# What's the deal with the gyroscope?

In this article ("The problem with physics", Tony Rothman, ABC science) the author says in the 5$^\textrm{th}$ paragraph:

For example, one needs only first-semester equations to describe reasonably well the behaviour of a gyroscope; engineers can then go off and build gyrocompasses that guide aircraft or missiles to their destinations. But if you merely ask: "At what, exactly, is the gyroscope pointed?" you are plunged headlong into one of physics' deepest questions, one that led Einstein to develop his general theory of relativity — and that, even today, has no definitive answer. I know of no undergraduate textbook that acknowledges the question."

What is the issue he is referring to?

-
This has the potential to stray into philosophy. –  dmckee Dec 7 '12 at 16:46