You have a new summer job with NASA and are working on astronomical observations using electromagnetic radiation that is not in the visible range. Your supervisor has explained 21­cm radiation to you and that it is used for a number of observations of interstellar hydrogen. She explains that 21-cm radiation is in the microwave region of the electromagnetic spectrum and comes from a hyperfine splitting of the electron ground state of hydrogen. It is similar to the Zeeman effect, except that it is the spin states that are split, and the magnetic field is internal to the atom: it comes from the magnetic field due to the nucleus. When the atom makes a transition from the higher state to the lower state, a 21-cm photon is emitted. Based on the fact that the radiation is of wavelength 21 cm, you wish to determine an approximate value for the average magnitude of the magnetic field in which the electron resides.