1. Science is awesome.
The products of science are impressive, powerful, and dangerous. Scientific knowledge and understanding inspires technology. It gives us the World Wide Web, smartphones, supercomputers, spacecraft, robots, and weapons of mass destruction. Our lives are easier and more connected than those of our ancestors. Progress costs us much in privacy, security, and freedom. Medical innovations such as vaccines, antibiotics, pain-killers, contraceptives, anti-depressants, MRIs and mammograms extend our lives while making us more dependent upon them as nostrums and panaceas. Genetic engineering in plants and animals is remarkable but provokes neophobia and paranoia. What if its ubiquitous use threatens natural resource sustainability? Science enables people to do immoral things. Drones and clones are scary.
2. Science defies common-sense and challenges established world-views.
"Seeing is believing" but collective experience tells us not to believe everything we see. Common-sense says that whatever occurs happens for a reason, but physicists say otherwise. Modern physics finds that some events are uncaused when we can't help but think that every thing and every event has a cause. Subatomic particles can come into existence and perish by virtue of spontaneous energy fluctuations in a vacuum. Even the entire universe whose present form emerged in a cosmic explosion 13.7 billion years ago may not have had an ultimate or first cause. Some scientific models continue to suggest an eternal, cyclical, or oscillatory universe rather than a single creation event. Cosmologists say that the universe doesn't have a center and doesn't have an edge.
Science progresses by upsetting and superseding old world-views. Scholars in ancient and medieval times believed Earth was the fixed center of the cosmos, that there are only as many basic, unchanging kinds of organisms as God separately created, and that there are just four elements which comprise everything: earth, air, fire, water. But the history of science is a tale of numerous rejections of old beliefs. For almost 2000 years physicians practiced blood-letting, believing that good health required the delicate balance of bodily fluids: blood, yellow bile, phlegm, and black bile. Empirical observations revealed that bloodletting killed more people than it healed. Nobody still thinks disease is caused by angry gods or evil demons. We now treat mental illness without trepanations or exorcisms.
3. Scientists make contrary and even contradictory claims.
Researchers report that recent studies show low carbohydrate diets are healthier than low fat diets. If true, this contradicts established scientific findings and subsequent recommendations to reduce fats more than carbohydrates in one’s diet. They’ve reversed recommendations on salt and cholesterol intake as well. What are we supposed to believe when authorities change their minds?
Mainstream reports of science often distort the significance of some research, especially conclusions based on small samples or low quality, preliminary studies. Bad science makes headlines in part due to the politics of science itself. Often a specialist in one discipline, say, a cardiothoracic surgeon with a popular television show, becomes an authority on nutrition for the general public. Beware the authoritative non-expert. Physicians get the science wrong. Some doctors are scientists but most are not.
A “Referendum on Alcohol in the Practice of Medicine” prepared for the U.S. Congress in 1922 revealed that over 50% of physicians surveyed continued to prescribe “spiritus fermenti” or whisky, wine and beer as a necessary therapeutic agent for treating influenza, pneumonia, heart failure, shock, anemia, diabetes, cancer, asthma, dyspepsia, snakebite, lactation problems, and old age. So far no randomized controlled clinical trial (RCT) on even moderate alcohol consumption and mortality outcomes has been done. The medicinal benefits of alcohol have yet to be found. We must fact-check all sources of information, but when is the last time you looked at scientific literature?
4. Science is hard to do and assess, it is especially difficult for non-experts to understand.
The general public cannot easily check whether what scientist's assert is true. Scientists study complex, difficult to observe phenomena. They do so by drawing finer distinctions than common-sense and ordinary language permits. Without advanced training or at least a college course in inductive reasoning or statistics, most people who acquire a scientific conclusion from non-expert, second-hand sources cannot process it competently. We like stories not statistics. Ordinary people trust personal experiences and testimony but scientists rank types of evidence differently. In science any hypothesis is incredible if it cannot be falsified by experiment (i.e. tested with the possibility of being rejected).
Use science databases such as NCBI or PubMed. Do an online search with terms that narrow the field to higher quality sources, e.g. “low carbohydrate diet versus low fat diet meta-analysis randomized controlled”.
Here is rough guide to spotting bad science. Also, Trish Greenhalgh (1997) has a nice series of very short must read articles on "How To Read a Paper” that explain how to interpret different kinds of research papers.
5. Scientists doubt or reject what most people believe.
Most Americans believe in supernaturals (Harris Poll, 2013). People think that supernaturals explain events, but scientists don’t. Angels visit, ghosts haunt, devils make us sin, gods make and destroy worlds. For scientists, and methodological naturalists in general, supernaturals are superfluous. This is why so many are atheists (Pew Research, 2009). Science abjures faith and demands testable evidence. Its predictions are dire. All of this alienates scientists from non-scientists.
When beliefs are threatened by new facts, people grasp onto unfalsifiable justifications. Motivated reasoning and confirmation bias affects negatively our ability to evaluate scientific evidence. So when scientists tell us what we don’t want to hear we are dubious. We just don’t want to listen to people who are so negative all of the time.