Chasing Ghosts of the Universe

You probably heard that matter is pretty much an empty space. It's true. Everything is made of tiny particles with nuclei in their centers and clouds of electrons orbiting around. If we take hydrogen (H), for example, the smallest atom with just one proton in the nucleus orbiting by just one electron, and if we scale the proton to be the basketball size, the orbit of the electron in diameter would be something about 15 km. Both the nucleus and electrons are electromagnetically charged, keeping everything in stable equilibrium, and also inside the nucleus, two more fundamental forces—strong and weak nuclear interactions—are keeping all the matter and energy in line. However, the smallest atom in the universe is not the smallest, standalone system we know of. According to the standard model, all atoms and complex molecules found in nature or artificially produced are made of fundamental particles. Something we cannot cut into smaller pieces. Electron is one of them. But there are more. So far, as far as we know, if we count all of those basic particles inside protons or neutrons and those that represents force carriers in addition to the "god" particle that makes all the mass possible, there are exactly 17 of them. But one of them deserves its own story to tell. It's nickname is "the ghost particle," and it is literally capable of passing through any mountain like it is made of cheese.