SETI Revisited

SETI stands for the Search for Extra-Terrestrial Intelligence.  It was a hot subject in the past but enthusiasm seems to have died down since.  In fact, it's died down to the point where I almost lost track of the fact that I had done a post on the subject in 2010 (see http://sigma5.blogspot.com/2010/11/seti.html).  Have I change my mind since then?  No!  This piece comes to essentially the same conclusion the previous one did.  It just gets there by a different path.

The experts (actually the media and here I include even the science media) tell us that, like so many subjects in our modern times, there are exactly two positions.  Position (1) is "There are no extra-terrestrials so it's a waste of time and pure stupidity to look for them".  Position (2) is "It is very likely, bordering on certainty, that extra-terrestrials exist so we should try hard to find them". As with nearly every example of this idea that there are always exactly two positions, there are other possibilities.  And a third possibility is where I will end up.  But first, as is frequently the case with my posts, I am going to start with some history.

Speculation about beings from somewhere else is as old as human thought.  The classic example is "the Gods".  The ancient Greeks, for instance, invented a whole pantheon of Gods and placed them up on Mount Olympus.  I am not that familiar with Islam, but the case with Christianity runs in a rough parallel.  You have the nuclear family of God the Father, Jesus the Son, and the Holy Spirit (familial relationship unknown).  But then you have a Heaven headed by God the Father who is assisted by angels and that is populated by the redeemed, a Hell headed by Satan who is assisted by fallen angels and that is populated by the condemned.  The redeemed and the condemned are the souls of people who have died.  There is also Purgatory and (maybe or maybe not) Limbo to round out the list of non-earthly locations and their inhabitants.  Other religions and cultures invented other non-human creatures.  I am going to bundle them all together into a single group of non-scientific attempts at ETs.

The first scientific effort at a transportation mechanism for getting off earth was done by Jules Verne.  In 1865 he published "From the Earth to the Moon".  The method he used was a giant artillery gun.  For many reasons it would not work but the idea is not completely ridiculous from a scientific standpoint.  In fact, a design called a "rail gun" has been put forward.  It is more akin to a super-train but the basic idea of using a gun-like approach as a substitute for the first stage of a rocket is an entirely reasonable one.  The rail gun avoids the extreme acceleration of a classic artillery type gun.  And the addition of stages that use non-gun technologies allows for an ability to control and steer the vehicle.  The reduction in the amount of acceleration required and the addition of a steering ability address the two most serious problems with the pure artillery approach.

In 1897 H. G. Wells published "The War of the Worlds".  In Verne's book his travelers were attempting to reach the moon.  They failed and only managed to go around it.  They also encountered no aliens.  In the Wells book it is the aliens, specifically Martians, that come to us.  Wells is purposely vague about the technology the Martians employed.  Details of propulsion systems, etc. are completely lacking.  While not the first, it was by far the most popular early example of the "bad aliens are coming to get us" genre.  It definitely popularized the idea that there might be other creatures out there and that these creatures might be quite unlike us.

Both Verne and Wells prized scientific verisimilitude.  The Verne book was definitely what would now be called Hard Science Fiction, science fiction where the science is taken seriously and frequently figures critically in the plot.  Wells was scientifically very literate but chose to concentrate more on the non-science aspects in his story.  And someone who came along only slightly later and who was also extremely popular in his time was Edgar Rice Burroughs.  He is mostly famous for his many "Tarzan" books.  But he also created a series that was wildly popular in it's time, his "Barsoon" series.  The first few books featured hero John Carter who is transported to Mars (called Barsoon in the books) by what can best be described as magical means.  Burroughs had no interest in scientific accuracy.  But he did populate Mars with a number of fanciful races.  The books were heavy on action and adventure with a dash of romance thrown in.  Their big contribution was to make the idea of travel to other planets (and later star systems) very popular.

It was pretty obvious from the start of the twentieth century and even more so as the century wore on that the Moon was lifeless.  So attention shifted to Mars and Venus.  Burroughs in setting his stories on a fictional Mars fed the interest in Mars and the possibility of life there.  This idea was mainstream science at the time.  Schiaparelli, a noted astronomer of the time, believed he saw canals on Mars.  All telescopic observation of the period was done entirely by eye.  Photography did not come into general use until after Schiaparelli's time.  If you squint in order to make out just that little bit more detail it is easy to introduce distortions and that's what he did.  It took decades for equipment to improve enough to convince scientists that the canals did not exist.  But at the time Burroughs started writing the Barsoon books (1912) life on Mars was a mainstream scientific idea.

