Why physics should be the same in all inertial frame? One of the postulates of special relativity is that physics should be the same in all inertial frame.
Suppose we have two observers $A$ and $B$ suppose that $A$ is accelerated.
Now suppose that we have an event $E$ we probability $P$ such that this event is not influenced neither by $A$ or $B$ and in the frame of  the event $E$ we have an observer C.
If $C$ send the result of event (the probability $P$) i do not see why
result of $A$ and $B$ would differ? Or in another word why their physics should be different ?
 A: In class we learnt that this is because of Einstein's observation that it's not possible to tell two uniformly moving frames apart. Only with acceleration does it become possible to distinguish different motions. 
A: Given the duality and symmetry of electromagnetism, Einstein had a deep conviction that the universe as a whole was inherently symmetrical. That's why the dominant at the time aether paradigm did not appeal to him, with its preferred reference frame of the aether. 
The "unsuccessful attempts to discover any motion of the earth relatively to the light medium" gave him an excuse, basically, to get rid of the reference frame of the aether and make all reference frames equal and symmetrical. As part of this transition to a paradigm of pure relativity, he postulated that the laws of physics are the same in all reference frames - again, based on his conviction in the symmetries of the universe. The experimental evidence at the time seemingly supported this conviction, which further reinforced it. 
According to the literature, this was done on aesthetic grounds. It seems to me, though, that Einstein was driven to find the most generic solution possible and he really believed that symmetry was the answer to that.
