The theory of relativity usually covers two interrelated theories of Albert Einstein: special relativity published in 1905 and general relativity published in 1915. Special relativity applies to all physical phenomena in the absence of gravity. General relativity explains the law of gravitation and its relationship to other forces in nature.
The theory of relativity was developed by Albert Einstein in the early 1900s due to the inability of classical physics to explain certain observations. It has two components, special relativity and general relativity.
Special relativity is based on the key concepts of a constant speed of light and physical events must look the same for all observers and apply to all physical phenomena without significant gravitation. General relativity is the idea that space and time are two aspects of space-time, and what we perceive as gravity is the deformation of space-time.
Scientists studying the cosmos have a preferred philosophy known as the “mediocrity principle,” which essentially suggests that there really is nothing special about the Earth, the Sun, or the Milky Way compared to the rest of the world. ‘universe.
Now, new research from the University of Colorado at Boulder (CU Boulder) adds another piece of evidence to the case of mediocrity: galaxies are, on average, at rest from the early universe. Jeremy Darling, a professor of astrophysics at CU Boulder, published this new cosmological finding on May 26, 2022 in the Astrophysical Journal Letters.
This image, taken from a combination of photos from September 2003 to January 2004 captured by NASA / ESA’s Hubble Space Telescope, shows nearly 10,000 galaxies in the deepest visible light image in the cosmos, cutting billions of light years. Credit: Image courtesy of NASA, ESA, S. Beckwith (STScI), HUDF Team
“What this research is telling us is that we have a fun movement, but this fun movement is consistent with everything we know about the universe; there’s nothing special here,” Darling said. “We are not special as galaxies or observers.”
About 35 years ago, researchers discovered the cosmic microwave background, which is the electromagnetic radiation left over from the formation of the universe during the Big Bang. The cosmic microwave background seems warmer in the direction of our motion and cooler away from the direction of our motion.
From this glow of the early universe, scientists can infer that the Sun, and the Earth orbiting around it, is moving in a certain direction, at a certain speed. Researchers find that our inferred speed is a fraction of a percentage of the speed of light, small but not zero.
Astrophysics professor Jeremy Darling studies the evolution of galaxies, massive black holes, star formation, and cosmology. Credit: University of Colorado at Boulder
Scientists can independently prove this inference by counting the galaxies that are visible from Earth or adding their brightness. They can do this thanks in large part to Albert Einstein’s 1905 theory of special relativity, which explains how speed affects time and space. In this application, a person on Earth looking at the universe in one direction, the same direction in which the Sun and Earth move, should see brighter, bluer, more concentrated galaxies. Similarly, looking in the other direction, the person should see darker, redder, and more spaced galaxies.
But when researchers have tried to count galaxies in recent years, a process that is difficult to do accurately, they have found figures that suggest the Sun is moving much faster than previously thought, which is at odds with cosmology. standard.
“It’s hard to count galaxies across the sky; you’re usually stuck with one hemisphere or less,” Darling said. “And in addition, our own galaxy gets in the way. It has dust that will make you find fewer galaxies and make them look fainter as you get closer to our galaxy.
Darling was intrigued and perplexed by this cosmological puzzle, so he decided to investigate for himself. I also knew that there were two recently published surveys that could help improve the accuracy of a galaxy count and shed light on the mystery of speed: one called the Very Large Array Sky Survey (VLASS) in New Mexico, and the other called Rapid Australian. Square Kilometer Array Pathfinder Continuum Survey (RACS) in Australia.
“I love the idea that this basic principle that Einstein told us a long time ago is something you can see. It’s a really esoteric thing that seems super weird, but if you go out to count galaxies, you could see that net effect. it’s as esoteric or weird as you might think. ” “Jeremy Darling.”
Taken together, these surveys allowed Darling to study the entire sky by combining views from the northern and southern hemispheres. It is important to note that the new surveys also used radio waves, which made it easier to “see” through the dust of the Milky Way, thus improving the view of the universe.
When Darling analyzed the surveys, he found that the number of galaxies and their brightness matched perfectly with the speed that the researchers had previously deduced from the cosmic microwave background.
“We find a bright direction and a faint direction: we find a direction where there are more galaxies and a direction where there are fewer galaxies,” he said. “The big difference is that it aligns with the early universe from the cosmic microwave background and has the right speed. Our cosmology is fine.”
Because Darling’s findings differ from previous results, his article is likely to lead to several follow-up studies to confirm or discuss his findings.
But in addition to advancing the field of cosmology, the findings are a good real example of Einstein’s theory of special relativity, and show how researchers are still putting the theory into practice, more than 100 years after the famous physicist first proposed it. .
“I love the idea that this basic principle that Einstein told us a long time ago is something you can see,” Darling said. “It’s a really esoteric thing that seems super weird, but if you go out to count galaxies, you could see that net effect. It’s not as esoteric or weird as you might think.”
Reference: “The Universe is Brighter in the Direction of Our Motion: Galaxy Counts and Fluxes are consistent with the CMB Dipole” by Jeremy Darling, May 26, 2022, Astrophysical Journal Letters.DOI: 10.3847 / 2041-8213 / ac6f08