Where are the Aliens? Interview With a SETI Researcher
Some future searches for alien civilizations will focus on potentially habitable planets, like in the Kepler 62 system, seen here in this artist illustration. Credit: NASA Ames/JPL-Caltech.
Discovering life beyond Earth has always been considered by some to be the holy grail of science. However, no little green men or even measly microbes have been conclusively found. But this hasn’t dampened the enthusiasm among astronomers who are still searching the cosmos for signs of extra-terrestrial life. The current leading search method uses giant radio dishes to scan the stars, listening for possible faint signals coming from distant civilizations.
National Geographic News caught up with SETI (Search for Extraterrestrial Intelligence) radio astronomer, Andrew Siemion, who is based at the University of California at Berkeley, to chat about how astronomers listen for aliens.
What kind of alien signals are scientists looking for?
There are intentional signals – much like a lighthouse or a beacon – [that] can produce an emission intentionally designed to produce a signal so that other intelligent life know they exist.
Then there is leakage signal — akin to our aircraft radar, and TV broadcasts. A signal like this, however, would have to be very powerful for us to be able to detect this right now from Earth. For example, the farthest we could detect signals like what we are leaking right now with our current technology is probably at best only 1 light year out. [The nearest star to Earth is Proxima Centauri at 4.3 light years.]
However if we allow extraterrestrial (ET) telescopes to get large – say a radio telescope that has the diameter of the Earth – then they could detect very weak signals.
Many in the SETI community believe that the first signals we may detect will not be leakage signals but intentional ones designed to notify others of their presence.
But new telescopes are coming online soon, like the Square Kilometer Array, the largest radio telescope ever built in history. It will have 10 times the collecting area of the Arecibo radio telescope in Puerto Rico, and will be sensitive enough to ET signal leakage from 5 to 10 stars of the nearest stars.
Any region of the sky that current searches find particularly exciting?
In just the last two years NASA’s Kepler planet-hunting mission has taught us is that most stars have planets. We are also learning that the habitable zones are much broader than what we [previously] thought. We know there are lots of way to get the heat needed to keep water in its liquid form. What this means is that we are really starting to expand our ideas about the kind of conditions that would be necessary for life to emerge. At SETI today, we not only do all-sky surveys, but more and more targeted searches too – focusing on the nearest stars to the Earth.
Research is showing us that 10 to 15% of stars have a planet in the habitable zone -where liquid water could exist on the surface.
Because our equipment is not that sensitive it’s best for us to look at stars that are closest to Earth.
One of my proposed studies plans on focusing on just that – the 100 nearest stars to the Earth.
What are the biggest advances since the start of SETI that allow us to focus these searches?
Technologically we have gotten larger and larger telescopes and faster and faster computers. And for radio SETI, the sensitivity of our experiments and the amount of radio channels we can explore is directly related to how fast our computers are. Because we don’t know where ET might be broadcasting it’s a good idea to look at as many channels as possible. The first experiments decades ago could look at only 10 channels, and now we can look at billions.
Looking into the future, in perhaps a decade time, we might be able to explore the entire radio spectrum over the entire sky.
So what this means to me is that, if, after a couple of more decades of searching we haven’t discovered a signal, we may have to fundamentally rethink the way we conduct the search for ET.
What do you think are the chances of finding an ET signal?
Overall the SETI community is optimistic since we continue to learn more about astrobiology, and that conditions suitable for life may be quite ubiquitous and technology is getter faster and more sensitive.
But the bottom line is that we really don’t know since we are constantly restricted by the fact that we only have a single example of life anywhere in the universe. That severely limits the amount of statistics we can apply.
If we could find just one more genesis of life- even if it was just a lonely microbe – I could answer this question much more scientifically and quantitatively.
Why do you think we haven’t stumbled across a signal yet?
The famous Fermi Paradox asks just that: if intelligent life is so common then where are they? My personal opinion is that electrical engineers in the cosmos are pretty rare.
I think life is pretty common and even intelligent life might be relatively common but technological civilizations like our own may be relatively rare.
If every star had a planet with intelligent life just like our own, were long lasting and survive their technological development, and was altruistic and decided to signal its presence, we would have already detected something.
So clearly intelligent life is not that common. But we need to explore much more of the radio spectrum to really say something more profound about how rare civilizations like our own might be.
What is the most likely form of a signal we might find a signal?
It might very well happen while an astronomer is conducting a new kind of experiment, maybe something that looks at dark energy or dark matter, something that is very sensitive and they encounter something in their observational data they did not expect.
Perhaps after exhausting all possibilities they may come to the most amazing conclusion about where that anomalous feature in their data is coming from.
What would be our response to a true detection?
Any potential signal will need to be confirmed if it is extraterrestrial in origin. After conducting internal tests to confirm that it is indeed real, we would ask other observatories to check out the candidate signal to look for confirmation.
The world would find out pretty quickly too if this happens- mostly likely through twitter.
We are committed to openness and nobody wants to keep secrets. It would also be impossible for anyone to block our ability for us to see extraterrestrial signals.
So if the signals are out there – we will find them. There is nothing between the researchers and the sky. Rest assured there is no ‘secret black box’ installed on our telescopes that filters out our data – we see everything.
What are your personal thoughts about Roswell and other UFO reports?
I personally think it’s largely a psychological phenomena influenced by the media and technological development, and by the fact that we are a very young space-aware society.
I have never seen any evidence that would lead me to believe that Earth has ever been visited by any extraterrestrial intelligence.
Astronomers are constantly looking at the sky at all wavelengths, with giant telescopes that are sensitive to little blips of light from across the universe, as well as powerful radars that scan the skies around the Earth- and there is no evidence of anything happening.
Being in science, in fact I think it would be nearly impossible to keep any secret like this.
At the end of the day we require evidence – and in the absence of that- we can’t just conjecture some fantastic happening that is unsupported.
