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?
 A: I don't know Tony Rothman so I don't know exactly what I had in mind, but I expect he's referring to Mach's principle.
When he says:

I know of no undergraduate textbook that acknowledges the question

there is a very good reason for this. Physics is concerned with the construction of predictive mathematical models of the real world and Mach's principle plays no part on this. It may or may not be true that thinking about Mach's principle helped Einstein to formulate General Relativity, but GR is not a formulation of Mach's principle and the extent to which GR includes Mach's principle depends on who you ask and what exactly you mean by "Mach's principle" anyway. See Is Mach's Principle Wrong? for more on this.
A:   Gyroscope is a widely used device, in many fields are widely used, today let me introduce gyroscope in the balance of the application of the car to explain the working principle of the gyroscope.
   The gyroscope is an angular motion detection device which uses the moment of momentum of a high-speed rotating body to sense the shell relative to the inertial space around one or two axes orthogonal to the rotation axis.Angular motion detection devices based on other principles perform the same function, also called gyroscopes.

The history of gyroscopes Gyro instrument was first used in navigation, but with the development of science and technology, it has been widely used in aviation and aerospace industry.Gyro instrument can not only be used as an indicator instrument, but more importantly, it can be used as a sensitive element in the automatic control system, which can be used as a signal sensor.According to the need, gyro instruments can provide accurate azimuth, level, position, speed and acceleration signals, so that the pilot or with automatic navigator to control aircraft, ships or space shuttle and other vehicles according to a certain course of flight, and in the guidance of missiles, satellite carriers or space exploration rockets and other vehicles,Then the attitude control and orbit control of the vehicle are completed directly by using these signals.As a stabilizer, gyro instrument can make the train running on the monorail, can reduce the ship in the wind and waves swing, can make the camera installed on the plane or satellite relative ground stability, and so on.As a precision test instrument, gyro instruments can provide accurate azimuth datum for surface facilities, mine tunnels, underground railways, oil drilling and missile silos.It can be seen that the scope of application of gyro instruments is quite extensive, and it plays an important role in the construction of modern national defense and national economy.
The application of gyroscope in balancing vehicle
If  you are interested in Gyroscope and wants to learn more, you can conta us.
https://www.ericcogyro.com/application/
