Let's look at experts. Sir Isaac Newton (1642-1727) was a mathematician and scientist. Newton has to be the greatest and most influential scientist who has ever lived. He laid the foundation for classical mechanics, and his genius transformed our understanding of science, particularly in the areas of physics, mathematics and astronomy. What's not widely known is that Newton spent most of his waking hours on alchemy; his experiments included trying to turn lead into gold. Though he wrote volumes on alchemy, after his death Britain's Royal Society deemed that they were "not fit to be printed."
Lord William Thomson Kelvin (1824-1907) was a Belfast-born British mathematical physicist and engineer. Kelvin's major contribution was in thermodynamics, and he is widely recognized for determining the correct value of absolute zero, approximately minus 273 degrees Celsius. In his honor, absolute temperatures are expressed in Kelvin units. Being an expert in one field doesn't spare one from being an arrogant amateur in others. Based on his knowledge of heat dissipation, Kelvin criticized geologists of his day and claimed that Earth was between 20 million and 100 million years old. Kelvin also said that "X-rays will prove to be a hoax," but he changed his mind after he experienced an X-ray of his own hand. Kelvin also predicted, "I can state flatly that heavier-than-air flying machines are impossible."
Linus Pauling (1901-94) was one of the most influential chemists in history. He was one of the founders of the field of quantum chemistry and is often called the father of molecular biology. Pauling won the Nobel Prize in chemistry in 1954 and the Nobel Peace Prize in 1962, making him the only person awarded two unshared Nobel Prizes. Later, he was awarded the International Lenin Prize for Strengthening Peace Among Peoples by the Soviet Union. Many of Pauling's colleagues who admired his scholarly work saw him as a naive spokesman for Soviet communism.
Despite his genius in science, Pauling peddled fringe ideas. In the 1970 edition of his book "Vitamin C and the Common Cold," he said that taking 1,000 milligrams of vitamin C daily will reduce the incidence of colds by 45 percent. In the book's 1976 revision, retitled "Vitamin C, the Common Cold and the Flu," he recommended higher vitamin C dosages. In his third revision, "Vitamin C and Cancer" (1979), Pauling claimed that high doses of vitamin C may also be effective against cancer. In another book, "How to Live Longer and Feel Better" (1986), Pauling argued that megadoses of vitamins, such as the 12,000 to 40,000 milligrams he took daily, "can increase your enjoyment of life and can help in controlling heart disease, cancer, and other diseases and in slowing down the process of aging." There's absolutely no research that backs up any of Pauling's vitamin C claims.
The take-home lesson is that experts are notoriously fallible outside of their fields of endeavor -- and especially so when making predictions. There tends to be an inverse relationship between a predictor's level of confidence and the accuracy of his prediction. Irving Fisher, a distinguished Yale University economics professor in 1929, predicted, "Stocks have reached what looks like a permanently high plateau." Three days later, the stock market crashed. In 1954, Dr. W.C. Heuper of the National Cancer Institute said, "If excessive smoking actually plays a role in the production of lung cancer, it seems to be a minor one." Thomas Watson, chairman of IBM, in 1943 allegedly said, "I think there is a world market for maybe five computers." "(Research on the atomic bomb) is the biggest fool thing we have ever done. The bomb will never go off, and I speak as an expert in explosives." That was Adm. William Leahy's prediction in 1945.
The bottom line is that the fact that a person has academic degrees, honors and status is no reason for us to abandon our tools of critical thinking.