What is the difference between engineering and science?

Engineers and scientists have a friendly rivalry.  A recent book The Essential Engineer - why science will not solve our global problems by Henry Petroski provides some quotable arguments:

"A scientist studies what is; an engineer creates what never was. By extension, science is the study of what is; engineering is the creation of what never was."

"Science is about knowing; engineering about doing."

"Engineers do not need to imagine the unimaginable; they have to imagine the manageable."

"As engineers, we were going to be in a position to change the world—not just study it."

"It is customary to think of engineering as a part of a trilogy, pure science, applied science, and engineering. It needs emphasis that this trilogy is only one of a triad of trilogies into which engineering fits. The first is pure science, applied science, engineering; the second is economic theory, finance, and engineering; and the third is social relations, industrial relations, engineering. Many engineering problems are as closely allied to social problems as they are to pure science."