GRE Prep: Simultaneity Questions - Answer: No, Never

[Solarmew]

i'm reading over the GRE prep book and i just got to the question:
"System S' travels with constant velocity v≠0 w.r.t. system S. If two events, separated by a distance x≠0, occur simultaneously at time t in S, do they occur simultaneously in S'?"
the answer is "No, never". But the "never" part kind of bothers me. If you held two flashlights in your hands and they both lit up at the same time while your friend was driving away from you maintaining the same distance to both lights, wouldn't the events also occur at the same time in their frame of reference?

 

[WannabeNewton]

In the book example the separation is along the direction of motion; in your example the separation is perpendicular to the direction of motion.

 

[Solarmew]

In the book example the separation is along the direction of motion; in your example the separation is perpendicular to the direction of motion.

errr... where does it say the separation is along the direction of motion?

 

[WannabeNewton]

It's assuming that the Lorentz boost is along the $x$-direction of frame $S$ with the two events having a non-zero spatial separation $x\neq 0$ in frame $S$. If the separation is purely perpendicular to the direction of motion (such as me holding a flashlight in each arm exactly side by side) then there won't be an anomaly. If the car is traveling along the $x$-direction in my frame and the separation between the flash lights is $\Delta y$ i.e. $\Delta x = 0$ and I turn them both on so that $\Delta t = 0$ then $\Delta t' = 0$ trivially by the Lorentz transformations for a boost along the $x$-direction.

 

[Solarmew]

It's assuming that the Lorentz boost is along the $x$-direction of frame $S$ with the two events having a non-zero spatial separation $x\neq 0$ in frame $S$. If the separation is purely perpendicular to the direction of motion (such as me holding a flashlight in each arm exactly side by side) then there won't be an anomaly.

what i typed up was the whole question ... i don't know what kind of assumptions are supposed to be made based on that information :\ ... maybe it's just poorly worded ...

 

[WannabeNewton]

Well solarmew (mew from pokemon? xD) I would have to agree that it isn't exactly worded in the most unambiguous fashion. As long as the direction of the Lorentz boost isn't exactly perpendicular to the direction of separation of the simultaneous events in frame $S$, you can agree with the text.

 

[Solarmew]

Well solarmew (mew from pokemon? xD) I would have to agree that it isn't exactly worded in the most unambiguous fashion. As long as the direction of the Lorentz boost isn't exactly perpendicular to the direction of separation of the simultaneous events in frame $S$, you can agree with the text.

fair enough :P and no, no pokemons XD just "mew" as in the sound a kitty makes :3

 

[WannabeNewton]

D'aww the pokemon is cooler :p xD

 

[WannabeNewton]

Good luck on your GRE by the way!

 

[Solarmew]

Good luck on your GRE by the way!

thanks, I'm going to need it X.X ... considering i have to take it this september, the same time the three-quarter quantum sequence starts ... -___________-

 

[micromass]

fair enough :P and no, no pokemons XD just "mew" as in the sound a kitty makes :3