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Voyager's Golden record was recorded in an analog way. Its lifespan perhaps 1 billion years.

Let's say that I would like to send an spacecraft with information recorded in digital. Which alternatives I have to record information avoiding data loss or corruption? Optical discs are discarded, because lifespan is limited to 10 or 20 years. Magnetic, well.. you know how unreliable were and also limited lifespan.

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  • $\begingroup$ This is a good question and I think there will be some interesting answers. If the aliens don't play the magnetic tapes they find too often and refrain from going directly from fast-forward to reverse without stopping first, then they should last a long time ;-) You'd be surprised how long a good eight track tape player can function in deep space! How was magnetic tape decay prevented in Voyager 1? $\endgroup$
    – uhoh
    Commented Oct 21, 2018 at 2:36
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    $\begingroup$ Well, magnetic tapes are for storing data currently for the mission. Let's suppose I just want to send a write-once or read-only record like the voyager gold record, which will never degrate as magnetic does. $\endgroup$ Commented Oct 21, 2018 at 2:42
  • $\begingroup$ The most long standing optical record is this: nature.com/articles/s41467-018-03589-y , claiming that discs will work after 600 years. $\endgroup$ Commented Oct 21, 2018 at 2:43
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    $\begingroup$ Here is another optical storage, Eternal 5D storage in quartz glass: computerworld.com/article/2483919/emerging-technology/… $\endgroup$ Commented Oct 21, 2018 at 2:59
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    $\begingroup$ Digital might not be a great option if you want it to be accessible by some alien civilization. The analog method used in the Voyager record was easily explained in a few simple line drawings. A digital scheme might call for a whole lot more complex explanations, especially if you need to employ compression and error correction schemes. $\endgroup$
    – Anthony X
    Commented Oct 21, 2018 at 22:16

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Optical discs are encoded by a digital pattern of pits in, typically, a single spiral track; the lifetime of a CD is constrained by the thinness of the substrate rather than the encoding method.

Therefore, a relatively thick golden record like Voyager’s, with an encoding like that of a CD, ought to be very durable, and laser-readable with a system similar to that of a CD player.

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  • $\begingroup$ Digital Discs would have terrible lifespan without some kind of error correction algorithm. The algorithm would need to be pre-agreed upon with the alien race. Analog would still decode with just with lots of noise. $\endgroup$
    – Aron
    Commented Oct 21, 2018 at 12:39
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    $\begingroup$ Any reasonably smart alien race could work out the ECC of compact discs. $\endgroup$ Commented Oct 21, 2018 at 14:39
  • $\begingroup$ Or, if you’re not confident of that, the first few blocks could be dedicated to explaining the encoding in a very redundant pictorial bitmap form. $\endgroup$ Commented Oct 21, 2018 at 18:55
  • $\begingroup$ You mean reverse engineering Reed Solomon without the plaintext? In the second example, you expect the aliens to be able to work out that they have a Digital Rosetta stone just by looking at it? The only reason we work out what the Rosetta stone was, was because a) we knew one of the languages and b) each language has a unique symbol/glyph/alphabet. Digital data by its nature is using the same symbology. $\endgroup$
    – Aron
    Commented Oct 22, 2018 at 0:44
  • $\begingroup$ OP asks about encoding; composition of the message is a different problem, but a very well understood one. See en.m.wikipedia.org/wiki/Cosmic_Call and space.stackexchange.com/q/21508/195 for starters. $\endgroup$ Commented Oct 22, 2018 at 10:30
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I found two options right now:

Fused silica and 5D quartz disks.

5D quartz disks have a capacity of 360 TB and its information can be retained million of years. They already used by Tesla in that car sent into space.

Fused silica was developed by Hitachi, and it's recorded almost in the same way as 5D quartz, with a femtosecond laser, also claiming to have million-years lifespan.

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  • $\begingroup$ For easier readout by an alien race restriction to a 2D recording might be better. $\endgroup$
    – Uwe
    Commented Oct 23, 2018 at 11:58
  • $\begingroup$ Perhaps, In the Hitachi's Fused silica demo, they saved information as 2D QR Codes, an approach similar could be used $\endgroup$ Commented Oct 23, 2018 at 15:18

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