The term “fringe science” is often used to refer to ideas and discussions that adapt the trappings of science but that, in one sense or another, don’t deserve it. Sometimes the term “fringe science” is meant to be kinder than “pseudoscience.” The implication is that a “fringe” scientist is making a rational effort at doing science but failing, whereas a “pseudoscientist” is either irrational, or knowingly fraudulent.
The difference between fringe and mainstream:
How these distinctions are to be drawn is of course often disputed. One point to keep in mind is that there is much that is fringe that was once quite mainstream. Astrology and alchemy were once taken very seriously indeed by some of the greatest scientific minds. Alchemy — the search for occult properties in matter, which often carried with it the self-assigned task of turning base metals into gold — fascinated no less of a scientist than Isaac Newton.
The difference between mainstream and fringe may be, then, that the mainstream keeps moving. The fringe science of any time is something that the mainstream has left behind.
Strange New Worlds:
A more contemporary example of mainstream science becoming fringe is eugenics, the idea that the human species can be improved and its problems solved by properly re-arranging the institutions relating to reproduction. It took a world war to consign that bad idea to the past or, at least, to the fringe.