  In the search for life in the cosmos, transiting exoplanets are currently our
best targets. In the search for life in the cosmos, transiting exoplanets are
currently our best targets. With thousands already detected, our search is
entering a new era of discovery with upcoming large telescopes that will look
for signs of life in the atmospheres of transiting worlds. However, the
universe is dynamic, and which stars in the solar neighborhood have a vantage
point to see Earth as a transiting planet and can identify its vibrant
biosphere since early human civilizations are unknown.
  Here we show that 1,715 stars within 326 light-years are in the right
position to have spotted life on a transiting Earth since early human
civilization, with an additional 319 stars entering this special vantage point
in the next 5,000 years. Among the stars are 7 known exoplanet hosts that hold
the vantage point to see Earth transit, including Ross-128, which saw Earth
transit in the past, Teegarden's Star, and Trappist-1, which will start to see
Earth transit in 29 and 1,642 years, respectively. We found that human-made
radio waves have swept over 75 of the closest stars on our list already.
