Assuming that physicists can solve the computing problems they face with the LSST, the results could be transformative. There are many reasons to want a 100-petabyte digital copy of the universe. For one, it would help map the expansion of space and time caused by the still-mysterious dark energy, discovered with the help of the LSST’s predecessor, the Big Throughput Camera, which Tyson and a collaborator built in 1996.
When that camera, which could cover a patch of the sky the size of a full moon in a single exposure, was installed on the Blanco Telescope in Chile, astrophysicists immediately discovered dozens of exploding stars called Type IA supernovae strewn across the sky that revealed that most stuff in the universe is unknown. Light from nearby supernovae appeared to have stretched more than it should have during its journey through the expanding cosmos compared with light from faraway ones. This suggested that the expansion of the universe had recently sped up, driven by dark energy.
With the LSST, scientists hope to precisely track the accelerating expansion of the universe and thus to better define the nature of dark energy. They aim to do this by mapping a sort of cosmic yardstick called baryon acoustic oscillations. The yardstick was created from sound waves that rippled through the universe when it was young and hot and became imprinted in the distribution of galaxies as it cooled and expanded. The oscillations indicate the size of space at every distance away from Earth — and thus at any point back in time.
Baryon acoustic oscillations are so enormous that a truly vast astronomical survey is needed to make them a convenient measuring tool. By cataloguing billions of galaxies, the LSST promises to measure the size of these resonances more accurately than any other existing or planned astronomical survey. “The idea is that with the LSST, we will have onion shells of galaxies at different distances and we can look for this pattern and trace the size of the resonant patterns as a function of time,” Szalay said. “This will be beautiful.”
But, Szalay added, “it will be a nontrivial task to actually milk the information out of the data.”
Reprinted with permission from Quanta Magazine, an editorially independent division of SimonsFoundation.org whose mission is to enhance public understanding of science by covering research developments and trends in mathematics and the physical and life sciences.