Venus was the other planet that was reasonably close.  Scientists of the time could not make out any detail when looking at Venus.  Scientists suspected this was because Venus had a thick atmosphere.  But they didn't know how thick nor much else about it because, among other things, spectroscopic techniques were not yet up to the task (see below for more on spectroscopy).  With little or no scientific information to go on, writers of the time were able to speculate much more widely about life on Venus.  Two popular ideas were of Venus as a steamy swamp (but not nearly as hot as the surface of Venus actually turned out to be) or of Venus as an ocean planet.  We now know that there is no water anywhere near the surface of Venus.

By the '20s the foundations of what we now call the Science Fiction genre were being laid.  Writers soon tired of Mars and Venus and set their sights much higher.  The propulsion systems in the stories of the day typically involved rockets to a greater or lesser extent.  But when it soon became necessary to travel faster than light rocket engines were supplemented by many of the ideas later popularized by the "Star Trek" TV show and its ilk.  Star Trek featured a "Warp Drive" where somehow the "speed of light" barrier was obliterated.  It and early versions of other ideas like "Jump" drives (you pop out of "real" space and, instantaneously or a short time later, pop back in somewhere else) show up in writings of this period.  None of these "faster than light" technologies currently looks feasible.

Meanwhile the complete scientific foundation for rocket flight was being laid down by one man, Robert Goddard.  Between about 1910 and about 1940 Goddard single handedly took rocketry from Chinese fireworks to a usable technology.  He invented the multistage rocket, pioneered the use of liquid fuels, developed a science of rocket nozzle design, developed the fundamentals of control and steering, etc.  Unfortunately, he was mostly ridiculed as some kind of wingnut in the U.S.  As a result he received meager funding and there was no follow up on his work here.  However, the Germans were paying attention.  They took his ideas, extended and refined them, and then used them to create the V-2, the first militarily useful rocket and the foundation of all civilian and military rocketry since.

Since Goddard and the work done in Nazi Germany during World War II little has changed.  The Saturn V used in the Apollo moon landing missions was a further evolution of the V-2.  Much of the development work on the Saturn V was overseen by Wernher von Braun, the chief Nazi rocket scientist.  Materials for building rocket structures, motors, controls, etc. have improved.  Computer technology has certainly made a big contribution.  But the fuels used are for the most part the ones Goddard identified and the Nazis used.  And there is very little difference in the performance of the brand new Falcon-9 from Elon Musk's Space-X and the von Braun Saturn V of the '60s.  (You can find more detail on the history of rocket technology at http://sigma5.blogspot.com/2010/11/space-shuttle-rip.html.  And here's a post on how little progress we have made on making rocket based access to space cheap:  http://sigma5.blogspot.com/2013/03/cheap-spaceflight.html.)  So, on the "getting to space" front, we are making little or no progress.  But maybe those aliens have made some kind of breakthrough that we don't even suspect.  If so, they have either not been here, or have left no identifiable tracks (or, more likely, garbage) behind.  But we can still point our telescopes at the sky and look for ETs, right?

Various people, typically Science Fiction fans, have long agitating for "us" (i.e. the Federal government) to do just that.  They lobbied NASA and other government supported institutions to go looking.  But fans were unable to generate enough enthusiasm within the government to support a long term or well funded search.  So they formed an organization of their own, the SETI Institute, in 1984.  One of the prime movers behind this was Frank Drake.  He was (and is) a well respected professional astronomer.  He is most noted in this context for creating the "Drake Equation" in 1961.  The equation calculates the number of civilizations in the Milky Way galaxy with which radio communication might be possible.  To calculate this number Drake suggests multiplying 7 specific factors together.

The problem is that the correct value for each of these seven factors is unknown.  Drake and people on his side of the argument, the "we should look and look hard" side, come up with estimates for each of the seven factors that suggest that the number of alien civilizations is high.  "Aliens are common, a dime a dozen, and thus easy to find."  People on the other side of the argument come up with estimates for each of the seven factors that suggest that the number of alien civilizations is low.  "There's no one out there or, if there's someone out there, they are too far away".  So the fight between the two sides has devolved into a argument over the appropriate values to plug into the Drake Equation.  It sounds very scientific but it's really not.

Now I want to drill down on one of the Drake parameters:  L - "the length of time for which such civilizations release detectable signals into space" (quotation taken directly from the Wikipedia article on the Drake Equation).  Now by "detectable signals" Drake specifically means "detectable radio signals".  I am going to skip over the "radio" part as I covered it in the earlier SETI post (see above for a link).  Instead I am going to perform a thought experiment.  Thought experiments are a wonderful invention.  Einstein is famous for making effective use of them and for making them a popular scientific tool.  In a thought experiment you do a "what if".  You assume something, whatever you want, and then you analyze the resulting situation to see what you can figure out.  This would seem to be a useless thing to do.  I hope that the following example will enlighten you as to just how useful a carefully constructed one can be.  So here goes.

