Have you ever seen a red raven?
Most likely not. Is that because all ravens are black?
Now you are probably hesitating with the answer.
By saying yes, you infer that all present, past and future ravens in the world and the rest of the universe are, were and will be black. To prove this, all ravens would have to be monitored over space and time.
Even if we limit the question to the earth and the present: it will still not be possible to determine, based on observation alone, whether every single raven is black.
The statement “All ravens are black” can thus not be confirmed 100 per cent.
Big surprise in Australia
Experience to date has taught us that all ravens are black and that there are probably no red ones. But it would only take the discovery of one to refute the above statement. The existence of the red raven cannot be ruled out – after all, it could exist.
This is exactly what happened in the past with another bird: the mute swan (scientific name: Cygnus olor). Originally, the white swan was only found in north-eastern Europe and parts of Asia. Kept as an ornamental bird in royal parks, it later spread to Central and Western Europe.
For this reason, the statement “All swans are white” was long regarded as an irrefutable fact in Europe. This changed abruptly in 1697 when Dutch sailors discovered the first black swan in Western Australia.
Today, the black swan (scientific name: Cygnus atratus) is kept as an ornamental bird in Europe. Some black swans have been released or have escaped and therefore live in the wild, for example around Lake Constance.
Ensuring safety and generating knowledge
Why the sudden interest in ornithology? What links these birds with the disposal of radioactive waste is the very essence of science, i.e. its prerequisites and limitations. “What can I know?”: for Immanuel Kant, this was one of philosophy’s fundamental questions. So how do you arrive at findings and how reliable are they?
Fundamental questions such as these are also of key importance to Nagra because planning and constructing the deep geological repository for radioactive waste is based on science. Nagra has thoroughly investigated the geology of Switzerland to find the safest site for the repository.
But how reliable are all these findings based on decades of research? Nagra was founded in 1972. In hindsight, we can see that some of our presumptions and assumptions turned out to be wrong.
In 1983, for example, Nagra came across something unexpected while drilling a deep borehole in Weiach in the Zürcher Unterland (the northern part of Canton Zürich) – a proverbial black swan. Instead of encountering the crystalline bedrock at a depth of 1,000 metres as expected, other deposits were found. These sediments belong to the so-called Permo-Carboniferous Trough.
Knowledge is only ever provisional
The discovery of black swans in the 17th century later led to the black swan becoming a metaphor. Black swans now stand for something considered inconceivable or downright impossible – which then occurs anyway.
In science, a black swan leads to a – usually abrupt – new insight, for example, that not all swans are white after all. In other words, the black swan teaches us that knowledge is only ever provisional. Something only holds true until the opposite is demonstrated.
In other words, black swans exist because, through observation alone, it cannot be proven that all swans are white. This is the central difficulty of so-called induction in empirical research, which is based on observation and experience.
Induction means that one infers, from observing individual swans, that they must all be white. Previous experience may support this conclusion, but whether a general statement such as “All swans are white” stands firm cannot be conclusively verified.
Blind to nasty surprises
In his book “The Black Swan: The Impact of the Highly Improbable”, Nassim Nicholas Taleb cites 9/11 as an example. For the maths professor and former stock market trader, a black swan has three characteristics.
First, the black swan is a statistical outlier that lies far beyond the expected. Second, it has a massive impact. Third, explanations for its occurrence or appearance are constructed in retrospect in an attempt to make it appear explicable and predictable.
Taleb speaks of a “blind spot to randomness”, in other words, to major deviations from what we have come to expect based on experience. Precisely because black swans appear unexpectedly, their impact is exacerbated. Or the fact that no one foresees them is what causes them in the first place. In short, they are a nasty surprise.
“Isn’t it amazing that an event can occur precisely because nobody foresees it?”, he writes. If aircraft hijackings such as those carried out on 9/11 had been anticipated, bulletproof cockpit doors could have been installed, potentially averting the devastating consequences of the attacks. Or if a tsunami as destructive as the one in Japan in 2011 had been expected, the nuclear power plants might never have been constructed right next to the ocean.
