estimates. Notably, the JWST measurements support the notion that the earlier results are not mere measurement errors, suggesting instead that something profound is amiss in our understanding of the universe.