Most of the cryptic stuff is a back-reference to the instructions on the record cover. JPL has a page devoted to the record cover instructions. The record comes with a needle, but (if I read the JPL site correctly) the turntable is supposed to be provided by the aliens. Enhancing the sound produced by the included stylus from a tiny whisper to something they can work with is also left to the aliens.
Basically, the aliens need to be able to figure out that we are obsessed by hydrogen atoms (lower right corner of the record cover) in order to get anywhere at all. They also need to figure out that we are using dots and dashes to indicate binary numbers. If they figure out that we are talking about hydrogen and the time it takes to transition between two electron states of a hydrogen atom, that gives them a time scale. If they figure out we are talking to them in binary numbers, that gives them the desired RPM of the record, in terms of hydrogen transitions, the playing time of the record (upper and middle left icons on the cover), and the start picture codes and number of horizontal and vertical scan lines for decoding the pictures (upper and middle right of the cover). An alien that manages to figure out what the fuck to do with the record at all is quite a ways along in figuring out what the cryptic pictures encoded on it are all about.
But for mere humans, here is a crib sheet I’ve put together, using the order of pictures on this page. Some images on that page are poorly cropped and others include extraneous data like the picture number, which I certainly hope we didn’t include in the actual scans that were encoded on the record, because the poor aliens are already going to be confused enough…
- Picture 1 is a circle, also depicted on the record cover, so they can be sure they're decoding all this crap correctly and at the right aspect ratio.
- Picture 2 repeats the pulsar map found on the lower left of the record cover, with a photo of a galaxy, to sort of help them figure out that we're talking about, you know, things in space with that pulsar map thing.
- Picture 3 gives them the binary symbols used on the cover and equates that to human numbers, and teaches them our mathematical symbology.
- Picture 4 is going to cause a lot of aliens to get headaches. Top left, it goes back to hydrogen and the transition state interval, but it also sort of assumes that the aliens will intuit that by the symbol "m" we are referring to the mass of a hydrogen atom. Top right is about the wavelength of atomic hydrogen radio emission (21cm). Below that, left column translates the transition state interval into human time scales (second, day, year), and the atomic mass into human masses (mass of a gram, kilogram, and of the earth). Right column translates the radio emission frequency into human distances: angstroms, meters, and kilometers.
- Pictures 5 and 6 attempt to convey the solar system (diameter, distance from sun, mass and rotation period for the sun and nine planets) . Good luck to any aliens who lack our tendency to take repeated things for granted, because the mass and exponent symbols are left off after the first couple of columns.
- Pictures 7-12 are photographs of some representative bodies in our solar system - the sun, with sunspots, a solar spectrum, the Moon I think, then some planets with their masses and diameters. But, poor aliens, the photo of Mars is identified as having a different mass (1/10 e for earth mass) than in picture 6 (11/100 earth mass).
- Picture 13 is a picture of part of the Earth, closer up to show clearly that it has an atmosphere and clouds. Overlaid on that are some symbols that we haven't bothered to teach the aliens yet, detailing the constituents of Earth's atmosphere.
- Picture 14 belatedly teaches the aliens our symbols for some common elements important to our biology (left half), and the atomic structure of nucleic acids (right half). For some reason the acids are labeled A S G T instead of A C G T.
- Pictures 15-16 expand on that with more details on DNA, including dimensions of the molecules in angstroms, and the number of base pairs found in humans (4 trillion if I count my zeros correctly - by this time the aliens are wondering if we *ever* bother to be consistent about things, seeing as we didn't give that number as an exponent like earlier).
- Picture 17: a photo of a cell, which makes sense seeing as DNA comes in cells.
- Pictures 18-26, anatomical drawings of a human male, except for the last one which mysteriously provides drawings in a completely different style for male and female reproductive anatomy, along with labels that, unlike all the labels up to now, are completely indecipherable to the aliens because they're in English. Also confusing to any alien scholars will be the (unexplained) mysterious uses of the classic male and female symbols, and the overlaying of schematics of male and female reproductive organs on top of a perfectly humdrum illustration of bones and muscles a few pictures before the more detailed anatomical drawings of reproductive organs.
- Picture 27, a drawing of human sperm and ova. By this point the aliens have figured out that we think these symbols (male and female) are super important for some reason, who knows why.
- Picture 28, a photograph of sperm and ova.
- Picture 29, cell division of a fertilized ova, with time scales.
- Picture 30, stages of development of a human embryo, with time scales. It probably would have been helpful to provide some of the intermediate steps between the first division of an ova and a full formed embryo, but I guess they had to cut some of the slides for lack of space.
- Picture 31, photograph of a human embryo.
- Picture 32, another headache inducing image, silhouettes of a man and woman, with a cutout showing a fetus inside the woman. Masses and dimensions of everybody provided. Maybe all the fetus imagery up to now was about a parasite that lives inside some humans? Maybe the parasites are the sentient creatures and the humans are merely their hosts? Who knows? Almost certainly not the aliens trying to figure this shit out.
Even if they know of sexually reproducing viviparous animals, I think they’re going to have trouble figuring all this crap out. And if there aren’t any viviparous species that they’re familiar with, if they don’t have two sexes, then they’re going to be doing a lot of whatever aliens do instead of scratching their heads. Another slide that didn’t make the cut would have been a photograph of two humans posed like the silhouettes.
- Pictures 33-36, human birth, infancy, childhood, with parenting and education. Assuming that they can figure out clothing, one hopes the aliens will be able to guess that we're showing them ourselves at various stages of life. If they can't figure out clothing, then they may not even be able to recognize all these people as belonging to the same species.
- Pictures 37-38, a partial silhouette and matching photograph. The silhouette tries to convey the age ranges of the people shown in the photo. God knows what they will make of the way the silhouette only gives information on certain individuals and leaves the rest out. Maybe it's a comment on the human caste or class system? Maybe only some of these animals in the photographs are sapient, and the rest just look similar but are actually just dumb animals who we keep around as livestock?
- Picture 39, another pseudopod scratcher. I really very much doubt that it will be at all clear that these are maps of a planet, that the event being shown is continental drift. Really the only clue is the time scale given, since everything else about the trio of maps is convention bound.
- Picture 40, percentages of the elements making up the earth's crust, along with the layers of the earth's interior: crust, mantle, liquid core, and inner core. The aliens need to have caught on back in the left half of picture 14 that we are using circles with numbers inside to designate elements, and that we are identifying elements by atomic number.
- Pictures 41-51, landscapes and vegetation of the Earth, with random humans and human artifacts. Picture 51 changes the subject abruptly from plants to insects, just to make things confusing.
- Picture 52, random drawings not to scale of humans and animals. Way to go, guys.
- Pictures 53-60, animals of the earth. The cutaway drawing (not a photo) of a seashell screams out "I don't really belong in this sequence."
- Pictures 61-62, another silhouette diagram with measurements paired with a scene of aboriginals hunting (I think?) an ibis. Again not all the creatures in the photo are called out in the silhouettes. It's almost as if humans regard some creatures as more worthy of notice than others.
- Pictures 63-end, lots more photos of humans and their works, divided into themes. Sometimes we get helpful scale measurements of things, sometimes not. The scuba diver photo includes a mysterious "H20" notation in the optimistic belief that it will help clarify that the human in the photo is underwater.
Well, that was a fun way to use up the afternoon. Hope this is helpful to those wishing for a decoder ring.
