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Wikipedia to the Moon (wikimedia.org)
146 points by chris_wot on Apr 21, 2016 | hide | past | web | favorite | 81 comments

The FAQ is much more illuminatng then the main page: https://meta.m.wikimedia.org/wiki/Wikipedia_to_the_Moon/FAQ

Also their list of vitial articles give an interesting insight into what they'll want to send up (depending on the medium they choose): https://en.wikipedia.org/wiki/Wikipedia:Vital_articles

If an alien makes it all the way to the moon with the tech to read the disc why wouldn't they hop on over to Earth where there would be much more data? When Carl Sagan did it it was much more evocative because Voyager will be traveling for thousands of years into deep space.

Well hypothetically if the Earth was destroyed by grey-goo or something, the disc would still be there.

But the other answer is that it's much easier to find. Where would you put a ceramic copy of wikipedia on Earth to maximize it's probability of being found? Anywhere you put it could get destroyed, buried, or stolen. Who knows what will happen to it over the Eons.

This disc will be on the surface of the moon forever. Anyone surveying the surface of the moon for unnatural objects will find it. Although that might take some advanced technology, it would be easier than surveying the Earth.

And while they might find many artifacts on Earth, locating that single copy of wikipedia out of all the other junk we've left behind is a bit improbable. We haven't covered the moon with much junk.

This disc will be on the surface of the moon forever.

Or until a meteorite hits it.

It's true. The surface of the Moon is a lot less peaceful than it seems. If you process the image, you can tell the affected area from a single meteorite strike is much bigger than the crater itself:


Has anyone compared the surface of the moon over time? We can count how many meteorites have hit the surface since we've been taking pictures of it, and we can also probably assess the actual damage they've caused.

How do "Earth-based observations of the dark portion of the moon" work?

Is that the dark part of the light side, where the sun won't overexpose the video?

It's as easy as night versus day.

Flashes from bolide strikes are actually easier to see on that part of the Moon where it's night. Where the Sun is above horizon on the Moon, the ambient light is drowning out any light-producing events.

> If an alien makes it all the way to the moon with the tech to read the disc why wouldn't they hop on over to Earth where there would be much more data?

If you read the FAQ[1], it says:

> [aliens] Probably not … but well, who knows? No, the Lunar challenge is mainly about pioneer spirit, curiosity, and visions for humanity. So, with the symbolic act of leaving a snapshot of human history on the surface of the Moon, we are thinking more about future generations than aliens.


The moon is much less dynamic than the earth, which could be covered in jungles or ice or something that makes it difficult to detect the (former) presence of intelligent life. IMO it's plausible that aliens might find artifacts on the moon that would then prompt a more in-depth exploration of the earth.

The zillion artificial satellites and other crap and debris orbiting the bigger, lusher body is probably a hint to said explorers, even with atmospheric orbital decay and perturbations over a long time scale. Earth orbit is our calling card for some time, even if we all die.

Especially if they have decent midrange sensors to display nearby craft, Earth will look like a swarm of bees. Run any orbital debris simulator if you don't believe me. It's a mess up there.

That's a good point. Found an interesting article about this:

> Orbits tend to decay over time, at a rate determined by the initial altitude. Anything above 2,000 km will take millennia to return to Earth, while satellites further down might take centuries or decades.


There are faint, faint wisps of Earth's atmosphere a fair distance out, which is the big part of an orbit's challenge. Perturbations from other bodies nearby (notably the Moon), deformities of Earth's gravity, and even solar weather and tiniest fractions of gases are other contributors on a long-enough time scale. Micrometeorites would probably be the big risk over time for our orbital monument to humanity, and I would expect Kessler syndrome, as dramatized in Gravity, to actually happen over a long enough period without human existence. (Hell, even with us around it's a possibility, but not as depicted in the film. It'd be slower. Some say it's already underway.)

Distant orbits might decay away from Earth given enough time and certain circumstances, oddly enough. A return to Earth is not guaranteed.

