Pioneering Measurement of Universe’s Expansion Reshapes Longstanding Debate

The universe is expanding. Weve known this since Edwin Hubble observed that distant galaxies are moving away from us in the 1920s. What weve NOT known – and what remains frustratingly unclear – is exactly how fast.

This might seem like an esoteric debate, but the precise measurements and the Hubble constant (as its called) is fundamental to our understanding of cosmology. Get it wrong and our models of the universes age, size, and ultimate fate are all off.

The problem is that different measurement methods give different answers. Measurements based on the cosmic microwave background – the radiation left over from the Big Bang – suggest one value. Measurements based on nearby astronomical objects like Cepheid variable stars and Type Ia supernovae suggest another, higher value.

The discrepancy is called the Hubble tension, and its been driving cosmologists slightly mad for years.

New measurements have now made the tension worse, not better. More precise observations have confirmed that both measurement methods are internally consistent – theyre not getting different answers due to errors. Theyre getting different answers because something about our understanding of the universe is incomplete.

The Hubble Space Telescope team has been refining distance measurements for years, and their latest work confirms the higher expansion rate with unprecedented precision.

What could resolve this? The options are all rather dramatic: dark energy might be more complex than we thought, there could be new physics in the early universe we havent accounted for, or theres some systematic error weve all missed despite years of looking. The James Webb Space Telescope is expected to contribute new data that might help resolve the tension. But it might also just confirm that both values are correct, which would be the most exciting and troubling outcome of all.

Sometimes the best science is when your measurements are so good they break your theory.