What is it?
When found by the artist, this small oyster shell had a perfectly round hole drilled into it, perhaps by a predator. The hole was a perfect fit for a light-emitting diode.
It dimly blinks the “Arecibo message,” a transmission sent towards star cluster Messier 13 from the then-new Arecibo radio telescope in 1974. Though it was considered a “message to aliens,” the Arecibo transmission was brief, less than three minutes in duration, and was sent only once. It was a demonstration of the telescope creators’ technical prowess more than an earnest attempt to advertise humanity.
The Arecibo message is binary and can be decoded to a 23x73 pixel image. The message itself included encoded descriptions of the human body, DNA, our solar system, and base-10 number system, among other things. It is unclear how clearly it could be interpreted by beings unlike us.
“Loopback” blinks its message about every two hours and fifteen minutes. The message itself is around 3 minutes in duration, at 8 bits/second. It operates on a coin cell battery. The battery life is months or longer.
“Loopback” refers to a computing concept. A loopback device appears to a computer as an external device, but is actually originating from the same computer. This is used for sending virtual “disk images,” which appear as a hard drive when used. In a sense, it listens to its own voice.