The Moon itself certainly is gradually moving away from Earth (and slowing down Earth's rotation in the process)

Indeed. That's one of those science nuggets I love telling people because it's universally accessible and blows everybody away. Suddenly makes galactic timescales and gravitation real for people.

(Or they're just being nice to me...)

Surviving artifacts are not a very good and coherent source of information for future archeologists, alien or human. After all, we are still kind of unsure about construction methods of Egyptian pyramids, which are less than 5000 years old.

And past civilizations at least seemed to have cared much more about longevity of their creations than we do, we can not even store our digital photos reliably over a decade without active replication. Without projects like this, future researchers will have to put the whole picture together using only plastic bottles and broken vinyl records :)

I've started using M-DISC Blu-rays for my backups, which are supposed to last for quite a long time. I don't know how long they will actually last in real-world conditions, but I'm hoping its long enough that if I ever need them, they'll still work.

As for preserving things for future generations, I don't know of any good storage techniques. The problem with M-DISCs and other mad-high-density digital storage is that the readers will (most likely) be completely unavailable long before the all of the discs have degraded.

Perhaps we should engrave our data in 2D barcodes, alongside some readable instructions describing how the data can be decoded... Wouldn't have anywhere near the density of optical, magnetic or flash storage though. The whole situation does "worry" me a little, I agree entirely about future researchers not having much to go on.


It's a symbolic act just like the Voyager was.

They should team up with the Time Capsule to Mars project (http://www.timecapsuletomars.com/) which ostensibly will use quartz storage technology to send millions of photos to Mars. If the quartz memory is for real, it should be able to store Wikipedia.

The deadline for the Lunar X Prize is next year, and according to wikipedia one of the teams has a launch contract with SpaceX. Does SpaceX have a rocket capable of making it to the moon?

It looks like a falcon 9 can get payloads to TLI: http://space.stackexchange.com/questions/8511/how-will-the-f...

SpaceX just goes into Earth orbit, the team's job is to get to the moon.

At least that's what the FAQ says [0]:

> [Part-Time Scientists] will join a commercial space flight, e. g. a rocket launch to orbit. From there, their own lunar lander module will travel to the Moon, the final task being to land safely and release the rover.

[0] https://meta.m.wikimedia.org/wiki/Wikipedia_to_the_Moon/FAQ#...

Please note that the ability to "making to to <somewhere>" is all about Delta-V. Which varies wildly with payload size.

To be precise, it varies according to the equation:

Delta-V = Exhaust velocity x natural log(mass full / mass empty).

As the "mass empty" is very dependent on the payload size, it will indeed change a lot!

As an aside, I'm always pleasantly surprised by how many kids and teenagers know the Tsiolkovsky rocket equation from playing KSP and watching Scott Manley videos!

See for example, New Horizons:


For those too lazy to go read: biggest rocket available + very light probe = very fast travel

Another interesting read in this aspect is the Dawn Spacecraft, which had a big delta-v because of its ionic thrusters: https://en.wikipedia.org/wiki/Dawn_%28spacecraft%29#Propulsi...

20GB? What kind of disc are they using? Why not use a 200GB MicroSD? That would be way more efficient.

2 200GB MicroSDs would give you 400GB of storage weighing in at only 1 gram.


> Can’t we use some other medium with more space?

> The conditions in space prove hostile to many data mediums. Traditional CDs or DVDs would be destroyed in space, because they are composed of layers and would come undone. It’s different with a medium made of ceramics. Also, you have to consider the dimensions and weight of your medium. The ceramic disc is light enough and resilient.

I'm guessing microSD cards are not radiation hardened.

Wonder how much lead you'd have to wrap an sd card & reader in for it to be "safe" for space travel.

If you want as much protection as Earth's atmosphere provides, 25 inches. At least that gives as much mass in between the card and space as the atmosphere does. (1 atm is about 30in of mercury, lead is 11/13 as dense as mercury...)

But it isn't just about mass, there's density to consider... we aren't sending up computing devices into space wrapped in 25 inches of lead... so I'm guessing that far less is actually needed.

Why not send a few SmartMedia cards, a Zip Disk, or a few 3½-inch floppies?

