The necessity of introducing complex number structure into physics and the root of the most important physical meaning of complex number lies in the mathematical structure defined by the law of motion of quantum mechanics. In the language of group theory, the conservation of probability requires that the mathematical structure of evolution law is unitary group U(n) (see https://en.wikipedia.org/wiki/unity _ (Physics)), and U(n) can be decomposed into orthogonal group O(n) and symplectic group SP (2n, r): U (n) in real number field. The physical meaning of R), O(n) is the conservation of probability, and the physical meaning of Sp(2n, r) is the law of motion defined by quantum mechanics.

For example, idle time:

Virtual time is to study the failure of BIGBANG's initial time and construct a virtual time axis which is 90 degrees from the time axis.

Personally, I still don't quite understand what metaphor the North Pole is used for.

If you know something about relativity, quantum physics, M theory, etc. You can imagine (completely inaccurate, only easy to understand):

The existing space-time model is two-dimensional, and the following model can be made very easy to understand.

1. Simply understand the three-dimensional space as a straight line 10 cm, starting at a point in the positive direction of the coordinate axis Y and ending at 10 cm after that point.

2. Simply understand time as the length of 10 minute, starting at a point in the positive direction of the coordinate axis X and ending at 10 cm after that point.

In this way, a space-time model is obtained: the x axis is time, and one centimeter corresponds to one minute; The y axis is the distance, and 1 cm stands for 1 cm.

Now we introduce virtual time.