Interesting Thought of the Day: The Galactic Internet is Out There
No, but what if? What if we’ve been going about the search for extra-terrestrial intelligence all wrong? Why do we expect anyone anywhere to be sending messages to a random little yellow dwarf star? I think no one’s sending us messages for the same reason that we’re not sending any messages to them: it’s ridiculous to expect that someone could be listening, in just the right place at just the right time on just the right frequency. It’s a cold, silent tragedy of the commons.
Instead, I started thinking about the problem of interstellar communication the other way around. I just assumed that a network of technological civilizations already exists, and asked what the protocol would be for connecting to it. Node discovery. Address acquisition. DHCP on a galactic scale. Maybe they don’t breathe oxygen, but I bet our alien friends have worked out the same fundamentals of network engineering that we have, and simple numbers says it’s much cheaper for us to announce our position than for them to search for us. It just makes sense in this galactic year’s current fiscal climate.
Right, so where is the nearest node of the galactic internet and how do we signal it?
First of all, a little reading of current SETI research has convinced me that we should be using lasers, not radio waves. It’s an old idea, going back at least to this 1965 article, however, a simple calculation in this 1999 paper from Harvard revealed that
A high-intensity pulsed laser, teamed with a moderate sized transmitting telescope, forms an efficient interstellar beacon. To a distant observer in the direction of its slender beam, such a laser transmitter, built with “Earth 2000″ technology only, would appear (during its brief pulse) a thousand times brighter than our sun in broadband visible light
The best part of this is, such a focussed pulse is in fact so bright that searching for a particular wavelength is unnecessary. A simple photon counter pointed through a telescope at the distant star — the Harvard team is using photomultiplier tubes — would be more than sensitive enough to distinguish a nanosecond pulse of optical photons of any frequency from the background light of our sun, over distances of hundreds or thousands of light years, depending on how strong the laser is. This completely eliminates the formidable frequency search problem.
Of course, we still have to figure out where to send our message. Again, I propose thinking like a network engineer, because network engineers clearly rule. Now that everyone uses the internet, they’re cool enough to have friends.
So, supposing you wanted to build the galactic internet, where do you put the nodes? And not just any nodes, but the big central nodes where expensive listening-post equipment would be scanning for messages from previously unknown civilizations. The five year-old in me wants to answer “at the bright stars!” but actually, this may not be the most practical answer. Instead, nodes need to be at the inhabited stars which are most “central” in the sense of minimizing both the communications lag (light is slow) and the number of links needed to cover all the civilizations in the galaxy. One way to to determine this formally would be to compute the minimum spanning tree of all inhabited systems, and then pick high-degree nodes in the tree as very likely locations for listening posts.
Except that we don’t really know what systems are inhabited (but we do have a growing catalog of extra-solar planets), or what the maximum practical range of interstellar optical communications might be (but we can guess), and there’s no reason to restrict the network topology to a tree (but we can still put cost constraints on the graph)… Still, no matter how far fetched this idea is, listening for messages sent to us so far hasn’t worked. Thinking about the problem from the other side — how one would build an galactic network that allows for new technological civilizations to make first contact — is certainly a strategy that’s never been tried.
And you gotta wonder what we might learn from a random page on Galactipedia.
