Short answers, pulled from the story.
Pseudoscience consists of statements, beliefs, or practices that claim to be scientific but are inherently incompatible with the scientific method. Key characteristics include unfalsifiable claims, reliance on confirmation bias, lack of openness to expert evaluation, and continued adherence after experimental discrediting.
James Pettit Andrews used the term in 1796 in reference to alchemy, making that one of the earliest recorded uses. The French physiologist Francois Magendie applied it in 1843 to phrenology, and a formal definition appeared in an 1844 article in the Northern Journal of Medicine.
Karl Popper argued that falsifiability is the key criterion: a theory is scientific if there is some possible observation that could prove it wrong. He used astrology and psychoanalysis as examples of pseudoscience, and Einstein's theory of relativity as an example of science, because relativity made a risky, testable prediction about light bending near the Sun.
Pseudoscientific health claims can lead people to forgo effective medical treatments, resulting in illness and death. Andrew Wakefield's retracted study linking vaccines to autism fuelled a movement that persuaded large numbers of parents not to vaccinate their children. Robert O. Young was sentenced to three years in jail in 2017 for promoting an alkaline diet as medicine without a licence.
The U.S. National Science Foundation reported that pseudoscientific beliefs became more widespread during the 1990s, peaked around 2001, and decreased only slightly since. Surveys indicate about a third of adult Americans consider astrology to be scientific.
Early-twentieth-century eugenic pseudoscience directly influenced public policy, including the Immigration Act of 1924 in the United States, which sought to restrict immigration from Asia and parts of Europe. The journal Nature has published multiple editorials warning researchers that extremists seek to misuse population genetics and ancient DNA research to support racial hierarchies.