I wonder what the estimated cost per GB will be for this data transfer?

I bet they can get the data there faster than it'd take for me to upload it anywhere using Time Warner Cable.

How long would it survive there? The surface of the moon is a pretty hostile environment, I would think.

It's a ceramic disc. Since there is no wind erosion, if it doesn't get direct hit, it should last quite some time. Footprints from first landing are still there - and are expected to be for at least next 10 million years - so you can expect finely-engraved piece of rock to last much longer.

There is still radiation erosion. It may corrupt the data if it is packed too tightly.

Many people mistakenly think the moon gets hit all the time by meteors because of the craters. Most of the craters scientist believe were formed during the lunar cataclysm [1] not to mention the moon has zero erosion and geo activity.

That being said no one is sure how often it gets hit but it is logically far far less than Earth.

[1]: https://en.wikipedia.org/wiki/Late_Heavy_Bombardment

Sending an archive of YouTube would be much more useful for any aliens that happen to drop by. YT comes far closer to The Sum of All Human Knowledge than Wikipedia.

I'm not sure that's correct. Wikipedia contains detailed articles on many very obscure subjects. Searching for such topics on YouTube usually gives disappointing results.

Wikipedia is missing some material though. A better choice might be the google book project or libgen, which contains a ton of obscure books and scientific papers. But compressing it all to 20 GB would be difficult or impossible. Much easier than compressing Youtube though.

Video broadcasts of humans being human conveys a lot more information than a written language they don't understand (they may not even have the concept of a written language) and don't have any reference points to.

Admittedly, with YouTube they might get the idea that humans communicate with each other mainly via the medium of song and that cats are sacred, but at least they'd learn something

That's my point: They're assuming the aliens want to know about detailed, encyclopedic subjects. But what if they just want to know about Kim Kardashian?


That's more than anyone ever needs to know about Kim Kardashian.

20GB of disk-space would be very restrictive for video.

The should use some middle-out compression.

The problem then becomes creating a simple to explain and process video and audio encoding scheme that also doesn't take up massive amounts of space. Compared to that doing the same for text is easy.

Well, they'd certainly learn a lot about cats!

They have 20 GB? I downloaded the entire English wiki 4 years ago (just the text of articles, not photos) and it was 12 GB.

Now it's ~55 GB uncompressed and as you said that's without images, audio, and more.

I meant compressed. Text compresses really well.

It does indeed. However compression may cause problems for future beings discovering or understanding the data.

Keep in mind they have to understand the text and image encodings. The concept of glyphs themselves, even. Words. Language. Bytes (why 8 bits). Bits. Knowledge expressed as sentences. How to read the media. Compression would be just another thing.

There's a pretty big hurdle to comprehension even without compression because we are thinking in human terms. Imagine all of the prerequisite human knowledge you overlook to even approach the concept of an encyclopedic article describing something. Aliens might share knowledge by hitting each other with telepathic darts for all we know, having a completely different understanding and implementation of information, and words might require years of study on their part to comprehend. Even the golden record carries a lot of assumptions. What we know about the universe is not necessarily final, even with rudimentary things like information theory.

In the end it's a bunch of bytes, numbers really, on a disc. What are numbers, even? What if they have a totally different non-numeric system to quantify and explain their existence?

Think about finding an extraterrestrial storage device like this from our perspective. I'd safely predict 20 years before we even extract one byte of data, and a lot of that time would be arguing over it, probably. Although thinking about an alien Nobel ceremony for cracking the "extraterrestrial ceramic Wikipedia" is a pretty amusing thought.

One of my favorite short stories is That Alien Message: http://lesswrong.com/lw/qk/that_alien_message/

Its about humanity trying to reverse engineer a message from space that has very few bits. One of the morals is that humans would be able to decode crazy encodings provided enough time. And more data helps a lot. With 20 GB, even compressed, common patterns could quickly be found.

I don't believe for a moment a race advanced enough to recover the disc wouldn't understand it.

Me neither, to be clear. Just saying that compression is but one drop in the bucket.

