Other than NGT being a popular scientist but no where near the leading expert, there is a big difference between being able to explain how something works and knowing it exists and being able to observe it's effects or measure them in fine detail. It's the same false argument against evolution, that because we call it a theory, because we don't absolutely know all the mechanisms, that that some how means it "doesn't exist". That is not at all what it means.
djones51, Neil deGrasse Tyson admits that gravity can't be explained! Interesting.....