The largest study of galaxies ever made suggests that our space is not as cumbersome as it should be. This lack of rigidity may mean that there is a discrepancy with that of Einstein theory of general relativitywhich scientists use to understand how structures in our universe have evolved over 13 billion years.
“If this discrepancy is true, then perhaps Einstein was wrong,” said Niall Jeffrey, one of the co-leaders of the Dark Energy Study (DES) and a cosmologist at the École Normale Supérieure in Paris. told BBC News
The DES team compiled a catalog of hundreds of millions of galaxies and used small distortions in the shapes of these galaxies to measure the life statistics of the universe. Almost all of these measurements confirm the predominance Big bang model of cosmology, in which all the matter in the universe expands from a mind-bogglingly hot, incredibly tiny point.
Connected: From the Big Bang to the present: Pictures of our universe through time
But one of these measurements ̵
While some news headlines already proclaim that Einstein was wrong and physicists need to reconsider their models, the reality is much more nuanced. This is because the discrepancy is not yet a statistical helmet.
The largest study to date
More than 400 scientists from 25 institutions in seven countries are working on DES, one of the largest astronomical collaborations in history. The team used the 4-meter Victor M Blanco telescope at the Cerro Tololo Inter-American Observatory in Chile to stare at one-eighth of the entire night sky for 758 nights of observation.
The monitoring project started in 2013 and ended in 2019. But monitoring was the easiest part – it took DES two years to publish its latest results, which report data from only the first three years of monitoring.
And it’s stunning.
The release, described in an avalanche of 29 scientific papers, contains detailed observations of 226 million galaxies, making it the largest and most detailed study of galaxies in history.
This huge catalog still represents less than a tenth of one percent of all galaxies in the observable universe, but that’s a start.
Taking the measure of space
DES uses its treasury of galaxies to study two key features of our space. One is called the space network. It turns out that galaxies are not scattered randomly in the universe, but instead are organized in the largest model found in nature. On the largest scale, astronomers have discovered giant clusters of galaxies called clusters, long strands of galaxies, wide walls, and vast empty space cavities.
The space network is a dynamic object and it has evolved in its current state over billions of years. Astrophysicists believe that matter in the universe has long been much more evenly distributed. By studying the evolution of the space network, DES scientists can understand what the universe is made of and how it behaves. This is because the contents of the universe dictate how it will evolve, just as changing the ingredients in your favorite cake recipe changes the way it comes out of the oven.
DES also uses something called a weak gravitational lens. From Einstein’s general theory of relativity we know that the object gravity can bend the path of light. The most famous examples of this come from galactic clusters; their incredible mass can distort so much light from the background galaxies that these galaxies appear strongly stretched and elongated to observers.
Connected: 8 ways you can see Einstein’s theory of relativity in real life
DES uses a much finer version of this lens effect. He is looking for small changes in the shapes of galaxies due to the light from these galaxies passing through billions of light-years of space. By comparing these galactic shapes with what we know galaxies look like from near-universe studies, DES astronomers can map the distribution of matter in space.
Something is out of the question
DES’s collaboration compared their results with those of other large studies, such as Planck’s study of the cosmic microwave background, the echo of the Big Bang, revealed in the faint glow of radiation that spans the universe. Their results are almost identical to existing observations and the prevailing cosmological theory: We live in an expanding universe about 13.7 billion years old, whose mass energy is made up of approximately one-third of matter (most of which is dark matter) and the rest of dark energy.
But one measurement stood out: a parameter called S8, which characterizes the amount of rigidity in the universe. The higher the value of S8, the more densely the matter accumulates. The new results from DES favor a value for S8 of 0.776, while the older results from Planck show a slightly higher value, 0.832.
Planck’s results come from measurements of the early universe, while DES’s results come from later in the universe. These two numbers must agree, and if they are really different, then our understanding of how giant structures grow and evolve in space – which is based on our understanding of gravity through Einstein’s general theory of relativity – may be wrong. Since no one expected to find this discrepancy, astrophysicists have not studied exactly which parts of relativity can be flawed.
Set the titles welcoming the results of DES as a big crack in the foundations of our modern cosmological theories. “I spent my life working on this theory [of structure formation] and my heart tells me I don’t want to see it collapse, “Carlos Frank, a cosmologist at the University of Durham in England who was not affiliated with DES, told BBC News. But my brain tells me that the measurements were correct, and we need to look at the possibility of new physics. “
But what these titles (and articles) neglect to mention is the uncertainty. Each measurement brings uncertainty – scientists can be so accurate given the amount of data available. When statistical uncertainties are included, DES and Planck results usually overlap. Not much – so the difference is worth digging deeper – but not enough to trigger the alarm bells. In the language of statistics, both measurements are excluded by only 2.3 standard deviations, which means that if there is really no real difference between the S8 values and the observations have to be repeated 100 times, they will give the same (or greater) difference. times. This is far from the 5 standard deviations that are usually needed to herald a new discovery.
Let’s see what the data for another three years.
Originally published in Live Science.