# Can data be sent using Gravitational Waves across solar systems?

According to wiki,

The speed of gravitational waves in the general theory of relativity is equal to the speed of light in a vacuum

Not bad enough to send data (message or information) to other solar systems. Is it possible to somehow inject our data into the waves and send to other corners of space? If yes, what is the probability that data loss won't occur.

• Are we producing the waves or just hijacking passing gravitational waves that are going in the right direction? – Bellerophon Aug 1 '17 at 6:56
• Yes I am somehow producing the waves as well as using already created waves to inject data into it..So both are true. – Karan Desai Aug 1 '17 at 6:58
• Could downvoters explain their reasons as a courtesy to the OP and to the rest of WB SE. Your views might be enlightening. – a4android Aug 2 '17 at 5:33
• Food for thought: Google gravitational wave communication superconductive helium and you’ll find some ideas; enough to make up some plausible fictional descriptions. – JDługosz Aug 2 '17 at 6:45
• @KaranDesai Your question looks fine to me. Unless it becomes an ongoing pattern I wouldn't worry about 1 or 2 downvotes if the question is otherwise well received. – Tim B Aug 9 '17 at 20:00

Frankly no. The idea of using gravitational waves as a medium of communications isn't bad of itself. At first glance, it does look like a good idea. The real problems are with transmitting and receiving gravitational waves.

The typical source of gravitational waves is a pair of black holes colliding, but any moving masses will generate gravitational waves. However, the masses involved are of the order of stellar masses. usually many times the mass of the Sun.

Because the moving masses in a gravitational wave transmitter will be so high, this makes sending gravitational waves effectively impractical to the point of being impossible.

The receivers of gravitational waves are gigantic precision instruments and likely to be on such scales into any foreseeable future. More information about them can be found here.

As for imposing data on existing or passing gravitating waves probably also requires the manipulation of stellar scale masses. The same problems discussed above will apply.

However, in principle, if a sufficiently advanced technological civilization existed that could routinely manipulate stellar mass objects capable of generating gravitational waves, then they could use gravitational waves as a communications medium. This seems to be too big a step for any civilization and they would be able to access easier methods for communicating data.

• But, when you can move stars around, you can as well put a lid on them and turn them into signal lanterns. – PTwr Aug 1 '17 at 13:26
• even if you had the technology for gravity wave communication why would you not use EM waves to communicate? – jk. Aug 1 '17 at 14:32
• I feel like it's more likely that a civilization would develop the ability to detect much smaller amplitude gravitational waves than it is that they start manipulating stars to send messages. – Shufflepants Aug 1 '17 at 14:32
• @jk. Because if you actually had the ability to send and receive gravity wave signals relatively cheaply, you don't have to worry about shielding. And EM signal can be blocked by a planet or a star, or even some charged space gas, but gravity waves pass through all of those. They'd even pass through black holes unobstructed. – Shufflepants Aug 1 '17 at 14:34
• @jk. What does that have to do with what I said? I wasn't implying that it would allow you to send signals when some one else is trying to stop you, only that you wouldn't have to worry about mother nature getting in your way. – Shufflepants Aug 1 '17 at 14:40

In principle the answer to your question is YES. We have a wave travelling at speed of light which is not absorbed by the medium (so no dust clouds inbetween like for the visible light).

However, we are barely able to detect waves generated by enormous (even for astronomical scales) events. This means that to generate and modulate such waves with a meaningful signal to noise ratio (you don't want your gravitational wave radio to be disturbed by a close passing by truck, don't you?) we should put so much effort and use so much energy that it would be much more practical to use more conventional electromagnetic waves.

• +1 Noted, it will be too expensive and energy consuming. Will be taking care while developing my world – Karan Desai Aug 2 '17 at 5:35

In order to effectively transmit information and prevent data loss, interference must be kept to a minimum.

In other words, all other sources of gravitational waves must be either disabled or perfectly predictable.

Since the first option seems unfeasible, we must use the second. Now, this does lead to one requirement: at least one side of the communication must know exactly what effects existing gravitational waves will have on the communication, based on the precise location of the other side.

Either the receiver must be able to subtract the interference from the signal they received to arrive at the message, or the sender must pre-subtract the interference from their signal so that it arrives at the sender as a message.

