the color of the coat they wear or the gizmos they work with. They are defined by what is in their heads and how they think.
Science is a way of thinking about the world, not how you dress or what toys you play with. Science is thinking critically about phenomena in the natural world and trying to find ways to test hypotheses, or preliminary explanations, about how the world works. As the philosopher George Santayana wrote, “Science is nothing but developed perception, interpreted intent, common sense rounded out and minutely articulated.”4 All science is about testing hypotheses and finding out their validity by further observations and experiments. Scientists generally aren’t trying to prove their hypotheses but to disprove them. As British philosopher Sir Karl Popper pointed out many years ago, it’s far easier to prove a hypothesis wrong (falsify it) than it is to prove it right (verify it). The famous example is the classic philosophical statement “All swans are white.” No number of white swans proves that statement true, but a single nonwhite swan proves it false. Indeed, there are black swans in Australia (fig. 1.1). If your hypothesis has been tested and found false, you must abandon it and move on to another explanation—perhaps one suggested by your previous failure. Popper titled one of his books Conjectures and Refutations, a nice summary of the scientific method in a single phrase.
This idea surprises a lot of people, but it is true. Strictly speaking, science is about proving ideas wrong and moving on, not proving them right. Scientists are not looking for “final truth” or proving something “absolutely true.” Scientific explanations must always be open to further scrutiny and testing; they are tentative and must be capable of being rejected. As the famous philosopher Bertrand Russell wrote, “It is not what the man of science believes that distinguishes him, but how and why he believes it. His beliefs are tentative, not dogmatic; they are based on evidence, not on authority or intuition.”5 Whether religious, political, or social, ideas that cannot be tested are not scientific; they are dogma. This immediately distinguishes science from many other areas of human thought. For example, we might say that “Zeus caused the lightning and thunder,” but this is a religious belief. It is not a testable scientific idea. Marxism and many other dogmatic worldviews also make broad statements about the world that cannot be tested but are articles of faith among the believers, so nothing would ever prove them false. When dogmatists (religious or otherwise) have their sacrosanct ideas challenged, they will not admit that the idea has been falsified. They stubbornly insist they are right, or they find some dodge to salvage at least some of their false notions.
Figure 1.1. Not all swans are white. This is the Australian black swan. (Courtesy Wikimedia Commons.)
Thus, science is very different from what most people think it is. When scientists speak to each other, they are not after “truth.” They are careful not to use the words true or fact, and strictly speaking, we don’t “prove things true.” Instead, scientists are trying to test and falsify, and test again, until an idea is well corroborated (not “proven true”). What most people would call a “fact” is an “extremely well-supported explanation.” To a scientist, the highest form of a corroborated hypothesis is a theory, a group of interrelated and well-corroborated hypotheses and observations that have received widespread acceptance because they explain so much.
Sadly, the public uses these words and concepts very differently. In everyday usage, theory means a wild speculative idea, like “theories of why JFK was assassinated.” Creationists take advantage of the confusion and exploit this meaning of the word by denigrating evolution as “just a theory.” Well, gravity is just a theory too, but the objects around you are not floating around in the air. Thanks to the germ theory of disease, we believe that bacteria and viruses are the major causes of diseases, not some sort of “ill humor” in your blood that your doctor would remove by bleeding you with leeches.
Likewise, in the public debate about scientific topics, science deniers will put down an idea they oppose (like climate change) by saying that it’s not “proven true” or “100 percent true.” Nothing in science is “proven true,” and everything has probabilities associated with it. I can’t say that I can “prove” you would die if you jumped off a twenty-story building, but I can say that it’s likely to happen with a 99 percent probability—and most nonsuicidal people will not take that less than 1 percent chance that they won’t die.
As Carl Sagan said, “Skeptical scrutiny is the means, in both science and religion, by which deep thoughts can be winnowed from deep nonsense.”6 Science is basically applied skepticism. We try to be skeptical of all ideas until they have been tested and corroborated again and again, and then we only give our provisional assent. We don’t believe in an idea; we accept it based on evidence. (Believe is a religious and cultural word, not a scientific one.) Most humans are cautious of people trying to sell them worthless junk or politicians making impractical promises or swindlers trying to con them into believing something or buying something. We all know that advertising is exaggerated or deceptive or distorted, and in many cases, it is an outright lie. We try to look for good products and avoid junk when we are shopping, and we employ the old Latin maxim caveat emptor, “let the buyer beware.” Yet many people won’t employ the same skepticism to outlandish claims about religious miracles or UFOs or Bigfoot or a wide variety of paranormal ideas that sucker people every day. Most of the ideas in this book fall within the realm of outlandish and even bizarre, but there are plenty of believers. Yet these same people are skeptical elsewhere in their lives and won’t fall for a deceptive ad on TV or the internet or a telemarketer trying to sell them something.
Scientists are humans too, and although they try to be hard-boiled skeptics, they cannot avoid falling for the traps in thinking and sometimes embrace ideas that fit what they want to believe rather than what is. As Carl Sagan wrote, “There are many hypotheses in science which are wrong. That’s perfectly all right; they’re the aperture to finding out what’s right. Science is a self-correcting process. To be accepted, new ideas must survive the most rigorous standards of evidence and scrutiny.”7 For this reason, there is an important quality control mechanism built into the fabric of science: peer review. This is very different from the internet, which is a giant cesspool of garbage and bad ideas with no fact-checking, and it is very different from partisan media outlets, which have given up reporting anything “fair and balanced” but churn out nonstop propaganda.
Scientists, on the other hand, must submit their ideas to the harsh review and scrutiny of other scientists before they can be published. Usually these reviews are anonymous, and they can be sent to any qualified scientist, including your worst critic. If your idea is rejected, you can give up, or you can try to do a better job of supporting your hypothesis and submit it again. Peer review weeds out the bad ideas in science, and after a harsh round of review before publication, and an even harsher scrutiny in the years after publication, most ideas in science that have survived many years are probably true and have passed quality control.
Peer review is particularly important in evaluating our own ideas, since we are inclined to think our own ideas are right and cannot judge them critically. As the Nobel Prize–winning Caltech physicist Richard Feynman said, “The first principle is that you must not fool yourself and you are the easiest person to fool.”8 Many scientific experiments are run by the double-blind method, in which neither the subjects of the experiments nor the investigators know what is in sample A or sample B. In a double-blind experiment, the samples are coded so that no one knows what is in each sample, and only after the experiment is over do the scientists find out whether the results agree with their expectations or not. As Feynman said, “It doesn’t matter how beautiful your theory is, it doesn’t matter how smart you are. If it doesn’t agree with experiment, it’s wrong.”9 Ultimately, bad ideas are weeded out, and good ones survive to become the established framework of scientific theory that all scientists
