One of the biggest flags of someone talking nonsense is when they claim to have discovered something revolutionary that no one else has found before. Of course, every new thing has to be discovered at some point, but it’s always worth asking yourself whether the person who found it was who you would expect.
For example, many crackpots will claim to have discovered a revolutionary new scientific theory, in spite of having little or no training as a scientist. This doesn’t mean that they might not have an insight, but it sure is a serious flag. In any given field of science, many scientists are spending much of their lives (more than the 40 hours a week that they nominally work, in fact) thinking about their subject. They certainly can’t have every possible insight or find every useful way of looking at the universe, but with all of that time, odds are in favor of any major discoveries coming from that community. So when the revolutionary discovery comes from someone outside the field, be wary.
It’s also worth remember that most scientific and engineering breakthroughs really aren’t revolutionary. If you think carefully about it, most things are incremental: small steps forward all add up to major progress, but it isn’t just one person or team in one fell swoop that makes the advancement. It’s a community of people over a long period of time. And even when there’s an apparent breakthrough, it’s often been anticipated by other teams. Usually, other teams were competing for the same objective. Most major ideas in science or in technology come out of their eras when people were thinking about certain things that led them to those ideas. It’s seldom just one person who has the entire idea by themselves.
For example, Newton may have invented the Calculus, but so did Leibniz, it appears. Newton’s laws of motion were distinctly discussed in Galileo’s work, although perhaps less clearly and certainly with less result. Newton’s law of universal gravitation was being considered by other contemporaries like Hooke, Wren, and Halley, although they couldn’t show that it yielded the right planetary motion. Most parts of Einstein’s theory of Special Relativity were being toss around by other physicists before he published. (Einstein himself was not an outsider, either. He was a patent-clerk, but he was also a physicist who simply couldn’t find another job at the time.)
So when someone claims to have discovered something revolutionary, be skeptical. Be skeptical when it’s an abstract discovery that asks for nothing from you — apart from you attention — and be extra skeptical if they want money or something else.