# How can I store energy/data reliably for 300 million years?

Following this question: How can I implement time travel on a somewhat realistic way?

Considering I have a way of getting energy into the past (as said on the previous question), I need a way of storing energy (or anything that can store data) until 300 million years later, as this would work as communications.

Assume that the sender and receiver know the communication system used.

So, how can I store energy/data reliably for 300 mil years (1 terabyte)?

Requirements:

• you can use unproved tech, but the answers closer to modern day tech will be preferred over normal ones.

• method Is bound by gravity (so keeps around the same star).

• What's the maximum size? What's the storage conditions (temp/atmosphere/geological)? Is it online or offline (needs specialized equipment to read) storage? Commented Apr 12, 2021 at 4:10
• Also, what does "store energy" mean? A chunk of frozen oxygen and a separate chunk of frozen hydrogen can store energy for 300 million years but that's probably not what you're looking for. Commented Apr 12, 2021 at 4:11
• en.wikipedia.org/wiki/HD-Rosetta Commented Apr 12, 2021 at 4:23
• I don't think you understand what data or energy are if you think they are interchangeable.
– John
Commented Apr 12, 2021 at 14:21
• Storing energy for 300m years is easy, and has already been done. Grow plants. Bury them. 300m years later, pump out the oil or mine the coal. But as the answer point out, "energy" and "data" are completely different things. Commented Apr 13, 2021 at 12:35

You come from the future, therefore you know there is still life. Encode your information into the mitochondrial DNA of species you know will have living descendants in the epoch where you want to send the message.

Mitochondrial DNA is carried along from only one of the two parents, so it doesn't get mixed with sexual reproduction.

Even though random mutation can happen, with a large enough sample the receiver can statistically reconstruct the original message.

• Comments are not for extended discussion; this conversation has been moved to chat.
– L.Dutch
Commented Apr 13, 2021 at 5:53

Quartz crystal memory discs will easily last the 300 million years required and already exist as a product.

Quartz memory discs

But remember there's a difference between storing the information and then being able to access and read it at some unspecified time the remote future. You need the reading technology to last as well. So you may prefer to etch the design of the laser/reader into metal tablets and put both the discs (which can hold a huge amount of data) and the tablets in the vacuum of space. Preferably in an asteroid in a stable orbit.

Addendum: Alternately you could I suppose place readers and a sample power source for them alongside the plates in the asteroid. They may not last but at least whoever recovers them can take them apart and compare them to the diagrams on the plates to build a working copy.

Energy is much harder - the only energy source that would last the time required without complex technology would be potential energy. Which the asteroid would have if diverted at the appropriate time into the appropriate orbit. And if that's difficult just store everything on the moon as someone else has suggested.

• This is probably the best option. Storage should either be in space in an orbit far off the ecliptic plane (less stuff to run into) or on a geologically inactive planet (Mars, the Moon) in a location deep enough to avoid damage from meteor strikes (note the large craters on the Moon). Commented Apr 12, 2021 at 14:54
• Don't bother storing energy. We've already got a source of energy that will last that long: the Sun. Part of the design of your laser/reader should include solar cells for power. Or just assume that whatever intelligent species exists that far in the future with the means and knowledge to build your device will be also able to produce the necessary energy one way or another. Commented Apr 12, 2021 at 17:50
• @DarrelHoffman Nothing electronic is going to be functional after 1000 years, let alone 350 million years. Atomic diffusion, sublimation, molecular decay, etc. are going to kill it even if left perfectly undisturbed. Commented Apr 13, 2021 at 3:30
• @GrumpyYoungMan Yeah, I wasn't suggesting that any device would last that long. The poster suggested storing designs for a device, which someone in the far future would have to read and build in their time, not that the device itself would last until then. I was just saying that design should feature solar cells, or maybe instructions to create a suitable power supply, but if said future society has the means to retrieve designs from an asteroid, interpret them and build the device, they've clearly got some sort of power supply they can use. Commented Apr 13, 2021 at 13:40

### Put it on the Moon.

The Moon is a nearly unchanging environment, without geological or atmospheric variations over time that might damage your system. The only thing you'd really need to worry about are meteor impacts, and you can account for this by simply taking a map of the Moon from the future, comparing it to the map you've taken of the Moon in the past, and then placing your cache within a crater that has survived unchanged between those two epochs.

