The Hubble Constant Is Not a Constant. Three Measurements Prove It.: Big Flare-Up Theory

63 km/s/Mpc. 68 km/s/Mpc. 73 km/s/Mpc. A true fundamental constant of nature does not depend on how you measure it.

The Hubble constant is supposed to be one of the most fundamental numbers in cosmology. It describes the rate at which the universe is expanding. Every galaxy's recession velocity, divided by its distance, should give the same number. That number is called H₀.

Three of the most precise measurements ever made of H₀ have returned three different numbers. The discrepancy between them has now exceeded 6 sigma, a statistical significance that, in particle physics, is the threshold for claiming a discovery. In cosmology, it is the Hubble tension, and it remains unresolved.

The Big Flare-Up Theory does not need to resolve it. It predicts it.

The Three Values

73 km/s/Mpc, from the cosmic distance ladder using Cepheid variable stars and Type Ia supernovae (Riess et al., multiple papers). This is the local measurement, based on objects within a few billion light years.

68 km/s/Mpc, from the Cosmic Microwave Background as analysed by the Planck satellite (Planck Collaboration 2018). This is the early-universe measurement, extrapolated forward using LCDM model assumptions.

63 km/s/Mpc, from galaxy group infall dynamics, specifically the M81 and Centaurus A groups (Wagner, Benisty and Karachentsev, 2026). This is the most recent independent measurement, and the lowest value yet obtained.

Three methodologies. Three precision measurements. Three different answers. And a directional trend: local measurements are converging toward lower values as precision improves.

What a True Constant Would Look Like

If H₀ is a true fundamental constant describing the uniform expansion of space, all measurement methods should converge on the same value as precision improves. Discrepancies between early and late universe measurements would indicate systematic errors in one or both methods, and those errors would be identified and corrected.

This is not what is happening. The discrepancy has grown as measurements have become more precise. The 2026 measurement adds a third distinct value from a completely independent methodology. The spread is not shrinking. It is expanding.

The BFUT Prediction

In the Big Flare-Up Theory, the Hubble relationship is an emergent statistical property of a gravitationally sorted galaxy population, not a fundamental constant of universal expansion. Different measurement methods probe different scales, populations, and epochs of the sorting process. They are expected to return different values.

Furthermore, BFUT predicts a directional trend: local measurements, which probe more recently sorted populations in our immediate cosmic neighbourhood, will trend toward lower values as instruments improve. The sequence 73, 68, 63, three measurements in reverse chronological order of distance probed, is exactly this trend.

Prediction 5 of the BFUT research paper states explicitly: the Hubble tension will persist and local measurements will trend downward. This prediction was made before the 63 km/s/Mpc result was published. That result confirmed it.

The Original Value

Edwin Hubble's original measurement in 1929 was approximately 500 km/s/Mpc. This implied a universe younger than the Earth itself, a contradiction that required decades of revision to resolve. The constant has since been revised from 500 to 73 to 68 to 63.

A quantity that has been revised by 87% since its first measurement, and that currently returns three different values from three independent methods, is not a fundamental constant of nature. It is a statistical property of an observed sample, and its behaviour is exactly what gravitational sorting predicts.

The Sound Horizon Discrepancy

Beyond the direct measurements of H₀, there is a related tension in the sound horizon, the distance sound waves travelled in the early universe plasma before recombination, which leaves an imprint on both the CMB power spectrum and the large-scale distribution of galaxies (Baryon Acoustic Oscillations). The sound horizon calibrated from the CMB implies a value of H₀ around 67-68 km/s/Mpc when the standard model is assumed. The sound horizon calibrated from BAO data in the local universe implies a slightly different value. This discrepancy has resisted resolution and has led some researchers to propose early dark energy, a modification to the model in the pre-recombination era, as a possible solution.

In BFUT, both measurements are probing different aspects of the same statistical population. The CMB sound horizon measurement is a model-dependent derivation that assumes LCDM expansion history. The BAO measurement is observational but interpreted through the same model framework. Neither is a model-independent direct measurement of a universal constant. Both reflect the properties of our local region's astrophysical history rather than a fundamental universal parameter.

The Original Hubble Error and Its Consequences

Hubble's original value of 500 km/s/Mpc was wrong by approximately a factor of seven. The primary error was in the distance calibration using Cepheid variable stars, the same method still used today at the top of the distance ladder. Hubble confused two types of Cepheid variables with different period-luminosity relations, a mistake identified by Walter Baade in 1952 using the 200-inch Palomar telescope. Once corrected, the value dropped to approximately 250 km/s/Mpc. Further refinements through the 20th century brought it to the current 73 km/s/Mpc range.

The consequence of the original error was that Einstein abandoned the cosmological constant. The universe appeared to be expanding at a rate implying an age of approximately 2 billion years, less than the geological age of the Earth. This was a crisis for the Big Bang model that motivated the steady-state alternative and drove decades of debate. The crisis was resolved by the revision of Hubble's constant, not by any new fundamental physics. The instability of the Hubble constant, from 500 to 73, a factor of seven revision over 90 years, with a further threefold spread between current measurements, is a feature of a statistical quantity, not a fundamental constant.

The Forthcoming Resolution

The Vera C. Rubin Observatory's Legacy Survey of Space and Time (LSST) will measure millions of Type Ia supernovae over a decade, providing the statistical power to resolve whether the Hubble tension reflects systematic errors in current measurements or genuine physics beyond the standard model. From the BFUT perspective, the expected outcome is continued divergence: as LSST probes larger volumes and smaller scales simultaneously, the statistical spread in effective H₀ measurements will increase rather than converge, confirming that the Hubble relationship is scale-dependent and therefore emergent rather than fundamental.