SETI

SETI stands for the Search for Extraterrestrial Intelligence.  I have been reading Science Fiction since I was a kid.  So I am very comfortable with the idea of space aliens.  So, I am all in favor of SETI, right?  Wrong!

The first possible reason to be anti-SETI is a belief that space aliens don't exist.  I don't subscribe to that idea.  I think there's a good chance they do exist but I'm not sure.  I think that puts me in line with what most people think.  There is a line of thinking recently popularized by Steven Hawking that it might be dangerous for space aliens to discover us because they would do bad things to us (cut to innumerable horror movie plots).  I think this is a possibility.  But its not my main reason to forgo the hunt.

My main reason for being against SETI is ignorance.  I don't think we know what we are doing.  There has been a conventional wisdom going back 60 or more years about how to go about the search.  It revolves around radio.  What you do is hook up a powerful radio receiver and listen.  The first serious attempts to do this happened in the '60s.  And almost immediately we got a "hit".  The Astronomers who got the hit dubbed it LGM-1, the LGM standing for Little Green Men.  So we discovered actual aliens in the '60s?  Well, not exactly.

It turns out that what the Astronomers found is now called a Pulsar.  A Pulsar is a peculiar type of star.  For reasons I am not going to go into it puts out a very powerful radio signal that repeats itself.  The repeat period is a few seconds or less so in effect it pings at us.  At the time no one knew that such a thing as a Pulsar could exist.  Now they are a common subject of study by Astronomers and we know that there are lots of Pulsars all over the place.  It took almost no time to figure out that that early signal was not from an alien and only a few years for a basic understanding of Pulsars to emerge.  But up until that time if you had played a recording of that first signal to most people they would have said "it's definitely a space alien".

So is one "oops" enough to doom the whole enterprise?  No!  But it does provide validation for the idea that we don't know what we are doing when it comes to looking for space aliens.  The search has gotten more sophisticated since.  But it is has stuck with the "look for an intelligent radio signal" idea.  Sticking with this idea for so long demonstrates a fundamental lack of imagination.  The theory has been and continues to be that we can detect "intelligent" radio signals over longer distances than just about anything else.  But even with radio signals, it's harder to look over large distances than you would think.

During the '60s and '70s this approach seemed very sensible.  The strongest signals we humans generated were radio and TV signals, for the most part.  The modulation technique (the way you added the "signal" to the broadcast) used for these signals was very simple because the complexity of the receiver had to be very low to keep the cost of radios and TVs down.  But now, only a few decades later, we use much more complex modulation techniques.  This is because it is now cheap to put a computer into something like a cell phone.  The complex processing the receiver can do means a lot of things are now possible.  But it also means that the signal now looks a lot more like noise than those old signals did.  So the amount of effort it takes to make sense of the signal is now a lot greater.  And this makes the signal a lot harder for some alien to pick out of the background.  Another thing that is happening is that the power of the broadcast signal is going way down.  This is so that we can use the same frequency over and over.  Now imagine an advanced civilization doing just what we are doing only more so.  It may be very hard to detect them by just looking for a strong simple radio signal.

In fact, we really don't know what to look for.  So I don't think we should actively look.  Does that mean I don't think we should look at all?  Again, no.  Consider the natives that first encountered Christopher Columbus.  Let's say they wanted to search for aliens, in this case people from Europe.  What would they do?  Well, they would have limited technology.  Their best bet would be to station lookouts on mountains.  These would be able to see perhaps 15 miles out into the ocean.  This would not work very well.

But consider what happened when Christopher Columbus showed up.  Were the natives in any doubt that "aliens" had arrived?  No!  They came in a giant canoe of alien design.  They wore alien clothes, spoke an alien language, and had alien technology.  The fact that the natives had no high tech toys in no way diminished their ability to determine that they were in the presence of aliens.  And to discover, or in this case be discovered by, aliens all they had to do was to go about their normal course of business.  Once the encounter happened, they were in no doubt that they were being subjected to an alien invasion.

So I think no special search is necessary.  As in the "Columbus" case, the aliens have the better technology so they can project evidence of their existence much further than we can.  And aliens are alien.  We will not have any problem figuring out that they are alien when they make their presence known.  Given this, I am opposed to spending public money on SETI.  Although non-zero, I consider the chances of an active search producing results to be so small that the expenditure of public money solely for a SETI search is unjustified.  However, if some SETI searching can be done "on the side" and at no additional cost, I am OK with that.  Paul Allen has provided funding for the Allen Telescope Array, which is affiliated with the SETI Institute.  As a private citizen, he can spend his money as he wishes.  I am not adamantly opposed to SETI funding because SETI initiatives have provided "spin off" benefits.  So the money spent has not been a complete waste.

(Added 1/6/2011) The January 2011 Scientific American contains an article on SETI entitled "Contact:  The Day After" by Tim Folger.  It is a pretty standard piece.  Quoting:  "SETI's instruments are designed to search for steady, periodic narrowband pulses -- carrier waves powerful enough to be detectable across many light-years."  Old fashioned radio signals consists of a "carrier" wave, the central frequency of the signal.  It is surrounded by "side bands", one at a frequency range just below the carrier frequency and one other just above.  But it turns out all the signal information is embedded in either side band.  So you can suppress the carrier and one of the side bands and you are left with a "single side band" (SSB) signal.  This saves bandwidth and transmitter power.  It just requires a slightly more complicated receiver.  So if our aliens are transmitting SSB signals the SETI search won't find them.  SSB is old technology.  A popular newer technology is called "spread spectrum".  It works just like you think it does.  These are just two specific examples of how our use of radio is moving from simple, SETI detectable, signalling to signalling that looks more and more like noise.  Who knows what we will be doing a hundred years from now.  But whatever it is, it will probably be hard to detect with a simple SETI search.