ATOMS MAKE UP ONLY 4% OF THE UNIVERSE. In an interview with Brian Bolduc (Wall Street Journal March 10-11), physicist Michio Kaku says that the belief from only 10 years ago that the universe is mostly made up of atoms has been overturned. Now it is thought that atoms make up only 4% of the universe. The rest is dark matter and dark energy—and we don’t much about either of them.
Also, when I was growing up, there were thought to be three types of elementary particle—protons, electrons and neutrons. Now there are thought to be thousands of elementary particles.