Why does light reach the lorry's back faster than its front from outside?

[almirza]

help , a hard question!

hi friend , i have a question please help.

there is a lorry with a boy inside it handing a lamp & there is a boy outside the lorry.
When the lorry is in a stationary position both boys notice that the light is reaching to the both sides ( front & back) of the lorry at the same time.
But when the lorry is moving the boy who is inside the lorry notice the same thing , but the boy who is outside the lorry notice that the light is reaching to the back of the lorry faster than reaching to the front.

So , who is right ? & why?

( hint:discovery(theory) or something happened in 1905 is involving )

 

[daniel_i_l]

They are both right, SR says that no frame is more "correct" than any other frame if all frames are moving with a constant speed.
Since the train is moving at a speed relative to the boy outside of the train then the boy outside the train sees events happening at different times when for the boy in the train they happen at the same time. Because the speed of light is the same in all frames, no matter how fast the frames are moving relative to each other.