From the June 2015 issue

Web Extra: How Big Bang ripples make the ideal cosmic ruler

Astronomers will make a 3-D map of the universe thanks to sound waves from the beginning of time called baryon acoustic oscillations.
By | Published: June 29, 2015 | Last updated on May 18, 2023
Kitt Peak Observatory will avoid closing down it’s 4-meter Mayall Telescope thanks to a new dark energy survey that will make use of cosmic ripples from the Big Bang.
Baryon acoustic oscillations show how galaxies and other matter tend to clump in spheres, which originated as waves in the early universe. Measuring these spheres lets astronomers determine the structure and evolution of the cosmos.
Zosia Rostomian (LBNL)
The August 2015 issue of Astronomy takes readers inside “Kitt Peak Observatory’s second chance at life,” which is banking on a powerful tool called the Dark Energy Spectroscopic Instrument. Astronomers hope this intense survey will help them study one of the most mysterious forces known, dark energy, and lead to a better understanding of cosmic structure thanks to sound waves from the beginning of time. Finding the remains of these ripples, called baryon acoustic oscillations (BAOs), will give them a cosmic ruler to measure the distance between galaxies.

In “How astronomers measure the cosmos,” C. Renee James explains in detail how astronomers are using these BAOs to find the universe’s expansion rate today.

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