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I am familiar with the inverse-square law and how detrimental it will be to the power of radio signals as they advance outwards in space. Assume we have two (or why not more?) interstellar colonies, relatively nearby one another—eg. Sol and Proxima—in desperate need to transmit millions of terabytes (petabytes? exabytes? potentially a lot more) of information reliably, per second.
What kind of energy output would we be looking at? My initial solution was to create some mythical device that could alter the wavelength or frequency of the starlight at the sender star system just enough so that the receiver star system could pick it up. However, this seems like an immense build even for our advanced culture, and I'm not sold that it would work at all.
My second solution was to build many, many, many lasers which would transmit said information. I don't know much about the range of lasers, and I'm fairly certain that even though the photons are ~parallel, they are subject to the inverse-square law, and thus degrade over distance.

In essence, What method(s) should an advanced, interstellar culture employ to exchange millions of terabytes per second with a neighboring star system, and what would the energy bill look like?

Edit: I am looking for EM-based methods, ones that would not require relays (which themselves could require maintenance or repairs). I am also looking for a most scientific answer. One that conforms to our current understanding of science. Small latencies are not an issue, given that the information will be traveling several light-years, however, as I've said, I'd like for the method to be primarily EM-based.

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    $\begingroup$ You state a measure of throughput ("millions of terabytes per second"), but I don't see anything about allowable latency. Are you fine with latency on the order of propagation delay at the speed of light? (In other words, would a plain old EM solution like those we have on Earth today, just scaled up for interstellar distances, cut it for your use case?) $\endgroup$ – a CVn Apr 15 '18 at 10:42
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    $\begingroup$ The delay introduced by relay stations is almost certainly going to be completely negligible compared to the speed of light delay between star systems. $\endgroup$ – a CVn Apr 15 '18 at 11:04
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    $\begingroup$ "my only concern with the concept is maintenance and repair" That's certainly fair enough. You might want to Edit your question to incorporate the issues raised in the comments so far. Comments can be deleted at almost any time for almost any reason, and people shouldn't need to look through a lengthy comment discussion to find details relevant to answering the question. $\endgroup$ – a CVn Apr 15 '18 at 11:19
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    $\begingroup$ So Petabytes per second with a 4 year latency is satisfactory? $\endgroup$ – pojo-guy Apr 15 '18 at 12:39
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    $\begingroup$ @pojo-guy Yes, that's quite right. $\endgroup$ – B.fox Apr 15 '18 at 13:21
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There are two ways to approach this:

  1. Build a massive laser transmitter which can push a high quality beam through interstellar distances. By this I mean something like Robert L Forward's proposal to send an interstellar lightsail from Earth to a star system (Roundtrip Interstellar Travel Using Laser-Pushed Lightsails). The laser transmitter punches out power at a terawatt level and the beam is focused by a fresnel lens thousands of kilometres in diameter. Forward had a similar idea dubbed "Starwisp" using microwave beams as well.

The size and power of the laser or microwave beam allows it to overcome some of the blockages and "noise" it would encounter in interstellar space, while the massive focusing lens provides the means to fine tune the beam onto a cooperative receiver.

enter image description here

Starwisp. Replace the spacecraft with a receiving antenna at the destination for interstellar communications

  1. Build an interstellar "Sneakernet". High bandwidth is still possible by transporting physical media from place to place. In Marshal Savage's book "The Millennial Project", he postulates that an advanced human civilization would create giant mass drivers spanning most of the distance of the Solar System to accelerate and decelerate pods to .9*c*, as a means of allowing people to move rapidly between star systems. At these velocities, the passengers will experience time travelling at a slower rate compared to the outside frame of reference. While slower than a massively powerful laser beam a sneaker net pod full of the equivalent of DVD's will actually be transmitting more data. Amazon Web Services has announced 100 Petabyte "Sneakernet" contained in a shipping container towed by a truck.

According to the CEO, uploading an exabyte of data would take 26 years using a 10 Gbps link. But that same amount of data could be moved in just six months using the throughput of 10 Snowmobile deliveries.

Extrapolate this to a pod full of 22nd century data storage units and you have the idea.

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  • $\begingroup$ en.m.wikipedia.org/wiki/Beam_divergence would make option 1 really hard. I can't do math right now but I'm pretty sure this solution would work at interplanetary distances, but not on interstellar ones. Option 2. was suggested by me in the comments and in response OP edited question to exclude this possibility. $\endgroup$ – Mołot Apr 16 '18 at 6:48
  • $\begingroup$ Forward's calculations indicate that the beam can deliver enough energy at a distance of several light years to drive a solar sail, and it is certainly focused to hit a cooperative target at that distance. The OP may choose to exclude "sneaker nets", but the bandwidth advantage is undeniable. That might be the "go to" solution because it is both more efficient and versatile (a cargo pod may deliver more than just information in memory banks). $\endgroup$ – Thucydides Apr 16 '18 at 13:35
  • $\begingroup$ Despite my wish for an EM-based method, I've come to accept option 2. It poses a lot of benefits I can't ignore, ones that an EM-based method cannot deliver. Thank you for your answer! $\endgroup$ – B.fox Apr 16 '18 at 14:19
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You could use sub-atomic particles or maybe neutrinos and tachyons as alternatives to light. There are a couple of studies that's how they travel at the speed of light and you may want to check if this is a bit more reliable or easier to implement than beaming light from one system to another.

Or if you want to really bend it out of current scientific abilities, you can have tiny space/time wormholes that are stable enough for your data packets to go through from one solar system to another. That would be fast.

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  • $\begingroup$ Subatomic particles are still subject to the inverse-square law and thus are subject of the issue. In my question, I said I was looking for a most scientific answer and wormholes are presently outside that category. Thank you for attempting a solution, but I'm afraid this answers nothing of my question. $\endgroup$ – B.fox Apr 16 '18 at 14:07
  • $\begingroup$ How about the wormholes? $\endgroup$ – Arkhaine Apr 17 '18 at 23:00
  • $\begingroup$ as I said, wormholes are outside the catergory of scientific. They exist in math only. $\endgroup$ – B.fox Apr 17 '18 at 23:34

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