Quantum field theory is the natural extension of quantum mechanics to adopt the special relativistic symmetries of the space-time. Attempts towards marriage of general relativity and quantum mechanics would leads to quantum gravity. There are two kinds of fundamental problems in these theories. The first kind is, in fact, the fundamental problems of quantum mechanics itself, transported to quantum field theory and quantum gravity. For example, the meaning of quantum measurement and quantum reality, causality and Bohm's model. The second kind of fundamental issues arises from combining relativity and quantum mechanics, including: the velocity of interaction, the meaning of particle and field, Bohmian quantum field theory and quantum gravity, and the problem of time.

## • Fundamental problems in Quantum Gravity and Quantum Filed Theory

Quantum field theory is the natural extension of quantum mechanics to adopt the special relativistic symmetries of the space-time. Attempts towards marriage of general relativity and quantum mechanics would leads to quantum gravity. There are two kinds of fundamental problems in these theories. The first kind is, in fact, the fundamental problems of quantum mechanics itself, transported to quantum field theory and quantum gravity. For example, the meaning of quantum measurement and quantum reality, causality and Bohm's model. The second kind of fundamental issues arises from combining relativity and quantum mechanics, including: the velocity of interaction, the meaning of particle and field, Bohmian quantum field theory and quantum gravity, and the problem of time.