Gravity is so strange that it forces cosmologists to accept one of two equally radical conclusions: dark matter exists, or the fundamental rules of gravity need a massive revision. To resolve this debate, scientists have embarked on the largest study of gravity to date and found that the wisdom of ancient physics is powerful for the most puzzling observations.
In a study published this week Physical review lettersAn international team of astronomers tested space observations against Albert Einstein’s general theory of relativity based on Isaac Newton’s basic laws of gravity. now, general relativity— which defines gravity as distortions in space — is one of the most successful ideas in the history of science. What’s “new” about the study is that it conclusively demonstrates that even the largest, most distant structures in the universe follow similar rules of gravity that we experience every day.
This creates a barrier to alternative theories that attempt to modify the fundamental laws of gravity to explain the observational inconsistencies in cosmology. That said, the basic rules are correct – there’s something else we’re not seeing. Many scientists say that this “something” is dark matter.
“Despite so many unanswered questions, gravity remains one of the most interesting areas of research,” said Patricio Gallardo, one of the study’s authors and an astrophysicist at the University of Pennsylvania. statement. “It’s a naturally attractive field.”
Something outside
Famous astronomer Vera Rubin in the 1970s found rotating galaxies seemed to defy the laws of gravity. By the way, Newtonian logic states that stars farther from the center of the galaxy should orbit more slowly than stars in the center, where the starlight is concentrated. But Ruby’s observations revealed that the exact opposite was true, and that the stars in the fringe were also moving at the same speed.
According to Gallardo, similar inconsistencies are seen in galaxy clusters, some of which are “moving too fast for the amount of matter visible in them,” he said. “That’s the central puzzle. Either gravity behaves differently on very large scales, or the universe contains extra matter that we can’t directly see.”
Enter dark matter
Dark matter—the invisible stuff that makes up 85% of the mass of the universe—was introduced (partially) to solve this problem. Although researchers have not found direct evidence for dark matter, there is a strong consensus that its existence solves many unexplained phenomena in space.
Of course, since we haven’t discovered dark matter yet, not all scientists believe in dark matter offers many alternative explanations. But many new studies like this one broad map of dark matterconsistently reaching conclusions in favor of the existence of dark matter.
Newton, Einstein, gravity
This includes the most recent study collecting data on galaxy clusters observed by the Atacama Cosmology Telescope (ACT) in Chile and the Sloan Digital Sky Survey in New Mexico. Researchers tracked down a particular source of light emitted about 380,000 years after the Big Bang. Every time this ancient light source flies past giant galaxy clusters, its motion is slightly bent by gravity.
During the analysis, the team measured these small changes in hundreds of thousands of galaxy clusters separated by tens of millions of light years. The calculations were in perfect agreement with what Newton’s and Einstein’s theories predicted about the effect of gravity on this light source.
“Our analysis here is quite general—it is not based on a specific cosmology,” the researchers noted in the paper. However, the modified laws of gravity were not as successful as the conventional equations, they added. Therefore, if the laws of gravity are good, the inconsistency must be in something we can’t see – something like dark matter.
