How did the universe begin? This profound question is at the heart of NASA's upcoming mission featuring the compact SPHEREx space telescope, which is set to launch on a SpaceX Falcon 9 rocket from Vandenberg Space Force Base, no earlier than Tuesday night. This innovative telescope, which operates on less power than a standard refrigerator, will embark on a mission to investigate the universe's origins and the theory of cosmic inflation.
SPHEREx, an acronym for Spectro-Photometer for the History of the Universe, Epoch of Reionization, and Ices Explorer, will survey the entire sky in 102 different wavelengths every six months. The primary objective of this mission is to delve into the theory of cosmic inflation, which posits that shortly after the big bang, the universe underwent a rapid and exponential expansion. This event is not characterized by a slow and steady growth; rather, it represents a dramatic transformation from a minuscule size to an immense cosmic scale in a remarkably brief timeframe.
Phil Korngut, an astrophysicist at Caltech and the SPHEREx instrument scientist, emphasizes the significance of this inquiry: “How can you ask a bigger question than ‘What was it like at the origin of the universe?’” The telescope aims to gather light from approximately 450 million galaxies, creating a comprehensive three-dimensional map of the universe and tracking its evolution over time. By analyzing the positions of galaxies within vast regions of cosmic space, SPHEREx will contribute valuable data that may help clarify how the early universe appeared before achieving its current expansive state.
One of the unique aspects of the SPHEREx mission is its ability to observe the distribution of galaxies. Rather than being randomly scattered, these galaxies form clusters, superclusters, and filament-like structures, interspersed with voids. By examining these large-scale structures, scientists hope to gather evidence regarding the universe's inflationary period, thereby narrowing down the various inflation theories currently under consideration. As James Fanson, project manager for SPHEREx at NASA’s Jet Propulsion Laboratory, notes, “In trying to expose these theories to hard data, and narrow the range of possibilities, a mission like SPHEREx could lead to a new understanding of fundamental physics.”
While much of what physicists know about the universe has been derived from particle accelerators, such as those located near Geneva, the universe itself serves as a colossal high-energy laboratory. Fanson explains, “There’s a limit in what we can do with particle accelerators on the ground... But the universe is really a high-energy experiment.” This mission presents an opportunity to uncover fundamental insights into the universe's beginnings, potentially revealing energetic processes that trace back to the big bang singularity.
Previous astronomical surveys have focused on large numbers of galaxies; however, SPHEREx will take a different approach by scanning the entire sky. “We’re casting a broader net,” states James Bock, the mission’s lead scientist from Caltech. “We’re interested in these statistical fluctuations on large scales, where the signature of inflation is the cleanest.” In addition to studying galactic distributions, the telescope will also seek evidence of water and organic molecules in star-forming regions within our own galaxy.
The concept of inflationary theory emerged in the late 1970s and early 1980s as physicists sought to explain the uniformity observed in the universe at its largest scales, including the cosmic microwave background radiation. One of the founding figures of this theory, MIT physicist Alan Guth, argued that the appearance of the cosmos could be understood through a brief period of inflation. In an article published in the MIT Physics Annual 2002, Guth stated, “The theory says nothing about the underlying physics of the primordial bang... The inflationary universe theory, on the other hand, is a description of the bang itself.”
Despite the advancements in understanding cosmic inflation, many questions remain unanswered. Jo Dunkley, an astrophysicist at Princeton University, highlights this uncertainty: “We don’t yet know for sure if inflation happened... and if it did, we still want to know how it happened.” She believes that SPHEREx could provide new insights into inflation theory by measuring the distribution of galaxies and detecting subtle signatures in their positioning.
Michael Turner, a cosmologist at UCLA and one of the architects of inflation theory, adds that the relationship between inflation and the big bang is complex and not fully understood. One possibility suggests that an inflationary event could have constituted our big bang, with anything preceding that likely beyond our measurement capabilities. Conversely, for those who subscribe to the multiverse theory, there may have been countless big bangs creating regions of the universe that remain unseen. This tantalizing notion invites contemplation about the vast possibilities that lie beyond our observable universe.