Imagine a solar system exactly like ours.  Same sun.  Same planets.  Everything is exactly the same.  Everything formed at the same time as ours actually did.  And it evolved in exactly the same way as ours.  The only thing we change is that we displace it by 50 light years.  So what we have is a solar system just like ours that is fifty light years away.  Why?  Well, we can now ask ourselves questions about what we could learn about this solar system.  Since it is exactly identical to ours we can figure out exactly what the result of any measurement we might want to make would be.  And we are going to start out assuming that this "twin earth" solar system shares our exact identical history.  If we could instantaneously transport ourselves to the twin earth and go to same place there as we would here and buy a newspaper (or turn on the TV or whatever) we would see exactly the same thing we actually see right now on the real earth when we do the same thing.  We will relax this assumption later but for now "that's the way it is".

OK.  Now lets go back in history.  And let's do something really extreme.  Let's force the twin sun to go supernova.  I know our sun hasn't gone supernova but the question I want to get at is if the twin sun had would we now be able to tell.  If this happened more than about 2,500 years ago there would be no record.  The Chinese started recording interesting happenings in the sky at about that time.  In the rest of the world between then and quite recently, the odd shepherd might have noticed.  But even for something as gigantic and spectacular as a supernova there would be no written record anywhere in the world outside China and perhaps one or two other places.  There's a much better chance there would be a record elsewhere if it happened roughly 500 or less years ago.  But there would also be no record, even in China, if it happened more than about 2,500 years ago.  2,500 years represents less than one millionth of the time the earth has been in existence.  For everything but the last millionth of the lifetime of the earth a civilization could do pretty much anything except visit us and we wouldn't notice it.  That's bad but it gets worse.

Let's take something else that seems pretty obvious.  Our atmosphere is about 20% Oxygen.  This is unnatural.  Free Oxygen is very reactive.  Combine it with Iron, for instance, and you get rust.  Combine it with Hydrogen and you get water.  Oxygen likes a lot to be combined with other elements to form things that are not gasses so they fall out of the atmosphere.  Now there has been a lot of Oxygen in our atmosphere for billions of years.  So theoretically we could detect the Oxygen in the atmosphere of twin earth any time in the last billion or more years.  And here we are not trying to pull of the same kind of one in a million shot.  Well, actually we are trying to pull something off that is even harder.  Sure the Oxygen has been there since, like, forever.  But how long have we been able to detect it?  The answer turns out to be a whole lot less than 2,500 years.

The way you detect the Oxygen is with something called a spectrograph.  It acts like a prism and spreads light out into its components.  And the best way to do this used to be with a photograph.  But being able to do a spectrograph through a telescope has only been possible in the last few decades.  We have only had a spectrograph of the atmosphere of Venus for a few decades (see above) and Venus is right next door.  And there is another problem that crops up when we are trying to take a spectrograph of the atmosphere of our twin earth.  Twin earth is very close to an extremely bright object, twin sun.  Even with the best technology we have now it is very hard to get a spectrograph of the atmosphere of any of the many exo-planets we have been able to discover in the last few years.  It certainly would not be possible to pull this off  before the launch of the Hubble Space Telescope.  And that happened in 1990.  So detecting something as obvious as the Oxygen atmosphere of our twin earth has been possible for less than 25 years.

So we're back to Drake's old standby, radio waves.  Our ability to create and detect radio waves dates back to the late 19th century.  But artificial radio waves of any power only date back to roughly a hundred years ago.  De Forest invented the Triode, the first electronic amplifier in 1906.  It took a while to adapt it to radio use.  So the first regular radio broadcasts of any power coincide with World War I.  And by modern standards these were low power signals.  High power signals date back to the '30s with the spread of commercial radio stations.  Two other sources of high power signals are Radar , which dates back to World War II and TV, which dates back to the '50s.  So in round numbers you are talking about 70 years.  Drake assumed that once begun we would always broadcast high powered radio signals.  So, although high powered radio signals would have started emanating from twin earth 70 years ago and started arriving here 20 years ago, Drake assumes that window of opportunity is actually much wider.

Let's say that the history of twin earth is actually shifted 100 years.  Their history is a hundred years ahead of ours.  (This is me relaxing that assumption I warned you I would relax.)  In this case twin earth would be broadcasting powerful radio signals long enough that the first would have arrived 120 years ago.  But communication requires a sender and a receiver.  We have had the technology to receive radio signals for only about 120 years so it does us no good to shift the history of twin earth by more than 100 years.  But fair is fair.  So let's peer into the future right here on earth.  As I observed in my previous SETI post our use of radio is continuing to evolve.

