Differential equations are math equations that relate a function to its rate of change. They model how quantities evolve in time or space, and appear in physics, biology, and economics.
Differential equations won't help you much in the design of aeroplanes - not yet, anyhow. Nevil Shute
I became an atheist because, as a graduate student studying quantum physics, life seemed to be reducible to second-order differential equations. Mathematics, chemistry and physics had it all. And I didn't see any need to go beyond that. Francis Collins
A baby is lots more fun than differential equations. Robert A. Heinlein
Any progress in the theory of partial differential equations must also bring about a progress in Mechanics. Carl Gustav Jacob Jacobi
Baseball players or cricketers do not need to be able to solve explicitly the non-linear differential equations which govern the flight of the ball. They just catch it. Paul Ormerod
The emphasis on mathematical methods seems to be shifted more towards combinatorics and set theory - and away from the algorithm of differential equations which dominates mathematical physics. John von Neumann