Galactic formation back in the day is the result of sound waves. Sound waves! What the fuck. Now there’s something I hadn’t thought of when it came to how the Universe formed. However, usually when I think about the Universe forming I end up picturing (invariably) the Multiverse and then I’m onto imagining myself in present day riding a T. Rex with Jesus to the Drive Thru at Taco Bell.
Sound waves that rang out in the early universe sculpted its structure. The best measurement yet of their imprint on galaxies is a boon to dark-energy studies.
About 30,000 years after the big bang, matter collapsed around dense seeds of dark matter. Outward pressure from photons caused the collapsing matter to rebound, creating acoustic waves, like ripples in a pond. These ripples expanded until the universe cooled to a certain temperature, stalling the waves. More matter existed at the centres and edges of these ripples, and therefore should have led to more galaxies there.
This is exactly what the Baryon Oscillation Spectroscopic Survey (BOSS) sees in a study of 265,000 galaxies. When the BOSS team measured the distance between pairs of galaxies between 4.5 billion and 6.3 billion light years from Earth, they found an excess of galaxy pairs separated by 500 million light years.
That is the expected radius of the sound waves — if the universe’s expansion has been accelerated in line with the leading model of dark energy. Called the cosmological constant, the model suggests that the amount of energy in a given volume of space does not vary with time.
All right, they lost me there towards the end. I checked out, beginning to imagine riding my T. Rex, mowing a fucking taco or twelve with the Good Lord.