Glass disc sends sci-fi into space

The spaceman onboard Musk's Tesla Roadstar has some high-tech cargo.

When Elon Musk sent his Tesla Roadster into space aboard SpaceX's Falcon Heavy rocket last year, the spacesuit-clad mannequin in the driver's seat had a few essentials packed.

A copy of Douglas Adams' The Hitchhiker's Guide to the Galaxy was stored in the glovebox, and David Bowie's Space Oddity was programmed to play repeatedly on the car stereo. Less noticed was a coin-sized, transparent disc secured in a case. It did not look like much, but for professor Peter Kazansky and his team at Southampton University's Optoelectronics Research Centre, it was a major moment.

Recorded on the disc, in a series of tiny etchings, was a special code containing Foundation, Isaac Asimov's science fiction trilogy. The piece of glass, which could withstand extreme heat, cold and impacts, can be expected to survive for several billion years, more than long enough for a future alien species to find it.

Kazansky says the team has had no shortage of requests to create time capsules to be sent to the moon and Mars, but his "storage crystal" technology could also have uses on Earth.

Last year, the world created 33 zettabytes (or 33 trillion gigabytes) of data, a number that is expected to rise to 175 zettabytes in 2025. According to storage company Seagate, that is equivalent to a stack of DVDs circling the Earth 222 times. Increasingly strict data laws mean it must be properly stored and processed, a laborious and expensive task.

For long-term storage, such as the archives of video, audio and text that film studios, museums and big companies maintain, we still largely rely on magnetic tape. The technology is nearly a century old, but no economically viable alternative has been found.

"For archival systems tape is really the go-to technology," says Robert Grass of the Functional Materials Laboratory at the Swiss research institution ETH Zurich. He says the technology remains significantly cheaper and longer-lasting than hard disks, which can wear out in as little as three years.

Despite significant advances in magnetic tape technology, however, it is not progressing as quickly as data is being created, meaning increasing amounts of physical space must be put aside for storage.

Tape must also be replaced every 20 years or so, and is far from faultless, says Grass, due to the fragility of the tape itself and the risk of magnetic interference.

If we want films, recordings and literature to stick around for millennia, we are left with the choice of replacing the tapes every two decades, or finding a method that is faster, smaller and more efficient.

Last week, researchers at Microsoft in Cambridge claimed the latest breakthrough on this front, when they condensed a copy of the 1978 film Superman on to a piece of quartz glass the size of a drinks coaster (the movie was chosen because the technology has been compared to the "memory crystals" Superman uses to access recordings of his parents). The researchers had worked with Kazansky's team at Southampton University.

Nanoscale indentations known as "voxels" are made inside the glass using a series of laser pulses, creating a pattern that can be decoded by shining polarised light through the glass. On a basic level, this works in a similar way to how a record player decodes a signal from an LP's grooves.

But because each voxel holds more information — space in three dimensions, its angle and the way it refracts light — substantially more data can be stored. In theory, a CD-sized piece of glass could store 360 terabytes — more than half a million regular CDs. The glass was found to be exceptionally sturdy — still readable when Microsoft's researchers boiled, oven baked and scratched it.

Although the idea has been around for several years, Kazansky says the breakthrough was in being able to read the data fast enough. However, it is still too expensive to be commercially viable.