Einstein wins again: Strange theories of gravity take a hit from new observations
By Don Lincoln | Published: 2024-11-27 15:30:00 | Source: Hard Science – Big Think
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Modern astronomy has a nasty secret: astronomers don’t understand how the universe works. Galaxies rotate faster than can be explained by observed matter and the well-established laws of physics. Individual galaxies within vast groups of galaxies are moving so fast that these groups should not exist. When researchers look at very distant galaxies, they are distorted because space acts like a giant lens. This distortion is more than Einstein’s theory of relativity can explain.
Scientists have proposed a number of different explanations for these observations. Most commonly, the universe is dominated by an invisible form of matter called… Dark matterThis increases the force of gravity that governs the universe. But dark matter has never been directly observed, and because it has proven elusive, some scientists prefer a different explanation.
If what we observe cannot be explained by the known laws of physics, then the known laws of physics are probably wrong—or at least incomplete. Perhaps the accepted theory of gravity needs revision. Or perhaps what describes the behavior of matter in the solar system does not hold true when applied to the entire universe. Understanding what is going on is one of the most pressing goals of astronomy Recent advertisement By a group of researchers who have influenced this problem.
the Dark energy spectroscopy instrument DESI uses the Mayall Telescope at Kitt Peak National Observatory in Arizona to survey the universe. DESI can image thousands of distant galaxies at the same time. Using 5,000 positioners, the device can measure the spectrum of light from each galaxy across wavelengths from 380 to 980 nanometers. This range includes ultraviolet light, the entire visible spectrum, and some infrared light.
DESI began operations in 2021 and has done so Announce Results of the first year’s analysis of recorded data. They studied nearly 5 million galaxies, at distances ranging from our cosmic neighborhood to those so far away that the light observed by DESI was emitted 11 billion years ago. The DESI tool allowed astronomers to create an unprecedented 3D map of the universe representing 20% of the entire sky.
Astronomers have long known that the universe’s galaxies are not distributed smoothly throughout space. On length scales of approximately hundreds of millions of light-years, galaxies are clustered together on giant sheets surrounding enormous voids, which contain very few galaxies. In many respects, the distribution of galaxies resembles the foam on the top of a quickly drawn pint of beer, with galaxies on the surfaces of the bubbles.
The volume of voids – the size of bubbles in the beer analogy – is related to the speed of sound in the early universe. As in air, sound in the early universe was composed of regions of higher and lower density. Areas of higher density created areas of higher gravity, which pulled matter in that direction. At the same time, sparsely populated regions lost the pull of gravity, resulting in the foamy cosmic structure we see today.
The recent announcement from the DESI collaboration investigated the size of bubbles at different distances from Earth. Since the speed of light is finite, this is equivalent to looking back in time, when the universe was only 20% of its current age.
By studying the size of bubbles as a function of time, scientists were able to test Einstein’s theory of relativity, the currently accepted theory of gravity. This provided an ideal test to see whether Einstein was right, or whether his theory didn’t work on cosmic scales. If the latter is true, scientists will have to invent an improved theory of gravity.
However, DESI measurements were in good agreement with relativity. While this measurement does not rule out all possible extended theories of gravity, it certainly rules out some, and will prompt astronomers to reconsider their proposed extensions of Einstein’s theory.
This latter result uses only one year of DESI data and reflects a more complex analysis than ours advertisement Last April using the same data. However, there is more data to be analysed. DESI is currently in the fourth year of a planned five-year monitoring program.
The researchers are analyzing data from the first three years of data, which they hope to announce in the spring of 2025. The latest announcement is consistent with the April 2024 results, which hinted that the energy field driving the accelerating expansion of the universe may change over time. If this result is reached through analysis of the larger data set, it will dramatically change our understanding of the nature of the universe.
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