As I observed in my previous post, TV has already evolved from Analog to Digital.  The digital signal is harder to detect.  But how long will broadcast television last?  When I wrote the post in late 2010 it was already true that most people got their TV over a "cable" and not through the air.  Since then streaming over the internet has become popular.  This has put in jeopardy the whole "send your show out over a channel" model of how TV shows get to us.  If we get everything as a streaming signal over the internet then the whole justification for "TV channels" goes away.  In addition, the broadcast frequencies get more valuable every day.  They can be repurposed to support even more mobile internet use and the mobile companies are willing to pay big bucks to get control of them.  At some point the few people who watch TV shows "over the air" will diminish to the point where broadcasting them makes no sense at all.  That's probably already true but current broadcast TV stations are worried that if they stop broadcasting they will lose various legal rights that are necessary for them to be able to stay in business.

The same kind of thing is happening with radio stations.  Traditional radio stations used something called "AM".  AM uses a signal structure that makes it easy for SETI receivers to detect.  But then FM became popular in the '60s.  Since then we have moved on to digital radio and, of course, audio streaming across the internet.  AM still lives.  But I don't know for how long.  FM seems to be doing OK at this point but it has passed it's prime.  It is easy to imagine both AM and FM radio gone 50 years from now.  So high powered "station" based radio and TV broadcasts might only exist for about 100 years.  The military still uses high powered radar. So that signal is still available.  But the sensitivity and sophistication of radar receivers keeps improving.  So the power of broadcast signals keeps decreasing in all but a few cases.  And the signal complexity across the board keeps increasing.  So, like radio and TV, the "window of availability" of radar may turn out to be roughly 100 years.

I think I have now convinced you of the value of my specific thought experiment.  And I hope I have also convinced you of the value of a well constructed thought experiment.  Scientists now use them frequently and widely.  Now back to the issue at hand.

In our thought experiment we have assumed we are looking for a civilization exactly like ours in every detail.  If you are using the SETI approach that's as good as it gets.  A truly alien civilization may not use radio at all.  Or they may use it is some way that renders their signals entirely unrecognizable to us.  We just don't know.  Besides the specific technical problems I have described I believe there are a lot of implicit assumptions about how an alien civilization operate embedded in the SETI way of thinking.  And apparently I am not the only one who has noticed.

In 2001 the SETI Institute embarked on a project originally called the "One Hectare Telescope".  (A hectare is about 2.5 Acres.)  It was renamed "The Allen Telescope Array" when Paul Allen of Microsoft fame pledged (and eventually delivered) $30 million to the project.  The project was supposed to construct an array of 350 interconnected radio receiving dishes.  This was supposed to enable a thorough search of the skies for SETI signals.  Due to technical problems and cost overruns only 42 dishes have been installed.  That's enough to do interesting things but the ATA is not as sensitive (able to detect weak signals) as it would be if it was fully built out and there is no obvious source for more money.  Allen eventually decided to cap his contribution and pull out.  The University of California at Berkeley was originally involved but they have also pulled out.  The project has been limping along on fumes for the last few years.  And, of course, they have yet to find even a hint of an ET.

So I circle back to where I ended my earlier post.  I do not fall into the "they're everywhere" Drake camp.  Nor do I fall into the "there are no ETs" camp.  I do not know if there are ETs out there or not.  Instead I think we ought to "keep looking up".  We should keep doing the things astronomers and others who look at the sky do.  But I don't think we should do any kind of special ET search.  Instead we should do what we are already doing, looking for the unexpected.  Alien life is alien.  That means two things.  First, it behaves like life.  It modifies its environment to look and be unnatural.  (See the whole Oxygen discussion above.)  Life manifests itself as the unexpected, the unusual, the unnatural.  Second, it is alien.  It is not "us" so it will not behave like we would behave in the same situation.  Again, being on the lookout for the unexpected, the unusual, the unnatural is the right strategy for finding them if they are there to be found.

But that's what scientists do.  The unexpected, the unusual, the unnatural is what they live for.  A scientist going about the business doing science is the best "alien detector" there is.  Doing some kind of special SETI search wastes resources that could be more productively used doing other things.  Even in its current form, the ATA can do valuable science.  But it needs to be configured and used in such a way as to maximize the science product.  The useful scientific work it can do under the current setup has turned out to be so modest that it justifies neither its current operating cost nor the cost of building it out the rest of the way.  And the chances of it finding an ET before someone else does are vanishingly small.