Understanding how the universe has evolved can explain how it will end. One of the biggest mysteries in studying the cosmos is dark energy, the unknown component that causes the universe to expand faster and faster.
Unknown Property of the Universe
In 1998, two independent groups of scientists discovered that the universe's expansion rate is accelerating instead of slowing down. The acceleration appears to be triggered by the repulsive property of space, dubbed "dark energy."
For more than 20 years, astronomers have tried to decode the secrets of this elusive substance which appears to be pulling the universe apart. It is theorized that dark energy may not be a substance but a force or an intrinsic property of space itself.
The standard model of cosmology suggests that dark energy is unwavering across the cosmos and throughout time, making it a fundamental property of space. However, the largest survey of the cosmic history of the universe indicates that dark energy may evolve with time rather than remain constant.
If these findings hold for future observations, cosmologists may have to explore systematic uncertainties in the prevailing Lambda CDM model. This model is a mathematical depiction of the universe in which lambda represents dark energy. As more data about dark energy is expected to come within the next few years, the emerging interpretations about its evolution could also change.
New Cosmological Model
To study the effect of dark energy on the evolution of the universe, a scientific research instrument was developed to conduct spectrographic astronomical surveys of distant galaxies. Known as the Dark Energy Spectroscopic Instrument (DESI), the ground-based survey was perched atop the Nicholas U. Mayall 4-meter telescope at Kitt Peak National Observatory in Arizona.
Using observations from DESI, astronomers can measure the universe's expansion rate over the past 11 billion years. This is the first time experts have measured the expansion history of the young cosmos with a precision better than 1%. This gives us the best view yet of how the universe evolved.
On April 4, the DESI collaboration shared the largest-ever 3D map of the universe, which also includes high-precision measurements of the cosmic expansion rate. In its first year of operations, DESI has proven to be twice as powerful as its predecessor, the Sloan Digital Sky Survey, which took almost a decade to build a similar 3D map.
Aside from the countless galaxy clusters grouped like knotted threads, the new 3D map also features a faint pattern in the early universe called Baryon Acoustic Oscillations (BAO). By mapping the sizes of the frozen BAOs, astronomers were able to estimate the distances between galaxies and infer the rate at which the universe expands at various points in time.
The initial conclusion that dark energy could evolve with time comes from a preliminary analysis of DESI data combined with other cosmological instruments. The scientists discovered that a varying dark energy model agreed better with the data than the standard cosmological model. According to DESI co-spokesperson Kyle Dawson, dark energy is transitioning from being a strong driver of the accelerated cosmic expansion rate to tapering off to some degree.
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