In reference to Coyoteman's objections, there exists evidence of a worldwide physical collapse of all major civilizations around 2350 B.C.: Comets and Disaster in the Bronze Age. Also, there are a number of scientists (e.g. Lanza) who posit that time is an illusion. Indeed, Einstein said that "reality is an illusion, albeit a very persistent one." He was speaking of local realism here, but the same concept is often extended to the whole.
Therefore, it is inaccurate to say that science has "debunked" either a belief in the Noah flood or a 6,000 year old universe. It can however be said that the mainstream view of science is thus and so.
Can a belief ever be "debunked" by anything since beliefs only exist in mind?