What came before the Big Bang?
If the universe began billions of years ago with the Big Bang, what preceded it? According to renowned physicist Stephen William Hawking, PhD: Nothing. However, no one can know for sure; any events that happened before the universe came into existence are without “observational consequence,” as Hawking put it, and therefore, we “may as well cut them out of the theory, and say that time began at the Big Bang.”
What is dark matter?
Courtesy NASA/JPL-Caltech/ESA/Institute of Astrophysics of Andalusia, University of Basque Country/JHU
Everything and everyone is made up of “baryonic matter:” protons, neutrons, and electrons. Until about 30 years ago, astronomers thought that the universe followed the same rules—it was entirely baryonic matter. Over the last few decades, however, scientists have found that only 5 percent of the universe is composed of baryonic matter—and they can’t even detect the other 95 percent. Scientists believe that some 25 percent consists of dark matter—but nobody can say definitively what dark matter actually is or what it’s made of yet. Don’t miss these other science mysteries no one has figured out yet.