Tax day is April 18 this year. It's an annual event greeted with groans and occasionally panic across the country. "In this world nothing can be said to be certain, except death and taxes," Benjamin Franklin wrote in a 1789 letter.
Franklin wasn't lamenting having to pay his taxes. Instead, prior to that passage, Franklin expressed his concerns about the durability of the Constitution, and it makes sense that a scientist would harbor a sense of uncertainty about the document that would guide the major political experiment that was the fledgling republic.
In the sciences, a sure thing is elusive; uncertainty is the norm.
Scientific research is an iterative process. A hypothesis is formulated; research is undertaken; evidence is gathered; results are analyzed. Uncertainty doesn't mean a lack of understanding so much as it provides opportunities for further study.
As the Union of Concerned Scientists, a scientific advocacy organization, explains in an article about climate change: "To most of us, uncertainty means not knowing. To scientists, however, uncertainty is how well something is known."
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Scientists express their degree of certainty by presenting qualified conclusions based on their results, explaining potential limitations of their methodology and shining a light on potential sources of error for the sake of transparency. Scientific findings have to be reproducible to be reliable, but even that isn't exactly proof of a theory.
"The very expression ‘scientifically proven' is a contradiction in terms," physicist Carlo Rovelli said in a 2012 interview. "There is nothing that is scientifically proven."
Certainty is described in terms of confidence, and scientists have their own terminology for explaining their level of assurance in their findings. Take the 2012 discovery of the Higgs boson, an elementary particle in the Standard Model of physics first theorized in the 1960s, also known as the "god particle."
"We observe in our data clear signs of a new particle, at the level of five sigma, in the mass region around 126 GeV," Fabiola Gianotti, spokeswoman for the Atlas experiment at the LHC, said upon the discovery of the Higgs.
Five sigma is the confidence level required by particle physicists to claim a new discovery, and represents a 1-in-3.5 million probability that the observation is the result of random chance rather than a real effect.
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Certainty and probability are related but not necessarily interchangeable terms. Certainty deals with confidence surrounding the facts; probability concerns the likelihood of a particular outcome.
The Intergovernmental Panel on Climate Change (IPCC), for example, uses different terminology to distinguish between facts and forecasts. A statement with a nine out of 10 chance of being true would be described as "very high confidence," while an outcome with a 90 percent chance of occurring is "very likely."
Improbable or outlier events don't necessarily reflect a lack of certainty on the part of the scientists who study them.
To provide a handful of scenarios: There is a 12 percent chance in the next decade that Earth will be hit by a megaflare that causes trillions of dollars in damage.
The Cascadia fault line in the Pacific Northwest has a one-in-three chance of experiencing a major catastrophic earthquake in the next 50 years.
The probability of a caldera-forming eruption at Yellowstone stands around 1 in 730,000 or 0.00014 percent.
The degree of certainty in each of these cases depends on the methodology used and measurements taken by the scientists responsible for the forecasts.
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The sciences may be full of uncertainty, but unfortunately for tax filers, math is absolute. Be sure to file your taxes April 18!
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