The Cosmic Microwave Background Provides a Refined View of Our Universe

Peter Lobner, 12 January 2021

The Atacama Cosmology Telescope (ACT) is a six-meter (19.7 foot) radio telescope designed to make high-resolution, microwave-wavelength surveys of the cosmic microwave background (CMB).  It is located at a remote site in the Atacama Desert at an elevation of 5,190 meters (17,030 feet) in northern Chile. 

The ACT site.  Source: ACT Collaboration

ACT observes in three frequency bands (148, 218 and 277 GHz) and has a resolution of 1.3 arc minutes at 148 GHz, near the peak of the CMB spectrum.  This is significantly higher than the 5-10 arc minute resolution of the Planck spacecraft, which observed the CMB from 2009 to 2013 in the frequency range from 30 to 857 GHz. You’ll find a detailed description of the Atacama Cosmology Telescope (ACT) at the following link:

I reported on key results of the Planck CMB survey results in my post at the following link:

New results from the ACT survey, reported in December 2020, affirm the Planck CMB survey results.  

  • The universe is isotropic
  • The estimate of the age of the universe was refined to 13.77 billion years old ± 0.04 billion years, overlapping uncertainty bands with the 2015 Planck estimate of 13.813 ± 0.038 billion years
  • The value of the Hubble constant was refined to 67.6 kilometers / second / megaparsec, up slightly from the 2018 Planck estimate of 67.4 kilometers / second / megaparsec.  The significant difference from the value derived from astrophysical measurements, 73.5 km / second / megaparsec, remains unexplained.
ACT high resolution image of the isotropic cosmic background radiation covering a section of the sky 50 times the width of a full moon. This image represents a region of space 20 billion light-years across. Source: ACT Collaboration via EarthSky

For more information: