A fair amount of pseudo-science begins as blue-sky, basic scientific hypotheses and experiments. Hypotheses can challenge basic accepted notions, or begin with them, and may yet somehow go off the rails. How does this happen, and at what point do scientific inquiries become obsessive or pathological? Consider N-rays.
Shortly after the discovery of X-rays, Prosper-René Blondlot was conducting experiments on electromagnetic radiation, specifically attempting to observe polarized X-rays, when he noticed apparently changes in the brightness of photographed sparks in an x-ray beam. Unable to account for the changed brightness according to current knowledge about X-rays, he proposed that a new form of radiation was being observed which he called N-rays. Using “detectors” made of a dim phosphorescent material, researchers around the world began perceiving N-rays, concluding similarly that unexpected increases in luminosity that they perceived were corroboration of the new form of radiation. Within a few years, over 300 papers were published on the subject. When some rather notable scientists, including Lord Kelvin, failed to be able to reproduce the results, doubt about the existence of N-rays began to grow. Only when Robert Wood visited Blondlot’s lab, and surreptitiously replaced a part of the apparatus and test materials during the course of the experiment, and Blondlot noted no change in his detection of N-rays, did it become clear that what was being perceived did not exist. It was the hopeful observation of a researcher who, like several hundred others around the globe, was seeing something he wanted to see. He lacked equipoise: he had become vested in a certain result.
Another more recent example is the Pons and Fleischmann “cold fusion” debacle. These scientists working at the University of Utah were attempting to create “cold fusion” in a crystal lattice, an attempted shortcut to the high-energy fusion that has only so far been achieved in H-bombs and Tokomak and inertial confinement reactors (both high-energy), to a limited degree. Having observed some rather remarkable heat and supposed neutron radiation from their setup, they rushed to tell the world. Part of their rush may have apparently been to achieve priority in getting a patent on their process, but instead of going through the usual peer-review procedure, they convened a press conference to announce they had achieved fusion at room temperature. Their science was based on a a falsifiable hypothesis, and there are theoretically some conditions under which low energy nuclear reactions could occur, but their experiment was not the success they had claimed. Within a few weeks, labs around the world were announcing their failures to produce anything like the temperatures that Pons and Fleischmann reported, and no neutron radiation, which would have been a necessary fingerprint of a fusion reaction. Some interesting chemistry may have been occurring, but not fusion. The negative results of other labs falsified the science, just as Wood’s fiddling with the apparatus did in the N-rays case, and pursuit thereafter, at least of the Pons and Fleischmann process for cold fusion, became pseudoscientific (as indeed, people are still attempting to reproduce their result, though not with any willing, respectable funders).
Recently, there have been some rather breathless accounts of the discovery of a new form of propulsion that appears to violate the Newtonian law of conservation of momentum. It uses no propellant, and yet has been reported to produce thrust via creation of microwaves in a certain-shaped cavity. The EM-drive was first developed by British scientist Roger Shawyer, versions of which have been tested by labs in China, the US (at the Johnson Space Center, NASA) and now Germany. So far, in each of the labs conducting tests, force has been observed at varying levels, and in each of the slightly varying experimental setups. So far, no one can account for the force measured, and even while all labs are measuring force while trying to eliminate experimental artifacts that might create false positives, no negative or falsifying experiments have yet shown EM-drives to be totally fruitless. Something interesting may be happening, and no doubt still more labs will attempt to replicate force, measure possible thrust, and may even try to create working prototypes, unless someone falsifies the hypothesis. This can be done by a) locating the experimental artifact that is causing measurements of force where there is no real thrust, or b) replicating the experiment and measuring no force (perhaps having eliminated somehow whatever effects may be causing false positive results).
Has the EM-drive slipped over the line yet toward pseudo-science? Not yet. However, with each new experiment, the apparent thrust measured appears to be dwindling, which may be because indeed there is something going on that causes false positive measurements. There is certainly reason to remain skeptical, especially since the proposed propulsion system appears to violate a basic, well-accepted physical law. Of course, many of us hope for cheaper, better, more efficient means to achieve long distance space travel, and the EM-drive may lead to such technology, but it may well not and we should pursue any and all theoretically feasible means besides the EM-drive, considering it could well turn out to be just like N-rays or cold fusion.