How to decode the images on the Voyager Golden Record

[semiotix]

@Xuth

Also, I’m sure this is not the best way to get things to Ron Barry.

Mail him a golden record. He likes that.

[L0ki]

No respect needed! I’m just some kibitzer criticising the efforts of people far more knowledgeable and qualified than I am in pretty much every field.

I’m very impressed by how much information it was possible to cram in and clearly a lot of thought went in to trying to make the information universally comprehensible (to a crack team of highly clever people - which is fair enough, you’d hope that an alien space probe would be handed over to really clever people to play with).

I may have misunderstood parts of your OP (well, let’s be honest, large parts of it went over my head with great big whooshing noises) but it seemed to me that there were a number of areas where you ended up having to guess and make adjustments based on your knowledge of what the images are supposed to look like.

For example:

@boingboing

Though, if I were actually a Kerbal, I wouldn’t know anything about a record to begin with, so just being human means I already had a quite few spoilers in hand. Maybe, if I were twenty years younger, I wouldn’t have known what a record was and I wouldn’t have had the hint that the marks on the upper-left diagrams were timing information? I think I got that from the waveform, but I can’t say for sure how I pieced it all together.

@boingboing

Figure 7a, below, had been bothering me for a while, but I’d been so focused on trace boundaries, jitter, aspect ratios, shadows/anti-shadows, that I’d not really paid it much attention. It finally occurred to me that, if this image were lit from the bottom left, the shadowed part of the moon should be the same darkness as space behind it. I eventually realized that my images were inverted - negatives of themselves.

@boingboing

They were very low-contrast, so I experimented with some expansion functions to enhance the detail in the middle range while throwing some out in the whites and blacks.

@boingboing

I knew what was being communicated, but I needed to figure out how the Kerbals would work that out before proceeding. I hated these slides. At the time I first saw them, I was still having major contrast issues, so there was ZERO detail in them. They were greyish rectangular blobs. Even boosting the contrast considerably, it’s incredibly difficult to spot any information. There’s an X in the middle of the second image, and all three appear to have two very faint, horizontal lines through them. I’ve no clue how these are telling Kerbals anything at all. I would guess that the X is where human luminous efficiency is at its peak, but I’m clueless.

One of many, many guesses finally paid off.

Are these areas that someone with more knowledge in a particular field wouldn’t need to guess, they’d be able to know based on other information on the record - assuming they worked out that they were supposed to play the record in the first place?

[euansmith]

Thank you for that fulsome response. What prompted my comment was the hands holding a frog picture.

[Glaurung]

The frog pic was my second place candidate for “does not belong in this sequence of Earth’s animal life”. I think they were working from a limited slide deck, as someone suggested upthread. And a limited circle of friends with slide decks they could borrow from.

[euansmith]

It is weird to be reminded that not so long ago there wasn’t Google Images. We lived like barbarians, eating rocks and leafs and living under cars.

[westcarleton]

Analog video signals need DC restoration; standard TV stuff. Those signals may have had some high-pass filtering done before he got them, you can work it out from the decay times of the pulses.

[csilvest]

@FrontierJustice

This has always kinda blown my mind. There’s a bravery and optimism in executing something like this that I have trouble wrapping my head around. Visionary nerds rock.

My wife says we’re just sending a menu and Google Maps directions to hungry aliens; they’re so advanced we’re just cattle to them.

@FrontierJustice

About to have one of those moments when I get mad a Carl Sagan for dying all over again.

Sagan came back to life?

[FrontierJustice]

@csilvest

About to have one of those moments when I get mad a Carl Sagan for dying all over again.

Sagan came back to life?

Yeah, I guess that reads kinda weird. But you get it.

[Ron_Barry]

It’s true that I had an unfair leg-up, just knowing what a record was. The moon shot, even in negative, still looks like a cratered moon. Being human, the fact that the image was so recognizable was actually a disadvantage. I think the Kerbals would have taken a more objective approach and realized the negative mistake sooner - probably using similar logic to what I applied.

Unfortunately, I had to cut a lot of detail to keep the article brief. Early on, the images I pulled from the data were incredibly faint and heavily biased toward the center point. I’ve done some photography in my time, so I’m familiar with what it takes to restore a photo when part of the dynamic range isn’t used. I wrote a bunch of code to generate histograms of each image, found that the vast majority of the detail was in less than a fifth of the range, and applied a non-linear filter to try to restore some contrast out of that narrow band. (That entire process got reduced to the “expansion functions” quote. =]

As for your last question, a chemist or physicist would probably be working with the signals geek in charge of the decode. The fact that I was terrible at chemistry and dropped out of a college physics program and still managed to work it out, suggests that it’s not a very difficult puzzle to crack. I have to admit that I’d love to dig up an actual chemist, show them those ^*#&^) slides, and see if 1) they fail to recognize them as Voyager data and 2) can work out the puzzle.

[Ron_Barry]

Heh heh! I’d love one! …and a turntable… and a place to put it… and a way to keep the cats off of it…

[Ron_Barry]

I gather that soundcloud has compressed Dave’s .wav into an unusable mp3. I uploaded the 384kHz .wav to the same folder where I dropped the images. See the text of the article for the link.

[Xuth]

Sweet. Thank you for uploading the raw “audio” file. I’m downloading it now.

[Drew_G]

This message requires you to be fairly clever, but then, it was designed to be hopefully-readable to Alien SETI programs.

Would your average human know how to decode a reply sent in a similar format?

[euansmith]

Thanks for all your hard work on this.