From the opening onward this is just delightful. :)
To actually respond to your question though: why would you think you can’t use something that moves slowly to detect something moving fast?
We do that all the time.
More specifically, we detect fast things by looking at the imprint they leave on the environment alongside some measure of time of impact. That is you don’t have one item that’s faster and catches up whose response you look at, rather many items sirens across space.
I can measure the speed of a blazing fast car with ambling tumbleweeds by moving a line of those tumbleweeds perpendicular to the car and then seeing how many were displaced, for example. Doesn’t matter that the tumbleweed moved more slowly than the car.
As for why scientists mostly assume FTL doesn’t exist (aside from some theoretical Gabe’s with oddly shaped space):
We not only haven’t we observed FTL, but our (thus far hugely accurate) models of physics work partly based on the assumption that light is a speed limit. (Because energy has mass and as you add energy to something to speed it up it becomes more massive this requiring more energy to speed up further and so on.)
Could some form of particle we don’t know about travel FTL? Of course! Could the particles we don’t know about perhaps travel faster than light in certain scenarios we don’t know about it understand? Of course! Almost any decent scientist will tell you that there’s still tons to learn about the universe. No one pretends we understand it all — that’s why we have scientists. We (scientists) are excited by new discoveries that upturn previous theory. Science loves discovering things that break rules or ways of breaking rules!!! That’s one of the joys of science.
BUT, part of science is exploring new ideas and also reconciling them with what we observe. So far we simply haven’t seen any evidence of FTL (information transfer - you can define “objects” in ways that allow FTL, but it ends up being basically meaningless). Maybe we will discover something. Theorists are constantly considering new ideas and experimentalist sate constantly collecting data and comparing it to theory. But, thus far, we’ve got neither evidence of FTL or strong reason to suspect it exists.
A book you might like about a theory that involved the speed of light changing over time (by an accomplished and readable physicist) is <strong>Faster Than the Speed of Light</strong>, by João Magueijo. Fun book and discusses how new ideas and “accepted” theory mix in the actual works of theoretical physics as lived by scientists. The idea that there’s “a” uniform opinion of science is a simplification of what actually goes on in living fields.
This is the book that I was talking about: http://www.amazon.com/Faster-Than-Speed-Light-Speculation/dp/1422358836; What do scientists think about the author and his arguments?