04 Dec 23
Hubble tension is the fact two measurement techniques give different rates for the expansion of the universe, 244,000 Km/hr per megaparsec Vs 264,000 for the other.
There is a new theory on what causes that:
https://phys.org/news/2023-12-explanation-hubble-tension.html
That we may live in a relatively sparse bubble about 3 billion light years across, which is a small amount of space compared to the whole universe, the average density being less here giving rise to differing methods of measurement of the expansion velocity.