The point that this known universe goes back into a singularity has been established (orthodox?) since Hubble.
This is misinforming.
The Hubble constant was arbitrarily obtained based what is now knows as inaccurate classing of galaxies into groups regarding luminosity. "Standard candles" used in measurement of distance.
Remember that this is also actually theory. Not fact. It's unprovable. Our best guess would be using triangulation or radar, problem with radar is it only reaches our solar system and even if we could send microwaves to the nearest galaxies we'd have to wait a hundred years to get the signals back.
Triangulation or more accurately parallax is the only real way we have of measuring distance without factoring in unproven variables like luminosity of candles as it is now shown that similar galaxy "candles" have different luminosities which points to the failure of the Hubble constant.
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Parallax is a proven, reliable way of measuring distance. Trigonometry provides the means to calculate the perpendicular distance from the base of an isosceles triangle to the apex, given the length of the baseline and the size of the angles at either end. The accuracy of triangulation depends critically upon the length of the baseline in proportion to the distance to the target, so as to avoid too narrow an angle at the apex. The diameter of the Earth’s orbit about the Sun provides a baseline that is 2 Astronomical Units long, giving an outer limit of accurate measurement of 300 light years, that's as far as astronomy is accurate, no more. As we send sats out further we can increase the baseline giving us accuracy at longer distances.
Anything further is based upon the notion that we can identify so-called standard candles, which are classes of recognisable objects that all have the same level of intrinsic brightness.
Problems with this, the main one is calibration, precisely determining the absolute magnitude of the candle. The second problem is establishing which objects qualify for membership of a particular class of candles.
A stock method for extra-galactic distance measurement is given by the rate of oscillation of stars known as Cepheid Variables. There is a definite correlation between the time taken for a variable star to fluctuate and how bright it appears to be. Unfortunately, improved instrumentation has subsequently shown that Cepheid Variables are in fact not a class of standard candles at all. Supernovae (exploding stars) are also invoked as standard candles, to measure distances appreciably greater than those apparently given by period-luminosity in variable stars. They have since been exposed as having non-standard intrinsic brightness.
There is reason for doubt on the Hubble constant, a lot rests on it and it needs to be solid but atm it is anything but.
Each step on Hubble's extragalactic distance ladder introduces more uncertainty