If you had one negative number in it, then the product would be a negative number and, if you took a root of that, then you might get an imaginarynumber.
如果这当中有一个负数,乘积就会变成负的,如果你对一个负数开根号,你就会得到一个虚数。
3
The universal gravitation field is described by imaginarynumber in the paper. It's energy density is negative real number. And it accord with conservation of energy.