Here\u2019s what you\u2019ll learn when you read this story:<\/p>\n
The universe is expanding faster every second, and physicists still can\u2019t fully explain why.<\/p>\n<\/li>\n
A new study connects the force binding quarks together to the mystery of dark energy.<\/p>\n<\/li>\n
Upcoming telescopes could soon reveal whether this nuclear-scale idea works at cosmic scale.<\/p>\n<\/li>\n<\/ul>\n
What humanity has learned about the cosmos within just the past century is difficult to overstate. A little more than a century ago, American astronomer Edwin Hubble used the 100-inch Hooker Telescope at California’s Mount Wilson Observatory to identify a Cepheid variable star far outside our Milky Way in the Andromeda Galaxy. Six years later, Hubble also discerned that the known universe\u2014already growing in the minds of scientists year by year\u2014was literally expanding<\/a>.<\/p>\n But that wasn\u2019t the end of this head-scratching revelation, because in 1998 two independent teams of astronomers confirmed that the expansion Hubble had discovered was also accelerating. Exploring these two ideas, scientists developed the Hubble constant<\/a>, which measures the current rate of expansion, and the cosmological constant, a theoretical prediction of space-time that explains this acceleration. Albert Einstein first introduced the idea of the cosmological constant in 1917, and it\u2019s the cornerstone of Lambda Cold Dark Matter, or \u039bCDM, our current best guess at how the universe works. In this model, the cosmological constant represents a mysterious dark energy that permeates all of space and drives the universe\u2019s accelerating expansion, while cold dark matter accounts for the invisible mass that shapes the large-scale structure of galaxies.<\/p>\n The \u039bCDM theory has proven successful in describing cosmological observations, but it has some shortcomings, particularly one known as the \u201ccosmological constant problem.\u201d Simply put, quantum field theories predict that vacuum energy densities should exceed what we observe in the universe by roughly 120 orders of magnitude. So yeah, it\u2019s a big problem. These mathematical inconsistencies have led scientists to pursue other ideas<\/a>. One of them, published<\/a> last month in the journal Universe, asks if the mechanics behind the strong nuclear force\u2014which holds atoms together and is one of the four fundamental forces in the universe\u2014could play a much larger role than scientists realize.<\/p>\n \u201cResults from the Dark Energy Spectroscopic Instrument (DESI)<\/a> have hinted at deviations from a pure \u039bCDM expansion, favoring scenarios with a mildly dynamical dark energy component,\u201d the authors write in the study. \u201cThis ongoing debate highlights the need for novel perspectives grounded in well-established physics.\u201d<\/p>\n This \u201cnovel perspective\u201d looks at the expansion rate of the universe and its interaction with the realm of quantum chromodynamics<\/a>, the overarching theory of how quarks and gluons form protons and neutrons, and specifically an idea known as \u201cquark confinement.\u201d This simply means quarks and gluons are never found in isolation; they\u2019re bound together to form these various hadrons. Using a model of nuclear theory called the \u201cPolyakov\u2013Nambu\u2013Jona-Lasinio model,\u201d the authors effectively linked the quark vacuum to the rate at which the universe expands, and found that the overall effect mimics dark energy.<\/p>\n \u201cQuantum Chromodynamics, the gauge theory of the strong nuclear force<\/a>, governs the behavior of strongly interacting matter and features a rich vacuum structure shaped by phenomena such as confinement and spontaneous chiral symmetry breaking,\u201d the authors write. \u201cThe expansion of the Universe could influence the QCD vacuum structure, potentially inducing effective contributions to dark energy.\u201d<\/p>\n Not content with just theoretical musings, the team then tested this new framework against low-redshift cosmological objects, including quasars, hydrogen-II galaxies (useful for studying the universe\u2019s structure), and Type Ia supernovae\u2014a common \u201cstandard candle\u201d for measuring universal distances. Using Bayesian<\/a> statistical methods, the team found that this new exponent (which they termed \u201cd\u201d) came close to zero, suggesting that the model closely mimicked the observable universe.<\/p>\n