Xi'an Stele

Illustration of a Hungarian Hajduk, from an 1703 book from Bavaria.

In 1974, the Arecibo Observatory was used to send the first known intentional radio message transmission into space

01The 1974 Arecibo Message was aimed at globular cluster M13 — 25,000 light-years away, arrival date roughly 26,974 AD.
02Stephen Hawking publicly warned that contacting aliens could be analogous to Native Americans meeting Columbus — and we know how that ended.
03METI International transmitted 'Sonar' toward GJ 273, a nearby star, in 2017 without any international consensus or oversight body approving it.

A 279-cm limestone stele erected in Tang China in 781 AD records Christianity in Classical Chinese and Syriac — buried, forgotten, rediscovered in 1625. It calls God 'the Lord of the Luminous Religion.'