I've decided that conjecture, especially exemplified by Mach's principle, is the greatest bat-tool in a good crackpot scientist's utility belt.
Mach's principle concerns junk like: Say you are spinning and looking at the stars, and "the stars are whirling around you and your arms are pulled away from your body." The conjecture in a nutshell is that there is some physical law relating the two.
What is so great about a conjecture stated as such (Mach actually expressed it differently), is that it doesn't have to explain anything or even make specific testable claims. It doesn't even have to be right to be useful. Mach's principle can be as simple as "There is some relation between my arms pulling away, and the stars spinning around me." This sounds like pure crackpot science, but if you allow the relation between arms and stars to be very indirect and very loose, then you can find some truth in it. And it is in investigating the relationship where the value of the conjecture becomes real. In the case of Mach's principle, Einstein used it as a guiding factor in developing general relativity. A conjecture might be expressed as a puzzle, a question of "why?" or "how are these things related?"; the conjecture may even be silly, while the answer to the puzzle may be immensely important.
I believe a lot of crackpots fail by trying to provide explanations for what they don't understand. They could simply side-step the lack of understanding and provide conjectures that suggest that things are related without delving into the details of their mechanisms.
I should know not to dismiss a silly idea as worthless. The following is an idea I've mentioned before. If properly stated as a conjecture, it should allow for further development.
Preamble:
A point observer does not directly perceive distance. Distance is only extrapolated from multiple observations from different locations or times. A point observer essentially observes the universe as a 2-dimensional spherical surface around it.
The apparent size of an object (as observed visually via light) is inversely proportional to the square of the distance between object and observer. The gravitational attraction is also inversely proportional to the square of the distance. The conjecture is that the two are related according to some aspect of perception.
Or basically, it is not a coincidence that the perceived size of a mass is equal to the perceived gravitational pull. One must accept the measurement of "depth" (a third dimension that can make an object appear in size inversely proportional to the cube of the distance to the object) as unperceived or excluded from the definition of "observation".
Here's where I go back to typical crackpot science.
Time relativity suggests that time and distance might be pure fabrications of observation. They are an effect of perception, rather than an aspect of the physical nature of the universe. So it may be that the way we perceive the universe is entirely illusory. Further it may be that geometry (Euclidean geometry and possibly Cartesian coordinates) is a product of the same illusory effect.
We perceive the universe as such: Everything that is a distance of r away from me (the observer) lies on a sphere of radius r, where the area of the sphere is proportional to r2. Everything that is farther away from us exists on an imaginary sphere that is larger the farther it is from us. In a way, there is "more stuff" farther away from us. Also, the same object takes up proportionally less of a farther imaginary sphere, and since all of these spheres appear the same size to the observer (they each basically take up all of the observational area all around us), farther objects appear smaller and have less gravitational attraction.
The next step involves some complicated imagination, similar to trying to visualize extra spacial dimensions. I think that the true nature of the universe (its physical geometry, if it has one) is not at all like the observational reality, where everything can be described in terms of spheres that grow with distance. ... In conclusion, uh...
TO BE CONTINUED... ?
