The rapidly accelerating rate of discovery of exoplanets has been dubbed the “golden age of discovery” of these planets,
with an increasing number approaching Earth-like terrestrial planets, in habitable zones. Improving capability of both
ground-based and space-based instrumentation permits the examination of a given exoplanet’s transmission and
reflectance spectra that may hold clues to a habitable environment, and possibly, an indication of extraterrestrial life. To
provide a context for assessing these clues, we consider how Earth would have appeared to an observer at interstellar
distances, and how this appearance would have changed from shortly after its formation, to the present.
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