Qualla: Atacama Cosmology Telescope

Atacama Cosmology Telescope: Introduction

Mon, 23 Mar 2026 00:00:00 GMT

Photo credit The original uploader was Ahincks at English Wikipedia., CC BY 3.0. At 5,190 meters above sea level, the air is too thin to breathe comfortably but almost perfectly transparent to microwaves. That is why the Atacama Cosmology Telescope sat here on Cerro Toco, in one of the driest places on Earth, scanning the sky not for stars but for something far older -- the cosmic microwave background, the faint thermal afterglow of the Big Bang itself. From 2007 to 2022, this six-meter dish listened to radiation that had been traveling for 13.8 billion years, and in those whispers it found evidence of dark energy, measured the motions of galaxy clusters, and discovered the most massive galaxy cluster merger ever observed.

Image: The original uploader was Ahincks at English Wikipedia. | CC BY 3.0

Atacama Cosmology Telescope: Why the Desert Speaks

Mon, 23 Mar 2026 00:00:00 GMT

Photo credit Ana Raquel Hernandes from Brazil, CC BY-SA 2.0. Water vapor is the enemy of cosmic microwave background research. Even trace amounts of atmospheric moisture emit microwave radiation that contaminates the faint signals from the early universe. The Atacama Desert's Chajnantor Plateau offers a rare combination: extreme altitude, ...

Image: Ana Raquel Hernandes from Brazil | CC BY-SA 2.0

Atacama Cosmology Telescope: A Machine for Hearing the Big Bang

Mon, 23 Mar 2026 00:00:00 GMT

Photo credit M. Devlin., CC BY-SA 4.0. The telescope itself was an off-axis Gregorian design -- a 6-meter primary mirror and a 2-meter secondary, both assembled from dozens of precision-aligned aluminum panels. Unlike conventional telescopes that track objects across the sky, ACT kept a fixed elevation and swept back ...

Image: M. Devlin. | CC BY-SA 4.0

Atacama Cosmology Telescope: Firsts Written in Ancient Light

Mon, 23 Mar 2026 00:00:00 GMT

Photo credit Chile_location_map.svg: NordNordWest derivative work: Виктор В (talk), CC BY-SA 3.0. ACT's list of scientific firsts reads like a catalog of fundamental discoveries. It was the first experiment to detect seven acoustic peaks in the power spectrum of the cosmic microwave background -- ripples in the primordial plasma that encode the geometry and composition of the...

Image: Chile_location_map.svg: NordNordWest derivative work: Виктор В (talk) | CC BY-SA 3.0

Atacama Cosmology Telescope: A Global Collaboration at the Edge of the Atmosphere

Mon, 23 Mar 2026 00:00:00 GMT

Photo credit Layon Art, CC BY-SA 3.0. Funded by the U.S. National Science Foundation, ACT was a collaboration spanning more than thirty institutions across four continents, from Princeton and Cornell to the Pontificia Universidad Catolica de Chile, from Cardiff University to the University of KwaZulu-Natal in South A...

Image: Layon Art | CC BY-SA 3.0