# How, exactly, does the precise measurement of the CMB's polarization modes and temperature fluctuations tell us the value of Hubble's 'constant'?

Amidst all the talk a year and change ago about the value of the Hubble parameter reached by the Planck satellite team, and how it's value differed from the value reached by the 'distance-ladder' team(s), I've yet to read an explanation of how precise measurement of the cosmic microwave background's 'temperature' fluctuations and E-mode polarization(s) ultimately give you a value for Hubble's 'constant'...

I presume the answer is a bit complicated, or I probably would have found it somewhere...

Also, the Planck satellite shut down or whatever in 2013, and this news came out only last year...

• The short, but unsatisfactory, answer is that the power spectrum of angular fluctuations in the CMB is sensitive to the value of $H_0$. But you'll want to know why... – ProfRob Nov 12 '20 at 12:27
• Yes, I DO want to know why.... Thank you for whatever help you can provide though, Rob.... – Kurt Hikes Dec 7 '20 at 1:20
• A recent issue of 'New Scientist' magazine devoted its Cover story to the discrepancy between the Planck/CMB value of Hubble's 'constant' and the cosmic-distance-ladder/type-1a-supernova value... November 28-December 4, 2020 issue titled Beyond Space-Time by Stuart Clark... – Kurt Hikes Dec 7 '20 at 1:25