# The nature of time, according to quantum field theory

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.

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$$|\psi_\text{answer to your question}\rangle=\frac{|\text{yes}\rangle +|\text{no}\rangle}{\sqrt{2}}\neq|\text{maybe}\rangle$$. Pretty much sums it up. –  Manishearth Mar 14 '12 at 9:09
More on the concept of time: physics.stackexchange.com/q/16688/2451 and physics.stackexchange.com/q/15371/2451 –  Qmechanic Mar 14 '12 at 15:42