You could do something like the Rosetta disk, where you just physically engrave the glyphs.


Of course then you need to work out what the language is actually saying, but plain "glyph retrieval" can be done with a desktop microscope and some time. An alien that operates in a roughly human way (has eyes, language, linear writing) would probably understand that it encodes meaning, even if it ends up like Linear A and undecipherable.

That's a very inefficient way to store the data. You couldn't fit all of wikipedia onto one of those disks like that. I would only do that for the instructions, and pictures would be better than glyphs. Or pictures next to words, so they have at least an idea on how to decrypt it.

Once you introduce a few words, the rest may be decipherable from context, especially with such a large corpus. E.g. certain words will cluster together often, and once you know one, you can guess at the others, which lets you guess at others, and so on.

> Think about finding an extraterrestrial storage device like this from our perspective.

Let's suppose the aliens already did this, but instead of a small disc, they wanted to send a message that no intelligent being could miss. Over a short span of 150,000 years, they redirected a bunch meteors into the moon in a pattern that encodes the last few digits of pi in a simplified resonant-fractal numbering system, which proves they know the angular momentum of the universe with fair precision. Clear and convincing evidence that would be visible throughout the solar system.

So yeah, I think no matter what we do to try to communicate with an alien intelligence, they would have to be very much like us (probably our own descendants or - who knows - ancestors) to even recognize the presence of the simplest message, much less decode it.

> the last few digits of pi

There is no last digit of pi.

Well of course not if your number system doesn't even exhibit fractal resonance in holistic projective encodings, given the angular momentum of the universe.

Imagine how disappointed the aliens will be to find our disc full of the boring old "discoveries" of a barely space-fairing species. Nothing to see here, move along.

Nah, the aliens are bound to have tons of post-doc archaeologists looking for faculty positions.

Besides, you have all the character bios for the full Marvel universe(s)...

I'm only half being sarcastic, as I've gotten lost in some of those articles trying to figure out who someone is... while I'm not sure of the encyclopedic value of those articles, they definitely have some entertainment value. For that matter, it may be worth clarifying fictional characters from those that are historic, or based on historic events.

One concept that always got me is the premise of an alien culture without sarcasm. They would have a very hard time with human culture/history.

I do sometimes wonder what the future people are going to make of the hundreds of thousands of words of argument over en-dash, em-dash, hyphen and minus.

Mexican-American war had twenty thousand words of discussion over what dash to use, and that knowledge isn't transferable even to other dashes used in title on WP.

Here's 15,000 words on dashes. The result? No concensus.

Memes, too. "You mean ancient humans argued as an interconnected species over the color of a dress?"

I'm waiting for the meme that conclusively starts a war. The assassination of Archduke Franz Ferdinand in 72 point Impact. That'll be a fun one for future history books to explain.

Perhaps, but surely some compression is reasonable. You could shorten common words to much shorter sequences of bits without losing any information.

Any civilization capable of retrieving the disk should understand enough about information theory to undo compression. Instructions can also be explained in detail with pictures at the beginning, uncompressed.

That's an interesting question. I don't know if Lincos, which is the most conspicuous attempt at creating a self-explanatory language for aliens, included any kind of compression. Self-explanatory compression seems difficult to achieve, though maybe once you have the motion of equality, you can start giving examples of equivalent plain and compressed texts.

Then any damage to these instructions will be critical.

Copies of it could be distributed throughout the data. However I'm not sure what tolerance to damage is expected. How long is this disc supposed to last? How much damage will occur in that time? What's the tradeoff between compressing the data and it's expected lifespan?

Encoding choice should cause problems too.

So go with the four-years-ago version.

> I downloaded the entire English wiki 4 years ago

The linked article makes a big point about it not just being the English wiki, but 300 languages instead.

Yes, but with 20 GB, you could fit the English wiki and then still have 8 GB left for other languages, which tend to have smaller wikis.

Sneakernet on steriods.

On asteroids.

Now I understand why they were begging for donations all the time

How to downwote comment on the HN? I only see "upvote" button.

You need to be at a certain karma level to downvote.

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