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In a college town, I wonder if the law of diminishing marginal utility applies to a product like this.

Yesterday’s WSJ discussed the SETI@home project, noting that its pie-in-the-sky mission is diverting useful resources that could otherwise be used to analyze protein synthesis, help with cancer research and model the climate.

Back in my last year of high school, my friends and I created a SETI@home team called “The Vatos” — as we were fond of the quixotic notion that we could find another Wow! signal. Seven years later, about the only thing discovered is a bunch of lonely pulsars.

Nevertheless, astronomers such as Peter Backus noted, that over the past 50 years of listening and searching, only a very small portion of the sky has ever been scanned. And in his view it is improbable that given the resources currently devoted to scanning the cosmos, that these signals will be found. However I doubt that even with an exponential increase in resources that any signal will be detected.

While I do not think that SETI is a religion, I find myself in agreement with individuals like Frank Tipler, who believe that SETI projects are largely a waste of resources… because ET probably does not exist anywhere in this galaxy.

Decades old debate

Back in the 1970’s and ’80s, two astronomers - John Barrow and Frank Tipler - were shaking up the SETI landscape by suggesting that if advanced civilizations exist somewhere in the galaxy, we would already know about it.

They proposed that an advanced civilization would create and use von Neumann probes to explore the galaxy. These probes are named after the German mathematician - John von Neumann - who conjured up a contraption that could self-replicate itself entirely, from any given material. And because of its inherently robust qualities, they would be an ideal candidate for the dangers of space flight.

The basic idea that Barrow and Tipler were theorizing was that a probe would, however slowly, be launched from the Home planet, land on an asteroid, meteor, comet or even another planet and create a copy of itself from the available material. These probes could continue replicating and hopping across solar systems until they had effectively populated the galaxy. And while traversing the vast expanses of the Milky Way they would leave messenger ships behind to further explore regions or even assimilate and create “sentient” planetoids (e.g. Matrioshka Brain, Jupiter Brain).

While this sounds far fetched and something shown late at night on SciFi, the math behind it is fairly compelling.

Let us assume that humanity manages to create a self-replicating nanofactory system that can be launched safely into space. While on its way to acquire targets, ground controllers could continually update its computer systems with new designs for when it replicates itself (such as how to build a faster rocket or more capable computer). It can then proceed to land on a foreign body and begin the process of replication (the replication process could be continuously fine-tuned and optimized through either its own dynamic AI or from information sent to it via the engineers on Earth).

Off the drawing board

As of this writing, the fastest man-made object launched into space was the recent New Horizons probe to Pluto (technically speaking, Voyager 1 is moving slightly faster). It is traveling at approximately 37,700 mph. Not assuming gravity assists, here are some important numbers to keep in mind.

One light-year is 5,878,625,373,183 miles. It would take 158,881,766 hours for the craft to travel that distance, which is about 18,100 years. The Milky Way is about 100,000 light-years in diameter. So it would therefore take around 20 billion years to reach every corner of the galaxy.

While that sounds like an incredibly long time, consider this: the example above used available rocket technology today based largely on chemical reactions. If another kind of propellant or engine is used to power the probes acceleration (e.g. fusion, ion thruster, solar sails), the duration for exploration could be reduced significantly.

For instance, several days ago I discussed Project Babylon which was essentially a very large artillery piece capable of shooting several tons of cargo into space. Similarly, the Navy is working on a ballistics project called DD(X) which uses railguns to lob 40 pound projectiles into Low-Earth Orbit.

As a result, many moons from now it may be possible to use a very long and powerful railgun to launch von Neumann probes at speeds around 1-2% the speed of light. Thus, it would take only 10 million years to explore the entire galaxy. And several hundred million more to explore many others.

The Right Stuff

I mention this seemingly feasible scenario not to disprove the existence of extraterrestrial life, but to shed light on the fact that if advanced civilizations like our own existed, it would probably have visited us by now (or is on its way as we speak). [Note: I have previously criticized UFOlogy here and here. See also debunking from Space.com here and here.]

Carl Sagan and other pro-SETI astronomers had rebuttals (1 2) back when the debate was in full swing. These consisted largely of prescribing the farcical Prime Directive into the aliens’ ethical system of practice. And at that point the debate gets tied up forever, because every Tom, Dick and Harry can just as easily come up with a reason as to why a hypothetical Spock is or is not interacting with us.

For better and for worse we already launch probes into space, so if given the ability to make the probes more effective with self-replicating systems, why would we not? It would be an extremely cheap, quick and easy way to explore the surrounding solar systems without having to brave the solar elements with our frail bodies. And assuming that intelligent life arises via biological processes, would not an alien civilization be confronted with the same decision?

Perhaps SETI will find something one day, I would not invest in it though. Check out the Singularity instead.