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As this progress continues, galaxy clusters and cosmic filaments are moving farther apart, leading scientists to hypothesize that the universe’s average temperature will gradually decrease.
According to recent research from the Center for Cosmology and Astroparticle Physics (CCAPP) at The Ohio State University in the United States, it appears that the universe is actually getting warmer as time goes on.
After examining the thermal history of the universe over the past 10 billion years, the research team concluded that the average temperature of cosmic gas has increased more than tenfold.
Led by Yi-Kuan Chiang, a research fellow at CCAPP, and including members from the Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU), Johns Hopkins University, and the Max Planck Institute, the study utilized data on the Large-Scale Structure (LSS) of the universe. This refers to models of galaxies and matter on the largest cosmic scales, which are a result of the gravitational collapse of dark matter and gas.
“Our new measurement directly confirms Jim Peebles’s work – the 2019 Nobel Laureate in Physics – who theorized how large-scale structure forms in the universe. As the universe evolves, gravitational forces pull together dark matter and gas in space to form galaxies and clusters of galaxies. This gravitational collapse heats up gas to extremely high temperatures,” explained Dr. Chiang.
To measure changes in temperature over the past 10 billion years, Chiang and his colleagues combined data from the European Space Agency’s Planck satellite, which explored the Cosmic Microwave Background (CMB) temperature, and the Sloan Digital Sky Survey (SDSS), a massive multi-spectral survey that has created the most detailed 3D maps of the universe.
From this dataset, the research team cross-compared eight maps of the intensity of the cosmic microwave background from Planck with over 2 million redshift spectra references from SDSS. Combining redshift measurements (commonly used to determine the velocity of objects moving away from us) with temperature estimates based on light, the researchers compared the temperature of distant gas clouds with those closer to Earth.
From this, the research team could confirm that the average temperature of primordial cosmic gas (around 4 billion years after the Big Bang) was lower than it is now. This is clearly due to the gravitational collapse of the universe’s structure over time, a trend that will continue and intensify as the universe’s expansion accelerates.
The universe is warming up due to the process of structure and galaxy formation, unrelated to changes in Earth’s temperature.
As the universe develops, gravitational forces pull together dark matter and gas in space to form galaxies and clusters of galaxies. This gravitational collapse heats up gas to extremely high temperatures. These phenomena occur on vastly different scales and are entirely unconnected.
In the past, many astronomers argued that the universe would continue to cool as it expands. However, Chiang and his collaborators have pointed out that scientists can track the process of cosmic structure formation by “checking the temperature” of the universe.
On one hand, scientists suggest that a feasible solution to the Fermi Paradox is that extraterrestrial intelligences (ETI) are not active. Based partly on the thermodynamics of computing (Landauer’s principle), the argument is that as the universe cools, advanced life forms might be able to extract more from their superstructures. Moreover, if the universe is getting warmer over time, it implies that the likelihood of the emergence of life will decrease over time due to increasing cosmic radiation.