A great ‘wall’ of galaxies has been found stretching across the Universe
The mathematics proposed by Albert Einstein to explain the workings of the Earth’s gravity in the early 20th century is still going strong.
In one of the largest relativity tests to date, a large team of astronomers has mapped the distribution of nearly six million galaxies over the 11 billion years of Earth’s history.
The way that gravity binds these galaxies together in the lines of the cosmic web against the outward pull of the Universe’s expansion, and the way that the web evolves over time, is exactly what Einstein’s famous theory predicted.
It is, perhaps, the largest test of all relativity to date, spanning much of the 13.8-billion-year history of the Universe—meaning that the theory stands on a scale both large and small.
The findings have been submitted for publication, and are available in three new versions uploaded to arXiv prior to peer review.
“The connection has been tested mainly on the scale of the solar system, but we also wanted to check that our hypothesis works on larger scales,” says astronomer Pauline Zarrouk of the French National Center for Scientific Research.
“Studying the scale created by the galaxies allows us to directly test our theories and, so far, we are in line with predictions based on cosmological scales.”
Gravity is the key to how the Universe works. We don’t know what or why it is, just that things with weight tend to attract other things with mass; that the power of attraction is closely related to quantity; and that it changes the geometry of space-time around the mass.
It also acts as the glue that holds the Earth together. Great gravitational fields made of dark matter span the entire Universe in a spider web; and most of the things in the Universe are distributed along the lines and nodes of this cosmic web.
It is possible and measurable and, so far, has been overestimated and explained by the theory of general relativity. But finding flaws in theory can yield answers to some of the most thorny problems, such as the irreconcilable differences between quantum mechanics and classical physics. So scientists keep poking around to see if the Universe looks like what relativity says it should, at all scales.
This brings us to the Lawrence Berkeley National Laboratory led Dark Energy Spectroscopic Instrument (DESI), a major international collaboration currently working to map the observable Universe to reveal its greatest mysteries. It has been active since 2019; The new results are based on a detailed and extended analysis of the first year of data obtained by the instrument.
The DESI Collaboration used the data to conduct a painstaking analysis of 5.7 million galaxies and quasars in the history of the Universe, revealing their growth, evolution, and distribution along the cosmic web since the early Universe 11 billion years ago.
This diagram shows how the force of gravity changes the distribution of galaxies in the Universe. (Claire Lamman and Michael Rashkovetskyi/DESI collaboration)
They used the theory of relativity to predict the growth and distribution of the cosmic web, and found that the Earth we live in behaved in the way that relativity says it should, on an epic cosmic scale. Add some gravity, or take some away, and the Universe wouldn’t look the same.
The results follow a paper earlier this year that measured the rate of expansion of the Universe based on the atmospheric remnants of acoustic waves that froze when the atomic vapor that filled the early Earth died out. The DESI Collaboration hopes that ongoing experiments will continue to shed light on Earth’s evolution and, in turn, the mysterious forces that drive it.
“This is the first time that DESI has looked at the growth of a cosmic structure,” says physicist Dragan Huterer of the University of Michigan. “We’re demonstrating a whole new capability to explore enhanced gravity and improve the constraints on dark energy models. And that’s just the tip of the iceberg.”
DESI is located at the Mayall Telescope in Arizona, seen here during the 2023 Geminid shower. (KPNO/NOIRLab/NSF/AURA/R. Sparks)
The results also put constraints on the upper limit of the mass of the neutrino, a ‘ghost’ particle that we have not been able to measure precisely.
The review is still ongoing, as is the work of the Partnership. Researchers are currently analyzing data from the first three years of DESI’s operation. By the time the instrument finishes its mission, it will have collected data on 40 million galaxies and quasars.
Among the strong hopes is that it will help to reveal the nature of darkness, which is mysterious and invisible something else the role of increasing gravitational force in the Universe; and the dark, hidden power that cannot be seen something else is responsible for driving the various accelerated expansion of the Universe.
“Dark matter makes up about a quarter of the Universe, and dark energy makes up the other 70 percent, and we don’t really know what the rest is,” says physicist Mark Maus of Lawrence Berkeley National Laboratory and the University of California Berkeley.
“The idea that we can take pictures of Earth and solve these big, important questions is really disturbing.”
These team papers are now available on the preprint server arXiv.