The first deliberate attempt to contact ET was in 1972, with the launch of NASA’s Pioneer 10 space probe. This carried a gold-plated aluminium plaque bearing pictures of a male and a female nude and graphical information about the origin of the craft, in the (extremely unlikely) event of it being intercepted by aliens. Pioneer 10 is currently on the fringes of the solar system on course for a star 68 light years away. Pioneer 11, launched in 1973, also carries a plaque.
Since then, numerous other messages have been broadcast to the stars, including a giant Doritos advert beamed from the Arctic archipelago of Svalbard to a solar system 42 light years away. Such messages are controversial, however: some scientists believe we should keep our heads down so as not to alert malicious aliens to our feeble presence. More.
See also: How do we grapple with the idea that ET might not be out there?
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