Proponents of dark matter theorize that most of the known universe is actually made of material that does not interact with light, making it invisible and undetectable, but that this material is a large part of the gravitational attraction between galaxies. A counter-explanation introduced by the Israeli physicist Mordehai Milgrom in 1983, the MOdified Newtonian Dynamics (MOND) theory, says that this gravitational attraction exists because the rules of gravity are slightly changed. Instead of attributing the excess of gravitational attraction to unseen, undetectable dark matter, MOND suggests that gravity at low accelerations is stronger than pure Newtonian understanding would be expected. In addition, MOND makes a bold prediction: the internal movements of an object in the cosmos should not only depend on the mass of the object itself, but also on the gravitational attraction of all other masses in the Universe – the so-called external field effect. Now, astrophysicists in South Korea, the United Kingdom and the United States are reporting a detection of this external field effect in 153 galaxies on disk from the Spitzer Photometry and Accurate Rotation Curves (SPARC) database.
Messier 63 (also known as M63, NGC 5055 and the Sunflower Galaxy), a spiral galaxy located about 29.5 million light-years away in the constellation Canes Venatici, has the strongest external field among the SPARC galaxies. Image credit: NASA / ESA / Hubble.
“The external field effect is a unique MOND signature that does not appear in Newton-Einstein gravity,” said co-author Dr. Stacy McGaugh, a researcher in the Department of Astronomy at Case Western Reserve University.
“This has no analogy in conventional theory with dark matter. Detecting this effect is a real scratch. “
“I worked on the assumption that dark matter exists, so this result really surprised me,” said lead author Dr. Kyu-Hyun Chae, a researcher in the Department of Physics and Astronomy at Sejong University.
“Initially, I was reluctant to interpret our own results in favor of MOND. But now I cannot deny that the results, as they stand, clearly support the WORLD, rather than the dark matter hypothesis. “
The scientists analyzed 153 rotation curves of the disk galaxies in the SPARC sample.
They deduced the effect of the external field by observing that galaxies in strong external fields slowed down or showed decreasing rotational curves, more frequently than galaxies in weaker external fields, as only MOND predicted.
“I was skeptical of the results at first because the effect of the external field on the rotation curves is expected to be very small,” said Dr. McGaugh.
“I spent months checking different systems. Finally, it became clear that we have a real and solid detection. “
“Skepticism is part of the scientific process and understands the reluctance of many scientists to consider the WORLD as a possibility,” she added.
“I came from the same place as those in the dark matter community. It hurts me to think we could be so wrong. But Milgrom predicted this over 30 years ago with MOND. No other theory anticipated the observed behavior. “
The team ‘s work was published in Astrophysics journal.
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Kyu-Hyun Chae et al. 2020. Testing the strong principle of equivalence: detecting the effect of the external field in galaxies supported by rotation. APJ 904, 51; doi: 10.3847 / 1538-4357 / abbb96
This article is based on text provided by Case Western Reserve University.