Gravity can exist without mass

Dr. Richard Lieu from the University of Alabama in Huntsville has proposed a new theory that explains gravity without the need for dark matter, suggesting that gravity can exist without mass. His research aims to find alternative solutions to the equations of general relativity. He believes that the extra gravity needed to hold galaxies and clusters together may arise from shell-like structures called topological defects, which were likely created during a major transition in the early universe.