  Microlensing is proving to be one of the best techniques to detect distant,
low-mass planets around the most common stars in the Galaxy. In principle,
Earth's microlensing signal could offer the chance for other technological
civilisations to find the Earth across Galactic distances. We consider the
photometric microlensing signal of Earth to other potential technological
civilisations and dub the regions of our Galaxy from which Earth's photometric
microlensing signal is most readily observable as the "Earth Microlensing Zone"
(EMZ). The EMZ can be thought of as the microlensing analogue of the Earth
Transit Zone (ETZ) from where observers see Earth transit the Sun. Just as for
the ETZ, the EMZ could represent a game-theoretic Schelling point for targeted
searches for extra-terrestrial intelligence (SETI). To compute the EMZ, we use
the Gaia DR2 catalogue with magnitude G<20 to generate Earth microlensing
probability and detection rate maps to other observers. Whilst our Solar system
is a multi-planet system, we show that Earth's photometric microlensing
signature is almost always well approximated by a binary lens assumption. We
then show that the Earth is in fact well-hidden to observers with technology
comparable to our own. Specifically, even if observers are located around every
Gaia DR2 star with G<20, we expect photometric microlensing signatures from the
Earth to be observable on average only tens per year by any of them. In
addition, the EMZs overlap with the ETZ near the Galactic centre which could be
the main areas for future SETI searches.