Unlike asteroids and other smaller bodies in the Solar System, the Moon is gravitationally locked to the Earth, so you won't need to worry about losing it 300 million years later.

• You could have multiple caches, too, to minimize the chances of losing it in a micro meteor strike. Commented Apr 12, 2021 at 13:08
• note: "nearly unchanging" on astronomical timescales, but it does have wild temperature fluctuations every month Commented Apr 12, 2021 at 17:50
• @user253751 Unless you're in a crater at the poles...then it's just freezing cold forever.
– J...
Commented Apr 12, 2021 at 18:42
• Don't forget to bury them. At least 12 inches deep according to the rock erosion rates due to micrometerites. Commented Apr 13, 2021 at 14:21
• Nothing exposed to the sun is going to retain data for 300 million years, especially not without an atmosphere nor sufficient magnetic field. Burying it at the moons north or south poles are you best options. Commented Apr 13, 2021 at 23:24

Storing data in energy for 300 million years is trivial. We are receiving data that was sent just after the creation of the universe. We are talking billions of years, not millions, that this data has lasted. The data is so intact that we are still able to get an abundance of information from it. The only 'coding' necessary is the natural 'coding' of information and data inherent in physics and cosmology.

A powerful enough laser beam of light, encoded with data, projected from within our solar system by a strong enough source, will survive for billions of years. In fact, there is a great portion of the EM spectrum that one could use. The bit rate, however, would probably not be in bps but more like bits per hours or days. A slow minutes-long or hours-long blinking. However, once sent, there would be no way humans could have ever modified or interfered with it. It would be, as far as we are concerned with our current technology, hack-proof. No encryption necessary. It could even be sent in analog form, but there would be losses of information and error correction is complicated.

Being able to catch UP to that light in order to read it, is another thing. One would presumably have to travel FTL.

But there IS a way to get it to 'come back' to us without us going after it. Aim it at a huge galactic-sized 'mirror' or 'reflector' 150 million light years away, and read the reflected data 150 million years later. How that reflector gets there, whether it is human-made, purpose-built, a natural formation, or whatever seems to fall into the category of 'can do whatever you want for your answer'. Of course, it would have to be well timed, and aimed at where the reflector is GOING to be in 150 million years, and the return reflected signal aimed at where the solar system is going to be 300 million years later, but it would be 'stored' for 300 million years, as required. And it is well within technology levels today, given the dedication of enough resources. Absolutely nothing about it that is not within the current bounds of conventional physics thinking. The technology for receiving it is already readily available. We have plenty of telescopes and receivers that would suffice. Even SETI could pick it up.

But, well, blink and you miss it.

@dhinson919 suggested an intriguing idea. By the correct positioning of black holes, dark matter, and such, use them as a gravitational lens to focus and direct an EM signal through the universe, much like we use fiber optic cable to channel laser beams. Using space itself as a storage media, the possibilities for storage are immense.

• OK, I seriously must upvote this just for proposing optical delay line memory on a galactic scale. I would seriously never have thought of such a crazy idea, but the best part is that it should, in theory, actually work (assuming rogue dust clouds in the ISM don’t cause you issues). Commented Apr 12, 2021 at 20:13
• @Austin Hemmelgarn And in some weird way, depending on how you communicate BACK in time, it can be made full duplex. The past could just keep sending sequential communications in response to your questions or queries. Commented Apr 12, 2021 at 21:34
• The secondary problem on how to build the reflector to last that long is unsolved, however ;) Commented Apr 13, 2021 at 22:07
• @tofro Well, they DO have 150 million years to figure it out before the signal gets there!!!! Commented Apr 13, 2021 at 23:14
• I was going to suggest using space as a data buffer for a directed electromagnetic signal but you beat me to it. However might I suggest instead of using a mirror to bounce the signal back you use a clever arrangement of gravitational lenses around the galaxy to bend it back. Similar to how we send probes into deep space using gravitational slingshots. Commented Apr 16, 2021 at 6:04

Use a physical storage system, in a very inert material.

Something like a gold platter. It must be completely chemically and radiologically inert.

Store it with massive internal errorchecking and redundancy, so that minor scratches or holes will not invalidate your data.

