Back in the late 1990s, scientists made a prediction about how much ordinary matter there is in the universe. They stated that there’s about 5% and that it should be a mix between dark matter and dark energy. However, when they counted up everything they were able to see at that time, they found out the number is not correct. That there were a lot less. The sum they found added up to half of that 5% of all the matter that was supposed to be in the universe. They called this problem the “missing baryon problem”, and for two decades, scientists looked for the missing matter.
But they did find it, with the help of a telescope and a new phenomenon happening in the sky.
So what happened with the matter?
So what we need to talk about is Baryon, which is a classification for types of particles, which includes neutrons and protons. Everything there is to know is made out of baryons.
Ever since the 1970s, scientists suspected that the universe is made out of dark matter and baryonic matter, but they did not know the exact ratios. Then, back in 1997, scientists from the University of California, San Diego, made the most out of the ratio of heavy hydrogen nuclei in order to find out that baryons should be the matter that was nowhere to be found.
Then, other scientists showed that there was a problem with that theory. The direct measure of baryons in the universe, which is estimated by a census of stars, galaxies, and the gas around them, were only added up the half of the initial missing matter.