To put it one way, a collection of Shakespeare's plays is richer than a phone book that uses the same number of letters; to put it another, the essence of information lies in the relationships among bits, not their sheer number.

We don't know what energy is, any more than we know what information is, but as a now robust scientific concept we can describe it in precise mathematical terms, and as a commodity we can measure, market, regulate and tax it.

The problem of defining exactly what is meant by the signal velocity, which cropped up as long ago as 1907, has not been solved.

Entropy is not about speeds or positions of particles, the way temperature and pressure and volume are, but about our lack of information.

This is not what I thought physics was about when I started out: I learned that the idea is to explain nature in terms of clearly understood mathematical laws; but perhaps comparisons are the best we can hope for.

The smell of subjectivity clings to the mechanical definition of complexity as stubbornly as it sticks to the definition of information.

In fact, an information theory that leaves out the issue of noise turns out to have no content.