Store it in a location that is unlikely to be disturbed over the requisite timespan.
Places like buried in a mine, on a tectonically boring continent. But that might be hard to find later. How about buried under a landmark crater on the Moon? Or on a known asteroid? Unfortunately 300 million years is long enough that no possible free-space orbit is going to be sufficiently predictable, even a Pluto-sized heliocentric orbit will have deviated beyond accurate prediction.

But most importantly: Redundancy. You want to store your data on many, many,many different locations.
Inevitably some of them will have been destroyed, gotten themselves eaten, damaged by meteors, stolen by cavemen and turned into earrings, or spontaneously combusted. Who knows what could go wrong?

As for storing energy, with sufficient accuracy to retain data? Not a chance! Not in one location, at least. You could always beam the datastream out, but the receiver would need to be 300 million lightyears away from the source, which might be inconvenient!

• The Voyager message is carried by a phonograph record, a 12-inch gold-plated copper disk Commented Apr 12, 2021 at 18:52
• @aliential yep. That's what inspired my original line of thought. Problem is, Voyager will be unfindable after 300 million years. After just 30000, it will pass close enough to Ross 248 to have its course changed by its gravity. After 300 million years, Voyager will have gone 2/3 of the way around the milky way galaxy, and will have had close encounters with hundreds of stars. Good luck finding that cosmic pinball after all that travel! Commented Apr 12, 2021 at 23:28
• @PcMan it's well known that V-ger will be discovered by some advanced AI civilization and transformed/perfected into an insatiably hungry monster devouring all in its path. Commented Apr 16, 2021 at 18:56

This is the stratigraphy of the Grand Canyon

As you can see it goes back to 500 million years ago, and it's basically a very large bar code.

Just encode the proper layering along the path of the Grand Canyon, and your message will be kindly exposed by the natural agents when the time is due.

• OUf, it will be hard to fit 1Terabyte of rock-layer barcode in there. Commented Apr 12, 2021 at 6:50
• How much do you think this would cost and how many years would it take to install? Commented Apr 13, 2021 at 12:36

## 300 Million Years is too long to trust any location or passive storage medium

Rocks could fall from the sky. The ground beneath your facility (on a geologically active world) could be subducted into magma. Celestial bodies could plunge into their parent stars!

You're going to need to design something intelligent, basically immortal, and mobile. Something smart enough, with good enough observational capacity, to see the asteroid coming and to move out of the way.

Ideally, you want a librarian which carries the library with it. This could be anything from a person-like creature (though biologically immortal) actively seeking unobtrusive places to wait out the ages, to a spaceship passively observing from a "safe" orbit, until that orbit doesn't seem safe enough, then moving to the next location - except for when it has to venture out to resupply, and then continue to wait. Whatever this thing is, it must be programmed to be intensely risk-averse, keeping out of the way and making sure it doesn't end up in a situation that might lead to a failure of its mission. To be triple-sure the data is preserved, have more than one librarian, each independently storing the data and avoiding the other librarians.

The main difficulty (besides designing an agent to last out the required length of time intact), is finding your librarian when the time has finally come (and convincing it to come out of hiding).

Bonus thought: Perhaps your librarian, after hundreds of millions of years, seeing itself failing, but totally dedicated to the mission of preservation, may in the final resort try to recruit someone else take up its task of protecting its store of data.

Energy and data are two different things. To preserve data by encoding in human (or any type of animal) DNA would not be reliable, because it assumes that humans would still be around in 300 million years. You could etch the data in thin gold plates. A real world example of this would be Voyager's Golden Record. However, there is still the issue of whether humans having knowledge of the ancient language would still be around to read it. The language and scientific knowledge would have to be preserved for the data itself to be relevant. But if the language is preserved, wouldn't the data be passed down too?

Encoding the information is no problem; carve a message into some stable material (I would recommend glass or gold) and store it somewhere safe. It is that second part that is the problem though. No matter what material you pick, erosion is going to wear it down.

The safest place to put it would be somewhere on the Moon. Just be careful and make sure you don't pick somewhere near an asteroid impact. Also, cover it with a thick sheet of lead to protect against radiation.

