People tend to look at “chance” with a mixture of excitement and apprehension. By “chance” we mean events that happen unpredictably, with no traceable cause, and certainly outside of our control. We use various words to refer to such situations: coincidence, luck, serendipity, providence, though the latter has a somewhat different meaning, associated with divine involvement, perhaps even a direct and specific action. Chance brings surprise, thus our excitement, but also apprehension, for we lose the ability to plan, prepare, and control at least some aspects of our lives.
In science, “chance” is referred to as “randomness” and is only described by probabilities. There are countless phenomena in nature that have some kind of randomness attached to them, ranging from the truly random, such as quantum effects, to quasi-random, such chaotic effects that start as predictable phenomena and quickly become totally erratic. And the fact that our world has some inherent unpredictability built into it raises a number of philosophical and even theological questions that are being discussed nowadays.
Two weeks ago, I took part in a conference in the US on ‘Randomness and (Divine) Providence’, a multi-faceted exploration and discussion among scientists, philosophers, and theologians from the three Abrahamic traditions. Scholars from 14 countries presented examples and ideas ranging from cosmic and biological phenomena to free will and divine providence (special divine action).
By chance (again), just as I was presenting one of the main examples of cosmic luck, namely the asteroid that “happened” to strike Earth 66 million years ago, leading to the extinction of the dinosaurs and paving the way for the emergence of primates and humans, the BBC was broadcasting a documentary titled The Day The Dinosaurs Died. It insisted that if the asteroid had hit in another place on our planet or at a different time, the dinosaurs would not have been exterminated — and we would not be here.
It’s not so simple. Once we fully understand the idea of randomness and the probability associated with any such event, a different conception of chance — and of history — emerges. It is true that the big asteroid that hit Earth (just off of the Mexican Yucatan peninsula) some 66 million years ago was a historic event. The blast it produced in the shallow sea was the equivalent of 10 billion Hiroshima-type atom bombs or 100 trillion tons of TNT; it released 10,000 billion tons of carbon dioxide (and even larger amounts of other matter), blocking sunlight for months and producing a cold and dead world, thus starving the dinosaurs to death. It was a sudden event by cosmic and geological scales, but a momentous one by all measures.
Many people often cite this event as an example of total randomness and chaos in the world, questioning the idea of a divine plan. Asteroids hit planets randomly, they say, the chance of us emerging out of that chaos is not only minuscule, it could not be seen as an inevitable outcome of cosmic or planetary history.
Very low probabilities
It’s not quite like that. Having studied the sizes and ages of craters on Earth, the Moon, and Mars, we now know the probabilities and timescales of all such strikes. In particular, 10km size asteroids strike every 100 million years or so, one kilometre meteoroids hit every million years or so, 100-metre rocks arrive at earth every 1,000 years or so, and so on. Even random events follow probabilistic and statistical laws, and this applies to numerous chancy phenomena, from everyday life to astronomy.
To state things more clearly, Earth was bound to be hit by a large asteroid, within a hundred million years or so. The probability of a dinosaur-exterminating asteroid hitting Earth during the last 300 million years was more than 99 per cent. Humans and other highly evolved creatures might not have existed in 2017, but intelligent and conscious creatures would have appeared sooner or later, since evolution was unfolding in full glory.
This question of the randomness of planetary history interests us humans personally but is also relevant to the search for life on other planets, especially the Earth-size ones that we have been discovering around other stars: can we make predictions about the possibility of life (primitive or advanced) existing there, or is it all random and subject to the rocks that happened to hit them at some point in their history? The short answer is: we can make predictions on a statistical basis but not for any individual case.
The point to take away from this story is that randomness is not totally lawless and forbidding of any prediction. Life is fragile, but it is also stubborn; once it appears somewhere, it will find niches of survival, and it will evolve. The great question is not whether asteroids, dinosaurs, and humans were random events, but rather whether life was pre-destined to appear on some planet somewhere and whether that emergence follows some law.
There’s still much to be learnt about the history of the cosmos, life, and humans. Scientists, philosophers, and theologians will be busy unpacking the knowledge we continue to gain for a long time.
Nidhal Guessoum is a professor of physics and astronomy at the American University of Sharjah. Twitter: @NidhalGuessoum.