Future Tense?

Phillip Helbig

The Observatory, 144, 1301, 193–194 (2024)

One of the hot topics in modern cosmology is the so-called "Hubble tension". There is no consensus as to which, if any, solution is correct. Many of the solutions are ad hoc, in the sense that it was the Hubble tension itself which led to their proposal; that is not necessary an indication that they must be wrong, and sometimes there is some additional justification. I'm happy to be corrected, but as far as I know there was no theory which predicted the current Hubble tension of about 6 km/s/Mpc (with statistical uncertainties claimed to be much smaller); while technically postdictions are just as good, predictions are more impressive. Whether the solution turns out to involve interesting new physics or some banal explanation, perhaps the most interesting result will be that a consensus on the cause of the Hubble tension will rule out all of the other proposed explanations with one fell swoop.