“What we know can’t really hurt us,” writes Taleb. However, as black swans cannot be predicted, “we have to be prepared for their existence instead of being presumptuous enough to try to predict them.”
According to him, the black waterfowl emerge from the gap between what we know and what we think we know. When this gap is large, a dangerous situation can arise. It is therefore wrong to treat the outlier, the extreme case, as an exception and sweep it under the carpet.
Assuming the worst
How does Nagra deal with black swans? It cannot dismiss their existence, either. Instead, it must try to envisage them and try not to exclude them altogether. For this reason, Nagra includes black swans into its what-if considerations. It accepts the unlikely, even the inconceivable and ultimately assumes the worst.
This could include the uncovering of the repository by glaciers from future ice ages or the formation of a fissure at a depth of around 800 metres, running right through the emplacement drifts and allowing large quantities of water to reach the radioactive waste.
Scenarios such as these have been ruled out on the basis of geological research to date. However, Nagra nevertheless treats them as black swans and takes them into account in its analyses and calculations. Its objective is to ensure that the deep geological repository remains as safe as possible for as long as possible.
“Nothing is certain but risk”: in contrast to Benjamin Franklin’s famous quote “Nothing is certain but death and taxes”, there is nothing facetious about the statement. Everything comes with a risk, therefore black swans cannot be ruled out. In acknowledgment of this truth, Nagra tries to take every risk into account, no matter how small, by including even highly unlikely scenarios in its analyses. This allows it to calculate the consequences of a possible black swan event.
Critics can provide Nagra with valuable information and draw its attention to potential blind spots – to new black swans, so to speak. However, there is a fine line between taking black swans into account because their inclusion can be justified or just because someone asserts their existence. What does this mean exactly?
Behind the maxim “Nothing is certain but risk” is a firm belief: just because something has never happened before does not mean it cannot happen. Because science cannot rule out the black swan, sceptics can claim it without having to prove it. It is like extraterrestrial life: it is impossible to exclude its existence in an infinite universe. Therefore, we can say that aliens exist without having to provide evidence.
The statement “All swans are white” has now been refuted. That is precisely why it is scientific: the statement fails in the face of observable reality, i.e. by spotting a black swan. Refutability, also known as falsification, is the criterion for something to be considered as scientific.
Statements such as “Aliens exist” or “Red ravens exist”, on the other hand, are not scientific because they cannot be falsified. The existence of such beings cannot be ruled out, so it can always be claimed without the need to provide evidence. That is unscientific. In this way, critics shield themselves from criticism.
A grain of truth – possibly
Every conspiracy narrative features a black swan. Two examples: Rather than condensation trails (contrails) of aircraft, these stripes appear because chemicals are sprayed (chemtrails) to manipulate people. Or: The USA was “really” behind the 9/11 attacks to create a pretext for the invasion of Afghanistan and Iraq.
No matter how many arguments can be held against such stories: they cannot be refuted 100 per cent. Conspiracy theorists always leave behind a residual probability, a kind of residual risk that they can invoke. They then retreat to this unassailable position, only because it cannot be refuted, and demand: “Prove to me that this is not the case!”
They simply reverse the burden of proof. It is now not up to them to demonstrate the existence of manipulative chemtrails – it is up to the doubting counterpart to prove that there are none. However, it is impossible to prove something that does not exist. It is like having to prove that you did not rob person X.
To the best of our knowledge
The statement “All swans are white” cannot be sufficiently proven even after observing millions of swans as it takes just one black swan to refute it.
The same applies to the deep geological repository for radioactive waste and the danger it could pose. “There is always a risk”: this statement is true and thus ultimately irrefutable, even though it does not really help us at all. The hazardous waste exists and requires finding the safest possible solution to dealing with it.
Immanuel Kant’s fundamental question “What can I know?” is not the only one. “What should I do?” is another important question. When handling radioactive waste, practical management and responsibility are also at stake – for example towards future generations, and to the best of our knowledge and belief.
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