Here’s what you’ll learn from reading this story:
-
Einstein’s Theory of General Relativity, a hugely important update to Newton’s Law of Universal Gravitation, is currently our best approximation of how the universe ticks.
-
But there are some holes in Einstein’s theory, including some gravitational strangeness around low-acceleration “broad-bin” stars.
-
A study claims that the behavior of these slow-moving celestial objects cannot be explained by a Newton-Einstein theory, which relies on dark matter, but can be explained by an idea known as Modified Newtonian Dynamics, or MOND.
In 1687, the English physicist Isaac Newton published his famous Law of Universal Gravitation. The idea that all objects attract in proportion to their mass was a revolutionary idea that became a great boon to understanding the ways of the universe. But even Newton’s influential work had its limitations—specifically, it could not explain gravitational phenomena such as black holes and gravitational waves.
Thankfully, Albert Einstein came along in the early 20th century to help move things along a bit with his Theory of General Relativity.
But space is a big place, and even Einsteins sometimes reach their limit. One of the best known of these limits is the center of a black hole, or singularity, where Einstein’s famous theory seems to break down completely. Now, a study by scientists at South Korea’s Sejong University suggests that another limit to Newton and Einstein’s conception of gravity can be found in the orbital motions of long-period, widely separated binary stars—also known simply as “wide binaries.” The results of this study were published in The Astrophysical Journal.
After analyzing 26,500 wide binaries within 650 light-years captured by the European Space Agency’s Gaia space observatory, co-author Kyu-Hyun Chae discovered something strange—when these celestial objects achieved extremely low orbital accelerations around 0.1 nanometers per square second, the observed accelerations were nearly 40 percent higher than Newtonian models’ 30 percent. predict However, if these accelerations were above 10 nanometers per second squared, they followed the Newton-Einstein theory as predicted. Something strange is happening specifically at these ultra-low accelerations.
In the standard model of gravity, this is where the concepts of dark matter become very important. Because scientists know nothing about this hypothetical form of matter and energy that is supposed to make up the majority of the universe, it is possible that dark matter is influencing this strange gravitational interaction. However, Chae argues that Modified Newtonian Dynamics, or MOND—first proposed by Israeli scientist Mordehai Milgrom in 1983—can explain (among other galactic anomalies) these low-acceleration deviations.
The most surprising element is that a theory of gravity influenced by MOND—also co-authored by Milgrom—explains this unexpected acceleration boost of 1.4 times. This theory is called A Quadratic Lagrangian, or AQUAL, and Chae says his work “represents direct evidence for the breakdown of standard gravity with weak acceleration.”
“This systematic deviation matches the boost factor that the AQUAL theory predicts for kinematic accelerations in circular orbits under the Galactic external field,” Chae says in the paper.
Similar to how the Newton-Einstein theory relies on the ever-dissolving particles known as dark matter, MOND has its own limitations and challenges. Chae’s study seems to be a big +1 in the pro column for Modified Newtonian Dynamics, but the theory is still just that—a theory. It will require much more observational support before it overturns our modern understanding of gravity and the universe we live in.
You can also Love