Radio atmospheric Radio atmospheric A radio atmospheric signal or sferic (sometimes also spelled "spheric") is a broadband electromagnetic impulse that occurs as a result of natural atmospheric lightning discharges. Sferics may propagate from their lightning source without major attenuation in the Earth–ionosphere waveguide, and can be received thousands of kilometres from their source. On a time-domain plot, a sferic may appear as a single high-amplitude spike in the time-domain data. On a spectrogram, a sferic appears as a vertical stripe (reflecting its broadband and impulsive nature) that may extend from a few kHz to several tens of kHz, depending on atmospheric conditions.
Earth–Moon–Earth communication since 2010 she has been using it in several of her art projects, including the live performance called OPTICKS, during which digital images are sent to the Moon and back in real time and projected live. Radio waves propagate in vacuum at the speed of light "c", exactly 299,792,458 m/s. Propagation time to the Moon and back ranges from 2.4 to 2.7 seconds, with an average of 2.56 seconds (distance from earth to the moon is 384,400 km). The Moon is nearly spherical, and its radius corresponds to about 5.8 milliseconds of wave travel time. The trailing parts of an