While SETI is indeed a long shot, we do have one example of a species that sends signals out into interstellar space: ourselves. This means that intelligent life in the universe is possible and proven. Further, it is possibly detectable if that intelligence uses any form of EM radiation to communicate as we have for years. It is therefore not without merit.
The SETI search I am involved with is not looking for a radio signal "beamed" directly at us. The assumption (and yes I do realize its an assumption) is that electromagnetic energy (EM) is the most efficient means of conveying information over vast distances. Gravity waves may also accomplish the same thing, however, we do not yet have that capability. So this leaves us with EM.
I personally believe for a race to become technologically advanced, it must have the ability to store and convey information over long distances. Since radio waves (I am including any EM in this such as RADAR, TV, microwave, etc.) are still the best method for accomplishing this, any other race would use/do the same. For about the past 60 years we have been isotropically radiating EM across a huge RF spectrum into outer space. What we are looking for with our SETI system, is another species that is doing the exact same thing we are. Unintentional radiation of EM into outer space.
This is why radio and/or
optics (I know of some people who are contemplating optical SETI) are the
best way to find other civilizations. The advancing sphere of radio noise
radiating from our planet now encompasses an area more than 120 light years
across. There are literally thousands of stars within that volume of space.
As we measure the heavens with more precise instrumentation we are finding
a plethora of planets orbiting other stars. A few years ago there were
many people who were quite skeptical about the possibility of extra solar
planetary systems. Statements were made like "just because there is one
known planetary system (ours), it doesn't mean there are others". It appears
now that planetary systems are the norm instead of the exception. I am
now hearing the same argument against the possibility of ET. I personally
do not "believe" ET is out there. I suspect ET is out there. We are finding
the building blocks of life through out the heavens. I also think life
is far more tenacious than most people believe. We even find life in the
sulfur volcanic vents on this planet.
If
we do find that extremely narrowband signal heralding the fact we aren't
the only intelligence in this vast universe, I think it would further our
understanding of our relationship with this universe. With C being the
fundamental limit (speed) of communication, "talking" with another race
would be quite impracticable. Not much of a conversation if you have to
wait 3000 years for a reply to your hello. Still we would know as a species
that we were not the only organisms contemplating the existence of the
universe. Finding another intelligent race would definitely redefine our
place in the universe.
We
both are quite aware just how far it is "out there". With the speed of
light being the fundamental limit for baryonic matter, it will be next
to impossible to travel between the stars (at least under our current level
of physics knowledge). So the universe may be populated with little isolated
bits of intelligence all wondering if any other species are out there.
Just
in the past few years we have advanced far enough in our technical prowess
to both "announce" to the universe we are here (radio waves) and to receive
the same from another species. With that in mind and the speed of light
being a constant in a vacuum, the expanding sphere of radio noise heralding
our presence has only gone about 60 light years or so. So there may be
an entire galactic community out there but our "knock" hasn't yet hit the
door so to speak.
Also
there may be thousands of intergalactic signals bouncing around but we
have not yet found the right frequency or built sensitive enough equipment
to receive them. We really are kind of in the back woods of this galaxy
2/3rds the way down one of the spiral arms. So have we been visited?I
don't think so, How would a race even know we were here to come and visit
us with out us heralding ourselves first. So far, radio is the only way
we have done that, and its not gotten very far out there yet.
So
the search I am involved in does not look for any radio signals purposely
beamed at us. I am looking for another race that has developed far enough
down the technological road to have developed radio like we have. There
appears to be only 4 fundamental forces in all of nature; Strong Force,
Weak Force, Gravity, and Electromagnetism EM. Both the strong force and
Weak force are confined to the nucleus of the atom. Gravity requires prodigious
amounts of energy to manipulate, so the only one that is practical for
long distance communication is EM. In an extremely short period of time,
we are using EM across the entire spectrum from basically DC to light.
We are now radiating that same spectrum into outer space. In fact at certain
frequencies, we are the brightest object in the known heavens. So what
we are looking for is a race that is doing the same thing we are, unintentional
radiation of radio wave into outer space in all directions.To
up the odds a bit, we have decided to point our dishes strait down our
own spiral arm. This gives us the maximum number of stars in each patch
of the sky we are looking at. We also are looking at multiple frequencies.
My modest little search is looking a 3.1 million frequencies for the duration
of any object in the beam path of our antennas.
