“Be careful. People like to be told what they already know. Remember that. They get uncomfortable when you tell them new things. New things…well, new things aren’t what they expect. They like to know that, say, a dog will bite a man. That is what dogs do. They don’t want to know that man bites a dog, because the world is not supposed to happen like that. In short, what people think they want is news, but what they really crave is olds…Not news but olds, telling people that what they think they already know is true.” –Terry Pratchett
We all like to think that our opinions are the result of years of hard-earned accumulation of knowledge. That we’ve gone and aggregated all of the relevant facts on a particular issue, put them together in the most sensible way, and that’s how we’ve arrived at our picture of the world.
But, of course, that isn’t the way we work at all.
Known as confirmation bias, it’s the very human tendency to, once we’ve formed an opinion, place our faith in the new evidence that appears to support that position, but to look for holes in the evidence that undermines or disagrees with that opinion.
In other words, changing our minds — especially once we’ve made our minds up — is extraordinarily difficult. The way we often deal with this, in the case of a divisive issue, is to think that the other side on an issue is (any combination of) misinformed, ignorant, foolish, or conspiring against the truth. And we often miss no opportunity to present them (and their position) as inferior to our own.
When was the last time you saw someone who held a passionate position on one side or another of a divisive issue actually change their mind and switch to the other side in the face of overwhelming evidence? It doesn’t happen very frequently, does it?
You may not see it very frequently in your own life, in politics, or most places that you look, but it happens all the time in science. Not for everyone, of course, but science is one of the only places where you’ll see a vast majority of scientific experts in their field change their mind on an issue based on the evidence that comes in.
When a uniform-temperature, all-sky microwave radiation background was discovered in the 1960s by Penzias and Wilson (above), it provided overwhelming scientific evidence supporting the Big Bang picture of the Universe, and disfavoring alternative explanations such as the Steady State theory. A few notable exceptions held out, but modern cosmology simply does not make sense without the Big Bang, and this was the observation that sealed it.
Same deal with evolution. Without it, modern biology — including genetics, DNA, and modern medicine — makes no sense. Evolution was an amazing idea that came in multiple variants for a time, but when the archaeological evidence of transitional fossils started pouring in, it became clear that all living things on the planet were descended from previous generations of living things dating back at least hundreds of millions of years. (We know that’s longer, now.) Even transitional forms for organisms like whales and dolphins exist, and when this type of evidence started rolling in, even the most skeptical of competent scientists started changing their minds.
And in a very notable recent example, climate science skeptics such as Richard Muller, above, are overwhelmingly concluding that there is a link between the observed rising temperatures of the Earth and the effects of human activity, once again in the face of overwhelming scientific evidence. As always, there are holdouts, but that does not change the scientific facts or conclusions.
My favorite example, though, of a scientist who held strong convictions on an issue, but changed their mind, dates back more than 400 years!
Towards the end of the 16th Century, after the death of Tycho Brahe, Johannes Kepler, pictured above, was — perhaps along with Galileo — the foremost astronomer in all of Europe. Much like Galileo, Kepler was intimately familiar with the work of Copernicus, and recognized how beautiful the possibility of a heliocentric Universe was.
After all, it could explain the retrograde motion of the planets — how some planets appeared to reverse direction with respect to the fixed stars — in their motion from night-to-night!
Instead of a stationary Earth, where the planets orbit the Earth in a superposition of circular orbits, occasionally reversing course and appearing to move backwards, the heliocentric model had the outer planets (Mars, Jupiter, Saturn, etc.) move backwards because the Earth, in its faster orbit around the Sun, overtook the outer planets in their position! (Mars, for those of you astutely watching it, is finishing up its retrograde motion as I write this!)
This is nearly a hundred years before Newton’s gravity, so there was the great question of how these orbits came to be. And Kepler’s idea was nothing short of genius. Sheer, unbridled, and beautiful genius.
Envisioning the six planets as being supported by the five Platonic solids with spheres inscribed/circumscribed upon them, the orbits would be defined by the circumferences of these spheres. It was a beautiful idea, with very explicit predictions for the ratios of the scales of the planetary orbits. Because there are only five Platonic solids and were only (at the time) six planets, this scheme was beautiful, compelling, and created an incredible buzz amongst scholars.
But unlike Galileo, Kepler had access to the finest data in the world: the observations of his predecessor, Tycho Brahe. And the data simply did not agree with Kepler’s theory. The orbits were all wrong.
Not by that much, mind you, but by enough that it clearly didn’t fit. At the time, there was tremendous prejudice in favor of the circle being the only acceptable shape for an orbit, but — ever the scientist — Kepler followed the data to its logical conclusion. He even rejected his beautiful Mysterium Cosmographicum, creating, instead, the model we use today.
They’re not circles, or a superposition of a number of circles at all; the orbits are ellipses! Planets move around the Sun with the Sun at one focus of an ellipse; the first of Kepler’s three laws of planetary motion!
And so Kepler was able to throw away the most beautiful idea he ever had, and in place of it, discover the way the Universe actually worked. And that’s my favorite example of defeating your own confirmation bias; from more than 400 years ago! That’s the reward of being honest with yourself, one of the most difficult things, apparently, for us, as humans, to do.
So let me ask you; what’s your favorite example, from your own life, of when you changed your mind on an issue, based on the new evidence that you learned and couldn’t ignore?