(ORDO NEWS) — For more than a century, astronomers have known that the universe is expanding after the Big Bang. For the first 8 billion years, the rate of expansion was relatively constant as it was held back by the force of gravity.
However, thanks to missions such as the Hubble Space Telescope, astronomers have since learned that the expansion rate was increasing roughly 5 billion years ago.
This has led to a widely held theory that a mysterious force (known as dark energy) is behind the expansion, while some insist that the force of gravity may have changed over time.
This is a controversial hypothesis because it means that Einstein’s general theory of relativity (which has been confirmed nine ways since Sunday) is wrong.
But according to a new study by the international Dark Energy Survey (DES) collaboration, the nature of gravity has remained the same throughout the history of the universe.
These results were made shortly before two next-generation space telescopes (Nancy Grace Roman and Euclid) are sent into space to take even more precise measurements. issues of gravity and its role in cosmic evolution.
The DES Collaboration brings together researchers from universities and institutions in the US, UK, Canada, Chile, Spain, Brazil, Germany, Japan, Italy, Australia, Norway, and Switzerland.
Their results from the third year of work were presented at the International Conference on Particle Physics and Cosmology (COSMO’22), which was held in Rio de Janeiro from 22 to 26 August.
They were also published in a paper titled “Results from Year Three of Dark Energy Research: Constraints on Lambda CDM Expansions with Weak Lensing and Galaxy Clustering” published in the Physical Review D journal of the American Physical Society.
Einstein’s general theory of relativity, which he completed in 1915, describes how the curvature of spacetime changes in the presence of gravity.
For more than a century, this theory has accurately predicted almost everything in our universe, from the orbit of Mercury and gravitational lensing to the existence of black holes.
But between the 1960s and 1990s, two inconsistencies were discovered that led astronomers to question whether Einstein’s theory was correct. First, astronomers have noticed that the gravitational effects of massive structures (such as galaxies and galaxy clusters) do not agree with their observed mass.
This gave rise to the theory that space is filled with invisible mass interacting with “normal” (also known as “luminous” or visible) matter via gravity.
Meanwhile, the observed expansion of the cosmos (and how it is subject to acceleration) has given rise to the theory of dark energy and the cosmological model of lambda cold dark matter (lambda-CDM).
Cold dark matter is an interpretation in which this mass is made up of large, slowly moving particles, and lambda represents dark energy. Theoretically, these two forces make up 95 percent of the entire mass and energy of the universe, but all attempts to find direct evidence of their existence have failed.
The only possible alternative is that the theory of relativity needs to be changed. to account for these discrepancies. To find out if this is the case, DES members used the 4-meter Victor M. Blanco Telescope at the Cerro Telolo Inter-American Observatory in Chile to observe galaxies up to 5 billion light-years away.
They hoped to determine whether gravity has changed over the past 5 billion years (since the acceleration began) or over cosmic distances. They also checked data from other telescopes, including the ESA Planck satellite, which has been mapping the cosmic microwave background (CMB) since 2009.
They paid close attention to how the images they saw contained subtle distortions due to dark matter (gravitational lenses).
As shown in the first image taken by the James Webb Space Telescope (JWST), scientists can infer the strength of gravity by analyzing the degree to which a gravitational lens distorts spacetime.
So far, the DES collaboration has measured the shapes of over 100 million galaxies, and all observations are in line with what General Relativity predicts. The good news is that Einstein’s theory is still correct, but that also means that the mystery of dark energy has yet to be solved.
Fortunately, astronomers won’t have to wait long for new and more detailed data to emerge. . The first is the ESA mission Euclid, which is scheduled to launch no later than 2023. This mission will map the geometry of the universe by looking back 8 billion years to measure the effects of dark matter and dark energy.
By May 2027, NASA’s Nancy Grace Roman Space Telescope will join it. , which will look back more than 11 billion years.
These will be the most detailed cosmological surveys ever undertaken and are expected to provide the most compelling evidence for (or against) the Lambda-CDM model.
Study co-author Agnes Ferte, who conducted the study as a JPL Postdoctoral Investigator, stated in a recent NASA press release:
“As measurements become more and more precise, there is still room to challenge Einstein’s theory of gravity needs to be done before we are ready for Euclid and Roman.
Therefore, it is very important that we continue to collaborate with scientists around the world on this issue, as we did with the Dark Energy Research.”
In addition, Webb’s observations of the earliest stars and galaxies in the universe will allow astronomers to chart the evolution of the cosmos from its earliest periods. These efforts may provide answers to some of the most pressing mysteries in the universe.
These include how the theory of relativity, the observed mass, and the expansion of the universe match up, but they can also provide insight into how gravity and other fundamental phenomena interact with the forces of the universe (as described in quantum mechanics) – The Theory of Everything (ToE).
If there is anything that characterizes the current era of astronomy, it is how long-term research and next-generation instruments are coming together to test what has so far been only theoretical material.
The potential breakthroughs they may lead to will no doubt delight and puzzle us. But, ultimately, they will revolutionize how we view the universe.
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