Hubble tension: measurement or physics?

Why do local measurements and the early-universe inference give different expansion rates? A good answer separates measurement disagreements from changes to the cosmological model.

Dru put the tension down to crowding on the local side in June. The JWST crowding test challenges that explanation; the TRGB paper remains to be read.

Sub-questions

• Does crowding bias the Cepheid distances?
• How do TRGB measurements compare?
• Which new physics could reconcile the measurements?

Start at the Hubble tension hub.