"In 1948, while working at Bell Labs, Claude Shannon published a paper that laid the groundwork of information theory. In that paper, Shannon formulated the basic model of transmitter, receiver and transmission channel that has driven communications engineering to date. But in the same study, Shannon also set out to define a fundamental limit to the amount of information that could be transmitted over such a link. He theorized that the amount of error-free data that could be transmitted over a channel of any given bandwidth was limited by noise. While more and more efficient technologies can be developed to push more data into a channel, there is a ceiling at which any gains of capacity would essentially be canceled out by noise. That fundamental limit became known as Shannon's Law." [read the rest of the article at Telephony]
He basically said physics says only some much data can be stuffed into a pipe - any pipe: fiber, copper, wavelength, spectrum.