Jack's Notes

In our universe, a Constant is a value that remains constant throughout space and throughout time. The Gravitational Constant, G, for example – so far as we can tell – remains regardless of when or where the measurement takes place. So too for the speed of light, which is always measured as .

The Hubble Constant however – the rate of recession of galaxies away from each other and therefore the rate of expansion of our universe – while appearing isotropic and homogeneous throughout space – appears to vary over time.

Because time and space are one, this difference manifests in our measurements of the “near” supernovae and the “distant” Cosmic Microwave Background radiation. The Cosmic Microwave Background, or CMB, is not distant in the sense that we are measuring it from far away in space. In reality, the CMB – being the radiation of energy from an event in the early universe – exists at every point in space at once, but originated far back in time.  

Thus, it is distant as in distant in time; while for supernovae, the fact that they are so relatively  “nearby,” means the light from their explosions is – while billions of years younger than the CMB – nevertheless reaching us at the exact same moment. 

These two measurements – the CMB from a point “far away” and therefore “long ago,” and the supernova from a point explosion which occurred “near” and therefore “recently” – provide different values for the rate of recessional velocity over distance which describes the overall expansion of our universe. 

The Hubble Tension is the discrepancy between the early and late rate of expansion, and the primary cosmological problem inherent in this tension is not that the rates are different, but that – following the subsequent long decay from the initial rate of inflation, the expansion of the universe is accelerating positively once again. It is as if an explosion has occurred, but rather than the pressure wave dying away, there is a secondary shockwave which once again accelerates the expansion of particles and spaces. 

Measurements of “early time” rate of expansion based on the CMB emitted just years after the Big Bang, give a smaller rate of , while the “late time” current expansion based on objects relatively close to Earth gives measurements of .

Current cosmological models do not provide a mechanism for secondary inflation. The author puts forward as a basis of argument that the Blast Wave physics of inflationary phenomena may be applied to inflationary cosmology in order to derive the Hubble Tension.