This paper discusses the use of very low frequency radio emission as a probe of astrophysical plasmas. The density distribution and the degree of turbulence of a plasma can be determined from its effect on background radio source. These same absorption phenomena can be used to determine magnetic field strengths within the plasma. Detection of unabsorbed synchrotron emission can provide information of the relativistic plsam component. Finally, time variable emission may prove useful in the detection of brown dwarfs and Jupiter‐like planets.