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- Homework Statement
- I can understand that the lightning coming from x=0 will reach to the assistant earlier, However, the question also asks for the time difference of the assistant receiving the lightning and this is the point I'm not sure about. My answer is 12km/c (c is the speed of light) Is this correct?

- Relevant Equations
- t=s/v

The way I was doing is that I list events

1. lightning hits x=0 this is (x_1=0,t_1)

2. lightning hits x=12 (x_2=12,t_2)

3. left lightning reaches "me" (x_3=9,t_3)

4. right lightning reaches "me" (x_4=9,t_4=t_3) t_4=t_3 since "I" see the lightning at the same time

Then the equation can be :

t_3=t_1+9/c

t_4=t_2+12-9/c=t_2+3/c

and since t_4=t_3 this implies t_2-t_1=6/c

Then it's possible to suppose t_1=0 and t_2=6/c

Then for the assistant:

1. lightning hits x=0 this is (x_1=0,t_1)

2. lightning hits x=12 (x_2=12,t_2)

3. left lightning reaches "me" (x_3'=3,t_3')

4. right lightning reaches "me" (x_4'=3,t_4'=t_3')

and t_3'=t_1+3/c=3/c

t_4'=t_2+12-3/c=6/c+9/c=15/c

The difference for the assistant is : 15/c-3/c=12/c