Schematic View of Hypothetical Extraterrestrial Emission in the Milky Way (IMAGE)
Caption
Schematic view of the Milky Way showing six isotropic extraterrestrial emission processes forming spherical shells filled by radio signals. The outer radii of the spherical shells are proportional to the time at which the signals were first emitted, while the thicknesses are proportional to the duration of the emissions. In this example, the Earth is illuminated by one of these signals.
Credit
Claudio Grimaldi / EPFL
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