For nearly a century, astronomers have understood that the universe is in an expanding state. Since the 1990s, they have understood that since 4 billion years ago, the rate of expansion has accelerated.
As this progresses, the clusters of galaxies and the galaxies of the universe become more and more apart, scientists hypothesize that the average temperature of the universe will gradually decrease.
According to new research by the Center for Astronomy and Astrophysics (CCAPP) at Ohio State University, USA, it seems that the universe is really warming as time passes.
After examining the heat history of the universe over the past 10 billion years, the team concluded that the average temperature of the cosmic gas has increased more than 10 times.
The study was led by Yi-Kuan Chiang, a research fellow at CCAP, and includes members from the Kavli Institute of Aerospace Physics and Mathematics (Kavli IPMU), Johns Hopkins University, and the Max-Planck Institute.
For the sake of research, the team of scientists examined thermal data on the Large Scale Structure (LSS) of the universe. This refers to the patterns of galaxies and matter on the largest cosmic scale, as a result of the gravitational collapse of dark matter and gas.
“Our new measurement provides direct confirmation of the work of Jim Peebles – the 2019 Nobel Prize winner in Physics – who laid down the theory of how large-scale structures form in the universe. As the universe develops, gravity pulls dark matter and gas in space together into galaxies and clusters. The drag is so intense that more and more gases are shocked and warmed up. Chiang explained.
To measure the changes in heat over the past 10 billion years, Chiang and his colleagues combined data from ESA’s Planck Infrared Astronomical Exploration Satellite and the Sloan Digital Sky Survey (SDSS). While Planck is Europe’s first mission to measure the temperature of the Cosmic Microwave Platform (CMB), the SDSS is a massive multispectral survey that has produced the most detailed 3D maps of the universe.
From these datasets, the team cross-compared eight sky intensity maps of Planck with 2 million spectral shift references from the SDSS. Combining redshift measurements (commonly used to determine how fast objects move away from us) and temperature estimates based on light, the team compared the temperatures of the clusters. Gas clouds are further away with clouds closer to Earth.
From there, the team was able to confirm that the average temperature of the gases in the early universe (about 4 billion after the Big Bang) was lower than today. This is obviously due to the gravitational collapse of the cosmic structure over time, a trend that will continue and become more acute as the expansion of the universe continues to accelerate.
The universe is warming due to the process of structural formation and natural galaxies, not related to changes in temperature on Earth.
As the universe developed, gravity pulled dark matter and space gas together into galaxies and clusters of galaxies. The drag was so intense that more and more the gas was shocked and heated up. These phenomena are happening on very different scales. They are completely disconnected.
In the past, many astronomers have argued that the universe will continue to cool as it expands. But in contrast, Chiang and his colleagues have shown that scientists can track the formation of a cosmic structure by “checking the temperature” of the universe.
On the one hand, scientists argue that a possible solution to the Fermi Paradox is that extraterrestrial intelligence (ETI) is not working. Partly based on computer thermodynamics (Landauer Principle), arguing that as the universe cools, advanced organisms will be able to get more out of their superstructures. Also, if the universe heats up over time, it means that the emergence of life will be less likely over time due to increased cosmic radiation.