The universe looks very different on different scales. Some of these scales appear very different to the ones with which we are most familiar. The scales of millimetres to hundreds of metres are the ones in which human beings either exist or are comfortable with comprehending. Beyond this limited range, our imaginations have to work harder.
Astrophysics encompasses every conceivable scale that the universe has to offer.
Quarks less than 10 -18 m. The smallest scale investigated so far, matter appears to be made of fundamental particles known as quarks . Rutherford scattering of very high energy electrons from accelerators indicates the quark to be at least 10,000 times smaller than the proton. Most of the mass of an atom is concentrated into its nucleus . The protons carry a positive electrical charge while the neutrons carry none.