The universe spins too fast and "dark matter" - a mysterious un-spottable something with gravity - was invented to explain it. For the math to work, there has to be twice as much dark matter as regular matter. Another school of thought makes the math work by predicting some new mechanism for gravity. This is not a small problem. Physicist, Dragan Hajdukovic of CERN proposes that dark matter is an illusion and no new principle is needed. Three ideas are melded to get there.
1. The emptiness of space (formerly the "ether") is now described as a quantum vacuum. Virtual particles and anti particles are winking in and out of existence in zero sum pairs all the time in this vacuum. A recent experiment helped prove the theory. Virtual (massless) photon-antiphoton pairs were slightly energized using the predicted Casimir effect and real photons emerged at the other end out of "nothingness". Hajdukovic proposes that virtual particles with mass wink in and out of existence as gravity dipoles.
2. Virtual particles that have mass would have gravity and virtual anti-particles would have anti-gravity of opposite charge. This is a shift from thinking that gravity was just gravity in the virtual scenario.