The nature of time, according to quantum field theory

Question

I will try my best to ask the question that best fits something I have been pondering on for a few days.

Are virtual particles really constantly popping in and out of existence? Or are they merely a mathematical bookkeeping device for quantum field theory?

Gordon Kane, director of the Michigan Center for Theoretical Physics at the University of Michigan at Ann Arbor, provides this answer.

Virtual particles are indeed real particles. Quantum theory predicts that every particle spends some time as a combination of other particles in all possible ways. These predictions are very well understood and tested. http://www.scientificamerican.com/article.cfm?id=are-virtual-particles-rea

We define a second by the "duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom" (from wikipedia). Or in other words, we define a second by movement of a certain amount of waves/particles.

Since virtual particles pop in and out of existence, could you still claim that these things have a movement on the quantum level? If not, then how do you explain time/spacetime in the eyes of quantum field theory? And how does quantum entanglement fit in to this picture?

I am not a scientist, so please forgive me if my understandings of these concepts are flawed.

Answer 1

1. Virtual particles do not pop in and out of existence - this is just a common misconception. See https://physics.stackexchange.com/a/22064/7924 and Chapter A8 of my theoretical physics FAQ.

2. The second is defined by a measurement procedure that can easily and reliably be replicated, not by reference to vague concepts.

3. In quantum field theory (as opposed to quantum gravity), time is simply a parameter that together with position serves as argument for the fields. Further explanation is neither given nor needed.

4. This has nothing to do with entanglement.