The search for life

Some 540 million years ago, diverse life forms suddenly began to emerge from the muddy ocean floors of planet Earth. This period is known as the Cambrian Explosion, and these aquatic critters are our ancient ancestors.

All complex life on Earth evolved from these underwater creatures. Scientists believe all it took was an ever-so-slight increase in ocean oxygen levels above a certain threshold.

We are now be in the midst of an explosion of artificial intelligence (AI). In the past few years, a burst of incredibly capable AI programs have showcased the rapid progress we’ve made in machine learning.

AI is now used in virtually all areas of science to help researchers with routine classification tasks. It’s also helping radio astronomers broaden the search for extraterrestrial life, and results so far have been promising.

Scientists searching for evidence of intelligent life beyond Earth have built an AI system that beats classical algorithms in signal detection tasks. It was trained to search through data from radio telescopes for signals that couldn’t be generated by natural astrophysical processes.

When it was fed a previously studied dataset, it discovered eight signals of interest the classic algorithm missed. To be clear, these signals are probably not from extraterrestrial intelligence, and are more likely rare cases of radio interference.

The main question with the SETI project is would it be able to recognise a signal from an alien species anyway? As humans we are biased to thinking life as being carbon based, probably with arms, legs, a head on top and speaking with an American accent.

However, when we look at the available elements, life could conceivably be based on any element which has the capacity to join with others in a great number of ways. Elements like hydrogen, oxygen, nitrogen, phosphorous and sulphur spring to mind. Should we come across a life-form based on any of these it is highly unlikely that we would be able to understand their thought processes, much less communicate with them.

Nonetheless, findings published today in Nature Astronomy highlight how AI techniques are sure to play a continued role in the search for extraterrestrial intelligence. AI-based systems are being increasingly used to classify signals found in massive amounts of radio data, helping speed-up the search for alien life.

AI algorithms do not “understand” or “think”. They do excel at pattern recognition, and have proven exceedingly useful for tasks such as classification – but they don’t have the ability to problem solve. They only do the specific tasks they were trained to do.

So although the idea of an AI detecting extraterrestrial intelligence sounds like the plot of an exciting science fiction novel, both terms are flawed: AI programs are not intelligent, and searches for extraterrestrial intelligence can’t find direct evidence of intelligence.

The AI is programmed to look for ‘signatures’ denoting a logical sequence in a set of radio signals. Technosignature searches have been likened to looking for a needle in a cosmic haystack. Radio telescopes produce huge volumes of data, and in it are huge amounts of interference from sources such as phones, WiFi and satellites. Search algorithms need to be able to sift out real technosignatures from “false positives”, and do so quickly.

Of these, eight signals have the characteristics of technosignatures, and couldn’t be attributed to radio interference. To try and verify these signals, SETI scientists went back to the telescope to re-observe all eight signals of interest. Unfortunately, they were not able to re-detect any of them in our follow-up observations. This would be logical if they were indeed alien communication; however, the SETI people have been fooled before by extraneous radio sources on Earth.

If astronomers do manage to detect a technosignature that can’t be explained away as interference, it would strongly suggest humans aren’t the sole creators of technology within the Galaxy. This would be one of the most profound discoveries imaginable.

At the same time, if we detect nothing, that doesn’t necessarily mean we’re the only technologically-capable “intelligent” species around. A non-detection could also mean we haven’t looked for the right type of signals, or our telescopes aren’t yet sensitive enough to detect faint transmissions from distant exoplanets.

Either way, we can’t reply to any signal because of the distances involved – it would take many years for our response to reach the original transmitter. This, of course assumes that the ‘alien’ is even interested in knowing we exist at all. It seems that a lot of effort is being put into a project for which the only feasible outcome would be the knowledge of whether or not we are alone in the universe. Simple logic says we are not alone but what real difference does that make?

Scientists use four steps before coming to a conclusion: After making observations and identifying a question or problem, scientists formulate an hypothesis. Hypotheses are statements that are limited in scope and regard specific situations. An hypothesis is a proposed explanation for an observation or phenomenon. It is a prediction that can be tested through experimentation.

A scientific model is a simplified representation of a complex system or phenomenon. It is used to explain and predict the behaviour of the system or phenomenon being modelled.

Theories are frameworks of hypotheses that have been repeatedly confirmed through experiments. They’re not really proven correct per se, but they’ve never actually been proven wrong so they can’t be discarded. New discoveries usually fit into existing theories, and it’s only after one of these discoveries can’t be reconciled with it that scientists try to modify the theory. Sometimes theories become laws.

A scientific law is a statement that describes what happens in the natural world. It is a statement that is always true under certain conditions and is independent of time and place. Examples of scientific laws include the law of gravity, the laws of thermodynamics, and the laws of motion.

Intelligent aliens have so far not made it to the hypothesis stage.