The elusive Planet Nine, which is theorized to be lurking somewhere in the outer reaches of the solar system, may not be a planet after all, a new study suggests. Instead, what we assumed to be a massive object could be evidence that gravity doesn't work like we thought it does. But the new theory doesn't sit well with everyone.
Isaac Newton's second law states that gravity tugging on an object is inversely proportional to the distance between the object and the object that is pulling it, meaning that gravity gets weaker as the distance between the two objects increases. But MOND tweaks this and suggests that past a certain distance, the gravitational pull is directly proportional to the distance, meaning the strength of the gravitational pull does not drop off as quickly at greater distances.
The researchers were surprised by their findings. The initial aim of their study was to"rule out" MOND as a possible explanation for Planet Nine. However, when they applied it to the problem, it seemed to solve the issue perfectly. However, MOND cannot explain all of the universe's missing mass and thus cannot completely rule out the idea of dark matter. And other studies suggested that to reconcile MOND with quantum mechanics and relativity,"funky" stuff needed to be added to existing theories, and some of those additions are problematic.Not everyone is convinced by this latest Planet Nine theory.