Heheh... I can make some comments on this instead!
Originally Posted by neila9876 Can you explain why light speed is a costant in SR 
If we're talking about the speed of light being the same for all observers in all reference frames, then that's an axiom of special relativity. That is, it must be true for any of the theory to work. Since experimental evidence seems to suggest that it does, we have to assume it is true.
However, if you're curious whether the speed of light in a vacuum, c = 299792458 m/s, is something which should be considered a 'constant', then it turns out that this seems to be true by experimental evidence. That is, even if SR were totally wrong, the speed of light in a vacuum is constant.
and why there is no magnetic monopole in one theory with one math/geometric method?

In electromagnetism (EM), Maxwell's equations are:
$\displaystyle \nabla \cdot E = \frac{\rho}{\epsilon_0}$
$\displaystyle \nabla \cdot B = 0$
$\displaystyle \nabla \times E =  \frac{\partial B}{\partial t}$
$\displaystyle \nabla \times B = \mu_0 J + \mu_0 \epsilon_0 \frac{\partial E}{\partial t}$
The second equation, $\displaystyle \nabla \cdot B = 0$, basically states that no magnetic monopoles exist, because if they did, it would be a nonzero term. In our case, experiment seems to suggest that EM is exactly given by these four equations, so we're forced to expect no magnetic monopoles until some experiment comes along and detects them (and no experiment has).
I think HallsOfIvy's point is that by reading articles and news, it's very easy to get the impression that all of these sorts of things are on the table for discussion... however, there's decades of research into many of the phenomena we're all interested in and, as far as most physicists are concerned, they are pretty much solved; they're not open problems. Therefore, perhaps the impression of chaos that you have is just consequence of the phase that all people experience when looking at something new; those times when all you need is the time and the effort to fill those knowledge gaps in with the work that has already been made. After the hard work is done, the uncertainties and chaos disappears as quickly as it came, leaving just the satisfaction of understanding and a relatively clearer mind.