Assuming that is not available, I would think about going really deep into some cave systems, especially if you need to dive to get there. The problem is that even though these systems can easily preserve things for billions years, it is hard to identify in advance which ones will still be around. In addition, if an earthquake or flash flood changes the structure of the caves, then any plans made before the timetravel on how to navigate the caves becomes useless.

My last option would be burying it in a bog or somewhere are you know sediment is going to collect. Hopefully, it will become part of a tar pit or sedimentary rock. Since this process itself takes millions of years, there is no guarantee that it will take place.

From other suggestions in comments to other answers, maybe we should not think miniaturized data storage, but go big. Really, REALLY big. So big you can read it from a very long distance. Make the entire surface of the Moon as the storage media. Use asteroids to engrave the surface. Those asteroid craters on the Moon are not random, they are a pattern intentionally laid down by some civilization, using well-aimed asteroids and kinetic impactors. A very large QR code, readable even as far away as from Earth. The entire SURFACE of the Moon as a gigantic billboard. Hidden, all that time, right in front of our eyes. Now all we have to do is develop the correct QR code reader. We just have to filter out the background noise from the random impacts, but huge craters are very resilient to erosion and decay. There will be some sign of them for far longer than 300 million years.

My answer is more about where to put it than how to store it. I agree with several existing answers that properly stored physically encoded inert materials could work, but how do you find them 300 million years later. For the answer we should ask what identifiable material do we have from 300 million years ago. The answer, fossils, lots of fossils.

1. Step one - in the present map existing fossil excavations from the desired time period, these tend to occur in groupings of sedimentary rock, and bonus are often in remote locations. You know based on the fossil finds that these locations are going to be stable for the required time frame, you may want to pick ones that have only recently been starting excavation to prevent disturbances in the recent past.
2. Pick one, use some simulations to predict where in the past these sites correspond to. Depending on the specifics of the time travel you may even be able to experimentally verify these predictions. Did it work, well yes we know it already worked, we found the message 6 months ago (time travel often leads to these kinds of weird causality issues)
3. In the past locate the site and bury your properly sealed and encoded time capsule in the mud at the sites. You may want to make them easier to find by marking them somehow, high density, ferrous, or radioactive materials would make them more detectable, to narrow down exactly where to dig. You could also put in some fake or real fossil in if you want to mess with the staff paleontologists (Who carved their initials into the Edaphosaurus bones!)
4. Wait 300 million years for the mud to turn into sedimentary rock.
5. Fund a fossil dig in your chosen location.
6. Find message capsule.
7. ????
8. Profit?

Write it on stone. Yeah, that's right. carve it on a giant stone sphere in geosynchronous orbit above earth. That's high enough that it's not going to degrade (if it isn't high enough, orbit it higher). A 9 mile diameter stone sphere ought to do it: area of a stone sphere
A=4*pi()r^2
Solve for r r=(A/(4
pi()))^.5
A= the area of all the data:
1byte=1 letter= 1 Inch^2 so
A=area of 1 terabyte of data A=1000000000000 inch^2 249.098 Miles^2 then r= 4.452 Mile diameter stone. Make it happen.

• You probably can get a bit higher storage density than 1 byte/in², even with carved stone.
– ojdo
Commented Apr 13, 2021 at 14:25
• It is a good idea, but A) A 9 mile sphere in geosynchronous orbit is due to attract lot of attention, and possibly visitors. B) there can be impacts with asteroids and/or satellites and C) the orbit will be affected by those impact and the attraction of the Moon and there is a very real chance of it falling to Earth (bringing yet more attention). Commented Apr 13, 2021 at 19:53
• I'm pretty sure someone engraved the moon with data important to us 300 million years ago. Commented Apr 13, 2021 at 22:09
• @tofro Hmmmm - those asteroid craters on the Moon are not random, they are a pattern intentionally laid down by some civilization, using well-aimed asteroids? A very large QR code, readable from Earth? Use the entire SURFACE of the Moon as a gigantic billboard? Hidden, all that time, right in front of our eyes. Now all we have to do is develop the correct QR code reader? Just have to filter out the background noise from the random impacts. Interesting. There definitely is a story in there. Commented Apr 16, 2021 at 13:38
• @JustinThymetheSecond The message is obviously under the craters and other remnants that time has left on the un-protected trabant. partially wiped-out and destroyed and not immediately visible under all that damage. Commented Apr 16, 2021 at 13:45