In the late 1990s, cosmologists made a prediction about how much ordinary matter there should be in the universe. About 5%, they estimated, should be regular stuff with the rest a mixture of dark matter and dark energy. But when cosmologists counted up everything they could see or measure at the time, they came up short. By a lot. The sum of all the ordinary matter that cosmologists measured only added up to about half of the 5% what was supposed to be in the universe. This is known as the “missing baryon problem” and for over 20 years, cosmologists…

This story continues at The Next Web