Though our ability to scientifically and satisfactorily answer the question, "So are we the only ones?" is not assured, the investigation of our biolotical aloneness in the universe is a fundamentally important task. It's a basic question in a series of basic questions--how did the universe get here? how did we get here? did others also get here? how will it all end for all of us?--and has philosophical, social, and scientific implications. If life is abundant, it must spring up pretty easily, and transitions like the one from 'organic molecule' to 'bonobo' must be ones the universe's rules compel it to follow.

We have now found organic molecules with 10+ atoms in interstellar space. We think tiny organisms might exist in subglacial Antarctic sheets. This stuff is persistent and dedicated to its own existence.

And while it's exciting to think that little green bacteria are drifting around in alien lakes, a) that's hard to prove, b) isn't it more exciting to think that, somewhere out there, a communicating being is watching Little Green Downton Abbey? Not that that's very much easier to prove. The universe is quite a large place and we would need to be looking in the right place at the right time in the right way to make a detection.

Scientists are looking for several different things when they investigate life in the universe, primarily under the categories of prebiotic compounds; evidence of tiny, stupid life (like certain metabolism-produced chemicals in planetary atmospheres); and smart, talkative life.

This XKCD comic shows the relative sizes of the 786 planets known in June of 2012. In February, 2013, there are 76 more. Click to enlarge.The latter category has received criticism in the past (and in Contact, DAVID DRUMLIN) for just searching the skies without much direction, using telescope time and computing power for a question whose answer we may never know. But in the past few years, the number of exoplanets (planets outside our solar system) has gone crazy. There are 862 confirmed and thousands more candidates.

SETI scientists can now be more picky with their targets, choosing not just stars like the Sun (which is how SETI began) and not just choosing stars that have planets but choosing stars that have rocky planets in habitable zones with temperatures that could support the kind of life with which we're familiar. Because exoplanet-finding technology blew up, exoplanet science blew up, and because exoplanet science blew up, SETI researchers have a better chance of finding something, and they are able to make meaningful statistics out of their data even if they do not find anything. Everybody wins.

A paper forthcoming in the Astrophysical Journal and currently available online describes the work of Siemion, et al., who looked directly at 86 planet candidates discovered using Kepler data

have temperatures between -46 and 224 F or

are in systems with 5+ planet candidates or

are in systems with a SuperEarth in a 50-or-more-day orbit.

The Green Bank Telescope is the world's largest steerable telescope, and it happens to be located in a really pretty spot. Convenient for SETI researchers. (Credit: Pocahontas County Visitors' Bureau)In other words, systems that could support life as we know it. They used the Green Bank Telescope to look for purposeful, synthetic radio waves coming these systems. Radio waves coming from astrophysical processes are "broadened," or spread out over a range of frequencies, even if it is a small range. So one way to create a signal that would make another civilization (us) stand up and say, "Hey, are you people-like?" is to send out a very narrow signal, spread over a very, very small range of frequencies.

Siemion and team looked for such waves. And, as the paper says, "Ultimately, experiments such as the one described here seek to firmly determine the number of other intelligent, communicative civilizations outside of Earth. However, in placing limits on the presence of intelligent life in the galaxy, we must very carefully qualify our limits with respect to the limitations of our experiment. In particular, we can offer no argument that an advanced, intelligent civilization necessarily produces narrow-band radio emission, either intentional or otherwise. Thus we are probing only a potential subset of such civilizations, where the size of the subset is difficult to estimate."

They did not detect any signals from extraterrestrial civilizations.

Combining that data with the paper's statement means that the conclusion is, essentially, "We succeeded in not finding any ETI that likes to broadcast this particular kind of radio wave and happens to have been doing it such that the radio waves would arrive at our telescopes while we were taking data."

It's a specific conclusion. It's a small answer to a small question that is part of a larger question. Small answer + small answer + small answer adds up in SETI work as it does in all science. And, as always, more research is needed.