So while this can be done for point-to-point communication, I do not believe it feasible for broadcasting.

• Noted. This might become my next question: How to disable or predict other source of gravitational waves? Thanks (y) – Karan Desai Aug 2 '17 at 5:36

I’ve seen articles about a scientist who endeavors to build such a device, and got funding to try building stuff with the goal of communications. I tracked down the underlying paper: arXiv:gr-qc/0702100v2 25 Feb 2007 «“Millikan oil drops” as quantum transducers between electromagnetic and gravitational radiation».

The paper is quite readable. You could simply have his idea be true in your universe, and use it as the bases of gravity radio.

Pairs of Planck-mass-scale drops of superuid helium coated by electrons (i.e., “Millikan oil drops”), when levitated in the presence of strong magnetic elds and at low temperatures, can be efficient quantum transducers between electromagnetic (EM) and gravitational (GR) radiation. A Hertz-like experiment, in which EM waves are converted at the source into GR waves, and then back-converted at the receiver from GR waves back into EM waves, should be practical to perform. This would open up observations of the gravity-wave analog of the Cosmic Microwave Background from the extremely early Big Bang, and also communications directly through the interior of the Earth.

The basic idea is that a pair of superfluid helium drops having plank mass and given a unit charge (by having one extra electron) will radiate and receive GR and EM at equal energy.

The superfluid drop acts as a single particle and doesn’t have the freedom to flex and move within the drop itself; it acts as a perfectly rigid uniformly charged particle.

• Very interesting..Thanks for referencing about the research paper :) – Karan Desai Aug 2 '17 at 7:50

Yes we could but it would be cheaper to not.
Detecting the wave is pretty easy - just bounce a laser for 2 miles.
What would be the problem is how to generate waves.
What LIGO and VIRGO detected was 1,3 billion light years away. And had a mass of 65 Suns.

It would be much easier to just build one Sun and use microlensing (because then you have 4 states to communicate) to send data. It would be also better because you could send different information in different directions.

• Interesting thought of generating a sun and use microlensing.. (y) – Karan Desai Aug 2 '17 at 5:37

One of the things not mentioned by other posts is that waves travel at different speeds depending on their frequency (whaaaat!): (So we know the speed of light is fixed right, but in reality it's not in a vacuum, i.e. that's exactly how rainbows and prisms work by having different speeds in the different substances), so we must assume that gravitational waves also have different speeds based upon frequency.

Ok, so let's look at the problem (which is a problem that data engineers have with things going down wires, and it is why you have a maximum length of USB cable, and ethernet etc before the signal has to be read and re-transmitted.

So the simplest form of data you can transmit is Morse, where you use a single frequency (as tight as possible) and you turn it on and off to give you a square wave. Then you use time or some such to indicate values, now what happens if you send a square wave down is that the edges of that square wave begin to blur with distance because of the different components traveling at different speeds, but it is the most effective.

If you then begin to try and send other things, such as phase shifted keying (such as RTTY, or PSK etc) (i.e. using a range of frequencies to send data, or even a sideband to send voice), then you would find that the different elements arrive at different times.

If you knew a bit about the transmission of the data, you could reconstruct (after listening over time) and design a protocol which allowed you to revert the data and recover it (i.e. a combination of re-phasing the signal together, as well as data hamming techniques such as that used in voyager etc) to get a semblance of data. If you didn't know what you were receiving, you would struggle to reconstruct it.

But we're talking on a galactic scale.

Also, can I just say, that things like spark gap transmitters are banned on earth for a reason: they annoy everything and cause interference. Imagine a race making a spark-gap gravitational wave radio. They would be annoying everyone and what kind of interference would it be generating for things?

Also appendment 2 - there's a lot of interest in sub-noise level protocols, such as Whisper. WSPR is a amateur radio data mode which relies on knowing when the signal is coming in, which allows you to sort of apply probability and see signals which are below a receivable signal-to-noise ratio. This idea is backward to conventional signal methods, where you transmit something above signal-to-noise that allows you to spot a signal and receive it. I.e. knowledge that there is a signal, lets you find it. If you didn't know what it was, and most importantly, when, WSPR is invisible.

• Being a beginner this indeed is a well framed answer. Thanks for explaining using detailed science based factors. – Karan Desai Aug 2 '17 at 5:40