The
other thing that makes this more exciting is the number of planets we keep
finding out there. As soon as the technology advanced far enough to detect
planets we found lots of them. It now appears that planets are the norm
instead of the exception.I remember
to this day a Physics Prof of mine stating in class that he personally
did not think we would ever find another planet outside of our solar system.
I personally believe that once we get our systems sensitive enough, we
will find lots of evidence for life as well. SETI is also a win-win situation.
If we are alone that in itself is extremely profound. If we are not, that
is equally profound. So SETI in either case will give us a better understanding
of our place in this universe.
Have you scanned the whole sky? That is, the whole sphere surrounding the earth?
Not a chance. That is a huge undertaking. What I am doing is looking down the arm of our own galaxy. This will give us the highest concentration of stars local to our own which should increase the probability of detection.
At all ranges of the spectrum?
There are two real sources of noise that limits the radio astronomer's ability to search for very weak signals. 1) The Galactic noise halo interferes with us below 1Ghz and noise due to earth's atmosphere interferes with us above about 10Ghz. This pretty much keeps all SETI searches (at least radio ones) between 1 and 10Ghz. Between the two, the noise is around the 2.7K background from 1.4 to 7Ghz. This is why most of the SETI searches are around the frequencies that the OH (hydroxyl) and H (hydrogen) molecules masers emit. This is the so-called water hole. OH H (tell me scientists don't have a sense of humor)
If you have to be selective, in areas scanned and in areas of the spectrum, how are the elections made?
For myself it was cost. I was able to use very high quality mass produce components out of the satellite industry for the frequencies I am scanning at. 3.7 - 4.2Ghz.
When will the full sky, full spectrum be completed?
I have absolutely no idea.
When it's all scanned, is SETI finished?
Not finished per say:
But in total absentia of any confirmed signal we will have a better understanding of just; a) how hard the search will become or b) the possibility we really are alone.
On the other hand,
if we do have a confirmed signal, is that the only other intelligent species
out there?
I really don't know. Maybe as our technology increases, the use of high power RF decreases. More and more we are turning to both digital cable and frequency hopping spread spectrum digital RF. It may hold true that high power RF is a very short-lived phenomena in any technological evolutionary ladder. If that is the case, SETI may be futile even if there are thousands of races right here on our doorstep.
Fermi's
Paradox:
We both are quite aware just how far it is "out there". With the speed of light being the fundamental limit for baryonic matter, it will be next to impossible to travel between the stars (at least under our current level of physics knowledge). So the universe may be populated with little isolated bits of intelligence all wondering if any other species are out there.
Just
in the past few years we have advanced far enough in our technical prowess
to both "announce" to the universe we are here (radio waves) and to receive
the same from another species. With that in mind and the speed of light
being a constant in a vacuum, the expanding sphere of radio noise heralding
our presence has only gone about 60 light years or so. So there may be
an entire galactic community out there but our "knock" hasn't yet hit the
door so to speak.
What about self-replicating
robots sending back information from interstellar space?
Two things. First, there may me thousands of races out there, but they are "stuck" just like we are by general relativity. Sigh! Second, the prodigious amount of time it would take to cross the galaxy at sub light speed would prohibit even the most ambitious race from basically spending the money and wasting the precious resources to attempt that feat. Also how long can a machine function and replicate without error entering the picture. Not unlike evolution. :)
Have you personally seen
a candidate signal?
Nary a peep. If I do find a signal, my first reaction will be to turn off the equipment, cut and run. I really don't know how I would feel about being the only one or one of only three people in the entire history of the human race to know we are not the only intelligence in the universe.
Question: whenever I have seen SETI-at-home at work, it has been analyzing 21cm data. Is the thinking that since much of RadioAstro observing is at 21cm the aliens would know this and therefore make sure that their special messages are at this wavelength. Are We beaming at this wavelength?
Fabulous question! Since
this is one of the coveted frequencies of radio astronomers, we have international
treaties to not broadcast at this frequency at all. So here we are looking
for signs of a narrowband signal heralding the fact that intelligent life
is not wholly constrained to this little dirt ball at this frequency. Now
if any intelligent race develops radio and radio astronomy, they too will
recognize the importance of this 21cm band. And they also may instigate
a SETI search using this frequency. So here is the question. Would they
hear us at that frequency? It is the one that we are not transmitting on
at all. I could just see 500 races all looking for each other at the very
frequency none of them are transmitting on due to the very nature of the
importance of that frequency to the exploration of the universe.