Higgs Boson

I just wished to know how do we determine the speed of light accurately. An experimental concept would be helpful but a theoretical approximation would do too .

But just consider something like the interpretations of the Schrodinger's Cat thought experiment, one of which prominently hypothesizes that until the time that we open the room and look at the cat to know, whether it is alive or dead, the cat is both alive and dead and "exists in something like simultaneous parts of the same universe." Now to a beginner like me this seems ridiculous. Also, basing a theory only, on statically derived data and whose predictions we can only comprehend or speculate as seems to have been illustrated above-is rather imprecise to a beginner like me however much abstraction it may epitomize. I mean lets say that even if every phenomena in nature can be predicted to a high degree of accuracy and corresponds to the quantum theory, the predictions of quantum theory do not assert anything clearly. As far as I have read and to put it rather bluntly" Quantum theory is a collection of statistical data which nobody understands to quote Richard Feynman. Atleast the underlying sentiment seems to convey so." I believe that not only does a good theory correspond to observations and make predictions but that it also makes sense (I don't know how can a theory make predictions, if it doesn't make sense.) Also, i would like to state that the point i had made earlier of highly idealised conditions was in the context that if those highly idealised circumstances are never naturally or artificially generated, what is the relevance of talking about them ? An example would be the above were the cat is either alive or dead. Speaking of that,(of course without using quantum mechanics in my case) how can we possibly confirm that whether the cat was alive or dead(or both!) without seeing the incident or recording the incident? In such a situation the highly idealised circumstance would be that no one records the incident and yet we come to know of the outcome, which is physically impossible. A similar kind of observation is also made in the Double Slit experiment. Please reply.

I would like a little clarification on the "Reason why quantum theory is accepted to be one of the foremost physical (metaphysical?) theory of nature". Currently have no knowledge about the intricacies of physics, having only skimmed over the basics of classical (newtonian) physics. I interpreted on an introduction to quantum theory, that the results that quantum theory predicts are in highly ideal conditions that can not be physically achieved by us or it considers possibilities which are beyond the feasible spectrum of environmental phenomena. How is the theory viable in this context ? Another example if the heisenberg principle states that we can never measure the position and momentum of an electron with certainty relative to one another, then speculating on the position and path of the electron in Young's double slit experiment becomes null, doesn't it. I mean suppose even if we only calculating the probability of the electron falling at one place on the screen by doing the experiment with one slit and then repeat the procedure with two slits, the experiment becomes null because the heisenberg principle (assuming it is true) clearly does not allow us to predict the path of the electron. Why don't we assume that the results should be within the expanse of the postulates of classical mechanics and relativity rather than supposedly inventing an entirely new theory to justify an experiment, the results of which are uncommon ? (Please ignore the factual inconsistencies if any and just look upon it as a meagre attempt to destabilise the oncoming quantum revolution.)