Figure 1 : Detectable domain for isotropic signals.

From: Signal coverage approach to the detection probability of hypothetical extraterrestrial emitters in the Milky Way

Figure 1

(A) Two-dimensional representation of a spherical shell signal of outer radiur R and shell thickness Δ emitted from . (B) The detectable domain formed by union of three spherical shells centered at E1, E2, and E3. In this example the Earth (red dot) intersects the shells of E1 and E3, but only E3 is within the observable radius Ro. (C) Schematic illustration of the location of the Earth within the Milky Way galaxy. The dashed circle represents the observable sphere of radius Ro centered about the Earth.