Action at a Distance Can Explain Dark Matter, Physicists Show

The Dark Matter Problem

• 💡 Most of the universe's matter is unknown, with dark matter being the prevailing theory, detectable only through its gravitational pull.
• ⚠️ Decades of astrophysical evidence show that Einstein's theory of general relativity doesn't correctly predict the observed space curvature in galaxies and galaxy clusters.
• 🎯 The standard solution is to postulate dark matter, but despite decades of searching, it has not been directly found, leading to scientific "embarrassment."

Non-Local Gravity Concept

• 🧠 A new paper proposes that gravity might not be local, meaning objects can influence each other without a signal, challenging the locality principle of modern physics.
• 🌌 This concept suggests that space curvature in one location is influenced by masses elsewhere, effectively appearing as "too much mass" in spacetime.
• 📜 Newtonian gravity was inherently non-local ("action at a distance"), a feature that bothered Newton but is now being re-examined in a new context.

Explaining Astrophysical Observations

• 🔭 The new non-local gravity theory claims to explain observations normally attributed to dark matter, without introducing new types of matter.
• 🧩 It offers a unified explanation by interpolating between dark matter-like behavior at large scales (galaxy clusters) and Modified Newtonian Dynamics (MOND)-like behavior at galactic scales.
• ✅ This approach addresses the limitations of both MOND (which works for galaxies but not clusters) and dark matter (which works for clusters but has issues with galaxies).

Challenges and Implications

• 🔬 The proposed theory involves highly complex differential equations that are difficult to work with and may not be easily compatible with quantum theory.
• 🚧 A key criticism is that the transition between MOND and dark matter regimes is "put in by hand" rather than emerging naturally from the formalism.
• 💬 Despite its challenges, the idea of non-local gravity is appealing because quantum theory is also non-local, suggesting a potential connection to quantum gravity.