In Stanley Kubrick’s “2001: A Space Odyssey” (1968), when a strange object is discovered on the Moon, researchers go to investigate it. They arrive on Clavius, a U.S. lunar base, from where they then fly by “Moonbus” to the Tycho crater. Embedded in it, they find a black, rectangular, 11-feet-high slab, whose sides are built to the ratio 1:4:9.
The Tycho Magnetic Anomaly One (or T.M.A.-1), as they call it, has been built by an advanced extraterrestrial civilization that had developed intergalactic travel, when we weren’t even around. When it’s exposed to sunlight, it beams a radio signal to Jupiter.
In an interview with World Science Festival, Paul Davies—the man entrusted to speak for all of humankind if ever we do hear from aliens—explained the reason the monolith was placed there.
As a radio signal would take 100,000 years to travel from one end of the Milky Way (diameter: 100,000 light-years) to the other, we’d have to wait that long to get a reply from any society beyond it.
Therefore, to bypass that problem, when our cosmic visitors swung by our planet in the very distant past, they left behind this communication tool that’d be awakened by radio chatter from Earth—an indicator that they’d made contact with an emergent civilization. It could then have instantaneous conversation with us through this device as if it were a telephone.