GRE Prep: Simultaneity Questions - Answer: No, Never

In summary, the conversation is discussing a question about whether two events that occur simultaneously in one system (S) will also occur simultaneously in another system (S') that is moving at a constant velocity with respect to S. The answer is "No, never" according to the GRE prep book, but this answer is questioned due to the possibility of the Lorentz boost being perpendicular to the direction of separation of the events. The ambiguity of the question's wording is also mentioned.
  • #1
Solarmew
37
1
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?
 
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  • #2
In the book example the separation is along the direction of motion; in your example the separation is perpendicular to the direction of motion.
 
  • #3
WannabeNewton said:
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? :rolleyes:
 
  • #4
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.
 
  • #5
WannabeNewton said:
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 ...
 
  • #6
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.
 
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  • #7
WannabeNewton said:
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
 
  • #8
D'aww the pokemon is cooler :p xD
 
  • #9
Good luck on your GRE by the way!
 
  • #10
WannabeNewton said:
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 ... -___________-
 
  • #11
Solarmew said:
fair enough :P and no, no pokemons XD just "mew" as in the sound a kitty makes :3

 
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FAQ: GRE Prep: Simultaneity Questions - Answer: No, Never

Can I skip the Simultaneity Questions on the GRE?

No, it is not recommended to skip any section or type of question on the GRE. Each question is designed to assess your skills and knowledge in a different aspect.

Are Simultaneity Questions more difficult than other types of GRE questions?

No, the difficulty level of Simultaneity Questions is similar to other types of questions on the GRE. It ultimately depends on your level of understanding and preparation.

Do I need to use a calculator for Simultaneity Questions?

No, the GRE does not allow the use of calculators. You will need to solve Simultaneity Questions manually using mental math and basic arithmetic skills.

Can I use a different method to solve Simultaneity Questions if I am not comfortable with the given method?

Yes, you can use any method that you are comfortable with as long as it leads to the correct answer. However, it is recommended to practice the given method to save time and avoid confusion during the exam.

Are there any tips for solving Simultaneity Questions on the GRE?

Yes, some tips for solving Simultaneity Questions include drawing diagrams, identifying patterns, and practicing with timed practice tests. It is also important to read the question carefully and double-check your calculations to avoid mistakes.

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