Not so fast on alien theories
It’s tempting to think we’re not alone. But we can’t jump to conclusions without evidence, writes Duncan Steel.
The opinion piece by Sarah Cruddas (The truth about aliens is out there, Jan 20) is a mishmash of half-truths and falsities simply repeating various preconceptions and misconceptions. This is not science.
For example, the quote stating that ‘‘The mathematical probability of life forms existing beyond our planet is overwhelming’’ is nonsense: no matter how many stars and planets are counted, if you multiply that huge number by zero then the answer you get is . . . well, zero.
It’s easy to get sucked in, not recognising the fallacies repeated. For example: the notion that, because life exists here, it must be common in the universe is invalid. Simply put, if life hadn’t developed on Earth and evolved into thinking beings able to ponder whether extraterrestrial life exists, then the question would never be asked.
That is, the framing of the question necessitates our existence. This is termed a conditional probability.
A similar logical trap is trying to calculate the probability of one of the elephants in Berlin Zoo being killed by the first bomb dropped on the city in World War II. We wouldn’t pose that question unless that lamentable event took place, and so our question is conditional on its occurrence.
Cruddas mentions the Drake
Equation. True, in recent decades we have narrowed down some of the input parameters (such as how many stars have orbiting planets, and what fraction of them have the right conditions for life), but if any parameter turns out to be zero, then the overall result is zero.
That is, we would deduce there to be no technological civilisations in the Milky Way, apart from humanity. That might be the case, or it might not. Jumping to conclusions at this stage of our ignorance doesn’t help.
A useful concept not mentioned is the Fermi Paradox, simply stated as: ‘‘So where are they?’’ It seems unlikely that Earth is home to the mostadvanced technological civilisation, if indeed there are others, given the solar system is only one-third the universe’s age.
That is, life on planets formed much earlier would have a headstart on us, and we might anticipate that our galaxy would be teeming with aliens zipping around in spaceships much more advanced than our own. So where are they?
This question is topical because it has just been announced that grains found in a meteorite that fell in Australia in 1969 are more than seven billion years old, whereas the solar system dates to just 4.53b; this is evidence of planetary systems existing billions of years before the Sun and its planets (including Earth) condensed from clouds of interstellar gas and dust. We are relative newbies in the Milky Way.
Does extraterrestrial life exist, then? The only answer I can give is: maybe. There is no definitive information on which to base a proper assessment.
Anyone imagining otherwise has jumped the gun. Yes, new data accumulates every year, but as of yet we simply do not have the information necessary for a proper prognosis.
There are two broad ways through which we might answer the question of whether alien life exists, or at least is likely:
■ Obtain substantive evidence of it, such as a structured radio signal; or
■ Develop a full understanding of how life originated and evolved on Earth.
Most people recognise the first method, often portrayed in TV documentaries and sci-fi movies; but avenue B largely escapes notice. If we knew how life began here, then we could say something useful about the chances of it occurring elsewhere, on some distant planet or remote comet.
Until then, we work in the dark. There are myriad things yet to be uncovered and understood, making scientific research hugely exciting.
But then I would say that, wouldn’t I?
The notion that, because life exists here, it must be common in the universe is invalid.