The 21st century – I say this as a sweeping bold statement, but I stand by it. The 21st century may be the century of non-linearity. We don’t know yet, but non-linear problems are becoming increasingly more trackable because of computational techniques. One of the reasons why linear problems were studied so extensively and were so useful is because a lot can be done sort of theoretically even if you couldn’t compute. And then, of course, later on when computational techniques – computational power was there, then they became even more – they were able to be exploited even more. What I wanna get to is the connection between the Fourier Transform and linear systems, and that’s gonna be primarily along the lines – so we definitely wanna see how the Fourier Transform applies to linear systems, again in a fairly limited way. ...

See the whole transcript at The Fourier Transform and its Applications - Lecture 23